Own Use Gas Model for Pre-Heaters Issue: 2.0

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Advantica Stoner

Professional Services

(Europe)

Technical Note Note MonthMay 20012002

OperatorOwn Use EyeGas TrackingModel for Pre-Heaters

Confidential Restricted Restricted to toTransco Transco & & Advantica Advantica

Prepared for: Prepared by: Prepared for: Prepared by: John Wilson Clive Whitehand, Chris P Waghorn, Matthew Mullen Peter Chambers C.P.Waghorn Transco Advantica Technologies Limited Transco Advantica Technologies Limited United Kingdom Ashby Road Norgas House Ashby Road Loughborough PO Box 1GB Loughborough Leicestershire Killingworth Leicestershire LE11 3GR Newcastle upon Tyne LE11 3GR United Kingdom United Kingdom United Kingdom Tel: +44(0)1509 282218 Tel: +44(0)1509 282525 Fax: +44(0)1509 283131 Fax: +44(0)1509 283131 E-mail: [email protected] E-mail: [email protected] Website: www.advanticatech.com Website: www.advanticatech.com CustomerCustomer Reference: Reference: Filename: Final_Own_Use_Gas_Tech_Note (2.0).doc IU2.36 Future Control Room

Advantica Stoner is a trading name of Advantica Technologies Ltd. Registered in England and Wales No. 3294136. Registered Office: 130 Jermyn Street, London, SW1Y 4UR, and of Stoner Associates Europe Ltd. Registered in England and Wales; No.2593248. Registered office as above. Confidential Page 1 30/09/2011

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Project Code : 1/03018

Distribution :

Name Company John Wilson Transco

Simon Ashmore Transco

Approval :

Author(s): Clive Whitehand, Chris P Waghorn, Matthew Mullen, Chris Robinson

Team Clive Whitehand Leader: Project Adrian Jickells. Manager:

Recipients of this page may obtain a copy of this note from: Advantica Technologies Ltd, Ashby Road, Loughborough, Leicestershire, LE11 3GR. Telephone 01509 282525 Facsimile 01509 283131

Glossary This section contains a brief description of each acronym and some commonly used terminology that are included within the document.

NTS pre-Heater: The heater itself consists of a gas burner and a large water container through which pipes carrying the H.P. gas are run.

LDZ pre-Heater: As above but for lower volumes and pressure gas.

HPMIS: High Pressure Metering Information system.

GTMS: Gas Transportation Management System.

SQL: Structured Query Language – used to carry out operations on data stored in database tables.

SCPN: Station Code Point Name.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Executive Summary

LDZ Shrinkage is comprised of three elements:

• Leakage from the low pressure asset. • Own Use Gas, the gas used for pre-heating to counter the Joule Thompson effect on pressure reduction. • Theft of gas deemed to be Transco responsibility.

Shrinkage gas is procured on the basis of factors applied to throughput. For the Gas Year 2001/2002 Transco proposed a national LDZ Shrinkage Factor of 0.86%. Each 0.01% of throughput represents around £0.5million shrinkage cost. Clearly there is a driver to make accurate assessments of usage and also identify measures to reduce levels. The national factor is comprised of LDZ specific factors for Leakage and national factors for Own Use Gas and Theft of Gas.

• Leakage (0.77%) • Own Use Gas (0.06%) • Theft of Gas (0.03%)

This project has been funded in two £50K phases and develops a new robust model indicating a saving of £2.5M in the assessment of OUG for the year 2000.

The Transco model used to assess the Own Use Gas component is a pragmatic approach, applying thermodynamic principles with a range of assumptions which includes all gas into an LDZ passes through one offtake, and is subject to a two stage pressure reduction process with a plant efficiency assumed to be 50%. Metered data where available is not used.

The intention of this work was to review the current Transco model, develop an enhanced model and make an assessment of OUG consumption for the calendar year 2000.

The new model is much more sophisticated in its analysis of the data. Advantica experience in both Network Modelling and Gas Quality issues have been applied to a newly created large data base with national hourly coverage for key parameters. This has led to the situation where many previous assumptions, areas overlooked and estimations have been swept away.

The assessment of OUG consumption has, as with all models, an uncertainty associated with it due to the confidence levels within the data input to the model. The major sources of uncertainty are the efficiencies of the water bath heaters.

The 95% confidence intervals, based on the uncertainty in the estimation of the missing data, were found to be 0.0139% and 0.0104%. On this basis the assessment of OUG consumption for the calendar year 2000 was calculated as 0.0113%.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Contents

1 Introduction ...... 5 2 Aims of the project...... 6 3 Data Collection ...... 7 3.1 HPMIS ...... 7 3.2 GTMS ...... 7 3.3 AT_LINK ...... 7 3.4 PRE-HEATER SURVEY DATA...... 8 3.4.1 Ground temperatures...... 8 4 Transco Model Review...... 9 4.1 PRINCIPLE...... 9 4.2 ASSUMPTIONS...... 9 4.3 INPUT DATA ...... 9 4.4 METHODOLOGY ...... 9 4.5 ASSESSMENT ...... 10 4.6 CONCLUSIONS...... 11 5 Advantica Model...... 12 5.1 THE METHOD ...... 12 5.2 NEGATIVE TEMPERATURE RISE ISSUES...... 13 5.3 MODEL VALIDATION...... 13 5.4 AREAS FOR FUTURE MODEL REFINEMENT...... 14 6 Database ...... 15 7 Accessing the Database ...... 16 8 Assumptions...... 18 8.1 PRE-HEATER EFFICIENCIES...... 18 8.2 PRE-HEATER OPERATING REGIMES...... 19 8.3 NTS OFF TAKES WITHOUT GTMS DATA...... 19 8.4 LDZ OFF TAKES ...... 19 9 Own Use Gas Consumption 2000 ...... 20 10 Uncertanties within the New Model ...... 21 11 Conclusions...... 22 12 Recommendations ...... 23 13 References...... 23 14 Acknowledgements...... 23 15 Appendices...... 24 15.1 APPENDIX 1 – DATA INPUT STATUS...... 24 15.1.1 Summary of GTMS NTS Off take Data...... 24 15.1.2 Summary of GTMS LTS Data ...... 25 15.2 APPENDIX 2 – GROUND TEMPERATURE GRAPHS ...... 28 15.3 APPENDIX 3 – MODEL VALIDATION...... 30 15.4 APPENDIX 4 – TRANSCO MODEL GRAPH ...... 35 15.5 APPENDIX 5 – USER GUIDE ...... 36 15.6 APPENDIX 6 – DEVELOPER’S GUIDE...... 38 15.7 APPENDIX 7 – USER INTERFACE ISSUES...... 49

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

1 INTRODUCTION LDZ Shrinkage is comprised of three elements:

• Leakage (0.77%) • Own Use Gas (0.06%) • Theft of Gas (0.03%)

The intention of this work was to review the current Transco model, develop an enhanced model and make an assessment of OUG consumption for the calendar year 2000.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

2 AIMS OF THE PROJECT • To establish the amount of gas consumed by Pressure Reduction Site (PRS) pre- heater hot water baths and boilers in 2000.

• To develop an accurate and robust model to produce an assessment of Own Use Gas consumption for year 2000.

• To identify what further data and developments are required to further enhance the model.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

3 DATA COLLECTION A variety of data sources were identified to generate a figure for the amount of OUG consumption for the year 2000. These are described in this section along with any issues or difficulties identified in collecting the data. 3.1 HPMIS

The HPMIS has pre-heater metered flow data manually recorded. Seventy-seven sites have basic data. This data is of generally poor quality and the following aspects have been noted.

• No validation or filtering is carried out; gross errors are not trapped or limited. • The data is recorded in a number of units ft3, m3 • Data may be either uncorrected or corrected for pressure. (Manually logged survey data has been used to try and correct the uncorrected data) • No indication is given that the meters read have ‘rolled over’ numerically. • When a monthly reading is missed an estimated data value may be used or the same value as the previous month or no data entered.

Consideration of the above points is advised when using HPMIS pre-heater metered flow data. Generally data sets for each site are incomplete having on average half the data required. Some statistical methods may be used to extend some data sets.

3.2 GTMS

A request was made listing all NTS off takes using pre-heating. The flow, inlet pressure, outlet pressure, and exit temperature codes and point names were forwarded to the GTMS team at Killingworth. Over 1GB of hourly data has been unpacked and checked for corrupt entries.

The raw data files have been incorporated into an Access 2000 database, as the data set is too large to be operated on using a spreadsheet.

Similarly for the LTS, a request was made, listing the sites that had pre-heating. The station and code point names were again forwarded to the GTMS team at Killingworth. Approximately double the amount of data as for the NTS has been unpacked, checked for corrupt entries and entered into the database.

The HPMIS and GTMS data for the NTS and LTS is summarised in Appendix 1. A key is shown at the top of the tables.

In total, data for approximately 260 sites has been unpacked, checked and entered into the database. Of these 260, approximately 90 are NTS off takes and 170 are LTS PRS.

3.3 AT_Link

At Link is both a Shipper facing and internal Transco system. It is used by Shippers for nominating their gas requirements (amount and destination) and by Transco to balance the National Transmission System. This system was used to provide the LDZ total throughput figure.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

3.4 Pre-Heater Survey Data

The data collected falls under two main headings, firstly site information and then heater information.

The site information section contains data such as the site name, number, the district the site is in etc. Also included in this section are more specific operational measurements and set-points, such as maximum throughput, inlet temperature, outlet temperature set-point, inlet pressure and outlet pressure. This site information, where present, has been entered into the database and could be used for reference values should any of these values be found to be missing at a later stage.

The heater information section is mainly concerned with a brief description of the type of heater, any unique identifier, the operational data such as burner rating, and information on the fittings in the heater control panel.

Some of this data has been manually entered into a database table. Some of the surveys contain many errors and most are incomplete. Though there is information on the heater reference number there is no consistent method used in the labelling technique. Therefore each heater is labelled either A, B or C etc.

The units of measure used on the sheets varied vastly from site to site. Some measured pressure in bar g, psi g or even inches wg. The rating of the heater was also given in mixed units. Where appropriate, the values have been converted before being entered into the database.

3.4.1 Ground temperatures

The Transco model for ground temperature has been reviewed and compared to PPS/R0253 Statistical Analysis of national and regional ground temperatures at pipeline cover depths in the united Kingdom, Ref [1]. The existing Transco model for ground temperature is given by LDZ in Appendix 2, figure 12.c.

Ref [1] was collated by geographical region and by maximum and minimum spread of temperatures. This has been assimilated into both LDZ and spot temperatures. Two ground depths were considered as shown in appendix 2, figures 12.d and 12.e.

Both models were in reasonable agreement at peak values; the minimum values differ across the LDZs by two degrees. The ground temperatures from Ref [1] have been used for the OUG model.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

4 TRANSCO MODEL REVIEW This section describes the Transco model currently used to estimates Own Use Gas pre- heater consumptions.

4.1 Principle

The model calculates the enthalpy change across a pressure reduction using the following correlation

H = 527.5[1-2.37e-3(P-10) + 4.14e-3T + 2.18E-6(P-10)1.5T]

where H is enthalpy, P is pressure in bar and T is temperature in C. H has been fitted for a range of normal UK natural gas compositions.

Then the enthalpy change H = f(P1,T1) – f(P2,T2),

Energy Q is then calculated for H and gas volume V from

Q = H . V

4.2 Assumptions

Two pressure reduction stages (called phase 1 and phase 2), going from NTS line pressure to 35 bar (for Off takes) and from 35 bar to 10 bar (for LDZ sites).

• Initial gas temperature is taken to be ground temperature • Final temperature is 0°C • Pre-heater efficiency of 50%

4.3 Input data

NTS line pressure and gas volumes taken from GTMS records.

Ground temperatures from historical measurements, allowing both geographical and seasonal variation.

4.4 Methodology

For each LDZ, from GTMS volumes are summed for each month, line pressure is averaged for the month.

Monthly totals by LDZ may be positive or negative depending on whether the Joule- Thompson cooling would take the final temperature above or below the assumed set-point of 0°C. Only positive elements are counted for the pre-heater duty. For each LDZ energy is summed for each month for phase one and phase two separately.

For yearly energy requirement, phases one and two are summed together.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

4.5 Assessment

Overall the principle is sound. However, at the level of the individual monthly figures by LDZ the results appear questionable:

a) Over all LDZs, for a large part of the year (July to November), pre-heat is low or zero. This is not borne out by the actual monthly pre-heater readings now available via HPMIS. b) For Dec 97 for instance, most phase one energies for LDZs are negative, i.e. showing no pre-heat requirement, whereas all phase two energies are positive. It cannot be realistic that in December most phase one are not requiring pre-heat but all phase two are. This is not an isolated observation – many more examples could be given. c) Even at the peak of pre-heat (due to lowest ground temperatures) there are still LDZs showing no pre-heat operation for phase 1.

The causes of these discrepancies lie in the assumptions employed: • Fixed intermediate pressure • Fixed final temperature • Use of monthly averaged pressures

The net result of these is that, while the overall energy sum is largely correct, the split between phase one and phase two is not.

Even the overall energy sum may not be fully correct for two reasons:

a) Assuming final temperature is 0°C whereas set-points do vary. b) The use of average monthly pressures.

The reasoning behind the latter cause is as follows:

Energy is the product of enthalpy change and flow. GTMS shows that inlet pressures and flows vary greatly, both on a daily and seasonal timescale.

The correlation for H is of the form

H = aP + bT + cPT

where the c term is about 1/100th of the a and b terms, i.e. small. With such a small cross term the correlation is essentially independently proportional to P and T. This should mean that averaging the pressure should not introduce large errors in H. However, energy is the product of H and flow, unlike H, flow is independent of pressure. Flow plotted against pressure for a sample of Off takes shows this clearly.

Energy is summed as 1/n Pi . 1/n  fi.

The more accurate way is to count each hourly pressure and flow record separately, i.e. 1/n Pi.fi. Because f is not proportional to P then

1/n Pi . 1/n  fi is not in general = 1/n Pi.fi

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

It is probable that taking monthly average pressures ‘misses’ the points of high pressure drop when pre-heat is required and therefore underestimates the times when final temperature is below the set-point.

Because of the unpredictable nature of the pressure and flow behaviour it is not possible to gauge precisely what effect the coarse averaging will have on the accuracy of the Transco method without making some detailed comparisons.

4.6 Conclusions

The principle of the model is sound but the accuracy of the calculation is questionable due to the assumptions made about pressures and temperatures, and the coarseness of the summation of enthalpy – volume products.

The calculation is probably accurate during the winter period of high pre-heat demand. The use of global fixed pressure drops from line pressure to 35 bar in Phase 1, the use of a fixed drop from 35 to 10 bar in phase 2 and a fixed outlet temperature give rise to a number of over and under estimates in the energy calculation which would occur outside of winter.

Each of the above conditions used and assumptions made give rise to inaccuracies in the model. In addition no confidence level assigned to the data and no evidence of validation has been found.

There is scope to improve the modelling method used to obtain the overall OUG assessment.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

5 ADVANTICA MODEL 5.1 The Method

P T P1F1 O 5 1 M

Figure 5.1: A Typical PRS.

The method is based around the equation 1 P(kJ h)/ = m ∆T Cp Equ 5.1 η Where m is the mass flow rate (kg/h), ∆T is the rise in temperature in the heater (deg C), Cp is the specific heat capacity of the gas (kJ/kg/K), η is the efficiency of the heater and P is the energy used in the heater (in kJ/h).

The mass flow rate is calculated using

m = SG DAIR Q Equ 5.2 Where Q is the flow through the heater.

The Joule-Thompson coefficient can vary with pressure. Therefore the Joule-Thompson coefficient used in the model is calculated from the equation

2 µ JT = − .0 00001P − .0 0004P + 543.0 Equ 5.3

Where P is the average pressure across the regulator. More information about this equation can be found in Ref [2].

Similarly, the Specific heat capacity can also vary with pressure and temperature. Specific heat capacity is therefore calculated using the following equation (also taken from Ref [2]).

Cp = (4×10−8 P 2 + 6×10−6 P + .0 0021)×(4×10− T 25 + .0 0028T + .1 0321)×1000 Equ 5.4

Again, P is the average pressure and T is the average temperature across the regulator.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Most of the data used in the calculation of the pre-heat requirement is from GTMS. However this doesn’t give us any data for the outlet temperature of the heater, only the outlet of the site. Therefore we have to use the Joule-Thompson equation to calculate the temperature of the gas entering the regulator based on the data we have for the gas leaving the regulator

The Joule-Thompson equation is;

TOUTLET = TINLET − µ JT (PIN − POUT ) Equ 5.5

Where µ JT is the Joule-Thompson coefficient. We know the outlet temperature of the regulator, the pressure at the inlet to the site and outlet of the regulator form GTMS so it is therefore easy to calculate the required temperature at the inlet of the regulator and subsequently the pre-heat requirements.

The energy used in the heater is given in kJ per hour. This is then converted to kWh by using the conversion factor 1/3600.

5.2 Negative Temperature Rise Issues

In some cases the temperature rise in the heaters has been calculated as a negative value. This occurs when the calculated regulator inlet temperature is lower than the ground temperature we are assuming at the inlet to the station.

In physical terms this would equate to a refrigeration process in the heater, which can never be the case.

This could occur if we have assumed incorrect ground temperatures in the model, if the pressure at the outlet is greater than at the inlet (possibly if the data obtained from GTMS is incorrect).

If the outlet pressure is greater than the inlet pressure (this should not be the case but has been observed) then in the Joule-Thompson equation we can see that we get;

T = T − µ (− ∆P) OUT REGIN JT  TOUT = TREGIN + µ JT ∆P

This therefore shows that the outlet temperature of the regulator is higher than the inlet temperature. As we already know from the GTMS data and past experience the outlet temperature to the site is generally lower than the inlet. If the inlet temperature to the regulator is smaller and we are assuming no pressure loss in any other part of the site this would imply there is refrigeration in the heater which, as stated before cannot physically happen.

5.3 Model validation

The previous model has been compared to HPMIS data for the pre-heater corrected metered flow for a number of SCPNs. A greater degree of confidence is placed on data used for Rawcliffe and Towton due to the data set being 70% complete, other SCPNs have data approaching 30% complete. The plots created can be seen in appendix 3.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

5.4 Areas for future Model refinement

The model contains a number of features that are not fully utilised at present. These features allow the network pre-heat requirement to be modelled in much more detail than the current use of the model allows. The features that are not currently used to their full potential are listed below.

• The model contains the ability to model each heater on a site separately. This would require data about individual flows. • Different efficiencies can be entered for each heater used in the model. This will increase the accuracy of the final result. • Different set-points for summer and winter months for each heater. Again, this will increase accuracy. • The monthly operating regimes can be assigned to each individual heater or groups of heaters, stating when the heater is on and off. This will allow for seasonal variation in pre-heat requirements to be modelled correctly. • A usage figure for each site used in the model can also be obtained if necessary. • An LDZ usage per month can be calculated.

All of these features may be implemented in the future if the relevant information sources become available. Minor changes to the user interface and database would allow for a much more accurate figure to be calculated.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

6 DATABASE All the data obtained from GTMS and the heater survey is stored in tables in an Access 2000 database. There are nine main tables used in the database. These are, tblHeaterData, tblInputData Mthly_Inputs, UserInputs, GroundTemps, Monthly_CV, Monthly_SG, ResultsTable and OutputRes.

The table, tblHeaterData, contains a number of different fields that contain specific information on every heater. This includes such things as the rating of the heater; the outlet set temperature, the date of installation and the make etc. This sheet is used as a reference sheet.

The tblInputData table contains the data from GTMS for each of the site in the model. The data is the hourly figures for each gas day for the year 2000 for the flow, inlet pressure, outlet pressure and outlet temperature. This means that there are approximately 4x8700 values for each site.

Mthly_Inputs is a reduced version of the hourly input table. The data has been filtered into monthly figures. The table contains a monthly total flow, an average inlet pressure, average outlet pressure and average outlet temperature. This was done using a query operating only on records where the outlet temperature fell below the outlet set-point. This prevents any months with small pre-heat being missed.

The last of the inputs tables is called UserInputs. This table is linked to the Excel front-end and contains all the data that the user has just entered. The table is updated by the user clicking “Finish” on the data input screens.

GroundTemps contains the inlet temperature data for the model. In this table is stored the ground temperature for each LDZ by month.

The model is run using queries written in SQL. The queries populate the columns in the table, ResultsTable, in the database. As the entire model can be broken down into distinct sections, so the queries have been written in this way. There is a query for the Joule- Thompson cooling effect (Equ 5.5, earlier), a second that then finds the required temperature rise in the heater, a third query that converts the volumetric flow per day into the mass flow per hour (Equ 5.2), and a final query that uses Equ 5.1 to calculate the pre- heating requirements.

The mass flow query only runs if the flow in the current record is greater than zero, if not then zero is recorded in the relevant cell. Likewise, the final query is only executed if the temperature rise in the heater is positive and the outlet temperature of the gas is below the site outlet temperature set-point stored in the database. If neither of these conditions are met or if the heater operating regime states that the heater is off, then the query simply returns a zero as the usage for that period.

Some of the heaters on the network are switched off during the summer months. These operating regimes vary throughout the LDZs. The database can check if the heater is on or off each month using the operating regimes field in the heater data table. If the heater is found to be off, then the record is skipped, otherwise if the heater is on the calculations are carried out as normal (see appendix 6 for more information).

When the above calculations are complete, another query is run to sum the total gas usage for each of the LDZs. This data is placed in a new table called tblOutputRes. This table is linked to the Excel user interface where the actual percentage of OUG is displayed.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

7 ACCESSING THE DATABASE To access the database in an easy and user-friendly way, a user interface has been created in Excel. The user interface consists of a number of different screens that can be navigated through easily using a selection of buttons on each screen. These screens have been designed so as to make them as easy to understand and use as possible. See figure 7.1 below for the main control screen.

Figure 7.1: The User Interface Main Control Screen The user can select one of five options. The first option allows the user to enter new data; the second then allows the user to run the model using the newly entered data. The third and fourth buttons run the model using the 2000 data stored in the database, either hourly or monthly. Individual LDZs or either the NTS or LTS sites can be chosen to be used by selecting one from the drop-down boxes at the bottom of the screen. The final option then allows the user to view the results from the last run. Whenever the user interface accesses the database, either to run a model or collect the results data, the user is asked to enter a password. More about the password can be found in the developer’s guide in appendix 6. On clicking the first button, “Input Summary Data”, the user is asked to input monthly data for each LDZ. The data that is required is, the flow through all the PRS’, the total flow through the LDZ, the average site inlet pressure, the average site outlet pressure and finally the average site outlet temperature. Data can be entered for NTS or LTS sites, using the relevant tables provided.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

If either of the 2000 options are selected then the data already stored in the database is used as inputs. This can be restricted to either an individual LDZ or just the NTS or LTS sites. The database has been password protected to prevent any unwanted changes being made to the data. The password must be entered whenever the database is opened, either by the user interface or by the user opening the database in the normal manner. More information on the password protection and how to use the user interface is given in the developer’s guide in appendix 6.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

8 ASSUMPTIONS Given the limitation of LDZ pre-heater dynamic data availability and other constraints (as described earlier in section 3 on Data Collection) a number of assumptions were made to enable an estimation for the amount of Own Use Gas used in 2000 to be calculated. These are:

• Initial gas inlet temperatures relate to the data entered into the database which varied seasonally within each LDZ throughout the year. • Heaters are assumed to be operational throughout the year. • Preheat requirements are assigned to each station rather than by heater. Site operating regimes were not available for individual heaters. • It is assumed that LDZ pre-heater efficiencies are the same as NTS pre-heater efficiencies. • Previously, global constants were assumed, these were: • Specific heat capacity 2.612 kJ / K / kg • SG 0.63 • Density of air. 1.2255 kg m-3 • CV 39 MJ m-3

• µ JT 0.44 º C / bar

As stated previously, µ JT and specific heat capacity (Cp) are now calculated. A monthly SG and CV for each LDZ have been obtained from official sites on the NTS. Therefore the only remaining hard-coded constant is the density of air.

8.1 Pre-heater Efficiencies

There is little information on pre-heater efficiencies and this has a large impact on OUG consumption. Assumptions are based on references to efficiencies in the following documents:

• E7 Transco technical Specification for Gas Fired Water Bath Heaters Part 1 Basic Heater requirements 1993. “Heat loss in flue gases shall not exceed 25% of gross heat input.”

“Heat losses from outer shell and associated gas pipe work shall not exceed 1% of the declared heater output.”

• Techniques for improving the operation of Water Bath Heaters at pressure reduction stations MRS N427

• Thermal efficiency of Water Bath Heaters at Alrewas AGI MRS 403 Quotes ranges 58 to 66.5%

• Efficiency tests on Water Bath Heaters at Coleshill AGI MRS I 2912 Quotes ranges 58 to 66.5%

The database allows each individual heater to be given its own efficiency rating. However due to the lack of data the model is run using an efficiency of 100% and then afterwards the efficiency term is introduced as described in the developer’s guide in appendix 6, below. Ranges of efficiencies were used to estimate OUG consumption for pre-heaters these are: 30%, 40%, 50%, 60%, and 70%.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

As stated above, it is assumed that LDZ pre-heater efficiencies are the same as NTS pre- heater efficiencies. 8.2 Pre-Heater Operating Regimes

Detailed information about the actual heater set-point was not available for approximately 25% of the heaters used in the model. Where this is the case an assumed outlet temperature set-point of 0 ºC has been used.

The database allows a summer and winter outlet set-point to be used. This is useful if any of the heater set-points are “backed-off” during the summer months.

It is assumed that the heaters used in the model operate using the same outlet set-point throughout the year. There is the functionality in the database however to enter generic heater monthly operating regimes that may be used with a number of different heaters on the network. A number relating to one of the operating regimes must be assigned to each heater. The database then uses this number to check in the operating regimes table if the heater is on or off for the particular month in question.

New operating regimes may be added, or old regimes can be edited in the database by the user if necessary. More information about this can be found in the developer’s guide in appendix 6.

8.3 NTS Off takes Without GTMS Data

The assumption used in the proposed model that NTS off takes are those listed on the GTMS system.

It has been noted that the set defined by HPMIS have minor differences.

8.4 LDZ Off takes

Due to the lack of telemetry data at some sites it was not possible to include all of the LDZs in the model, (see section 15.1). An NTS to LTS monthly scaling factor has been used to estimate the LTS off take OUG based on the usage at NTS off takes. LDZs that had data for both LTS and NTS off takes were used to find a suitable monthly scaling factor between the NTS and LTS pre-heat usages.The missing LTS (phase 2) usage was then estimated by multiplying NTS ( phase 1) usage by this monthly scaling factor.

The Scottish LDZ had no flow telemetry for any of the LTS sites. An estimate of the LTS flow was found using the demand forecast data for the year 2000 by finding the monthly scaling factors from the LDZ with LTS data in the database. Average pressure and temperatures were then used along with the estimated monthly flows to find the LTS OUG usage.

Previously, the Transco model for both Phase 1 and Phase 2 was extrapolated to the end of 2000, using data from previous years (see Appendix 4).

A growth factor used in forecasting was included in the modelling. This information was used to factor up NTS consumptions (based on GTMS data and the Advantica model for NTS sites) to total both NTS and LTS pre-heater consumptions.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

9 OWN USE GAS CONSUMPTION 2000 Based on the assumptions above and the model used, the following estimates of Own Use Gas Consumption were produced (Table 9.1). A 100% figure is provided for reference. The main uncertainties in the OUG consumption are:

• Pre-heater hot water bath efficiencies

• Control regime of pre-heaters (currently only assumed to be on when the outlet temperature is less than the outlet set-point)

• Ground temperature assumptions

• Estimating the usage of the missing LDZs using a scaling factor based on the LDZ data we have collected

Combined, these uncertainties could affect %OUG significantly. Further work is required to reduce these to reach a reliable result. Efficiency Total Flow (kWh) Total OUG (kWh) % OUG 100% 7.13E+11 4.03E+07 0.0057 70% 7.13E+11 5.76E+07 0.0081 60% 7.13E+11 6.72E+07 0.0094 50% 7.13E+11 8.07E+07 0.0113 40% 7.13E+11 1.01E+08 0.0141 30% 7.13E+11 1.34E+08 0.0188

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

10 UNCERTANTIES WITHIN THE NEW MODEL The final result has an uncertainty associated with it due to the confidence levels associated with the inputs to the model. The major source of uncertainty in the final result from the OUG model is the lack of data for heater efficiencies. As can be seen from table 9.1, above, the efficiency has a large effect on the overall outcome, possibly greater than 100%. A second source of uncertainty is in the assumptions that have been made when data is missing. Where LTS data was missing, the LTS usage figure was estimated by using either the relationship between the NTS and LTS for the other LDZs or an estimated flow from the demand forecast profiles. Due to the extremely large size of the uncertainty associated with the heater efficiencies and the much smaller but significant uncertainty in the estimated LTS consumptions for missing data sets, any other uncertainties in the model can be considered negligible. These other uncertainties may lie in the quality of the initial data (i.e. the flow calculations from GTMS etc.) and also in the some of the other assumptions that have been made, such as inlet temperatures, unknown set-points. Figures for the confidence in the final result have been calculated. The 95% confidence intervals based on the uncertainty in the estimation of the missing data were found to be 0.0102% and 0.0137%. (assuming a heater efficiency of 50%). Taking into account that the efficiency of the heaters may also vary, the actual OUG percentage figure may lie between 0.0073% (with 70% efficiency) and 0.0229% (with 30% efficiency selected).

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

11 CONCLUSIONS Table 11 details the improvements made in the proposed AdvanticaStoner model against the current Transco enthalpy method.

Data Parameter Transco Enthalpy Method Model AdvanticaStoner Model.

Inlet temperature T1 Ground temperature Ground temperature validated against second independent study.

Outlet temperature 0 (Global) Set point used by site or heater, T2 enhanced by use of seasonal operating strategy.

Use of Joule-Thompson parameters from published reference [2].

Efficiency 50% (Global) 50% may be varied to any preset value. Model has provision to accept value by individual heater when available.

Inlet pressure P1 Phase 1 Line pressure averaged Hourly read data from GTMS over whole hourly GTMS year

Phase 2 Constant 35 bar (Global)

Outlet pressure P1 Phase 1 Constant 35 Bar (global) Hourly read data from GTMS over whole year Phase 10bar (Global)

Specific Gravity Not used HPMIS official site (daily metered)

SG Used in calculation of mass flow rate

Specific Heat Not used Can vary with P or T Capacity Cp Calculated using published reference [2].

Gas density Averaged from previous years data Using SG and density of air

Data actions

Data granularity Monthly Hourly

Data integrity Average of global data set Average data within preheat selection criteria.

LDZ by month Yes, Phase 1 Phase 2 Yes, Phase 1 Phase 2

Data Validated No Yes

Data Secure No Yes Password protected

Table 11.1 Comparative summary of OUG models. A key advantage of the new model is that its base data is hourly and has the capability to calculate OUG by hour, then sum the hours by month to arrive at the assessment figure. The old model is based on the total monthly flow totals and uses an enthalpy method to calculate the OUG monthly value. In the assessment of OUG the processes involve many interdependencies (i.e. positive and negative interactions), non-linearity, etc. This means that the process running at X+1 for half the time and X-1 for the other half will not have the same response as the process running at X for the whole time. Advantica Stoner is a trading name of Advantica Technologies Ltd. Registered in England and Wales No. 3294136. Registered Office: 130 Jermyn Street, London, SW1Y 4UR, and of Stoner Associates Europe Ltd. Registered in England and Wales; No.2593248. Registered office as above. Confidential Page 22 30/09/2011

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

A model has been proposed which uses existing archived and telemetered network data stored in a database to form the basis for a more accurate predictive estimate for OUG. Where available, metered data has been used to validate the model.

12 RECOMMENDATIONS • A figure has been presented for OUG usage for the year 2000 over a range of global pre-heater efficiencies. • Further work is required to devise a better estimation of pre-heater efficiencies since this is one of the most significant factors in calculating own use gas consumption.

• Investigate whether control strategies exist for pre-heaters on a regional or LDZ basis.

• For GTMS sites with pre-heat but incomplete telemetry (for OUG), investigate methods of mapping to similar sites either geographically or by rating.

• Investigate the feasibility of using the proposed Advantica Stoner model to predict an assessment of OUG using year 2001 data together with the existing data set.

• Transco to investigate data integrity of metered OUG sites and potential expansion to other LDZs other than Yorkshire. This would enable a more thorough validation of future models .

• Recommendations regarding the user interface are given in Appendix 7.

13 REFERENCES

1 STATISTICAL ANALYSIS OF NATIONAL AND REGIONAL GROUND TEMPERATURES AT PIPELINE COVER DEPTHS IN THE UNITED KINGDOM PPS/R0253 C. Mirfin July 2000

2 THE RISKS OF SUPPLYING GAS FROM BACTON AND THEDDLETHORPE WITH HIGHER HYDROCARBON DEW TEMPERATURES R5474 C. Robinson, C.P. Waghorn and J.H. White October 2001 14 ACKNOWLEDGEMENTS Thanks to the following System Operation and Advantica personnel for both contributing to the experiments and providing valuable feedback. Simon Ashmore. Bill Parker. Katie Trevis. Andy Gordon.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15 APPENDICES 15.1 Appendix 1 – Data Input Status

15.1.1 Summary of GTMS NTS Off take Data GTMS data status Data problem either corrupt, not usable, SCPN not telemetered. Data pointa requested from GTMS at Killingworth Data received but not eneterd into data base Data received and copied into data base Data present from HPMIS for prehater flows some data is corrected for pressure.

East Anglia East Midlands North ea F1 P1 P4 T1 em F1 P1 P5 T1 no F1 P1 P5 T1

BACTN_O F1 P1 P5 T1 BLABY F1 P1 P5 T1 AUKND_O F1 P3 P5 T1 BACTN_O T2 BLYBRGH F1 P1 P5 T1 CORBRIDG F1 P3 P5 T1 BRISLY F1 P3 P5 T1 BRIGG F1 P3 P5 T1 COWBWLY F1 P1 P4 T2 GT_YMTH F1 P1 P5 T1 CALDCOT F1 P1 P5 T1 COWBWLY P2 T3 GWILBHM F1 P3 P5 T1 CORBY_P F1 P1 P5 T1 GUYZANCE F1 P3 P5 T1 KSLYN_P F1 P1 P5 T1 CURT_O F1 P1 P5 T1 HUMBLTON F1 P3 P5 T1 LTLBRFD F1 P1 P5 T1 CURT_P F1 P3 P5 T1 LBUR_O F1 P1 P5 T1 MTCHGRN F1 P3 P5 T1 GOSBRTN F1 P3 P5 T1 MLKNTHRP F1 P3 P5 T1 PBORO_P F1 P1 P5 T1 GOXHILL F1 P1 P2 T1 SALTW_O F1 P3 P5 T1 PGRN_NT F1 P1 P5 T1 KEADBY F1 P1 P5 T1 SELLFLD F1 P1 P5 T1 PGRN_SM F1 P1 P4 T1 KIRKSTD F1 P3 P5 T1 SHAP F1 P1 P5 T1 PTEYE_O F1 P3 P5 T1 MKTHARB F1 P1 P5 T1 SHAP IP2 T2 ROUDHTH F1 P3 P5 T1 SILKWIL F1 P3 P5 T1 TOWLAW F1 P3 P5 T1 ROYSTON F1 P3 P5 T1 STALBR0 F1 P1 P5 T1 WETHRAL F1 P3 P5 T1 RYEHSE F1 P3 P5 T1 SUTN_BR F1 P1 P5 T1 WHIT_O F1 P3 P5 T1 THED_O F1 P1 P5 T1 WINCH F1 P3 P5 T1 THED8T FSP1 P1 P5 T1 YELVRTN F1 P1 P5 T1 THED8T T2 TURLANG F1 P3 P5 T1 WALESBY F1 P4 P5 T1

North West North Thames Scotland nw nl F1 P1 P5 T1 sc F1 P1 P5 T1 BLACROD F1 P1 P3 T1 HRNDN_O F1 P1 P5 T1 ABER_O F1 P3 P5 T1 ECCLSTN F1 P1 P5 T1 HRNDN_P F1 P1 P5 T1 ARMADLE F1 P3 P5 T1 HAYSCHM F1 ODP1 P5 T1 LUXB_LN F1 P3 P5 T1 BALGRAY F1 P3 P5 T1 HOLMCHP F1 P1 P5 T1 WINK_NT F1 P1 P5 T1 BROXBRN F1 P3 P5 T1 ICIRUNC F1 P1 P5 T1 WINK_SE F1 P1 P5 T1 CARESTN F1 P3 P5 T1 LUPTN_O F1 P3 P5 T1 WINK_SO F1 P3 P5 T1 DRUM F1 P3 P5 T1 MALPAS F1 P1 P5 T1 FERG_O F1 P1 P5 T1 MICKTRF F1 P1 P5 T1 GLEN_O F1 P3 P5 T1 PART_O F1 P1 P3 T1 HUME F1 P3 P5 T1 PART_O F2 NO PREHEATERS KINKNOC F1 P3 P5 T1 RSECOTE F1 P1 P5 T1 LANGHLM F1 P3 P5 T1 SAMLSBY F1 P1 P5 T1 MOFAT_O F5 P1 P5 T1 SHELSTR F1 P1 P5 T1 NTH_HOW F1 P1 IP1 T1 WARBR_O F1 P1 P5 T1 PITCAIN F1 P3 P5 T1 WESTON F1 P1 P5 T1 SOUTRA F1 P3 P5 T1

South South East South West so F1 P1 P5 T1 se F1 P1 P5 T1 sw F1 P1 P5 T1 BRSFLDA F1 P1 P5 T1 FRNGHAM F1 P1 P5 T1 AYLSBRE F1 P1 P5 T1 BRSFLDB F1 P1 P5 T1 MEDWAY F1 P1 P5 T1 CIRNSTR F1 P1 P4 T2 DCTA_P F1 P1 P5 T1 SHORNE F1 P1 P5 T1 CIRNSTR P5 T1 DCTB_P F1 P1 T1 TATSFLD F1 P1 P5 T1 ESTNGRY F1 P4 P5 T1 HARDWICK F1 P1 P5 T1 EVESHAM F1 P1 P4 T1 IPSDN_O F1 P1 IP1 T1 ILCHR_O F1 P1 P5 T1 MAPPWDR F1 P1 P5 T1 KENN F1 P1 P5 T1 LITTDRW F1 P1 P5 T1 PUCK_O F1 P1 P5 T1 ROSS_SW F1 P1 P5 T1 SBANK_P F1 P1 P5 SEABANK F1 P1 P5 T1

West Midlands Wales North Yorkshire wm F1 P1 P5 T1 wa F1 P1 P5 T1 yo F1 P1 P5 T1 ALRE_EM F1 P1 P5 T1 DEESIDE F1 P1 P5 T1 ASSELBY F3 P1 P4 T2 ALRE_WM F1 P1 P5 T1 DOWLAIS F1 P1 P2 T1 ASSELBY F2 P5 T1 ASPLEY F1 P1 P5 T1 DOWLAIS P4 T2 P5 T3 BALDSBY F1 P1 P5 T1 AUDL_NW F1 P5 T1 DYFFRYN F1 P1 P5 T2 BPSLT_L F1 P1 P5 T1 AUSTREY F1 P1 P5 T1 DYFFRYN F7 P4 T1 BURL_B F1 P3 P5 T1 CHRCH_O F1 P1 P5 T1 GILWERN F1 P1 P5 T1 GANSTED F1 P1 P5 T1 LEAMNTN F1 P1 P5 T1 MAELOR F1 P1 P5 T1 PANNAL F1 P1 P5 T1 RUGBY F1 P1 P5 T1 PAUL_J CALC_F1 P1 P5 T1 RUGBY F3 HP3 P4 T2 PAUL_O F1 NO PREHEATERS T1 RUGBY F2 HP1 HP2 T3 PICKRNG F1 P1 P5 T1 SHUSTKE F1 P1 P5 T1 RAWCLFE F1 P1 P5 T1 STRAFRD F1 P1 P5 T1 TOWTN F1 P1 P5 T1

Figure 15.1: Database NTS off takes status sheet. Advantica Stoner is a trading name of Advantica Technologies Ltd. Registered in England and Wales No. 3294136. Registered Office: 130 Jermyn Street, London, SW1Y 4UR, and of Stoner Associates Europe Ltd. Registered in England and Wales; No.2593248. Registered office as above. Confidential Page 24 30/09/2011

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15.1.2 Summary of GTMS LTS Data

Key: Data problem, either corrput not telemetered Data received but not entered into database Data received and entered into database

East Anglia East Midlands North North West ea F1P1P4T1 em F1P1P5T1 no F1P1P5T1 nw F1P1P5T1

BALSHAM F1 HP1 IP1 T1 ANNESLEY F1 HP1 IP1 T1 BLAYDON F1 HP1 IP1 T1ACCRINGTONF1HP1MP1- BLACKFAN F1 HP1 MP1 - ANNESLEY F2 P1 P5 T1 CATTERIK - HP1 MP1 - ALTRCMOS F1 HP1 MP1 T1 BOURNEND F1 HP1 IP1 - ANNESLEY F3 P1 P5 T1 ELTRNHAM - HP1 MP1 T1 ALTRCMOS F1 P1 MP2 T1 BRAMFORD F1 HP1 MP1 - ANNKODAK - HP1 IP1 T1 HAZELRIG F1 HP1 IP1 T1ALTRCMOSF1P1LP1T1 BREDFLD F1 HP1 MP1 - ASFORDBY - - MP1 T1 KIRKTHAM - HP1 IP1 T1 ALTRCMRD F1 HP1 MP1 - BROOMFLD F1 HP1 IP1 - ASHLY_HY - - IP1 T1 LAMBLEY - HP1 MP1 T1 ATHTNENG F1 HP1 IP1 - BYRDSFM F1 HP1 IP1 - ATHRSTON F1 HP1 HP2 - MIDDMOOR F1 HP1 MP1 T1 BNFLCAPE F1 MP1 - - CHALKEND - HP1 HP2 - BART_NWD - HP1 MP1 T1 NEWBY - HP1 HP2 - BNFLSWCK F1 HP1 MP1 - CORTON F1 HP1 IP1 - BEESTON - IP1 - T1 PLAWSWTH F1 HP1 MP1 - BROCK -- -- CRANFLD F1 HP1 MP1 - BELNIE - - MP1 T1 SPRIN_LN - HP1 MP1 T1 CASTLERD - HP1 - T1 DAISYGRN F1 HP1 HP2 - BESSACAR F1 HP1 MP1 T1 THORVALE - HP1 MP1 - DURTNLNE F1 HP2 MP1 - DYESLANE F1 HP1 MP1 - BIRLEY F1 HP1 IP1 T1 USHAMOOR F1 HP1 MP1 T1 DUTTON F1 HP1 MP1 - ECARLTON F1 HP1 HP2 - BGYP_ELK F1 HP1 - T1 WEDMONLY F1 HP1 HP2 T1 EUXTON F1 HP1 MP1 - FLAGFEN F1 HP1 IP1 T1 BULLOCK F1 HP1 MP1 T1 GLAXO - - - - GANWIKFM F1 HP1MP1 - CAENBY F1 HP1IP1 T1 GRANGE F1 HP1 MP1 - GREENST F1 HP1 MP1 - CANDLSBY F1 HP1 MP1T1 GREENFLD F1 HP1 MP1 - GROVEFM F1 HP1MP1 - CATSHAW F1 HP1HP2 T1 GROTTON F1 HP1 MP1 - HATFIELD F1 HP1 MP1 - CHELASTN - HP1 LP1 T1 HAMBLETN F1 HP1 MP1 - KINSBNGN F1 HP1 MP1 - NOVARTIS F1 HP1 HP2 T1 HAYSCHM F1 - P5 T1 LANGHAM F1 HP1HP2 - CODINGTN F1 HP1IP1 T1 HELMSHOR F1 HP1 MP1 - LNKTSGRV F1HP1IP1 - CORBY F1HP1IP1 T1 HOLMCHP F2 P4 MP1 - MTCHNGRN F3HP1IP1 - CRICK - HP1MP1T1 HOOGREEN - - - - METTNGHM F1 HP1 IP1 - DRAKHOUS F1 HP1 MP1 T1 HORWICH - - P5 - MONKSGRN F1 HP1IP1 - EAGLE F1 HP1HP2 T1 ICIMACC - - - - NWALSHAM F1 HP1 IP1 T1 E_STOKE F1 HP1 MP1 T1 KELLETLN F1 HP1 MP1 - PBOROEYE F3 HP1 IP1 T2 EURO_NLG - HP1 MP1 T1 KINGSWAY F1 HP1 MP1 - ROUDMHTH - HP2 HP3 T2 FENCE_FM F1 HP1 MP1 T1 KOTERS - - - - RYEFARM F1 HP1 IP1 T1 FINDERN F1 HP1 MP1 T1 LEYLNDWA F1 HP1 IP1 - SPRNGFLD F1 HP1 HP2 T1 FRAMPTON - HP1 IP1 T1 LEYLNDWA F2 P1 P5 - STNSTDAB F1 HP1 IP1 - GIBB_MR - HP1 IP1 T1 MELLOR - HP1 IP1 - GIPSY_LA F1 HP1 MP1 T1 MICKTRF F2 P5 MP1 - GRIMSBY F1 HP1 MP1 T1 NEWTONWS - IP1 LP1 - GUILTHWT F1 HP1 IP1 T1 OAKWOOD F1 HP1 MP1 - HARBY - - MP1 T1 PADGATE F1 HP1 IP1 - HILTON - - MP1 T1 PADGATE F2 P1 P5 - KIRBY_BL - - MP1 T1 PASHTRIB F1 HP1 MP1 - L_RUD_FM - - IP1 T1 PHILLIPS - - - - LONG_BUC - HP1 IP1 T1 PRLONGRD F1 HP1 MP1 - MAGNA_PK - - MP1 T1 RAINOW - - - - MALTBY F1 HP1 MP1 T1 ROGERHEY F1 - IP1 T1 MELTN_RS F1 HP1 IP1 T1 SCOTFRTH F1 HP1 MP1 - MELTN_SP F1 HP1 IP1 T1 STANDISH F1 HP1 MP1 - MEYN_LAN - HP1 MP1 T1 STARLING - HP1 IP1 - MIDDLEME - HP1 IP1 T1 ULVERSTN F1 HP1 MP1 - NEW_ANNE - - MP1 T1 WHALYBRG F1 HP1 MP1 - NEWSTEAD F1 HP1 IP1 T1 WIDSBRST F1 HP1 MP1 - NOVARTIS F1 HP1 HP2 T1 WILMSLOW F1 HP1 MP1 - OWLER_B F1 HP1 MP1 T1 WLTNSUM F1 HP1 MP1 - OXTON - - MP1 T1 WOOLSTON - HP1 IP1 - PAPPLEWK F1 HP1 IP1 T1 WORSLEY - HP1 MP1 - PASTURE F1 HP1 IP1 T1 PASTURE F1 P1 P5 T2 PINCHBCK - HP1 IP1 T1 PLAYERS F1 HP1 HP2 T1 ROCKNGHM - HP1 IP1 T1 ROSINGTN - - MP1 T1 ROWSLEY F1 HP1 MP1 T1 SCM_CHP F1 HP1 HP2 T1 SHERNGTN - HP1 MP1 T1 SINFIN - - IP1 T1 STH_FEN - - MP1 T1 STH_WITH - - IP1 T1 STAINTON F1 HP1 IP1 T1 THULSTON F1 HP1 MP1 T1 TOYOTA F1 HP1 IP1 T1 TOYOTA F2 P1 P5 T1 UPPINGHM F1 - IP1 T1 WARNTNGE F1 HP1 IP1 - WEST_BRN - - MP1 T1 WOOTTON - HP1 MP1 T1

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

North Thames Scotland South South East nl F1P1P5T1 sc F1P1P5T1 so F1P1P5T1 se F1P1P5T1

AMSHM_RD F1 HP1 MP1 - AB_CITYG - HP1 IP1 T1 CROWTHRN F1 HP1 IP1 T1ANSTYSSXF1HP1IP1T1 BILERICY F1 HP1 MP1 T1 AB_CRAIB - HP1 IP2 T1 FROYLE F1 HP1 IP1 T1 ASHTEAD F1 HP1 IP1 T1 BROCK_HL F1 HP1 MP1 T1 ABERLADY - HP1 MP1 T1 HILLSIDE F1 HP1 MP1 T1 AYLESHAM F1 HP1 MP1 T1 CDWL_S_M (Brook Farm) F1 HP1 MP1 T1 ALLOA - HP1 IP1 T1 HORNDEAN F1 HP1 MP1 - BIGGIN_M F1 HP1 MP1 T1 CDWL_HTH F1HP1MP1T1 BALFARG - HP1MP1T1 LITLMORE F1HP1MP2T1BLEANF1HP1MP1T1 CDWL_S_M F1HP1MP1T1 BALFARG F1P1 P5 T2 LORDSWOODF1HP1IP2 T1BOXHILLF1HP1MP1T1 CHIGWELL F1 HP1 MP1 T1 BALLNGRY - HP1 MP1 T1 PARADISE F1 HP1 IP1 T2 CRANLIGH F1 HP1 MP1 T1 COLR_ROW F1 HP1 MP1 T1 BATHGATE - HP1 MP1 T1 PORTSDWN F1 HP1 IP1 T1 CRAWLY_I F1 HP1 IP1 T2 DODNHRST F1 HP1 MP1 T1 BATHVILL - HP1 MP1 T1 PURBROOK F1 HP1 MP1 -CROSSBSHF1HP1IP1T1 HARFIELD F1 HP1 MP1 - BOGTON - HP1 MP3 T1 SETLEY F1 HP1 IP1 T1 DORKING_M F1 HP1 MP2 T1 HRPS_HTH F1 HP1 MP1 - BUCKIE - HP1 IP1 T1 STARLOD F1 HP1 MP1 T1 DORKING_M F1 P1 P5 T2 ILFORD F1HP1MP1T1 BURGIE -HP1MP1T1 STONEHAM F1HP1MP1T1 ESHER F1 HP1 MP1 T1 MAGNL_RD F1HP1MP1T1 CMBSLANG - HP1IP1 T1 FOLKST_I F1 HP1 IP1 T1 MOUNTNSG F1HP1MP1T1 COLESSIE - HP1IP1 T1 FOLKST_I F1 P1 P5 T2 NRTHWOOD F1 HP1 MP1 - CONDORAT - HP1 MP1 T1 GODSTONE - HP1 MP1 T1 PUTWL_BR F1 HP1 MP1 T1 CONNBRDG - HP1 IP1 T1 HADLOW - HP1 IP1 T1 ROMFORD F1 HP1 MP1 T1 CUMBRNLD - HP1 MP1 T1 HAILSHAM F1 HP1 MP1 T1 S_OCKNDN F1 HP1 MP1 T1 DRAKEMYR - HP1 MP1 T1 HAYWDHTH F1 HP1 MP1 T1 STNS_BYP F1 HP1 MP1 - DUMFRIES - HP1 IP1 T1 HEATHFLD F1 HP1 MP1 T1 ST_LE_HP F1 HP1 MP1 T1 E_KLBRDE - HP1 MP1 T1 HORSHM_I F1 HP1 IP1 T1 TATL_END F1 HP1 MP1 T1 ELGIN - HP1 IP1 T1 HORSHM_I F2 P1 P5 T2 GARTCOSH - HP1 MP1 T1 HORSHM_I F3 P1 P5 T1 GRANGMTH - HP1 IP1 T1 HURSTGRN - HP1 IP1 T1 GREENOCK - HP1 IP1 T1 IGHTHAM F1 HP1 MP1 T1 HUNTLY - HP1 MP1 T1 JARVSBRK F1 HP1 MP1 T1 HUNTRSTN - HP1 IP1 T1 KEYSTREE F1 HP1 IP1 T1 INVRKIP - HP1 IP1 T1 LEEDS F1 HP1 MP1 T1 INVRNESS - HP1 IP1 T1 LIPTLANE F1 HP1 IP1 T1 KELSO - HP1 MP1 - LIPTLANE F2 P1 P5 T1 KELTY - HP1 MP1 T1 LIPTLANE F3 P1 P5 T1 KILBRCHN - HP1 IP1 T1 MURSTON F1 HP1 MP1 T1 KILSYTH - HP1 MP1 T1 ROCHST_M F1 HP1 MP1 T1 KRKLSTON - HP1 MP1 T1 ROLVENDN F1 HP1 MP1 T1 KRKNTLCH - HP1 MP1 T1 ROLVENDN F2 P1 P5 T1 LOCHMABN - HP1 IP1 T1 ROLVENDN F3 P1 P5 T1 LOGIRAIT - HP1 IP1 - RUMBCAST - HP1 MP1 T1 LNLTHGOW - HP1 MP1 - RYE - HP1 MP1 T1 MARYCLTR - HP1 IP1 T1 SCAAYLES F1 HP1 IP1 T1 MILNGAVI - HP1 MP1 T1 SHALFORD F1 HP1 IP1 T1 MILTON - HP1 MP1 T1 SHALFORD F2 P1 P5 T1 MOFFAT_M - IP1 MP1 - SHALFORD F3 P1 P5 T1 MOSSEND - HP1 MP1 T1 SHATRLNG - HP1 IP1 T1 MOSSMRN - HP1 IP1 T1 SNODLAND F1 HP1 MP1 T1 MUSLBRGH - HP1 MP1 T1 SNODLAND F1 P1 P5 T2 NAIRN - HP1 MP1 T1 STORNGTN - - MP1 T1 NORTHAYR - HP1 MP1 T1 STURRY F1 HP1 IP1 T1 NWTN_MRN - HP1 MP1 T1 UCKFIELD F1 HP1 MP1 T1 NWTN_STW - HP1 MP1 T1 UCKFIELD F2 P1 P5 T1 PETRCLTR - HP1 IP1 T1 UCKFIELD F3 P1 P5 T1 PRISDYKS - HP1 IP1 T1 WADHURST F1 - MP1 T1 ROTHES - HP1 IP1 T1 WOKING F1 HP1 MP1 T1 SGHTHILL - HP1 MP1 T1 WOKING F2 P1 P5 T2 SHLDHILL - HP1 IP1 T1 SOUTHAYR - HP1 MP2 T1 STIRLING - HP1 IP1 T1 STRAITON - HP1 MP1 T1 SWANSTRD - HP1 MP1 T1 TORRANCE - HP1 MP1 T1 TROON - HP1 MP1 T1 UDDNGSTN - HP1 MP1 T1 WESTHILL - HP1 MP1 T1

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

South West West Midlands Wales South Yorkshire sw F1 P1 P5 T1 wm F1 P1 P5 T1 wa F1 P1 P5 T1 yo F1 P1 P5 T1 T2

ALMNSBRY F1 HP1 MP1 T1 ATHSTN_W F1 HP1 MP1 T1 ABRAVON F1 HP1 MP1 T1 ABERFORD - HP1 MP1 T1 BARRNTN F1 HP1 MP1 T1 COVEN F1 HP1 IP1 T1 CAERWENT F1 HP1 HP4 T1 CAST_ING - HP1 IP1 T1 BERK_RD F1 HP1 MP1 T1 DUNKIRK F1 HP1 IP1 T1 CARDIGN F1 HP1 HP2 T1 CROSGTE - HP1 MP1 T1 BRISLNG F1 HP1 MP1 T1 EBSTREE F1 HP1 HP2 T1 CATSASH F1 HP1 MP1 T1 EGGBORO F1 HP1 IP1 T1 COALPIT F1 HP1 MP1 T1 ELLSMERE - HP1 MP1 T1 CEFNON F1 HP1 MP1 T1 GARFORTH F1 - MP1 T2 COFNSWL F1 HP1 IP1 T1 ESSINGTN F1 HP3 HP4 T1 CWMBRN_I F1 HP1 IP1 T1 WHITBY - HP1 MP1 T2 COFNSWL F1 P1 P5 T2 FRADLEY F1 HP1 MP1 T1 DINHBRD F1 - IP1 - HARTSHED - HP1 MP1 T1 COLD_LN F1 HP1 MP1 T1 FRANK_H F1 HP1 HP2 T1 FISHGARD - HP1 LP1 - HARSWELL - HP1 MP1 T2 CORSTON F1 HP1 IP1 T1 GOBOWEN - - MP1 T1 HEOLCYW F1 HP1 HP2 T1 LILEY_LN F1 HP1 HP2 T3 T4 DUKEBRK F1 HP1 IP1 T1 HAM_BISH - HP1 MP1 T1 LLNDVRY - HP1 LP1 - LOW_MOOR - HP1 MP1 T1 E_DUNDRY F1 HP1 IP1 T1 HINCKLEY F1 HP1 MP1 T1 LLNELLI F1 HP1 MP1 T1 NAYLOR_B F1 HP1 IP1 T1 FISHACR F1 HP1 IP1 T1 HURLEY - HP1 MP1 T1 LLNTNAM F1 HP1 MP1 T1 NAYLOR_B F2 P1 P5 T1 HALLEN - HP1 HP2 T1 KINGS_CO F1 HP1 MP1 T1 LLNTWIT F1 HP1 LP1 T1 PICK_OUT - HP1 HP3 T2 T1 HINTONC F1 HP1 MP1 T1 LANDWOOD F1 HP1 MP1 T1 NARBRTH F1 HP1 HP2 T1RAF_FYLD-HP1IP1T1 K_ST_MY F1 HP1 IP1 T1 OSWESTRY - - MP1 T1 NASHRD F1 HP1 IP1 T1 WHINGILL F1 HP1 IP1 T2 KIT_HILL F1 HP1 MP1 T1 ST_MRTNS - HP1 IP1 T1 NEATH_M F1 HP1 MP1 T1WHITBY-HP1MP1T2 LAPFORD F1 HP1 MP1 T1 SOUDLEY F1 HP1 MP1 T1 PENYBRN F1 HP1 IP1 T1 WHITE_RD F1 HP3 MP1 T4 T2 LISKARD F1 HP1 MP1 T1 STONE_X F1 HP1 MP1 T1 PNTRDWE F1 HP1 MP1 T1 CROOK F1 HP1 HP2 T3 T2 LYDFORD F1 HP1 IP1 T1 WHEAT_GR F1 HP1 IP1 T1 PNTRDLS F1 HP1 HP2 T1EBIERLEYF1HP1HP2T3T2 MALMSBY F1 HP1MP1T1 WHITNGTN F1 HP1MP1T1 PNTLLIW F1 HP1HP2 T1BULL_LNF1HP1HP2T3T2 MOREDON F1 HP1IP1 T1 WILDMOOR F1 HP1HP2 T1 PNTYCLN F1 IP1 MP1T1 NAILSEA F1 HP1 MP1 T1 RHIWDN_V F1 HP1 HP3 T1 PENNLEA F1 HP1 IP1 T1 RHWSAES F1 HP1 IP1 T1 ROBORO F1 HP1 MP1 T1 STATHAN F1 - MP1 - SHEPTON F1 HP1 MP1 T1 STREGIS F1 HP1 IP1 T1 SHMPTN F1 P1 P5 T1 THNMILF F1 HP1 - T1 ST_BLZY F1 HP1 MP1 T1 THNWELL F1 HP1 MP1 T1 TEINGRC F1 HP1 MP1 T1 YNYSALLN F1 HP1 MP1 T1 TWKSBRY F1 HP1 IP1 T1 UCKNGTN F1 HP1 HP2 T1 WATCHET F1 HP1 IP1 T1 Wales North WATCHET F1 P1 MP1 T1 wa F1 P1 P5 T1 WHTMNST F1 HP1 IP1 T1 WIXNFRD F1 HP1 IP1 T1 ABRGELE F1 HP1 MP1 T1 YATTON F1 HP1 MP1 T1 CHWILOG F1 HP1 HP2 T1 YEOVIL F1 HP1 IP1 T1 CLBAYCG F1 HP1 HP2 T1 ELLSMERE - HP1 MP1 T1 GOBOWEN - - MP1 T1 LEGACY F1 HP1 IP1 T1 LLNDRND - HP1 - - LLNWNDA F1 HP1 IP1 T1 MOATLNE F1 HP1 HP4 T1 MOCHDRE F1 MP1 - - VASTRE F1 HP1 MP1 T1 OSWESTRY - - MP1 T1 OVERTON F1 HP1 HP2 T1 ST_MRTNS - HP1 IP1 T1 TRYFIL F1 HP1 HP2 T1 WELSHPL F1 HP1 IP2 T1 YWAEN F1 HP1 HP2 T1 Figure 15.2: Database LTS sites status sheet.

The percentage of sites from which suitable data was acquired was:

• NTS: 64% • LTS: 34%

Giving an overall site coverage of 42% for hourly data over the year 2000.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15.2 Appendix 2 – Ground Temperature Graphs

18.0 16.0 EM EA 14.0 NE 12.0 NO 10.0 NT 8.0 NW 6.0 SC 4.0 SE 2.0 SO 0.0 SW

7 7 7 WM 98 9 9 97 ry 98 il 98 y e 97 ly st 97 r 97 u er 9 WA(N) rch 98 pr Ma Ju g be ber ber ruary 98a A Jun u mb m M e Janua A WA(S) Feb Octo ove Septem N Dec

Figure 15.3: Transco Ground Temperature Model

Ground tempetratures from PPS/R0253

20 30cm EM 18 30cm EA 16 30cm NE 14 30cm NO 12 30cm NT 10 30cm NW 8 30cm SC 6 30cm SE 4 30cm SO Temeprature Celcius Temeprature 2 30cm SW 0 30cm WM 0.0 5.0 10.0 15.0 30cm WA(N) 30cm WA(S) Months

Figure 15.4: BG technology 2000 ground temperature by LDZ normalised to 30cm

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Ground Temperatures from PPS/R0253

18 122cm EM 16 122cm EA 14 122cm NE 12 122cm NO 10 122cm NT 8 122cm NW 122cm SC 6 122cm SE 4 122cm SO 2 122cm SW Temperature Celcius Temperature 0 122cm WM 0.0 5.0 10.0 15.0 122cm WA(N) 122cm WA(S) Months

Figure 15.5: BG Technology 2000 ground temperature by LDZ normalised to 122cm

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15.3 Appendix 3 – Model Validation

Plots labelled Transco use corrected data from HPMIS.

Plots labelled Advantica use raw data processed using the above algorithm.

1.20E+06

1.00E+06

8.00E+05

6.00E+05 ARMADALE kWHrs 4.00E+05

2.00E+05

0.00E+00 1/1/00 2/1/00 3/1/00 4/1/00 5/1/00 6/1/00 7/1/00 8/1/00 9/1/00 10/1/00 11/1/00 12/1/00

Date

Figure 15.6: Armadale HPMIS consumptions

7.00E+05

6.00E+05

5.00E+05

4.00E+05 ARMADLE

kWHrs 3.00E+05

2.00E+05

1.00E+05

0.00E+00

0 0 0 0 0 -0 00 n-00 - -00 ar-00 pr- u Jul ct Feb-00M A May- J Aug Sep-00O Nov-00Dec-00 Months

Figure 15.7: Armadale Advantica Model

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

2.50E+05

2.00E+05

1.50E+05 SOUTRA

kWHrs 1.00E+05

5.00E+04

0.00E+00 1/1/00 2/1/00 3/1/00 4/1/00 5/1/00 6/1/00 7/1/00 8/1/00 9/1/00 10/1/00 11/1/00 12/1/00

Date

Figure 15.8: Soutra HPMIS consumptions

SOUTRA

2.50E+06

2.00E+06

1.50E+06 SOUTRA

kWHrs 1.00E+06

5.00E+05

0.00E+00 Feb- Mar- Apr- M Jun- Jul- Aug- Sep- Oct- Nov- Dec- 00 00 00 ay- 00 00 00 00 00 00 00 00 Months

Figure 15.9: Soutra Advantica Model

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

9.00E+06

8.00E+06

7.00E+06

6.00E+06

5.00E+06 Towton A+B+C

kWHrs 4.00E+06

3.00E+06

2.00E+06

1.00E+06

0.00E+00 1/4/00 2/4/00 3/4/00 4/4/00 5/4/00 6/4/00 7/4/00 8/4/00 9/4/00 10/4/00 11/4/00 12/4/00

Months

Figure 15.10: Towton HPMIS consumptions

4.50E+06

4.00E+06

3.50E+06

3.00E+06

2.50E+06 Towton

kWHrs 2.00E+06

1.50E+06

1.00E+06

5.00E+05

0.00E+00 Jan- Feb- Mar- Apr- May- Jun- Jul- Aug- Sep- Oct- Nov- Dec- 00 00 00 00 00 00 00 00 00 00 00 00 Months

Figure 15.11: Towton Advantica Model

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Ipsden

9.00E+04

8.00E+04 7.00E+04 6.00E+04

5.00E+04 Ipsden 4.00E+04 kWHrs 3.00E+04 2.00E+04 1.00E+04 0.00E+00 1/1/00 2/1/00 3/1/00 4/1/00 5/1/00 6/1/00 7/1/00 8/1/00 9/1/00 10/1/00 11/1/00 12/1/00

Months

Figure 15.12: Ipsden HPMIS Model

7.00E+05

6.00E+05

5.00E+05

4.00E+05 IPSDEN

kWHrs 3.00E+05

2.00E+05

1.00E+05

0.00E+00 Jan- Feb- Mar- Apr- May- Jun- Jul- Aug- Sep- Oct- Nov- Dec- 00 00 00 00 00 00 00 00 00 00 00 00 Months

Figure 15.13: Ipsden Advantica consumptions

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

4.50E+05

4.00E+05

3.50E+05

3.00E+05

2.50E+05 Rawclfe A+B+C

kWHrs 2.00E+05

1.50E+05

1.00E+05

5.00E+04

0.00E+00 2/1/00 3/1/00 4/1/00 5/1/00 6/1/00 7/1/00 8/1/00 9/1/00 10/1/00 11/1/00

Months

Figure 15.14: Rawcliffe HPMIS consumptions

3.50E+05

3.00E+05

2.50E+05

2.00E+05 Rawclfe

kWHrs 1.50E+05

1.00E+05

5.00E+04

0.00E+00 Jan- Feb- Mar- Apr- May- Jun- Jul- Aug- Sep- Oct- Nov- Dec- 00 00 00 00 00 00 00 00 00 00 00 00 Months

Figure 15.15: Rawcliffe Advantica Model

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15.4 Appendix 4 – Transco Model Graph

Total OUG use Phase 1 v Phase 2

Pha s e 1 Ph as e 2

3.00E+07

2.50E+07

2.00E+07

1.50E+07 kWh

1.00E+07

5.00E+06

0.00E+00

9 0 97 98 99 t- -98 t- -99 -99 t- -00 -00 ec-97 ug ec-98 pr ug ec-99 pr ug Jun-97 Aug-97 Oc D Feb-98 Apr-98 Jun-98A Oc D Feb-99 A Jun-9 A Oc D Feb-00 A Jun-0 A Oct-00 Dec-00 Month

Figure 15.16: Phase 1 and Phase 2 pre-heater consumptions based on Transco Model

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15.5 Appendix 5 – User Guide

The model must be installed on a machine with Access2000 and Excel2000 already installed upon it. The model should be installed into the D:\OUG_Model directory.

The first time the user interface is run the user is presented with a dialog asking if they wish to enable the macros. The user should tick the “Always trust content from this source” box and then click Enable. This will allow the user to use the interface without being asked to enable the macros each time.

When the user opens the user interface they are presented with the main control screen, as seen below in figure 15.17.

Input new data Run the model using into the model the new values

Run the model with Run the model the 2000 monthly with the 2000 data hourly data

View the results from the model

Select to use only a specified LDZ in the hourly Select to use only 2000 model NTS or LTS sites in the hourly 2000 model

Figure 15.17: The user interface main control screen

This screen allows the user to choose which data they would like to run through the model.

“Input Summary Data” allows the user to enter new data for each LDZ monthly. This data can then be processed using the “Run Summary Data” button.

The “Run Model Hourly” and “Run Model Monthly” buttons allow the user to run the year 2000 data that is stored in the database through the model. The user can choose to run specific LDZs, NTS or LTS sites by using the boxes at the bottom of the screen.

“View Results” allows the user to then go and view the results obtained from the model, split by each LDZ for the year. Advantica Stoner is a trading name of Advantica Technologies Ltd. Registered in England and Wales No. 3294136. Registered Office: 130 Jermyn Street, London, SW1Y 4UR, and of Stoner Associates Europe Ltd. Registered in England and Wales; No.2593248. Registered office as above. Confidential Page 36 30/09/2011

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

When the user chooses to run the model or view the results, the user interface opens the database. The user must therefore enter the database password in the dialog box that pops up (see the developer’s guide for details on how to change the password). When the user selects the “Input Summary Data” button they are presented with the first of the input screens (fig 15.18, below). There are five inputs screens in all. They allow the user to input PRS flows, average inlet and outlet pressures (inlet pressure must be higher than outlet pressure, see section 5.2, Negative Temperature Rise Issues for more detail), and average outlet temperatures, along with set-points to be used in the model (the model will only calculate pre-heat when the outlet temperature falls below the set-point). This data can be entered for NTS and LTS separately.

On these sheets are three buttons, “Back”, “Clear Inputs” and “More…”. “Back takes the user back to the previous screen, “Clear Inputs” clears the data from the cells on the current screen and “More…” takes the user to the next input screen. On the final input screen “More…” is replaced by “Finish”. Clicking this updates the table in the database and returns the user to the main control screen.

When the user selects to view the results, the user interface accesses the database to obtain the latest set of results. The database password must be entered when prompted. The results screen (fig 15.23, below) is shown. The results are split by LDZ total OUG for the year, with totals also shown. To return to the main control screen the user simply clicks the “Back to Main Screen” button.

Figures 15.18 to 15.22 below show all the input data screens in the user interface.

The monthly data can be updated with new flows etc. in the database. To do this the database must be opened in the normal way (again the password will be needed). The form that immediately pops up can be used to update any of the fields in the table. As they are changed in the form, the database tables are updated.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15.6 Appendix 6 – Developer’s Guide

The OUG model has been developed using an Access 2000 database due to the sheer amount of data. This database holds all the tables used in the calculations. The actual calculations are carried out on the data using some queries written in SQL and stored in the database. These queries are called directly from the Excel user interface. Inputs and results are passed between the user interface and the database using linked tables. These tables are regularly updated as necessary throughout the use of the model.

To access the database in a user-friendly manner a simple user interface has been created in Microsoft Excel using VBA. The user interface allows the user to navigate through the process of entering and retrieving the data in a way that is already familiar to them.

Both the database and user interface must be installed in the OUG_Model directory on the D:\ drive of the machine. This machine must already have a copy of Access 2000 and Excel 2000 installed.

The user progresses through each stage of the model using a selection of buttons on each screen. These buttons allow the user to progress through the model easily.

The database contains hourly and monthly data for the year 2000, obtained from the GTMS database. A model of this year can be run if required and can then be used for comparison purposes against any new model. The output from the model is an LDZ OUG usage for the entire year. The data must be entered monthly for each LDZ. The inputs are; total flow, average pressure in to the site, average outlet pressure and an average outlet temperature. The model assumes an average inlet temperature of ground temperature obtained from report PPS/R0253.

When the user interface is run the database must also be open to allow the linked tables to be updated. The user interface will try to do this automatically, though it may not always be the case. When the model has been run, the database must again be open to allow the results to be updated with the new calculated values.

Main Screen This sheet is used as the main control screen for the entire model. From this main control screen the user is given the option of either inputting new data, running the model with the new data, running the data for 2000 hourly or monthly and finally viewing the results obtained from the model run.

To run a new model, some new data must first be input. This is achieved by clicking on the “Input Data” button on the main control screen. This button will then open the input screens for each of the parameters in turn. This is described in more detail below.

After the new data has been entered the model can then be run using the “Run Model” button. This will update the linked table in Access with the new input data and call each of the required queries in turn. After the model has finished calculating, the results table in Excel is updated using the VBA script. The user can view the results by clicking on the “View Results” button on the main control screen.

The “Run 2000 Hourly” and “Run 2000 Monthly” buttons use the data already in the database to run a 2000 model. The queries are also run in turn and the results table is then updated as for the new model.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

The user can choose to run the hourly model using individual LDZs or with only the NTS or LTS sites included. These options can be selected by changing the combo boxes at the bottom of the main control screen. This alters the database table used in the model.

Again the user can view the results by clicking the “View Results” button on the main screen. This will bring up the results table where the user can look at the calculated results and also alter the efficiency of the heaters in the model.

Input Data Screens When the user has selected the “Input Data” button on the main window the screen depicted in figure 15.18 is shown.

Figure 15.18: The first data entry screen

• Back – returns the user to the main control screen • Clear Inputs – clears the current values from the tables • More… – takes the user to the next data entry screen

This screen allows the user to enter new monthly flow data for sites in the LTS and NTS. There is no check that any of the cells have been filled in before the user is allowed to progress. This allows the user to run the model for as many, or as few LDZs as they wish

There are two tables on this screen as the model calculates the OUG from the actual flow through the PRS’ with heaters on them. The flow may be different on the NTS and LTS sites used.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Figure 15.19: The second data entry screen

• Back – returns the user to the flow data entry screen • Clear Inputs – clears the current values from the tables • More… – takes the user to the next input screen

This screen allows the user to enter the total LDZ throughput. This figure is the figure used to find the overall OUG percentage.

When the user clicks “More…” they can then begin to enter the monthly pressure data on the next screen. This screen can be seen below.

Again the user has three buttons, “Back” takes them back to the screen shown above, “Clear Inputs” clears the current values from the table and “More…” allows the user to progress to the next data entry screen.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Figure 15.20: The NTS pressure data entry screen

• Back – returns the user to the pressure data entry screen • Clear Inputs – clears the current values from the tables • More – continues to the LTS pressure data input screen.

As before the user has three buttons. They can then go back to the previous screen (pressure data entry), clear the current values from the table or input LTS pressure values.

The site inlet and outlet pressures input are used to find the temperatures rise required in the heater.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Figure 15.21: The LTS pressure data input screen.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Figure 15.22: The outlet temperature input screen

Clicking “Finish” on this screen will update the inputs table in the database. Before this can be done however this table must be altered into a form that is acceptable and can be used by the model. Currently the tables have the LDZ down one axis and the months across the other. There are also five tables of data, whereas the model requires only one with all of the information in. The format of the table is LDZ, Month, Total Flow, PRS Flow, Average Inlet Pressure, Average Outlet Pressure and Average Outlet Temperature.

The alterations are made in the background on a separate sheet that alters the layout of each of the table by referencing them into a new table. This table then has to be copied with a paste special, values only selected. This linked tables in access cannot contain any formulae, only values.

The Queries After the user has clicked on the “Finish” button the user interface calls the queries needed to calculate the results. There are different queries for the 2000 hourly, 2000 monthly and the user entered inputs model. All of these queries are stored in the database and run directly from there.

Each of the queries and their function are described briefly in table 15.1, below, in order of execution.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Query Name Function DeleteResultsTable Deletes all the records from the results table so that no rogue values from previous runs of the model are accidentally included. DeleteOutputRes Deletes all the records from the table that is linked to the user interface. 1_Pop_Res / 5_Pop_MthlyRes Populates the results table with the input values that are required in the current run of the model. Whilst the table is being populated the JT coefficient is also being calculated. 1_Calc_JT / 5_Mnthly_Calc_JT Calculates the regulator inlet temperature using the Joule-Thompson equation. 2_Update_dT / 6_Update_dT Finds the temperature rise in the heater. Update_ResCp / Update_Mnthly_Cp Calculates the Specific Heat Capacity of the gas using the equation described earlier in section 5 above. 3_Calc_dM/dt / 7m_Calc_dM/dt Calculates the mass flow rate if the flow input is in MSCMD. 3a_Calc_dM/dt / 7k_Calc/dM/dt Calculates the mass flow rate if the flow inputs is in KSCMH. 4_CalculateEnergy/4a_CalculateEnergy/ Calculates the pre-heat energy requirement for 8_CalculateEnergy/8a_CalculateEnergy the current record. Output_Results_Monthly Collates the results into the linked table by LDZ, by month. QryScaleFactors Estimates the OUG usage for the missing LTS off takes using the method described above. OUG_kWh Converts the OUG usage from kJ per hour to kilowatt-hours.

Table 15.1: The 2000 Model Queries

There is provision in the database to allow the heater outlet temperature set-points to be “backed-off” i.e. lowered, during the summer months. This effectively turns the heater off but still allows for any exceptionally cold days. This is achieved by checking which month the record is in and then using this information to check the correct temperature set-point field in the heater data table that should be used from the heater data table.

After the energy calculation, a query checks the heater operating regime column from the heater data table. This field in the table contains a number that relates to a generic operating regime contained in a separate table. This table contains information about when a heater is switched on or off, monthly throughout the year. For example a regime of 0 in the table shows that the heater is on all the year, whereas a regime of 1 shows that the heater is switched off over the summer months (April to September inclusive). If the heater is off for the particular month in question then the result 0 is entered in the energy field of the results table. More information is currently needed to fully populate the operating regimes table.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

The user input model uses slightly different queries due to the difference in the input format. This is because the user model inputs are for LDZs only, as opposed to the year 2000 model that uses site specific information as inputs.

As there is no information available for the LDZ set-points in the model for user inputs, a set- point of 0 ºC has been assumed for all LDZs.

Table 15.2, below, briefly describes each of the queries for the user inputs OUG model in the order they are executed.

Query Function DeleteUserResultsTable Delete the records from the previous results table so that no records from previous runs are included. DeleteOutputRes Deletes records from the linked table to avoid unwanted records being transferred across.

User_PopRes Populates the results table with the data supplied by the user. User_Calc_JT Calculates the regulator inlet temperature using the Joule-Thompson equation. User_Update_dT Finds the temperature rise in the heater. User_Update_Cp Calculates the new Specific Heat Capacity for each record. User_dM/dt Calculate mass flow rate (all inputs must be in MSCMD therefore only one query is needed this time). User_OUG_Energy Calculates the OUG usage (in kJ per hour) for each of the records in turn. Output_User_Results Collates the results into the linked table. OUG_kWh Converts the OUG usage into kilowatt-hours (kWh).

Table 15.2: The User Model Queries and their Actions

Results Screen When all the required values have been entered, the user is then taken back to the main screen. From there they can then choose to run the model using the new values.

After running the model the user can view the most recently calculated results by clicking on the “View Results” button on the main control screen.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Figure 15.23: The User Interface Results Screen

The results screen shows the total OUG for each LDZ in kWh and the overall total. The first column shows the OUG usage in each LDZ if the heaters were all 100% efficient. The second column then calculates the OUG figure with a heater efficiency specified by the user in the edit cell provided. The efficiency is set at 50% default, but the user can enter any figure between 0 and 100%.

The percentage of OUG to total throughput for each LDZ is then calculated and shown in the blue column on the right, with a total for the whole system also shown separately below.

On this screen the user can edit any of the LDZ throughput figures and the calculations are automatically updated, giving a new OUG figure.

To return to the main screen the user can then simply click on the “Back to Main Screen” button to return to the main screen and then be able to run a new model.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

Updating the Monthly Data

Figure 15.24: Change monthly input data form.

The monthly input data can be altered by the user directly in the database. This form is available when the database is opened. The user can simply alter any of the data on the form and the database tables are updated automatically.

The flow and year can be updated to reflect any new data the may be available. To store this data, a copy of the MonthlyInputs.mdb file must be made. To look at this data again, the new MonthlyInputs.mdb file must be copied into the correct directory before the database or model is opened.

Clicking the “Update Monthly Data” button will delete the monthly inputs data table and re- populate it with the year 2000 monthly data taken from the hourly data. This will take into account any changes that have been made to the set-point or operating regime of the heaters.

Adding an Operating Regime Operating regimes can be added in the database. To do this the operating regimes table must be updated. A new operating regime number must be added to the table, along with twelve months. The flags must be set if the heater is turned on or unset if the heater is off. The number of the new operating regime must then be added to the correct heater in the heater data table.

If a month is missing from the operating regimes table then the model will assume that the heater is switched off for that month.

Changing the Database Password The database password can be changed by opening Access and selecting Open. Then select the database and choose to open exclusively. Then select Tools->Security->Unset Database Password. You will then be asked to input the current password. To choose a new password select Tools->Security->Set Database Password. You will then be asked to

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

input a new password and confirm it. Next time the model is run or the database is opened the new password will be used. The default password has been set as “oug2002”

The VBA code in Excel has also been password protected to prevent unwanted changes being made. The password to view the code is “advantica”.

The characters are case sensitive in both passwords, and apply to version 1.0 of the software.

Technical Note: Own Use Gas Model for Pre-Heaters Issue: 2.0

15.7 Appendix 7 – User Interface Issues

Whilst testing it was noted that there are a few minor aspects of the user interface that could not be addressed within the current scope of work and should be considered in future developments.

• The first and possibly major issue is that of the hourly model. As the amount of data is so large and there are a number of operations to perform, on a computer with a slow processor or a small amount of memory the process may hang. Work to improve the performance of the model may improve this. (A message box prompt has been inserted to prevent users from accidentally running this). • Add the functionality for the user to specify which monthly database to use in the model. This will allow data for new years to be added and saved in a different file to keep them all separate.

R 6413 September 2003

ABOVE-GROUND INSTALLATION SHRINKAGE - FINAL REPORT 2003

Confidential Restricted to, Network Policy & Advantica

PREPARED FOR: PREPARED BY: Jonathan Dennett P. Russell B. Lenton, P. Baldwin Advantica Ashby Road Network Policy Loughborough Leicestershire National Grid Transco, LE11 3GR NGT House, United Kingdom Warwick Technology Park, Tel: +44 (0)1509 28 2464 CV34 6DA Fax: +44 (0)1509 28 3119 E-mail: [email protected] Website: www.advantica.biz

Customer Reference:

Registered in England and Wales No. 3294136. Registered Office: 1-3 Strand, London, WC2N 5EH Report Number: R 6413 Issue: 1

Executive Summary Transcos main operation is the transport and distribution of natural gas (composed primarily of methane) throughout the UK. Natural gas is currently the preferred fossil fuel, due in part to its superior environmental performance. However, gas transmission requires both energy and material resources and is therefore a source of emissions and other wastes.

Methane is a potent greenhouse gas with a global warming potential (GWP) 21-23 times that of carbon dioxide over a 100 year time horizon. Potentially, Transcos most significant environmental issue is loss of methane from the system, with the associated impact being contribution to global climate change.

Transco is responsible for the gas lost from its system. Therefore, there is a commercial as well as environmental interest in having accurate quantification of lost gas. The principle source of leakage from Transcos system is the distribution mains. However, recent measurements have indicated that Above Ground Installations (AGIs), such as low pressure gasholders and pressure reduction stations, are a significant source of losses. As a result, Transco initiated a monitoring programme to quantify losses from its AGIs accurately.

The scope of this programme was distribution equipment operating within Transco Networks; and therefore upstream (National Transmission System) equipment and supply point metering equipment, was excluded from the scope of the investigation. This report presents the findings of this monitoring programme.

The result of the monitoring programme was the successful application of a combination of the Fugitive Measurement Device (FMD) and the Area Survey Vehicle to the measurement of gas leakage from AGIs.

To verify that the results are not an artefact of the experimental process Advantica engaged The University of Nottingham carry out an independent validation of the FMD technique employed. The University of Newcastle were also engaged to review of the statistical analysis carried out.

The results suggest that AGI emission is of the order of 24,965 tonnes per annum. A 90% confidence interval has been calculated in respect of these results, it is +/- 16.9% of the mean predicted total emissions for the total asset type, when the data are analysed by holder stations. The 90% confidence interval is +/- 16.5% for the predicted total emissions for the total asset type, when the data are analysed by holder. In addition working losses are calculated to be some 12,200 tonnes per annum.

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Project Code : 1/04036

Distribution Name Company Jonathan Dennett Network Policy National Grid Transco, NGT House, Warwick Technology Park, CV34 6DA

Recipients of this page may obtain a copy of this report from: Advantica, Ashby Road, Loughborough, Leicestershire, LE11 3GR. Telephone 01509 282000 Facsimile 01509 283131

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Contents

1 INTRODUCTION...... 1 2 BACKGROUND ...... 1 3 MEASUREMENT EQUIPMENT AND METHODOLOGY...... 2 3.1 Techniques Applied...... 2 3.1.1 Fugitive Measurement Device (FMD)...... 2 3.1.2 Area Survey Vehicle (ASV) ...... 3 3.2 The Sample Plan...... 5 3.3 DATA CAPTURE AND ANALYSIS...... 8 4 EXTERNAL VALIDATION ...... 9 4.1 Fugitive Measurement Device ...... 9 4.2 Statistics Verification ...... 9 5 RESULTS...... 10 5.1 Predicted Total Emissions...... 10 5.1.1 Predicted Total Emissions by Holder Stations ...... 10 5.1.2 Predicted Total Leakage by Holder...... 11 5.1.3 Number of Holders Population and Sample Comparison...... 13 5.2 ASV and FMD Comparison ...... 13 6 SUMMARY...... 14 7 REFERENCES...... 14 APPENDIX A DISTRIBUTION OF HOLDERS ...... 15 APPENDIX B ASV AND FMD ANALYSIS...... 16

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1 INTRODUCTION Transcos main operation is the transport and distribution of natural gas (composed primarily of methane) throughout the UK. Natural gas is currently the preferred fossil fuel, due in part to its superior environmental performance. However, gas transmission requires both energy and material resources and is therefore a source of emissions and other wastes. Methane is a potent greenhouse gas with a global warming potential (GWP) 21-23 times that of carbon dioxide over a 100 year time horizon. Potentially, Transcos most significant environmental issue is loss of methane from the system, with the associated impact being contribution to global climate change. Transco is responsible for the gas lost from its system. Therefore, there is a commercial as well as environmental interest in having accurate quantification of lost gas. The principle source of leakage from Transcos system is the distribution mains. However, recent measurements have indicated that Above Ground Installations (AGIs), such as low pressure gasholders and pressure reduction stations, are a significant source of losses. As a result, Transco initiated a monitoring programme to quantify losses from its AGIs accurately. For measurement purposes the AGI population may be broken down into the following categories:

• Holder stations • National transmission offtakes • Local transmission pressure reduction stations • District Governors • Service Governors The scope of this programme was distribution equipment operating within Transco Networks; and therefore upstream (National Transmission System) equipment and supply point metering equipment, was excluded from the scope of the investigation. This report presents the findings of this monitoring programme.

2 BACKGROUND Early in 2003 Transco requested that Advantica undertake a programme of tests to determine the leakage from its AGIs. (Advantica had previously undertaken some trials of the AGI leakage testing equipment to prove the technique.) AGIs are complex pieces of equipment comprising numerous valves, flanges, joints and vents. There is considerable scope for fugitive emissions, however until recently there was no practically feasible method for quantifying the leakage. Such measurements are now possible. It would clearly be impractical to attempt to measure the leakage from every AGI; consequently Transco requested that Advantica measure the leakage from a sample of the AGI population.

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3 MEASUREMENT EQUIPMENT AND METHODOLOGY 3.1 Techniques Applied Two techniques are applied, the principal one being the Fugitive Measurement Device (FMD), which is designed for the on-site monitoring of individual components. The second is the Area Survey Vehicle (ASV), which measures whole-site emissions by the monitoring of the emitted gas plume downwind. The latter is used only for holder stations where the nature and height of the holders precludes direct leakage measurement. Emissions from holder sites may arise from both the holders and from site auxiliary pipework and systems. Leakage from the auxiliary pipework on a holder site is measured using the FMD, and this value is subtracted from the ASV value to derive the actual holder losses.

3.1.1 Fugitive Measurement Device (FMD) The monitoring programme used GMI Gasurveyors (ppm range) or flame ionisation detectors (FIDs) to identify emissions from components and uses a Fugitive Measurement Device (FMD) to quantify these emissions. The FMD was designed and built by Advantica. Figure 1 shows the FMD in use.

Figure 1. The FMD in use A hose from the FMD is attached to a bagged component and a precise volume of air is drawn through. The Gasurveyor or FID measures the concentration of gas within the shroud. From this information, the quantity of methane or gas being lost from the emitting component can be calculated.

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The survey comprises three phases: 1) Identification of the components on site. For this purpose the site is divided into its key constituent parts (i.e. filters, regulator streams etc.) The number of fittings associated with each section is counted and recorded. 2) Screening of the components to determine the ones that are leaking. A Gasurveyor or FID is used to screen every component on the site to determine the ones that are leaking. Fittings that are found to be leaking are then tagged. 3) Measuring the leakage from each leaking component. Tagged fittings are shrouded with a bag. The FMD is then used to capture the emission and measure the quantity of gas being emitted.

The FMD gas flow is calibrated using a known emission source in the laboratory, and checked in the field using a simple flowmeter. The detection instruments are calibrated and certified at regular intervals, according to the manufacturers specifications. Internal calibration and testing indicates an accuracy in the order of +/- 5 to 10%.

3.1.2 Area Survey Vehicle (ASV) The ASV was developed by Advantica and has been in use for over 12 years. It contains both sensitive air quality monitoring instruments, including ppb-level detectors for methane and total hydrocarbons and sophisticated navigation systems for accurate location recording. The unit is driven repeatedly through the emitted gas plume downwind of an installation. This is done at a variety of distances, to record any plume of emissions. A highly sensitive meteorological mast is used to monitor windspeed, direction and atmospheric turbulence. The results of the plume measurement are then modelled directly using the real-time meteorological measurements to provide a calculation of the site emission rate. As an alternative to metrological measurements, a tracer gas may be used. Field tests supported by the National Physical Laboratory have established the accuracy of the technique to be typically +/-15% although it can be affected by adverse circumstances such as the proximity of buildings that affect the plume. The ASV and an example of the results are shown in Figure 2.

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Figure 2: Area Survey Vehicle and example of typical methane concentration measurements

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3.2 The Sample Plan

As there was limited existing relevant leakage information to assist in deriving the plan for monitoring a fully representative sample of the AGI population the physical characteristics and numbers in each asset group were considered in formulating the sample plan. The different asset groups, together with basic descriptions, are listed below.

• Holder stations Holder storage is employed on the gas supply system to meet the needs of variation in demand for gas over a 24 hour period i.e. between the early evening peak and the early hours of the morning off peak. Holder stations are large installations featuring an extensive array of equipment items in addition to the gas holders themselves1. All holder stations pre-date the conversion to natural gas (which occurred in the mid 1970s) and some are over 100 years old. The gasholders, and some of the associated equipment operate at low pressure (less than 75 mbarg). However, higher pressure gas may be present on site.

• National Transmission System offtakes Gas is transported from the beach terminals to the Transco Networks at very high pressure (typically over 70 barg.) The pressure has to be reduced and the flow rate controlled when the gas enters the local systems. These tasks are accomplished at the National Transmission System (NTS) offtakes. Certain equipment items within these sites are categorised as NTS equipment (and consequently outside of the scope of this study) however the majority of the equipment items on each site are part of the local transmission system (LTS).

• Local transmission pressure reduction stations Gas is transported within the Networks at pressures typically in the range 15 to 38 barg. Very few customers use gas at this pressure and therefore the pressure has to be reduced prior to dissemination to most customers. A stage of this pressure reduction occurs at the local transmission pressure reduction stations. Usually the output pressure of these installations is in the range 75 mbarg to 6.9 barg.

• District Governors District Governors supply gas into the lower pressure tiers for onward transporting to customers (through low pressure (LP) distribution mains less than 75mbarg, through medium pressure (MP) 75 mbarg 2 bar and through intermediate pressure (IP) 2

1 Holder stations may have one or more gas holders present.

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bar 7 bar). They operate with an inlet pressure of between 75 mbarg and 6.9 barg. They usually have an outlet pressure set point in the range 30 75 mbarg.

• Service Governors Service Governors commonly feed individual premises (mostly individual houses) and usually have an inlet pressure of less than 2 barg. They are the most common type of AGI, however they are typically very small being less than 300mm high.

The AGI leakage testing programme was designed to ensure that each of these asset groupings was considered in order to derive the mean leakage and a measure of statistical uncertainty for each category of asset. By reference to the total asset population information held in Transcos records the total level of leakage, and the overall level of uncertainty can be determined. As there was no previous knowledge of the level of possible emissions from AGIs it was necessary to devise a sampling plan based on the population data for each asset type within each Network. The plan also had to be consistent with the budget made available for the study. The AGIs have been stratified into five categories, by asset type namely, holder stations, district governors, service governors, LTS pressure reduction stations (PRS) and NTS offtakes. All sites were randomly selected within each NETWORK for each asset type. Random selection was required to ensure a non-biased sample, thus obtaining a representative sample of the population. Transco were involved in the selection process, identifying the sites available to allow Advantica to carry out the tests. Table 1 shows how the number of different asset types varies between Networks. (The data in the table was obtained from Transco.)

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Table 1: Transco AGI Population Data 2003 Holder District Service NTS Network Stations Governors Governors LTS PRS Offtakes Scotland 22 6291 37323 126 16 N 16 1941 1880 74 14 NW 41 1509 3500 159 11 Yorks 18 3455 821 115 10 EM 11 3904 12941 124 14 WM 4358478342769 Wales 5139544232865 EA 26 2294 4973 141 11 N-LN 26 1777 13,722 116 4 SE 37 3340 20000 130 5 S 17 4415 11693 216 4 SW 15 2289 10050 69 12 Total 238 36194 129160 1832 115

Table 2 below, shows the number of sites sampled in each Network grouped by asset type. Table 2: AGI Sample Plan

Holder District Service NTS Network Stations Governors Governors LTS PRS Offtakes Total Scotland 221 610645 N 213 38430 NW 414 311638 Yorks 222 39642 EM 269 52412112 WM 219 512947 Wales 210 314433 EA 314 413741 London 312 27428 SE 313 67635 South 217 611440 SW 322 410443 Sum 30 246 50 136 72 534

The sampling programme was extensive, involving the surveying of some 534 sites. A number of regional monitoring teams were formed, co-ordinated by Advantica that worked with the local network personnel. The latter provided access and facilities, and provided a safe working environment for the team. All the measurements were taken by Advantica personnel who had extensive field measurement experience and who had been trained in the use of the FMD. Table 3 shows the number of tests that were completed for each asset type within each Network.

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Table 3: AGI Sites Surveyed

Holder District Service Network Stations Governors Governors LTS PRS NT PRS Total Scotland 224 610648 North 012 38326 NW 413 39534 Yorks 222 38641 EM 271 52412114 WM 220 4131049 Wales 210 214432 EA 314 614744 London 111 510431 SE 213 78333 South 214 616341 SW 222 411443 Totals 24 246 54 145 67 536

Examining Tables 2 and 3 above it can be seen that there is some variation in the actual number of assets tested within each Network compared to the planned number. The overall number of test carried out was 536, compared to a sample plan of 534. The difference between the planned and actual number of holder stations surveyed was due to unavailability of sites during the summer months. It was believed to be inappropriate to obtain readings during a period when the holders were empty, as this could have resulted in an underestimate of the true level of emissions. The number of NTS pressure reduction stations monitored was also slightly less than the original plan this was partly as a result of some sites having two PRSs which were originally classified as two and subsequently counted as a single PRS. For all the other asset categories the intended plan was achieved or exceeded.

3.3 DATA CAPTURE AND ANALYSIS Following the survey, data was entered into a database to ensure consistency and to facilitate data analysis. The site survey information was entered, including location, type of site, survey team and date. Information on the fittings present on site were also added and details on the number of leaking fittings. For each leaking fitting, details were entered of fitting type and size, together with initial screening concentration, FMD sample flowrate and concentration. From this information, the leak rate is calculated in units of ml/min. The database allows queries to be undertaken which facilitate the analysis and summation of the data by Network, site, site type and fitting type. The national population of site types was tabulated and the information used to calculate the total AGI national emissions. The statistical analysis has been undertaken by stratifying the sample data by asset type, as defined in Section 3.2. The data collected is in the form of ml/min, and is then converted into cu.m/year. From this data, for each of the five strata (holder

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station, NTS offtake, LTS PRS, district governor and service governor), descriptive statistics were obtained. The descriptive statistics for each stratum include: number of samples, mean and standard deviation. This information provides an indication of the mean leakage for each of the asset groups and the variability surrounding the mean leakage.

The predicted total cu.m/year emission has been obtained for each asset group by multiplying the mean emission rate by the population size for that asset group. A 90% confidence interval has also been obtained for each asset group based on the predicted total cu.m/year emission. A 90% confidence interval has also been obtained for the overall predicted total cu.m/year by obtaining the overall weighted mean and weighted standard error. The results of this analysis are described in Section 5.1. As holder stations can have different numbers of holders, the statistical analysis described above has been undertaken in two ways. Firstly by examining the emissions per holder station, and secondly by examining the emissions per holder. As described in Section 3.1.2, the ASV has been utilized to obtained emission rates at holder stations. Statistical analysis has been undertaken to compare the results of the ASV tests and the FMD tests. As the ASV measures emissions from all AGIs in the locality, it has been necessary to combine all FMD emissions from all AGIs in the locality. Statistical inference tests have been carried out to compare the two sets of results. The results of this analysis are described in Section 5.2.

4 EXTERNAL VALIDATION 4.1 Fugitive Measurement Device The validity and accuracy of the FMD has been studied by the Air Pollution Section of the Environmental Department of the University of Nottingham. The team is lead by Dr Jeremy Colls. The study made an assessment of the instrument design and its operation, and analysed test and calibration results. The University of Nottingham report presenting the results of their study indicated an accuracy in the order of 5- 10%. (Ref 1)

4.2 Statistics Verification The Industrial Statistical Research Unit (ISRU) at the University of Newcastle, led by Dr Shirley Coleman, have reviewed the statistical analysis carried out. The validity and accuracy of the statistical results obtained have been assessed (Ref 2).

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5 RESULTS 5.1 Predicted Total Emissions As discussed in Section 3, the predicted total emissions have been statistically analysed in two ways; per holder station and per holder. Sections 5.1.1 and 5.1.2 detail the results of the analysis for each scenario.

5.1.1 Predicted Total Emissions by Holder Stations The mean emissions for each site type have been obtained, where site type for holders is holder station, along with the standard deviation of the mean emissions. The results are presented below, with emissions given in units of cu.m/year.

Table 4: The mean emissions and standard deviation for each site type.

Asset type Number surveyed Average measured Standard Deviation emission cu.m / measured emission year / site cu.m / year / site Holder station 24 13,461 24,898 District Governor 246 407 1,219 Service Governor 54 8 33 Local Transmission 145 6,485 10,447 NTS offtake 67 31,075 39,171

To obtain an overall AGI emission rate, and a measurement of the uncertainty of that rate, it is necessary to multiply the average emission rate for each asset category by the number within the population. Table 5 shows the predicted overall AGI leakage rates.

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Table 5: The Predicted Overall AGI Leakage Rate Asset Number in Predicted total Lower 90% Upper 90% type population emission cu m confidence confidence / year interval cu m / interval cu m year / year Holder Stations 238 3,203,718 1,213,953 5,193,483 District 36,194 14,727,339 10,101,060 19,353,617 Governor Service 129,160 986,782 35,536 1,938,029 Governor Local 1,832 11,880,520 9,265,958 14,495,082 transmission NTS offtake 115 3,573,625 2,668,328 4,478,922 Totals for 167,539 34,371,984 28,547,726 40,196,242 Asset Type Working na 16,712,329 na na Losses2 Total na 51,084,313 na na

Assuming a gas density of 0.73 kg / cu.m (as applied in respect of distribution mains leakage for the current gas year Shrinkage Factor) this implies total AGI emission of approximately 37,292 tonnes per annum, including working losses. The 90% confidence interval is calculated to be +/- 16.94% of the mean predicted total emissions for the total asset type, this does not include the working losses. The 90% confidence interval was calculated by obtaining the weighted mean and weighted standard error for the total population of asset types.

5.1.2 Predicted Total Leakage by Holder The mean emissions for each site type have been obtained, where site type for holders is number of holders, along with the standard deviation of the mean leakage. The results are presented below, with emissions given in units of cu. m/year.

2Working losses are emissions as a result of equipment venting as part of its normal operation. i.e. Not unintentional leakage.

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Table 6: The mean emissions and standard deviation for each site type.

Asset type Number surveyed Average measured Standard Deviation emission cu.m / measured emission year / site cu.m / year / site Holder 42 7,692 13,216 District Governor 246 407 1,219 Service Governor 54 8 33 Local Transmission 145 6,485 10,447 NTS offtake 67 31,075 39,171

To obtain an overall AGI emission rate, and a measurement of the uncertainty of that rate, it is necessary to multiply the average emission rate for each category of asset by the number within the population. The table below refers.

Table 7: The Predicted Overall AGI Leakage Rate Asset type Number in Predicted total Lower 90% Upper 90% population emission cu m / confidence confidence year interval cu m / interval cu year m / year Holder 394 3,030,648 1,708,934 4,352,362 District 36194 14,727,339 10,101,060 19,353,617 Governor Service 129160 986,782 35,536 1,938,029 Governor Local 1832 11,880,520 9,265,958 14,495,082 transmission NTS offtake 115 3,573,625 2,668,328 4,478,922 Totals for 167,695 34,198,914 28,567,773 39,830,055 Asset Type Working na 16,712,329 na na Losses2 Total na 50,911,243 na na

Assuming a gas density of 0.73 kg / cu.m (as applied in respect of distribution mains leakage for the current gas year Shrinkage Factor) this implies total AGI emission of approximately 37,165 tonnes per annum, including working losses. The 90% confidence interval has been calculated to be +/- 16.47% for the predicted total emission for the total asset type; this does not include the working losses. The 90%

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confidence interval has been calculated by obtaining the weighted mean and weighted standard error for the total population of asset types.

5.1.3 Number of Holders Population and Sample Comparison

As the sampling plan was not derived by considering the population of holders, but by the population of holder stations, it was necessary to ensure that the distribution of the sample holders is representative of that of the population of holders. This was achieved by comparing a histogram of the population of holders and the sample of holders and carrying out a statistical inference test. To examine the distribution of holders, the number of holder stations with 1, 2, 3, etc. holders has been obtained for both the population and sample data. The histogram of these distributions is contained in Figure A.1 in Appendix A. Examining Figure A.1 it appears that the distribution of the population and sample is consistent, with both distributions following a similar pattern. From a population of 238 holder stations, 130 have one holder, 74 have two holders and 34 have three or more holders. From a sample of 24 holder stations, 10 have one holder, 11 have two holders and 3 have three or more holders. This would indicate that the sample is representative of the population, even though there is a higher proportion of holder stations with 2 holders in the sample compared to the population. To verify this observation a statistical inference test known as the chi-squared goodness of fit test, has been carried out. The results of this analysis are contained in Appendix A and would suggest that the sample is representative of the population. Therefore no bias has been introduced by examining the predicted emissions by holders rather than holder stations.

5.2 ASV and FMD Comparison As described in Section 3.1.2, the ASV was utilized to obtain emission levels at holder stations, in addition to the FMD tests. The ASV was utilized at 8 of the 24 holder station sites. Statistical analysis has been undertaken to compare the results of the ASV tests and the FMD tests. As the ASV measures emissions from all AGIs in the locality, it has been necessary to combine the FMD emissions from all AGIs in the locality. The 8 holder stations where the ASV was used are detailed in Table B.1 in Appendix B. This table also contains details of the emission rate for both the ASV and FMD results and details of all sites required for the FMD results. Three of the eight sites require additional emission rates to be included in the FMD results, Bedford, Romford and Pocket Nook. In most cases the emission rate observed by the ASV is higher than that observed by the FMD. However, there are two occasions where the ASV emission rate is lower than the FMD emission rate. In these two cases it was noted that the angle of the ASV with respect to the site was poor.

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Appendix B, Figure B.1, contains a scatterplot of the ASV and FMD emission rates. Examining this figure it would appear that Pocket Nook, Becton and Partington all have the highest difference in emission rates from the ASV compared with the FMD. These generally show higher ASV emissions than the FMD emissions, apart from those for the Pocket Nook holder station.

To ascertain whether, or not, the observed difference in emission rates is significant statistical inference tests have been carried out. The details of these tests are described in Appendix B. The results of both tests would indicate that there is insufficient evidence to suggest a statistically significant difference between the ASV and FMD emission rates. Therefore, though the emission rates from the ASV are higher, they are not statistically significantly higher than that of the FMD. However, the sample size for this comparison is small. A larger sample size would give more confidence that the results obtained were not due to chance but due to a real effect.

6 SUMMARY

Advantica have successfully applied a combination of the Fugitive Measurement Device and the Area Survey Vehicle to the measurement of gas leakage from AGIs. To verify that the results are not an artefact of the experimental process, Advantica engaged The University of Nottingham carry out an independent validation of the FMD technique employed. This is detailed in Section 4 of this report. The University of Newcastle were also engaged to review the statistical analysis carried out as detailed in Section 5 of this report. The results suggest that AGI emission is of the order of 24,965 tonnes per annum. A 90% confidence interval has been calculated in respect of these results, it is +/- 16.9% of the mean predicted total emissions for the total asset type, when the data are analysed by holder stations. The 90% confidence interval is +/- 16.5% for the predicted total emissions for the total asset type, when the data are analysed by holders. In addition working losses are calculated to be some 12,200 tonnes per annum.

7 REFERENCES 1) Principle and operation of the Advantica Fugitive Measurement Device. Nottingham University Consultants Limited. July 2003. 2) Statistical verification of 2003 Above Ground Installation Leakage Tests Newcastle University Industrial Statistics Research Unit. August 2003.

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APPENDIX A DISTRIBUTION OF HOLDERS

Figure A.1

Numbr of Gas Holders per Holder Station

140

120

100 80 Population 60 Sample

40 20 0 Frequency of Holder Stations Holder of Frequency 123456More

Number of Gas Holders

A.1 CHI-SQUARED GOODNESS OF FIT TEST.

The quality of a sample being representative of a population can be measure statistically using the %2 goodness of fit test, where the %2 statistics are defined to be:

2 2 χ = ∑(Oi − Ei ) / Ei with n-1 degrees of freedom

Where Oi are the observed (sample) values, the Ei are the expected (population) values and n is the number of classes (in this case there are 3 classes, 1 holder, 2 holders and 3 or more holders).

The %2 statistic is calculated to be 2.194, which is between the 25% and 50% points for the %2 distribution with 2 degrees of freedom. This would suggest that there is no significant difference between the two distributions and therefore the sample is representative of the population.

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APPENDIX B ASV AND FMD ANALYSIS

Table B.1 Emission rates for ASV and FMD (ml/min)

Holder Site ASV emission Database items FMD emission rate rate (ml/min) making up site (ml/min) for all Sites

Beckton 284,000 Beckton PRS 255 80180

Bedford 40,290 Bedford holder PRS 1 14695

Bedford holder PRS 2

Bedford holder site

Hadleigh Rd, Ipswich 23,000 Hadleigh Road Holder 10430

Macclesfield 24,800 Macclesfield Holder 11425

Norwich 34,100 Norwich Holder site 47435

Partington 478,000 Partington Holder Site 198715

Romford 91,270 Romford Holder 110880

Romford PRS

Pocket Nook, StHelens 87,500 Pocket Nook 250

Pocket Nook

Figure B.1 Scatterplot of Emission Rates (ml/min).

Scatterplot of Emissions (ml/min)

600000

500000 Partington

400000

300000 Beckton ASV 200000 Pocket 100000 Romford Bedford Norwich 0 MacIpswich 050000100000150000200000250000

FMD

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B.1 ASV AND FMD COMPARISON PAIRED T-TEST.

As the data for both the ASV and FMD emissions are not normally distributed it has been necessary to transform both sets of data by taking the natural log of the values, which has allowed a paired t-test to be carried out. A paired t-test has been carried out on the transformed data with the objective of ascertaining whether there is a statistically significant difference between the ASV and FMD emissions. The paired t-test examines the mean difference between the two emission rates from each site. The calculation of the test statistic is formulated by:

x t = with n-1 degrees of freedom s / n where x is the mean difference between the ASV and FMD emission rates, s / n is the standard error of the difference and n is the number within the sample. The calculated test statistic for the ASV and FMD emissions is : t = 1.83 with 7 degrees of freedom. The calculated test statistic is between the 10% and 15% confidence levels of the t distribution with 7 degrees of freedom. This indicates that there is insufficient evidence to suggest that there is a significant difference between the ASV and FMD emission rates. A confidence level of 5% and below is the accepted statistical level for the difference to be classified as significant.

B.2 ASV AND FMD COMPARISON WILCOXON MATCHED PAIRS. The Wilcoxon Matched Pairs test is a nonparametric test, which does not require the data to be normally distributed. The object of the Wilcoxon Matched Pairs test is to ascertain whether there is a statistically significant difference between the ASV and FMD emissions. The Wilcoxon Matched Pairs examines the differences between the two data sets, ranking the differences in ascending order, using the signs and relative magnitudes of the data but not the actual values. The sum of the ranks for positive and negative differences are calculated and the test statistics is the smaller of the two sum ranked. The sum of the ranked difference for the ASV and FMD are:

t+ = 30

t- = 6 Therefore, the test statistics is t=6, the smaller of the two values. The 5% confidence level critical value is 3 for the Wilcoxon Matched Pairs with a sample size of 8. As the test statistic is greater than the critical value this would indicate that there is

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insufficient evidence to suggest that there is a significant difference between the ASV and FMD emissions rate.

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Asset Integrity Solutions

R6303 June 2003 REPORT ON THE 2002/3 NATIONAL LEAKAGE TEST PROGRAMME

Prepared for: Prepared by: Transco Kirsty Nelson Network Policy Advantica Limited 65 New Road Ashby Road Solihull Loughborough Leicestershire LE11 3GR United Kingdom

Tel: +44(0)1509 283221 Fax: +44(0)1509 283142 E-mail: [email protected] Website: www.advantica.biz

Report R6303

Executive Summary

Background

In 1992 British Gas commissioned a programme of leakage tests to quantify the leakage from its distribution system. The data, obtained in 1992, has subsequently been used to help determine the amount of LDZ leakage. However it was clear that the information was becoming dated and as a result Advantica were commissioned to carry out a new programme of tests.

Objectives

The objective of the test programme was to update the leakage rates that are used to assess overall distribution system leakage. There was an aspiration that the test programme should establish leakage rates with the total leakage estimate having a 90% confidence interval of r10% around the mean value.

The Test Programme

In order to meet the requirement for a r10% confidence interval around the mean, it was determined on the basis of the 1992 results that 840 tests should be carried out. In the event a total of 862 tests were carried out in the period from February 2002 to May 2003, providing 849 usable results. Leakage tests were carried out by specially trained teams to a schedule produced by Transco. The test equipment was specifically designed for the purpose by Advantica to give improved accuracy and efficiency of data collection.

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Results

The final results for the Combined Mains and Services are shown below, together with the 1992 results for comparison:

Material Planned 2002/3 National Leakage Tests 1992 National Leakage Tests 2002 (strata) number Lengths Number Mean St. Number of Mean St. of tests (km) of Tests Leakage Deviation Tests Leakage Deviation m3/hr/km @ m3/hr/km @ m3/hr/km @ m3/hr/km @ 30mbar 30mbar 30mbar 30mbar Steel 35 29 0.403 0.849 33 0.1828 0.4854 5375 <=3 Steel 35 33 0.469 0.964 33 0.4966 1.0943 4317 >=4 Pit Cast 35 34 0.2934 0.4639 21 0.676 0.7630 2930 <=3 Pit Cast 220 204 0.2247 0.4541 57 0.4669 0.9800 21505 4-5 Pit Cast 70 67 0.3777 0.699 22 0.3937 0.5610 11791 6-7 Pit Cast 60 56 0.286 0.4223 30 0.9706 0.9958 7135 8-11 Pit Cast 90 84 0.911 1.923 21 1.731 2.4040 6112 >=12 All Spun 90 139 0.166 0.3701 231 0.1941 0.2918 40516 Cast Ductile 80 75 0.1293 0.2984 40 0.2188 0.7906 8348 Iron <=5 Ductile 35 36 0.528 2.546 32 0.1297 0.2925 7628 Iron >=6 All PE 90 92 0.00954 0.02133 35 0.0438 0.1077 107441 Overall 840 849 0.1560 *se=0.0184 555 0.3041 *se=0.0315 223,098

*se= standard error

Conclusions

x The test programme was completed successfully. The test equipment worked well and the Advantica test teams met the test schedule required by Transco. x More tests were carried out than requested in the initial sampling plan. This was because some mains, particularly pipes that were recorded to be pit cast iron pipes, proved to be made of alternative materials. As a result of this some additional tests were undertaken in an attempt to achieve the initial sample plan. x In most cases the leakage rate for particular groups of mains were lower than found in 1992, principally, PE, Spun Cast and Pit Cast. Other materials such as Ductile Iron and Steel showed slightly worse results in some diameter categories.

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x The result for the whole Transco system was found to be 0.1560 m3/hr/km @ 30mbar compared to 0.3041 m3/hr/km @ 30mbar in 1992. The standard error in the measurement was 0.0184 m3/hr/km @ 30mbar compared with 0.0315 m3/hr/km @ 30mbar in 1992. Thus, whilst in absolute terms the standard error was lower, the 90% confidence interval expressed as a percentage of the total value was greater than expected at r19.4%. x Overall, the weighted average pipe leakage factor is almost half of the value that it was in 1992. This is principally due to the increased relative length of polyethylene (PE) pipe in the mains population, which has been associated with the replacement of metallic pipe. In addition the measured leakage performance of the pipe asset has improved in the more significant material strata.

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Project Code :1/02993

Distribution Name Company Mark Fairbairn Transco Jim OSullivan Dave Halsey Ruth Thompson Jon Butterworth Brian Popplestone Chris Murray Jeremy Bending Ed Bannock Ian Davis Peter Massey Bill Russell Jonathan Dennett

Author(s):

Project Manager:

Solution Director :

Recipients of this page may obtain a copy of this report from: Advantica Limited, Ashby Road, Loughborough, Leicestershire, LE11 3GR. Telephone 01509 282525 Facsimile 01509 283131

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Contents 1 Summary...... 1 2 The Advantica Project Brief ...... 2 3 The Sample Plan ...... 3 3.1 ESTABLISHING THE MATERIAL /DIAMETER TO BE TESTED...... 3 3.2 ESTABLISHING THE SAMPLE SIZE ...... 3 3.3 GUIDELINES FOR LDZ SELECTION OF SITES...... 5 3.4 SELECTION OF THE TEST SITES PROVIDED BY LDZ...... 5 4 The Testing Process ...... 6 4.1 TEST METHOD ...... 6 4.2 THE TEST EQUIPMENT ...... 6 4.3 TEST PROCEDURE...... 6 5 Staff Competence and Training ...... 8 5.1 TEST PROCEDURE AND EQUIPMENT VERIFICATION HASWELL CONSULTING ENGINEERS ...... 8 5.1.1 Scope of Work of Haswell Consulting Engineers...... 8 5.2 RESULTS OF HASWELL CONSULTING ENGINEERS AUDIT ...... 9 6 Testing Schedule ...... 9 7 Data Capture and Retention...... 10 7.1 DATA COLLECTION ...... 10 7.2 DATA VALIDATION...... 10 7.3 DERIVING LEAKAGE RATES ...... 10 7.4 TEST SECTION VOLUME ...... 11 7.5 COMBINED MAINS AND SERVICES LEAKAGE ...... 11 7.6 MAINS LEAKAGE...... 11 7.7 SERVICE LEAKAGE ...... 11 7.8 TOTAL MAINS AND SERVICE LEAKAGE ...... 12 8 Results ...... 13 8.1 COMBINED MAINS AND SERVICES LEAKAGE RATES ...... 13 8.2 MAINS ONLY LEAKAGE...... 14 8.3 SERVICE LEAKAGE RATES...... 14 8.4 TOTAL LEAKAGE...... 15 9 Discussion of Results...... 16 9.1 THE EFFECT OF PRESSURE ON THE ESTIMATE OF LEAKAGE ...... 16 9.2 THE EFFECT OF CHANGES IN MAINS POPULATION ...... 16 9.3 STATISTICAL VERIFICATION ...... 17 10 Conclusions...... 18 References...... 19 Appendix A Description of the Testing Process ...... 20 Appendix B Basic Leakage Measurement Principles ...... 26 Appendix C Test Site Schedule of Operations ...... 29 Appendix D Data Collection Pack...... 32 Appendix E Apportioning Leakage between Mains only and Per Service.... 41 Appendix F Results Excluding Site 3769...... 43 Appendix G Length of Mains Material ...... 47 Appendix H Changes to Materials ...... 48 Appendix I Test Locations and Basic Mains Data ...... 51 Page v

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Appendix J Rejected Tests...... 64

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1 SUMMARY In 1992 British Gas commissioned a programme of leakage tests (designated within this report as the NLT 1992). These tests were conducted to provide a quantified estimate of the leakage from its distribution system. Previous tests and assessments established that the distribution system is the largest single contributor of leakage from the whole gas transportation system. The NLT 1992 results provided statistically robust leakage data representative of this part of the system. The data, obtained in 1992, has subsequently been used to help determine the amount of LDZ leakage. However it was clear that the information was becoming dated and as a result Advantica were commissioned to carry out a new programme of tests at the request of Transco to provide a more up to date estimate of current leakage rates. Advantica designed the NLT 2002/3 test programme to address the issue of redefining mains and service leakage rates taking into account the following objectives: i. The test programme should establish leakage rates for the distribution mains and service populations, with the total leakage estimate having a 90% confidence interval of r 10% around the mean value. ii. The samples tested should be statistically sound and representative of the overall system population. iii. The methodologies used and results obtained should provide a credible and reliable estimate of leakage, which can be readily verified by independent audit. Professional external validation of each stage of testing (i.e. equipment design / training / testing programme and results analysis) has been undertaken. The shippers and Ofgem have been involved throughout the programme, including meetings to discuss the sampling plan, methodology and equipment; two opportunities to see a video of the Leakage Measurement Field Trials produced to demonstrate the validation work carried out on the equipment and procedures; a visit to a leakage test site at Slough during the testing programme; presentation of uncertainty analysis; and presentations of interim results. This report provides information on the background to, and development of, the chosen test techniques and methodologies. It details the internal and external verification of the methodologies and the tests themselves, discusses the organisation and implementation of the new tests and details the data analysis and results obtained.

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2 THE ADVANTICA PROJECT BRIEF Advantica was commissioned by Transco to perform leakage tests on a statistically defined set of mains units to produce a robust set of indicative leakage rates from which distribution system leakage could be estimated. The main elements of the project to be carried out by Advantica were as follows: x to design the sampling plan for test sites. This is discussed in detail in Section 3 of this report. x to design the test equipment in order to give an accurate measurement of the leakage from a distribution main. This is discussed in Section 4 of this report. x to design a test process to enable leakage to be measured for Mains and Services, Mains Only and Service Only in each category of the low-pressure distribution system. This is discussed in Section 4 of this report. x to provide competent operatives and carry out testing to a schedule defined by Transco. This is discussed in Section 5 of this report. x to produce a final report, present all of the information gathered and summarise the analysis of the results. This is discussed in Sections 7 to 10 of this report.

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3 THE SAMPLE PLAN The sampling plan was designed during the Autumn of 2001 to determine the numbers of sites to be selected in each material/diameter groups (stratum) in each LDZ. The methodology for establishing a sampling plan was similar to that used for the NLT in 1992. The results of that earlier programme were used to establish the number of tests that would be required.

3.1 Establishing the Material /Diameter to be tested. In the NLT 1992, there were 13 material/diameter groups (strata). It was decided that the groupings should remain consistent for NLT 2002/3, except for Spun Cast mains. In 1992, the Spun Cast mains were split into 3 diameter bands. The 1992 programme found that these Spun Cast groups had very similar mean and standard deviation values; therefore during NLT 2002/3 it was felt appropriate to have just one group covering Spun Cast. This resulted in eleven strata to be tested: x Ductile Iron <=5, x Ductile Iron >=6 x Pit Cast <=3 x Pit Cast 4-5 x Pit Cast 6-7 x Pit Cast 8-11 x Pit Cast >=12 x Spun Cast all diameters x Steel <=3 x Steel >= 4 x PE all diameters

3.2 Establishing the Sample Size The use of Stratified Random Sampling for the NLT 1992 tests produced a robust sampling plan. Combining this with prior knowledge of the mean and standard errors from categories tested during the 1992 tests, a robust sampling plan for 2002/3 was generated. By increasing the number of tests in a particular category, the standard error for that category is likely to reduce and this should in turn mean that the overall standard error will also reduce. Thus, as the number of tests is increased, the uncertainty around the mean leakage rate will be reduced.

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Clearly there are a large number of ways in which a new sample plan can be generated, by adjusting the number of tests in one or more of the 11 categories. By creating a spreadsheet model, containing the mean and standard deviation of all 11 categories, together with the updated mains population, a number of different scenarios were tested. The sample plan: x aspired to produce an overall uncertainty (90% confidence interval) around the weighted mean leakage rate of r10% of the mean; x intended to obtain at least 30 test results for each strata, with an aspiration that 35 results be produced for each stratum and x sought to minimise the overall number of tests required to obtain the required results. Given these constraints, the proposed sampling plan is presented in Table 1.

Table 1. Overall Sampling Plan Strata Material/Diameter Sample Size

Steel <=3 35 Steel >=4 35 Pit Cast <=3 35 Pit Cast 4-5 220 Pit Cast 6-7 70 Pit Cast 8-11 60 Pit Cast >=12 90 All Spun Cast 90 Ductile Iron <=5 80 Ductile Iron >=6 35 All PE 90

It was calculated that if the new tests yielded similar results to those obtained in 1992, the proposed sample plan would give a 90% confidence interval of r10.3% of the weighted mean leakage rate. More details of the sampling plan are given in Reference 1.

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3.3 Guidelines for LDZ selection of sites. The sample plan was based on the former LDZ organisational structure within Transco, which differs from the current Network structure. The sample size for each LDZ was allocated by identifying the proportion of mains population for each material/diameter within that LDZ (the populations that were used are shown in Reference 1). The numbers in the sampling plan refer to the number of mains units to be tested in each stratum. Although selection of these mains units was random for operational reasons, not every mains unit was suitable for testing. For example, the testing methodology required mains to be between 80 to 120m long. Clearly this excluded the potential to test main units that were much shorter or longer than this. As a result of this and other factors, guidelines were established to restrict the selection of mains to those that could be tested within reasonable practical constraints. Great care was taken to ensure that factors that might affect leakage such as diameter, material, soil type and joint type were not included in any of the criteria that would preclude a mains unit from being selected. As part of the site selection process, consideration was given to utilising mains identified for replacement in the mains replacement programme, where possible, as a source of test sites. This would provide efficiency saving arising from excavations and mobilisation of the contractors teams and minimising customer impact. However this gave rise to concern that the sample would not necessarily be random, as the cast iron test population would be skewed towards those mains that were due to be replaced. The impact of this policy is discussed in Appendix A and in ISRUs report which concluded that the use of replacement mains for the pit cast sample would if anything tend to over-estimate the leakage.

3.4 Selection of the Test Sites provided by LDZ. Based on the sampling plan, Transco undertook the entire random site selection process and notified Advantica of site locations and dates of tests. Advantica provided test teams and equipment to meet this schedule.

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4 THE TESTING PROCESS

4.1 Test Method The pressure decay method was chosen as the preferred method of testing because x It is passive. x Leakage is deduced from accurately measurable pressure drop rate. x Information on leakage as a function of pressure can be obtained in one test.

The decision to use this method, a description of how it works and site selection guidelines issued to LDZs are discussed in Appendix A.

4.2 The Test Equipment The leakage measurements were undertaken using a laptop PC driven package of equipment. The laptop automatically recorded the rate of pressure decay during standard, intermediate and known leak tests. From the collected data, both the volume of the main under test, and the natural leakage were calculated. The acoustic temperature measurement equipment allowed any changes in temperature to be accounted for during the data processing and leakage calculation.

A set of test equipment comprised: -

x Laptop PC complete with NLT software x Skid unit incorporating digital pressure transducer, flow meter and control valves. x Vent stack assembly x Modified end caps incorporating acoustic temperature measurement equipment x Umbilical connections between components x Ancillary tools and safety items.

A fuller description of the testing process is contained in Appendix A whilst Appendix B details the basic principles of leakage measurement by pressure decay methods.

4.3 Test Procedure The basic leakage measurement principles on which the test methodology has been based are detailed in Appendix B. The pressure decay site test procedure was however broadly as follows:

The test sections measuring 80 to 120 metres length were isolated, capped off and any associated service pipes capped on the customers side of the Emergency Control Valve. A rider from the upstream main maintained pressure in the test Page 6 of 64

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section. The laptop PC driven leakage measurement equipment was connected to the test main via a modified end cap. The isolated section was checked to ensure that no leaks were present in either the mains isolation fittings or the test equipment. The test section was pressurised where possible to a pressure above 30 mbarg. Once this had been done the section was fully isolated. The pressure was then allowed to decay due to leakage from the section under test (pipes with no leakage would not show any decay in pressure). The pressure and temperature change was continuously recorded on the laptop. The pressure was monitored by using a calibrated transducer. Temperature change was monitored using an acoustic temperature measurement technique.

After obtaining a set of initial pressure decay measurements, a leakage test with a known added constant leak was carried out. If the leakage was below a certain level, a further decay test was then undertaken with a larger known added leak.

From the three (or two if the pipework was not leaking) pressure decay curves obtained, the rate of gas leakage from the test section could be calculated without the requirement for prior knowledge of the exact volume of the pipe. This provided the combined leakage associated with both the main and the services at 30 mbarg. Previous analysis carried out on the data obtained from the NLT 1992 showed that leakage and pressure have a directly proportional relationship between 20 and 40 mbarg. (see Reference 2). This relationship allowed extrapolation of the data to be carried out where a suitable pressure could not be reached or where the test simply failed to cross the threshold value of 30 mbarg.

If, following the first test, the leakage from the buried mains and services was measured to be less than 0.003 m3/hr, no further testing was carried out, as it would not have been possible to identify the mains and service component of leakage at such very low leakage rates.

Provided that the pipework was leaking at a rate that was greater than 0.003 m3/hr the above sequence was then repeated at each of the following stages:

x after excavation of all the service tees. x after batch disconnection of all metallic services. x after batch disconnection of all PE services.

The final pressure decay test was therefore carried out on the main only. In this way, the components of leakage from the mains and services could be identified. This test procedure allowed an accurate leakage rate to be calculated for each site and within each site the leakage can be attributed into separate Mains Only leakage and Service leakage (and the service leakage can be separated into both Metallic and PE service categories). Appendix C details the schedule of operations carried out on a typical test site.

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5 STAFF COMPETENCE AND TRAINING

5.1 Overview It was vital that all testing took place consistently at all sites, to the required standard and in accordance with the test specification. In order to achieve this, training and assessment of all test teams took place prior to the commencement of the testing programme. All test teams were further audited and supported at their first test site to ensure correct application of the test methodology. To ensure consistency of approach at all times during the test programme, all important communications were made via email to each test team member. Each team also received a pack relating to each test site and written reminders were included in this pack to ensure consistent application of the testing procedure. All team members had access to a shared database on a computer that held up to date reference material, test dates and site information. Day to day enquiries from sites were dealt with via a telephone helpdesk, which was supported by a technical expert and project stream leaders. A sheet of contact numbers was included in the training pack and this also advised the test teams on the most appropriate person to contact for any type of query.

5.2 Test Procedure and Equipment Verification Haswell Consulting Engineers Transco engaged Haswell Consulting Engineers to undertake a continuing independent physical validation study during the programme.

5.2.1 Scope of Work of Haswell Consulting Engineers The scope of the work specified that as part of the audit process, the site audit would be conducted and would cover the following key objectives: x Carry out independent audits of each of the 24 test teams covering England, Scotland and Wales to ensure adherence to the test procedures. x Review methods of observation, calibration of equipment and other procedures and report on any impacts on data quality x Create a site audit report detailing observations at test sites and record and analyse any variance from the test procedures x Record on the audit forms any problems encountered at test sites x Assessment of problems encountered during the testing and possible implications on the confidence of the results

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x Ensure that samples such as soil and pipe materials are consistently recorded.

5.3 Results of Haswell Consulting Engineers Audit Haswells have produced a report detailing their findings. This is available under separate cover.

6 TESTING SCHEDULE The testing of mains and services commenced in February 2002 and was completed in May 2003. The numbers of test performed per month is shown in Table 2.

Table 2: Number of Tests Performed per Month

Month Number of Tests February 2002 6 March 2002 33 April 2002 71 May 2002 95 June 2002 75 July 2002 91 August 2002 114 September 2002 114 October 2002 95 November 2002 35 December 2002 13 January 2003 6 February 2003 26 March 2003 54 April 2003 33 May 2003 1

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7 DATA CAPTURE AND RETENTION.

7.1 Data Collection On completion of the tests at each site the disks containing the site, main, service and pressure decay test data were all dispatched to Advanticas Loughborough office with coupons taken from the pipe to provide material samples for analysis. In addition, gas samples were taken and analysed for MEG saturation values at all metallic sites. The data was used to compile a comprehensive database, which formed the basis for detailed analysis.

7.2 Data Validation Approximately 100,000 items of information were recorded at the test sites, and entered onto the Advantica database (items of data range from a diameter to a list of comments relating to a site). Validation procedures were used to identify data requiring investigation. Typical errors included pipe diameters recorded in inches rather than millimetres and occasional omitted measurements. Where problems arose on information recorded on site, these could usually be resolved by reference to the information recorded on the data recording form (a blank copy of which is shown in Appendix D). Where necessary, test teams were contacted to identify any missing data or to confirm certain values. All test teams had been instructed to retain a copy of all material dispatched to Loughborough to ensure that such queries could be resolved.

7.3 Deriving Leakage Rates At each site a series of tests was carried out, as outlined in Appendix C, generating a sequence of pressure decay readings. From these readings the leakage rate was derived at the Target Test Pressure (TTP), i.e. the pressure through which the readings should pass. The TTP was 30 mbarg, however tests were still carried out when the operating pressure of the mains system was different from 30 mbarg. and the leakage was scaled to 30 mbarg. using a proportional relationship. 30 mbarg. was chosen as the TTP as it was equivalent to the value used in the NLT 1992. The leakage rate was then calculated (in m3/hr), taking account of the derived rate of decay, associated temperature readings and the volume of the test section, and then normalised using the length of test section (to m3/hr /km).

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7.4 Test Section Volume The added leak approach to testing a main was devised to give a more accurate estimate of the volume of the test section than is obtained from dimensional measurements. This is detailed fully in the Watt Committee Report on the 1992 tests (Reference 3).

7.5 Combined Mains and Services Leakage For each site, the combined leakage attributable to mains and services was derived from the test carried out at the start of the test sequence, when all services were still connected and in an undisturbed state i.e. before excavation work had started to expose service connections on the test section. In total, one Standard Leak Test, one Known Leak Test and, where appropriate, one Intermediate Leak Test were undertaken at each site. The leakage rate for each material/diameter cell of the sampling plan was calculated as the average of all of the leakage rates in the cell. Using the techniques described above, combined mean leakage rates and confidence intervals for the mains and services were calculated for the 11 groups in the sampling plan.

7.6 Mains Leakage At sites other than those with leakage levels of less than 0.003 m3/hr, the leakage attributable solely to the mains was derived from the tests undertaken at the end of the test sequence when all the services were disconnected. Where the levels of leakage were negligible or zero, the test procedure ruled that services remained undisturbed. In these cases any leakage measured was attributed to the mains only, and the services attached to the main were attributed with zero leakage. Account was taken of the effect of excavating the main this is detailed for both Mains Only and individual Service type leakage in Appendix E. The leakage rates for each material/diameter group of the sampling plan were derived in the same way as for combined Mains and Services leakage rates, but using only the leakage rates attributable to the mains at each site. Confidence intervals for each groups mean leakage rate were derived as for the combined Mains and Services rates, and these were based on the distribution of the sample leakage rates in each group.

7.7 Service Leakage The leakage attributable to the services at each site was derived as the difference between the leakage rate for Mains and Services combined (Section 7.4) and that for mains only (section 7.5). This gave the best estimate of the leakage rate for the services attached to the test section, and avoided the inclusion of any effects caused by the disturbance of the service tees during testing.

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Account was taken of the effect of excavating the main this is detailed for both Mains Only and individual Service type leakage in Appendix E. However, this leakage rate relates to all the services attached, and consequently it was necessary to split this total rate between the metallic and non-metallic services. In the situation where only one batch of a distinct material was removed, the total service leakage was attributed to the services in the batch. Where two batches were removed, use was made of the tests carried out where the services were removed in batches, to obtain the effect on the leakage rate of each service material type. The total service leakage, at each site, was then apportioned to the metallic and non-metallic services in the same ratio. When leakage levels below 0.003 m3/hr were encountered during the Combined Mains and Service test, the test team carried out no further tests. Under these circumstances the test team remained on site until the contractors excavated the services. If this was not possible, then a follow up phone call was made by Advantica to the contractor to ask him to examine his records and to obtain the service information. These leakage rates for metallic and non-metallic services were then grouped to produce two service leakage rates. Leakage rates for services are quoted on a rate per service basis. A number of tests did not produce a full set of results because some or all of the data could not be collected. In some cases this was as a result of operational constraints (e.g. a service that disintegrated when exposed making further measurement of the leakage from that service impossible) or because a type of service pipe was not present (e.g. there may have been no metallic services at a site.) 24 sites did not have metallic services results, 32 sites did not have PE service results and 32 sites did not have Mains Only results.

7.8 Total Mains and Service Leakage The combined Mains and Service leakage rates derived in section 7.4 were used to calculate an estimate of the total leakage from the low pressure (LP) mains and service system. For each group in the sampling plan, the average leakage rate is weighted by the corresponding proportion of main in the population, and then summed over all eleven groups to give an estimate of the mean combined leakage rate for the system as a whole. The confidence interval that can be attached to this estimate is derived in a similar way from the individual confidence intervals for each of the combined Mains and Services group means.

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8 RESULTS The results presented in this Section represent the final leakage rates derived from the analysis of the data for the 2002/3 Leakage Test Programme. The leakage rates for each of the eleven groups of the sampling plan are shown for mains and services combined; for mains only; and for services only. Standard errors and sample sizes are provided for both mains and services combined and for mains only. The estimate of the mean leakage factor is presented. This has been calculated using the leakage rates for mains and services combined. The major points emerging from the results are discussed briefly in each of the sub-sections. Note: One site (number 3769) experienced significant leakage whilst producing an unusual pressure decay curve that has been difficult to explain. In spite of this it has been included in the analysis below because it was felt that it would be inappropriate to exclude it; Appendix F refers.

8.1 Combined Mains and Services Leakage Rates Leakage rates for Mains and Services combined were derived as described in Section 7.4 and are presented in Table 3 below. Also shown are the sample sizes obtained for each group. Due to the main tested at each site being a different length, the leakage rate obtained on each site was standardised to m3/hr/km. Appendix G shows the breakdown of mains population lengths by category.

Table 3: Combined Mains and Service Leakage Rates

Leakage Standard error Mains Number in Category m3/hr/km m3/hr/km Population sample @ 30 mbar @ 30 mbar (km) 2002 Steel <=3 0.403 0.1577 29 5375 Steel >=4 0.469 0.1678 33 4317 Pit Cast <=3 0.2934 0.0796 34 2930 Pit Cast 4-5 0.2247 0.0318 204 21505 Pit Cast 6-7 0.3777 0.0854 67 11791 Pit Cast 8-11 0.286 0.0564 56 7135 Pit Cast >=12 0.911 0.2098 84 6112 All Spun Cast 0.166 0.0314 139 40516 Ductile Iron <=5 0.1293 0.0345 75 8348 Ductile Iron >=6 0.528 0.4243 36 7628 All PE 0.00954 0.0022 92 107441 Total 0.1560 0.0184 849 223098

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8.2 Mains Only Leakage Leakage rates for Mains Only, i.e. excluding leakage from services connected to the mains, are shown in Table 4 and, as for the combined rates, sample sizes are shown for each group as these differ for some groups from the combined Mains and Service sample sizes.

Table 4: Mains Only Leakage Rates

Leakage Standard error Category m3/hr/km m3/hr/km Number in sample @ 30 mbar @ 30 mbar Steel <=3 0.39 0.1631 28 Steel >=4 0.44 0.1642 32 Pit Cast <=3 0.2748 0.0826 33 Pit Cast 4-5 0.1872 0.0311 197 Pit Cast 6-7 0.2883 0.0723 64 Pit Cast 8-11 0.2516 0.0570 53 Pit Cast >=12 0.852 0.2047 82 All Spun Cast 0.1228 0.0256 131 Ductile Iron <=5 0.0821 0.0273 72 Ductile Iron >=6 0.0658 0.0307 36 All PE 0.00725 0.0012 89 Total 0.1173 0.0104 817

8.3 Service Leakage Rates Service leakage rates are presented in Table 5 for four categories of services. Due to each site having a different number of services, the leakage was standardised to m3/hr/service.

Table 5: Service Leakage Rates

Number of Total number of services Leakage m3/hr/service Leakage m3/hr/service sites in sample 2002/3 1992 Metallic Service on Metallic 455 2619 0.0012092 0.0008297 Mains Metallic Service 5 14 0.0000000 0.0002361 on PE Mains PE Services on 492 2651 0.0002505 0.0003209 Metallic Mains PE Services on 81 770 0.0000000 0.00004188 PE Mains

Two of the 2002/3 categories have zero leakage. This is due to the low levels of leakage exhibited by the PE main in both categories. Only 3 of these sites continued testing after the Mains and Services Combined test. At these 3 sites, all leakage was attributed to the main only. At all other sites, when leakage was below the threshold, all leakage was attributed to the main only and zero leakage was attributed to the services. Page 14 of 64

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The term non-metallic service includes PE services with steel tails as well as those of purely PE construction. Consequently, the leakage rates for PE only services will be lower than the figures in Table 5. At a small number of sites, PVC services were found these have been included in the PE sample. In a small number of cases, lead and copper services were found. These have been included in the Metallic service sample. 8.4 Total Leakage The overall population results have a lower standard error than in 1992. The standard error in 1992 was 0.0315 m3/hr/km; the standard error in 2002/3 was 0.0184 m3/hr/km; this is a 42% reduction in the standard error. However the weighted mean leakage factor has reduced by 49% relative to what it was in 1992 (when the confidence interval was about r17% of the mean); consequently the criterion to obtain a 90% confidence interval around the mean of r10% has not been achieved. The confidence interval for these new tests is equivalent to r19.4% of the mean using the Combined Mains and Service means, standard errors and 2002 lengths shown in Section 8.1.

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9 DISCUSSION OF RESULTS

9.1 The Effect of Pressure on the Estimate of Leakage All of the results presented in Section 8 were derived from the rates of decay encountered in the tests at a 30 mbarg. pressure. Leakage rates at pressures other than 30 mbarg. could be derived from the rates of decay encountered during the tests at these pressures, though for pressures close to 30 mbarg. an approximate proportional relationship can be assumed under low flow conditions. This was shown during the 1992 tests when tests were undertaken at 20 mbarg. and 40 mbarg. to allow the effect of pressure on leakage to be assessed. This work (Ref 1) was carried out following the NLT 1992 and showed an approximately proportional amount of leakage over this range.

9.2 The Effect of Changes in Mains Population In Section 3, the lengths of mains in the LP Mains and Service system as held in the Transcos records were used in the allocation of sites to the cells of the sampling plan. These lengths were then used in Section 8 to calculate the overall leakage rate for the system using the derived leakage rates. In deriving the leakage rates, initially in some cases the cell to which each site was allocated in the original sampling plan (Table 1, section 3.2) was revised based on the outcome of a post-test metallography examination on the samples taken from the test mains; Appendix H refers. This resulted in some changes to the numbers of tests in each cell. These changes predominantly affected the Pit Cast and Spun Cast categories of mains, where there was a significant shift of sites from Pit Cast to Spun Cast. Although the shift in material type required no adjustments to the leakage rates because of the randomness of selection of the sample, it does have implications in respect of the likely lengths of Pit Cast and Spun Cast mains in the population. Thus, a significant proportion of mains believed to be Pit Cast are in fact Spun Cast. Were the records to be amended to compensate for this effect, the actual weighted mean leakage rate would reduce because Pit Cast mains have been measured to leak more rapidly than Spun Cast mains. The leakage rate for Spun Cast has been measured to be 0.166 m3/hr/km, whereas the weighted mean leakage rate measured for Pit Cast is 0.359 m3/hr/km. This means that Pit Cast iron mains leak at more than twice the rate of Spun Cast iron mains, so if the records overstate the length of Pit Cast, which they appear to do, then the leakage will also be overstated relative to the actual leakage.

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9.3 Statistical Verification As discussed in Section 3, a statistical sampling method aimed at identifying the number of mains units to be tested was devised during the NLT 1992. This method was used to provide the required confidence interval on the new set of results. The sampling method had been previously independently assessed. The Industrial Statistics Research Unit (ISRU) of the University of Newcastle upon Tyne undertook a review of the statistical work. This exercise was undertaken over the entire period of the tests, during which time Advantica staff worked closely with the staff of ISRU and responded to all of their comments, suggestions and requests for information. The ISRU were further invited to assess the analysis of the test results in relation to the calculation of leakage rates. This assessment was undertaken following the completion of the testing phase of the programme. The report of this assessment produced by the ISRU is given under separate cover. For reference, a list of basic main data for all sites is given in Appendix I and a list of rejected sites and reasons for rejection is given in Appendix J. Of the 849 sites tested, no repairs were carried out to the test sections prior to testing.

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10 CONCLUSIONS x The test programme was completed successfully. The test equipment worked well and the Advantica test teams met the test schedule required by Transco. x More tests were carried out than requested in the initial sampling plan (849 against 840). This was because some mains, particularly pipes that were recorded to be pit cast iron pipes, proved to be made of alternative materials. Appendix H refers. As a result of this some additional tests were undertaken in an attempt to achieve the initial sample plan. x In most cases the leakage rate for particular groups of mains were lower than found in 1992, principally, PE, Spun Cast and Pit Cast. Other materials such as Ductile Iron and Steel showed slightly worse results in some diameter categories. x The result for the whole Transco system was found to be 0.1560 m3/hr/km @ 30mbar compared to 0.3041 m3/hr/km @ 30mbar in 1992. The standard error in the measurement was 0.0184 m3/hr/km @ 30mbar compared with 0.0315 m3/hr/km @ 30mbar in 1992. Thus, whilst in absolute terms the standard error was lower, the 90% confidence interval expressed as a percentage of the total value was greater than expected at r19.4%. x Overall, the weighted average pipe leakage factor is almost half of the value that it was in 1992. This is principally due to the increased relative length of polyethylene (PE) pipe in the mains population, which has been associated with the replacement of metallic pipe. In addition the measured leakage performance of the pipe asset has improved in the more significant material strata.

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REFERENCES 1. R4778 Development of a Sampling Plan for Proposed 2002 National Leakage Tests Rosemary McAll 2. Unpublished report The 1992 National Leakage Tests: Analysis of Pressure and Leakage K Nelson, G Peters 3. Watt Committee Report (1992). 4. ERS 5487 Evaluation of Leakage Measurement Methods for the British Gas 1992 National Leakage Tests. DR Casson, G Peters, K Nelson 5. R3301 Improved commissioning tests for distribution mains RP Ashworth, SV Licciardi, MG James 6. R3034 The development and field trial of a new technique for the measurement of leakage in gas mains RP Ashworth, SV Licciardi

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Appendix A Description of the Testing Process

Previous Estimate of Leakage The previous major leakage survey (NLT 1992) is described in detail in the Watt Committee Report (Reference 3). These definitive results have been widely used in many areas of National Grid Transco, but no knowledge is held on the effect of pipe deterioration and/or system repairs and so no variation of leakage over time can be deduced. The effect of mains replacement can of course be taken account of by movement between categories of pipes.

Selection of Leakage Measurement Method The basic options for leakage measurement are by the direct flow or pressure decay techniques. In the direct flow method, the flow of gas required to maintain the pressure in the isolated section is measured, and this flow must equal the leakage flow at that pressure. Prior to the NLT 1992 this technique was extensively field evaluated by British Gas R&D (Reference 4). The accurate measurement of small flows proved to be difficult because of the performance of the supplying regulator, and particularly the inability to achieve a satisfactory steady state with fluctuating upstream conditions.

The pressure decay method is preferred because:

x It is passive. x Leakage is deduced from accurately measurable pressure drop rate. x Leakage vs. pressure data is provided in one test.

In order to quantify leakage from pressure data, the volume of the pipe under test is required. Because the actual volume of the isolated pipe is an unknown, it is estimated by performing a second pressure decay test with an additional measured leak. From two sets of decay data the volume can be calculated (note that this assumes that the natural leakage does not change between the two tests).

The pressure drop rate is also influenced significantly by any temperature change during the test. Even in buried pipe, the temperature can slowly change with the ambient ground and air temperature, and exposed pipe sections can cause significant sudden changes with direct sunlight. In the NLT 1992, temperature was monitored with a spot probe inserted into the main, and this (along with the manual data logging) was recognised as a major weakness in the overall system. Advantica have recently developed an Acoustic Temperature Measurement (ATM) system (Reference 5) for use during the commissioning pressure tests on large volume distribution mains. Using a loudspeaker and a microphone inserted at one end, this measures changes in sound speed along the test length, which accurately relates to temperature change of all the gas, not just that occurring at one point.

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In order to remove temperature change as an influence on the leakage data it is essential to measure it accurately. The ATM system was considered to be an essential ingredient for the revised leakage measurement system.

Another technology development aimed at reducing the excavation requirements was the use of double bag, virtual seal technology. The first generation was field trialled in 1999 (Reference 6), Due to excessive setting up costs and timescales, a reduced version of the double bag system was used in the NLT 2002/3.

The measurement equipment comprises:-

x Laptop and software o Logs all data o Controls the ATM system o On site sequencing o On site analysis x Skid Unit o ATM electronics o Digital Absolute Pressure transducer o Valves, under software control. x Vent stack and flow meter o Measured leak system for volume calculation o Additional leaks system for low leakage mains x End cap and in pipe speaker/microphone assemblies

The system, suitably documented for production, was developed to a demonstration of the package on a test facility by the end of 2000.

Before the equipment was field tested, a series of tests were performed using the Buried Pipe Facility at Loughborough. This testing included introducing a precise leak to the system to verify the results. During this test it became apparent that if there was only a small leakage on the test section, the small pressure drop gives insufficient data to calculate the pipeline volume. This led to the introduction of the Intermediate Leak Test (ILT) where an unknown leak was added to the pipeline to simulate a larger natural leak. The volume was then calculated using the Known Leak Test (KLT) and the Intermediate Leak Test and then this volume used to calculate the leakage rate using the Standard Leak Test (SLT). In conditions where the pipeline had a sufficient natural leak, there is no need to perform the ILT test.

A field trial took place near Northampton. During the day a number of minor software changes were recommended but the hardware performed perfectly. The changes were later incorporated into the software and a new version released.

Leakage measurement field trials took place during 2001 in order to prove the software and equipment, and also to prove the field procedures.

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All lessons learnt during these field trials were incorporated into the procedures and contributed to the NLT 2002/3 testing regime.

The Test Equipment Following the selection of the pressure decay method, test equipment and software was selected that would:-

i) be capable of meeting the required performance specification ii) be capable of repeated use iii) be robust iv) be user friendly v) require the minimum of maintenance

Each set of test equipment was assembled and calibrated prior to issue. All test equipment was re-calibrated in January 2003 in order to retain certification. The pressure gauge and flow meters were checked. No drift in equipment specification was observed during this exercise.

Software was produced to collect all pressure decay data and temperature data automatically throughout the course of the tests. The site-specific information was input manually by the test team at the end of the test day. In order that this data could be collected whilst the tests were taking place, a paper copy of the software screens was included in each test pack (called the Data Collection Pack), a copy of this is included in Appendix D. The test teams were required to return the completed data collection form, the disk with inputted data on it, and a sample of pipe from each trench (where available) along with completed health and safety risk assessment documentation.

Verification of Test Equipment During the field trial stage, Transco engaged Stone & Webster to undertake a verification study of the Procedure and Equipment. The agreed scope for the verification was as follows.

Scope of Work of Stone and Webster Engineering Consultants

The 2001 Leakage Measurement Field Trials tests were monitored and controlled by a laptop PC based application developed by Advantica and gas temperatures measured during the tests using an acoustic method, also developed by Advantica.

The scope of the study covered the following areas;

1. Basis of operation and mathematical calculations - Review mathematics used to calculate leakage rates. Review results recorded from witnessed field trials.

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2. Suitability of physical design for the intended purpose - Review "top level" Hardware overview drawings [2]. Review test methodology.

3. Site Processes, Procedures and Documentation - Review fitness for purpose of the detailed site procedures to deliver a robust leakage rate from the pressure decay tests.

Mr Bob Reed of Stone & Webster visited Advantica to undertake the work from 19th to 21st June 2001.

Advantica provided full access to all documentation including:

x Basic principles and Leakage Measurement Field Trials methodology. x Test procedures. x Site procedures.

An overview of the equipment and process in the laboratory was provided.

The Leakage Measurement Field Trials team from Advantica were made available for the duration of the verification processes and able to deal with all questions raised.

A visit to a Leakage Measurement Field Trials test was arranged supported by Advantica personnel.

Stone and Websters report is presented under separate cover.

Uncertainty Calculations for Test Equipment Transco engaged Advantica to undertake an uncertainty study on the test equipment. The uncertainty calculations were carried out in accordance with the ISO Guide to Expression of Uncertainty in Measurement (GUM). The individual measurements made during the Tests were identified and their uncertainties were estimated. A Monte-Carlo method was used to estimate the overall uncertainty of the leakage tests. The results of this analysis were subsequently presented to Gas Shippers and Ofgem. Advanticas report, which has already been shared with the Gas Shippers and Ofgem, is presented under separate cover.

Site Selection As part of the site selection process, consideration was given to utilising the mains replacement programme, where possible, as a source of test sites, thus providing efficiency savings arising from excavations and mobilisation of the contractors teams and minimising customer impact.

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Sites for the Ductile Iron strata were primarily stand alone tests as test sections included in the ductile iron replacement programme were more likely to be replaced due to their condition, which would have a potential bias on the results. Steel and PE have no replacement programmes, so these strata had to be stand alone tests. The guidelines for choosing mains were: x Replacement method by dead insertion to ensure minimum soil disturbance before testing, for Cast Iron. x Mains section length to be 80 120m x Ideally up to 20 single feed services to limit the resources needed on site for service replacement (but more if Transco Operations had the manpower to complete the work within a day). x Single material type and diameter x No commercial or multi-occupancy premises. x Pressure above 30 mbarg. available for testing (where not possible, use of interpolation accepted). x Access possible without road closure x Isolation possible without affecting other supplies x Cast Iron to be carried out in conjunction with scheduled replacement work, where possible, with supplementary stand alone tests scheduled for larger diameter pipes x Ductile Iron, Steel and PE to be stand alone tests With these criteria forming the basis of a set of procedures to guide LDZs through the selection process, each LDZ was actioned to provide test sites that complied with the sampling specification.

Implications of using the Mains Replacement Programme

Using sites taken from the Mains Replacement Programme gave rise to a concern that the sample would not necessarily be random. However as policy replacement is risk based, rather than condition based, there was not thought to be any significant bias from using a sample from this population of mains. This is discussed in more detail in the following paragraphs. Mains that have been programmed for policy replacement have a risk value that is above a stipulated threshold. The risk value is made up from the product of three factors, they are: x The Mains Fracture Factor

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x The Gas Ingress Factor and x The Consequence Factor. A high value for any of these three factors could move the risk value above the threshold for replacement. The likelihood of fracture will not necessarily be linked to a high leakage rate for mains, as the majority of leaks occur as a result of corrosion and joint failure however there may be some association between the two because a pipe weakened by corrosion may break more readily than one that is not corroded and as a result may demonstrate a higher propensity to fracture. The Gas Ingress Factor is based upon factors related to the location of a main such as its proximity to buildings, and as such should not be related to leakage. The Consequence Factor is based upon pressure and proximity to cellared property. Again, neither of these factors is expected to influence leakage. Thus a high-risk value may be weakly linked to a greater likelihood of leakage. However, this effect, if it exists at all, has not been quantified. Therefore selecting test units for testing from the population of mains programmed for policy replacement will if anything slightly overstate leakage, although it is unlikely to significantly bias the overall results.

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Appendix B Basic Leakage Measurement Principles

The leakage from the isolated section can be accurately calculated from the slope of the pressure versus time curve. As the pressure drops, leakage through the same leak path always decreases and so the slope of the pressure decay curve gets shallower.

The results are normalized to the leakage occurring at 30 mbarg. gauge pressure. It is important therefore that the pressure decay data goes through the 30 mbar point. Extrapolation to pressures outside the range can be done, but is not preferred

The measured pressure drop rate is primarily proportional to the size of the leak divided by physical internal volume of the pipe installation under test. For the same leak in a larger pipe volume, pressure will drop more slowly.

Pressure is also significantly affected by temperature change, which could occur during the test. Slight temperature change is induced when re-charging the pipe between decay tests, and large changes can also occur when local ambient conditions change (e.g. direct sunlight etc).

To summarise, in order to calculate accurate leakage the following data is required:-

x absolute pressure decay data versus time, passing through 30 mbar gauge. x atmospheric pressure data over the same time. x temperature data over the same time, the nominal ambient starting temp and the acoustically measured changes during the test. x the volume of the main

The volume of the main under test is not initially known to a sufficient degree of accuracy. Initially an estimation must be made from the known details of the pipe diameter and lengths, including the service lengths.

By performing another test with an extra known leak, the volume can be calculated more accurately. For this latter test, it is very important that the natural leakage remains the same. The pipe and fittings should not be disturbed during the whole test sequence.

Because the instantaneous added flow leak rate is measured throughout the second test, the calculation of volume takes place continuously through the data for the two tests where the gauge pressure is the same. At each selected gauge pressure by comparing the pressure decay slopes of each test it is possible to calculate the volume of the main, providing the natural leakage remains the same on the second test. The result is a set of volumes versus gauge pressure, which will be constant for perfect data.

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A problem to this approach occurs when natural leakage is very small, and the pressure drops only very slowly. When this is a problem an additional leak test is used to complement the natural leakage so that volume can be calculated. This volume is then used on the natural leakage data.

To summarise, the test sequence for a leakage test is :

x natural leak test to provide the basic pressure decay data. x added leak test is carried out if the natural leakage is very low, so that pressure drops enough to trigger the flow measurement. x known (+ added) leak test allows the volume calculation on either the natural leak or the natural+additional leak data

Basic theory behind the principles

PV mRT 1 only R stays constant during the test.

Test 1 dp R dT dm 1 (m 1 T 1 ) 2 dt V 1 dt 1 dt

Test 2 dp R dT dm 2 (m 2 T 2 ) 3 dt V 2 dt 2 dt

now the flow out in either test is dm p U q U Q where U etc 4 dt 0 RT

At the calibration gauge pressure point we know the deliberate Q, or (dm/dt)deliberate

Rearranging 2 & 3 above, for each test I

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At each matching gauge pressure, just so long as the natural leakage (or natural +additional) is exactly the same as it was in the first test, we can write

At equivalent gauge pressure point in each dataset we lookup / calculate the local p, T, dp/dt and dT/dt. dm dt Equation 5 is then used to give a value for i z for each set V i § dm · ¨ ¸ © dt ¹ V can then be calculated from V deliberate z2 z1

This V is then used with equation 2 to give the natural leakage dm1/dt versus gauge pressure.

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Appendix C Test Site Schedule of Operations This Appendix summarises the schedule of operations to be carried out on site.

No. Activity

1 Advantica test team arrive on site for 07.30 start time (or as otherwise agreed).

2 Carry out site specific risk assessment.

3 Share and discuss the Risk Assessment findings with the Transco Operations representative and request any significant findings from any risk assessment conducted by Transco, and any relevant precautions to be taken.

4 Verify that the test main meets the criteria for inclusion in the NLT 2002/3 programme, and that the site is adequately prepared.

5 Assemble test equipment.

6 Complete functional checks

7 Power down skid unit.

8 Transco Operations to commence isolation of all services by capping at outlet of meter control valve and report back to Advantica coordinator when complete.

9 Transco Operations to conduct bag stop operation to remove existing cap end, fit Advantica test cap end and ensure air is fully purged from test end.

10 Complete all connections between test cap end and skid and check with leak detection fluid to ensure leak free.

11 Power up skid unit and complete initial testing.

12 Transco Operations to remove bag tubes and cap main.

13 Transco Operations to fit and purge Advantica test rider assembly.

14 Transco Operations to remove overnight bypasses, plug/cap connections and monitor pressures on adjacent mains system.

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15 Check all connections at both ends of test main with leak detection fluid to ensure leak free.

16 1st pressure decay test (Full sequence)

Standard Leak Test

Intermediate Leak Test (if required)

Known Leak Test

17 After completion of the 1st full test sequence, if the measured leakage rate is less than 0.05 litres/min, then no further decay tests need be undertaken. Remove the Advantica test equipment and complete the site data collection exercise.

If the measured leakage rate is 0.05 litres/min (0.003 m3/hr) or greater then continue with the programme.

18 Transco Operations to excavate on main to expose all service tees.

19 Use this stage in schedule to gather as much supplementary site data as possible.

20 2nd pressure decay tests. (Full sequence)

Standard Leak Test

Intermediate Leak Test (if required)

Known Leak Test

21 Cut off all metallic services. Remove service tees, plug main and soap test to ensure no leaks.

22 3rd pressure decay tests. (Full sequence)

Standard Leak Test

Intermediate Leak Test (if required)

Known Leak Test 23 Cut off all PE services. Remove service tees, plug main and soap test to

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ensure no leaks.

24 4th pressure decay tests (Full sequence)

Standard Leak Test

Intermediate Leak Test (if required)

Known Leak Test

25 With assistance from Transco Operations, remove / recover NLT equipment.

26 Complete data collection and input to laptop. Save laptop files to disk and post one disk and pipe coupons to Advantica.

27 NLT procedure complete.

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Appendix D Data Collection Pack This Appendix shows a blank data collection form, a Test Filename sheet and a Returnable Items List. All items were sent to each test team for each test that they conducted.

Essential Site Information

Advantica Site ID m

Pipe Length m m

Supplied Nominal m mm Diameter

Supplied Nominal in Diameter

m Indicates these boxes are not optional and must be completed

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Site Information

General Site Address Options Project Type m Trench A Test End Position For LDZ

Advantica Site ID House Name/Number m EA EM Date of Test Today m Street Name m NL NO Event Start Now m Town m LDZ m NW SC Event End Now m OS Reference SE SO Data Cleaning Doc Yes No SW WA Trench B WM YK House Name/Number m

Street Name m

W eather Pressure Engineers

Please choose one of the following Initial Line Pres m mbar 1 m from each section 2 m Today Yesterday Transco Attributes Form m m Sunny and Dry m Serial Numbers Completed Yes No m Overcast m Skid m

m Raining m PIM Tool m

Laptop m m Calm

m W indy

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Section Lengths

Estimated Length of Individual Pipes m Lengths of main under garden (18ft : 5.5) Length of main under asphalt Estimated Number of Joints in Test Section Length of main under bituminious Depth of Cover at Trench A mm Length of main under unmade Depth of Cover at Trench B mm Length of main under concrete

Length of main under carriageway Length of main under cobbles

Length of main under Footpath Length of main under flags

Length of main under Verge Length of main under block paving

Length of main under private Length of main under other

Total Length Total length

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Opportunity Test

Metallic Pipe Samples

Sample Taken Yes No

Location Sample

Length Sample m

Storage Location

Contact

Contact Tel No.

Comments

Gas Conditioning Soil Project

MEG Conditioned Yes No Analysis Performed Yes No

Samples Taken Yes No Reference No.

Despatched Hertford Killingworth

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General Comments

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The following were items required for return by the test teams.

x One set of disks containing test data and results x One manual hard copy fully completed with test data x Coupon for Trench A and Trench B x Health and Safety sheet x Pipe Discriminator Sheet x TEAR attribute data collection form

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Appendix E Apportioning Leakage between Mains only and Per Service

This Appendix summarises the rules that were used when apportioning leakage between Mains Only and individual Services types.

The most important leakage value that needs to be obtained from the NLT 2002/3 tests is the Combined Mains and Services as this value is taken from the main in its most undisturbed state. Following on from this, it is necessary to make estimates of leakage from Mains Only and from each type of service material (PE/Metallic). However, measurements taken with regard to these are sometimes flawed due to the disturbance that is required to appraise them. In order to make our best estimate, rules governing this need to be defined.

It is assumed that, when looking individually at Mains Only leakage and Service leakage, for each site these should add up to the same amount as the Combined Mains and Service level. With this in mind, the following rules are those that will be used to apportion the leakage between Mains Only and Service leakage.

Up to 4 types of test are carried out per site. These are:

x Mains and Services Combined (1) x Mains and Services after excavation (2) x Mains and Services following disconnection of metallic services (3) x Mains Only (4)

Measurements in each were in litres per minute and all leakage figures would have been reported as a negative value. However, all leakage in this note is referred to as a positive value. This can be achieved by multiplying the reported leakage by 1.

Where more than one of each type of test has been carried out, the first result has been taken as the definitive result.

The following rules will be applied (tests are referred to by number (1) to (4) rather than full name):

x If (1) is less than 0.05 litres per minute, then Mains Only leakage = (1) and service leakage = zero x If (4) is greater than (1) and (1) is greater than or equal to 0.05 litres per minute, then Mains Only leakage = (1) and service leakage = zero x If (4) is less than (1) and (1) is greater than or equal to 0.05 litres per minute, then Mains Only leakage = (4) and service leakage needs to be apportioned as follows:

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o Leakage per metallic service = ( (2) (3) ) / No. of metallic services (except if (3)>(1) in which case assume that the value is zero) o Leakage per PE service = ( (3) (4) ) / No. of PE services (except if (4)>(3) in which case assume that the value is zero) o Once the above two sets of values have been computed, the difference between (1)-(4) needs to be apportioned in the same ratio.

A number of tests fell outside of the above criteria. In these cases the results were treated individually in a logical manner as far in line with the standard rules as possible. These individual sites were then verified by a second person. Cases where this occurred were:

x If Mains and Services (M&S) Excavated is lower than M&S. x If M&S Excavated has not been completed and M&S Batch 1 and Mains Only (MO) have been completed. x If there is M&S, M&S Excavated and MO, take account of the fact there is only one type of service material.

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Appendix F Results Excluding Site 3769

This analysis has been included within the report because site 3769 demonstrated high leakage (it was the second highest leaking site the highest leakage rate in the combined mains and services Ductile Iron >=6 category) and the rate of decay of pressure was unusual in that the pressure dropped in a stepped fashion. In spite of extensive checks of both the test equipment used and the test procedure that was used on the day no clear explanation for this has been found; consequently the results from site 3769 have been included with all the other test results.

The graph below shows the decay in pressure measured at site 3796 in respect of combined mains and service leakage.

When the metallic services were disconnected from the main at site 3769 the leakage rate reduced very substantially, consequently the gas must have been escaping from one of the metallic gas service pipes. (The leakage rate was actually 1.5 m3/hr at 30 mbarg. assuming that the soil did not contain the escaping gas this would require a hole of 6mm in diameter to be present. As this is a credible pipe

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defect there is no reason why the result should be excluded on the basis of physical plausibility.)

Figure G1 - Combined Mains and Services Leakage Rates Excluding Site 3769 Leakage Standard error Mains Number in Category m3/hr/km m3/hr/km Population sample @ 30 mbar @ 30 mbar (km) 2002 Steel <=3 0.403 0.1577 29 5375 Steel >=4 0.469 0.1678 33 4317 Pit Cast <=3 0.2934 0.0796 34 2930 Pit Cast 4-5 0.2247 0.0318 204 21505 Pit Cast 6-7 0.3777 0.0854 67 11791 Pit Cast 8-11 0.286 0.0564 56 7135 Pit Cast >=12 0.911 0.2098 84 6112 All Spun Cast 0.166 0.0314 139 40516 Ductile Iron <=5 0.1293 0.0345 75 8348 Ductile Iron >=6 0.1059 0.0436 35 7628 All PE 0.00954 0.0022 92 107441 Total 0.1416 0.0114 848 223098

Figure G2 - Mains Only Leakage Excluding Site 3769 Leakage Standard error Category m3/hr/km m3/hr/km Number in sample @ 30 mbar @ 30 mbar Steel <=3 0.39 0.1631 28 Steel >=4 0.44 0.1642 32 Pit Cast <=3 0.2748 0.0826 33 Pit Cast 4-5 0.1872 0.0311 197 Pit Cast 6-7 0.2883 0.0723 64 Pit Cast 8-11 0.2516 0.0570 53 Pit Cast >=12 0.852 0.2047 82 All Spun Cast 0.1228 0.0256 131 Ductile Iron <=5 0.0821 0.0273 72 Ductile Iron >=6 0.0654 0.0316 35 All PE 0.00725 0.0012 89 Total 0.1173 0.0104 816

Figure G3 - Service Leakage Rates Excluding Site 3769 Number of Total number of services Leakage m3/hr/service Leakage m3/hr/service sites in sample 2002/3 1992 Metallic Service on Metallic 454 2606 0.0006252 0.0008297 Mains Metallic Service 5 14 0.0000000 0.0002361 on PE Mains PE Services on 492 2651 0.0002505 0.0003209 Metallic Mains PE Services on 81 770 0.0000000 0.00004188 PE Mains

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Total Leakage Excluding Site 3769 Removing site 3769 has a significant effect on the mains and services combined leakage Ductile Iron >=6 and metallic services categories. It does little to influence the mains only Ductile Iron >=6 category because the escape was measured to be on a service pipe. Removing site 3769 from the results has a significant effect on the overall confidence interval. i.e. Without the site the confidence interval would have been r13.2% of the mean.

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Appendix G Length of Mains Material This Appendix summarises the LP lengths of main (in metres) following the data verification exercise along with an explanation of how groups outside of the 25 material/diameter categories were dealt with. These length figures were supplied by Transco.

Mains Lengths in m DI <=5" DI >=6" PC <=3" PC >=12" PC 4-5" PC 6-7" PC 8-11" PE SC <=5" SC >=8" SC 6-7" SC Total ST <=3" ST >=4" Total East Anglia 663432 658101 75741 197963 1102764 698046 367107 8449533 2166992 433595 733433 3334020 215897 116314 15878918 East Midlands 911558 676292 180201 365156 1990847 879643 635025 11767507 3398383 665559 878231 4942173 191073 267636 22807111 North 781929 582828 138351 224105 783008 349744 288465 6705836 2595119 547925 696566 3839610 400530 72393 14166799 North London 1013912 928282 20101 960424 1973886 1294360 729360 9080334 2168455 915024 921403 4004882 195911 281294 20482746 North West 863403 823353 936175 976012 2955864 1560811 997250 14997812 3027510 620361 939128 4586999 941893 279121 29918693 Scotland 448953 393877 352452 471649 1914912 1068921 682501 9493485 1168064 532776 604989 2305829 465151 282405 17880135 South Eastern 414549 503487 175010 1073358 4314962 2318151 1016554 9932575 1946049 401899 571469 2919417 178757 264051 23110871 South West 609398 682582 67447 315526 1059847 698256 492771 7334395 1262092 529648 496776 2288516 1234892 429502 15213132 Southern 416155 423355 125405 208816 1130859 572496 345408 8408994 2137916 527745 902640 3568301 416591 988179 16604559 Wales 449211 547362 79200 143179 856983 533126 248997 5910220 988743 283923 374006 1646672 247304 243195 10905449 West Midlands 586429 623431 524141 891845 2493118 1256386 969197 8184330 1870718 800052 679967 3350737 191460 778704 19849778 Yorkshire 1189297 785248 255670 283615 927813 561361 361887 7175645 2296026 653821 779238 3729085 695937 314287 16279845 Grand Total 8348226 7628198 2929894 6111648 21504863 11791301 7134522 107440666 25026067 6912328 8577846 40516241 5375396 4317081 223098036

Asbestos has been allocated into the Spun Cast category. Copper has been allocated into the Ductile Iron category. Flex Plastic and PVC have been allocated into the PE category.

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Lead and all other unknown materials have been left unaccounted for the lengths (in metres) of each of these categories are shown below.

Mapped Material Tag Tag Length Mapped (Accounted for) Asbestos AS SC 202773 Copper CO DI 1553 Flex Plastic FP PE 38 PVC PV PE 301219 505583 Unmapped (Unaccounted for) Lead LE n/a 581 Unknown ?? n/a 3484 4065

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Appendix H Changes to Materials

The tables below identify the differences that exist between Transcos records and the materials that were actually encountered during the testing programme. Each table refers to a category of material as recorded in the mains records and provides evidence of what was actually found on site. The percentages shown in the tables below may not add due to rounding errors.

Recorded Pit Cast Mains Actual Material Number Percentage PC 434 84.4 SC 63 12.3 DI 8 1.6 ST 8 1.6 PE 1 0.2 Total 514 100.0

Recorded Ductile Iron Mains Actual Material Number Percentage DI 102 81.0 SC 19 15.1 PC 4 3.2 ST 1 0.8 Total 126 100.0

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Recorded PE Mains Actual Material Number Percentage PE 91 100.0 Total 91 100.0

Recorded Steel Mains Actual Material Number Percentage ST 53 82.8 SC 7 10.9 PC 3 4.7 DI 1 1.6 Total 64 100.0

Recorded Spun Cast Mains Actual Material Number Percentage SC 48 96.0 PC 2 4.0 Total 50 100.0

Recorded Cast Iron Mains Actual Material Number Percentage SC 2 50.0 PC 2 50.0 Total 4 100.0

(SC = Spun Cast, DI = Ductile Iron, PC = Pit Cast, PE = Polyethylene, ST = Steel).

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This analysis shows that whilst the records in respect of PE mains were completely accurate the remaining categories were found to contain errors. In particular Ductile Iron, Pit Cast and Steel mains were actually found to contain a significant element of Spun Cast mains that have not been recorded as such. It is instructive to note that the mean leakage rate for Spun Cast mains is lower than that of the weighted average rates for each of the alternative categories. (The leakage rate measured for Spun Cast is 0.1660 m3/hr/km @ 30 mbarg; the weighted average for DI is 0.3376 m3/hr/km; the weighted average for Pit Cast is 0.3589 m3/hr/km and the weighted average for steel is 0.4324 m3/hr/km.) This means that if the mains population actually contains less Ductile Iron, Pit Cast and Steel and correspondingly more Spun Cast then the amount of leakage calculated by Transco will be more than the amount of actual leakage that is occurring. The following example demonstrates this effect. The actual sampled composition of mains that were thought to be Pit Cast, prior to testing, was 84.4% Pit Cast, 12.3% Spun Cast, 1.6% Ductile Iron, 1.6% Steel and 0.2% PE. A weighted average of the pipe leakage factors for this material composition is 0.335 m3/hr/km @ 30 mbarg. This contrasts with a weighted average (taking into account the different diameter strata) of 0.3589 m3/hr/km for pure Pit Cast. i.e. Using the Pit Cast factors to assess the leakage of the actually experienced material composition overstates the actual leakage by 7%. Note: If a mixed material site was found, the test was abandoned and these results are not included in the table above. Appendix J refers.

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Appendix I Test Locations and Basic Mains Data LDZ Address Main ID Site ID Material Diameter () EA Eastfield Grove, Peterborough 410841599 64 PC 3 EA Bowes Drive, Ongar 4.1E+08 65 PC 4 EA Nether Court, Halstead 411085547 82 DI 6 EA Eudo Road, Colchester 0411015176 89 SC 3 EA Northbrooks, Harlow 410111037 91 SC 4 EA Turners Close, Greensted Ongar 410066318 98 DI 4 EA Sandford, Peterborough 410808907 100 DI 6 EA Crabtree Road, Knebwoth 410469332 1126 PC 4 EA Winchester Road, Bedford 0410612006 1129 PC 4 EA Faraday Square, Bedford 0410612798 1131 PC 4 EA The Harebreaks, Watford NO Data Pa 1133 PC 4 EA Hillcrest, Sudbury 411114618 1136 SC 4 EA Shelley Road, Luton 410386530 1138 PC 6 EA Spixworth Road, Norwich 411251261 1140 PC 6 EA Mortimer Close, Luton 410375047 1153 SC 4 EA Linden Road, Dunstable 410435395 1154 SC 4 EA Sallows, Fenstanton 410709500 1155 SC 4 EA Vicarage Road, Buntingford 410553300 1160 ST 4 EA Dodds Close, Riseley, Bedford 0410621587 1161 ST 4 EA St Edmunds Walk, St Albans 410247648 1163 PE 3 EA Newlands Road, Westoning, Bedford 0410454514 1165 PE 3 EA Rush Green Road, Clacton On Sea 411047930 1166 PE 3 EA Sackville Way, West Bergholt, Colchester 0411131223 1167 PE 3 EA Beaconsfield Way, Epping 410060778 1169 PE 3 EA Lowestoft Road, Gorleston, Gt Yarmouth 0604453383 1170 PE 3 EA Festival Road, Potton, Sandy 410564782 1171 PE 3 EA West Avenue, Mayland, Chelmsford 411145184 1172 PE 3 EA Stanstead Road, Hoddesdon 602711309 1496 ST 3 EA Grange Road, Ickleton, Saffron Walden ea 95t 1499 PE 3 EA Lincoln Road Peterborough 410814584 2435 PC 12 EA Earlham Road Norwich 411211023 2437 PC 12 EA Spencer Walk, Rickmansworth 416212726 2537 DI 4 EA Harewood, Rickmansworth 410212942 2539 DI 4 EA Collingwood Rd Gt Yarmouth 411364502 2943 PC 4 EA Rushmere Rd Ipswich 041091283 2949 PC 6 EA Norwich Rd, Costessey, Norwich 411227084 2952 PC 6 EA The Street Brundall Norwich 411292060 2955 DI 6 EA Beaumayes Close Hemel Hempstead 410309515 3056 DI 4 EA Broadway Peterborough 410835588 3058 PC 4 EA Great Harrods, Walton 411136363 3500 DI 4 EA Orchard Way, Luton 410394555 3501 PC 4 EA Myrtle Road Ipswich 410934638 3502 PC 12 EA Alan Road, Ipswich 410926868 3503 PC 8 EA Belstead Road, Ipswich 410938067 3504 PC 6 EA 19 & 36 Souberie Avenue, Letchworth 410536691 3732 PC 4 EA Eastfield Road Peterborough 4072 DI 18 EM Cavendish Road, Barnsley 64431691 897 PC 3 EM Essex Road, Sheffield 65880816 903 PC 4 EM Old Hall Drive, Nottingham 65454917 904 PC 4 EM Intake Crescent, Dodsworth, Barnsley 64858730 909 PC 4 EM Causeway, Darlet Abbey, Derby 64780223 911 PC 4 EM Leinster Avenue, Doncaster 65124350 915 SC 4 EM Enfield Street, Beeston 64464625 917 SC 4 EM Springfield Road, Redhill, Nottingham 65715820 923 PC 4 EM Knighton Rise, Leicester 65649519 929 PC 4 EM Lingford, Cotgrave, Nottingham 64761448 933 DI 4 EM Redhill Lodge Drive, Redhill, Nottingham 65715702 935 SC 4 EM Kenilworth Road, Beeston, Nottingham 6446520 938 PC 4 EM Lilac Place, Kettering, Northants 65146198 939 SC 4 EM Asher Lane, Nottingham 65773495 942 PC 6 EM Park Road, Mickleover, Derby 65503827 943 DI 6 EM Shaftesbury Crescent, Derby 64838674 962 PC 14 Page 51 of 64

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EM Salisbury Road, Maltley, Rotherham 65420114 972 SC 3 EM Darley, Worsborough 66316241 973 SC 3 EM Hartland Drive, Sunnyhill, Derby 600974347 975 SC 4 EM Holdings Road, Sheffield 65907925 978 SC 4 EM Hambeleton Close, Elsecar, Barnsley 66412094 984 SC 3 EM Harewood Avenue, Barnsley 64435337 985 SC 3 EM Elm Tree Road, Rotherham 65417294 987 SC 6 EM Lodge Farm Lane, Arnold 65715584 1014 DI 6 EM Friars Road, Barnsley 64605865 1016 ST 3 EM West Common Gardens, Scunthorpe 65824658 1017 ST 4 EM Masfield Way, Corby 64749504 1026 SC 4 EM Ariston View, Sheffield 65834701 1031 PE 4 EM Derby Road, Ashbourne, Derby 64396324 1032 PE 3 EM Priory Avenue, Kirby-In -Ashfield, Notts 64377603 1035 PE 3 EM Eakring Road, Mansfield. 65430521 1037 PE 7 EM Newark Road, Ollerton 66363052 1040 PE 5 EM Doverbeck Close 66633970 1041 PE 3 EM Leas Hall Place, Sheffield 65919242 1042 PE 3 EM Wade Meadow, Sheffield 665560855 1046 PE 3 EM Mansfield Road, Doe Lea 66362174 1703 PC 3 EM Montrose Close, Stamford 66078184 1706 DI 4 EM Heaton Close, Dronfield 64875169 1966 DI 4 EM Constable Close, Drumfield, Sheffield 64874044 1967 DI 4 EM Streeley Road, Sheffield 65976708 2461 PC 4 EM Winchester Way, Barnsley 64381934 2468 DI 4 EM Gloucester Ave, Scunthorpe 65811285 2470 ST 6 EM Musters Road, West Bridgeford 66227776 2471 PC 10 EM Tavistock Road, West Bridgford 66232027 2930 PC 4 EM Godiva Crs, Bourne 64543801 2935 DI 4 EM Love Lane, Gainsborough 64941899 3165 PC 6 EM Braunstone Lane, Leicester 65221607 3166 PC 6 EM Chadwick Road, Sheffield 65859396 3169 PC 6 EM Carisbrooke Road, Leicester 65226059 3171 PC 8 EM Wordsworth Ave, Sheffield 65998163 3174 PC 12 EM Lindisfarne Rd, Corby 64748739 3180 ST 4 EM Ridgehill Grove, Sheffield 65956332 3584 PC 4 EM Hoober Ave, Sheffield 65909778 3585 PC 4 EM Stone Delf, Sheffield 65975460 3588 PC 4 EM Woodfield Rd, Doncaster 64423841 3591 PC 6 EM Balmoral Ave, Grimbsy 64985554 3595 PC 8 EM Windly Rd, Leicester 65314093 3598 PC 12 EM Cockayne Street, Derby 64361765 3964 PC 4 EM Longdales Road Lincoln 65337499 3966 PC 6 EM Glen Road, Sheffield 65893187 4055 PE 14 EM Riggs High Road, Stannington 65956721 4056 PC 4 EM Oldfield Avenue, Stannington 66082925 4059 PC 4 NL Lodge Avenue 510867869 603 PC 4 NL Whites Avenue 510937435 605 PC 4 NL Grosvenor Gardens 0510999651 610 PC 4 NL Elmcroft Avenue 0510827317 612 PC 4 NL Swan Way 179920 622 PC 5 NL Ashford Crescent 511003378 623 PC 4 NL Park Chase 510889434 624 PC 4 NL Kempton Avenue 0510858265 625 PC 4 NL Plumpton Avenue 510893524 626 SC 4 NL Goodwyn Avenue 510838889 627 SC 4 NL The Ridgeway 510923940 628 PC 4 NL Lodge Court 607909187 629 PC 4 NL Aylett Road 510785516 630 PC 4 NL Chartris Road 051080623 633 PC 4 NL Clinton Crescent 0510811666 635 PC 4 NL Clockhouse Lane 510811830 638 PC 4 NL Francais Road 510834392 639 PC 5 NL Green Dragon Lane 644 PC 7 NL Hoodcote Gardens 511027129 645 PC 6 NL Oakwood Drive 510943705 646 PC 6 NL Brook Road South 510797875 650 SC 6 NL Shanklin Road 0510904843 652 PC 6

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NL Grange Crescent 51083982 656 DI 6 NL Rowan Walk 510903813 658 PC 8 NL Deans Lane 0510943900 660 SC 8 NL Kingsland High Street 0150861062 671 PC 18 NL Esther Road 051082887 678 SC 4 NL Westall Road 510935188 683 PC 8 NL GEORGE 5th WAY 0151083663 685 SC 4 NL Berkeley Drive 051079084 688 SC 4 NL Carlisle Road NL 90R 691 SC 4 NL Shaftsbury Road 510910197 692 SC 4 NL Langley Drive 510863361 698 DI 4 NL Parkhurst Road 5108902024 703 DI 4 NL Staples Road 510916243 706 DI 4 NL Booker Lane 510793578 709 PC 4 NL Park Hill 510890211 713 DI 4 NL Marlborough Road 0510873940 715 DI 4 NL Old Ford Road 510886531 722 DI 10 NL Hall Crescent 510844083 729 ST 4 NL Underhill Road 510928138 731 ST 4 NL Appledore Close 510782401 732 PE 4 NL Evelyn Drive 0510829214 734 PE 7 NL Glanmor Road 510837197 735 PE 4 NL Latimer Close 510863992 737 PE 3 NL Mirador Cresvent 510878020 738 PE 3 NL Scarsdale Road 510908725 740 PE 3 NL James Bedford Close 510957994 744 PE 6 NL Southbourne Gardens 0510989 746 PE 10 NL Mimosa Close 510877881 749 DI 4 NL Conduit Way, Nw10 0510813744 1580 PC 8 NL Roding Road, Ig10 51090218 1582 PC 8 NL The Green, Ha1 510977826 1583 PC 8 NL High Road Rayleigh 510850127 1586 PC 14 NL Eastcote Road 510949203 1587 PC 12 NL Forest Edge 510833400 1591 PC 12 NL Wensleydale Avenue, Ig5 0510934596 1593 SC 12 NL Longleat Road, Enfield, Middx 511001843 1598 ST 3 NL Mile End Rd, E1 Wrong Map 1720 PC 20 NL Lynford Terrace, N9 511020999 1721 PC 12 NL Hatfield Road Stratford,E15 510846870 1727 PC 24 NL Wanstead Flats Centre Rd,E11 510992435 1728 PC 18 NL Whitehall Rd Woodford,E4 510833632 1729 PC 12 NL High Rd Woodford,Ig8 510850264 1730 PC 12 NL Cranbrook Rd Barkingside,Ig6 510816165 1731 PC 18 NL Chobham Rd Stratford,E15 510808566 1732 PC 24 NL High Rd Chadwell Heath,Rm6 0510853849 1733 PC 12 NL Brian Road Rm6 0510796059 1801 PC 6 NL Adelaide Gdns Rm6 510779138 1802 PC 6 NL Walton Road E12 510932135 1804 DI 4 NL Barley Lane Rm6 510786942 1806 DI 6 NL Runnymeade Gardens, Ub6 510904439 1811 PC 12 NL Stepney Way E1 510917319 1822 PC 24 NL Alverston Road E12 510781488 1823 DI 4 NL Albion Road Southend 510780116 1825 DI 4 NL Hall Road E6 510844189 2027 DI 4 NL Howards Road E13 51085510 2029 DI 4 NL Friary Road N12 511024257 2359 PC 6 NL Russell Lane N20 511026014 2360 PC 10 NL Geneva Gardens Rm6 510836486 2472 PC 4 NL Tolworth Gardens 510925895 2474 PC 4 NL Pemberton Gardens Rm6 510925895 2475 PC 4 NL Hathaway Road Grays 510846919 2476 PC 12 NL Canon Ave Rm6 510802240 2765 PC 6 NL Vicarage Lane, Chigford E4 510930113 2876 PC 4 NL Northdene, Chigwell 510965744 3037 DI 8 NO Barnard Road, Billingham 11827599 402 SC 3 NO Brinkburn Road, Stockton-On-Tees 11825736 405 PC 4 NO Chadburn Road, Stockton-On-Tees 11825744 407 PC 4 NO Addington Drive, Middlesborough 0011835681 410 SC 4

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NO Granville Road, Peterlee 11810709 416 SC 3 NO Greenock Road, Hartlepool 11832037 417 SC 3 NO Greetlands Road, Sunderland 11799328 418 SC 3 NO Greystoke Avenue, Sunderland 11799338 419 SC 3 NO Heath Close, Peterlee 11810784 420 SC 3 NO Humewood Grove, Stockton-On-Tees 11825276 421 SC 3 NO Greenside, Middlesborough 11839183 432 DI 4 NO Hawkshead Court, Newcastle Upon Tyne 11756978 433 DI 4 NO Holystone Avenue, Blyth 11745617 434 DI 4 NO Kensington Avenue, Newcastle Upon Tyne 11757039 435 SC 4 NO Otterburn Grove, Blyth 11745762 436 DI 4 NO Longbeck Road, New Marske, Redcar 11815599 447 DI 8 NO The Glebe, Morpeth 11787764 449 DI 8 NO Bede Terrace, Chester-Le-Street 0011693045 450 ST 3 NO Scafell Drive, Newcastle Upon Tyne 0011781503 452 PE 4 NO Brighton Grove, Newcastle Upon Tyne 11772698 454 PE 5 NO Sunderland Ave, Peterlee 11810288 459 PE 3 NO Morpeth Street, Peterlee 11810183 460 PE 3 NO Fourth Street, Bensham, Gateshead 11793387 462 PE 5 NO Harlsey Crescent, Stockton-On-Tees 11822375 1182 PC 4 NO Greenland Avenue, Middlesbrough 11837286 1183 PC 4 NO Regent Drive Whickham 11736077 1502 DI 6 NO Hawthorn Avenue Billingham 11827343 1504 PC 6 NO Grand Parade North Shields 11760423 1507 PC 12 NO North Road Seaham 11807721 1669 SC 8 NO Stratford Grove Newcastle 11785854 2114 PC 4 NO Gilverdale Way Cramlington 11741952 2216 DI 4 NO Leybourne Avenue Newcastle 11729362 2304 PC 4 NO Columbia Terrace Blythe 11744990 2307 DI 4 NO Wrentree Close, Redcar 0011814600 2335 DI 6 NO Field View Close, Middlesborough 11824795 3795 PC 3 NO Dees Avenue, Wallsend 11751361 3866 PC 4 NO York Crescent, Durham 11692450 3869 DI 4 NO The Byway, Darlington, County Durham 11705639 3920 PC 4 Sycamore Avenue, Thornaby, Stockton-On- NO 11820358 3925 PC 6 Tees, Cleveland NO Wharfedale Ave, Stockton 11827567 3932 PC 12 NO Panns Bank, Sunderland 11849994 3935 PC 12 NO Stokesley Crescent, Billingham, Cleveland 11827498 4009 PC 8 NO Stainsby Road, Middlesborough, Cleveland 11837390 4174 PC 8 NW Kenneth Grove, Leigh 311211740 755 PC 3 NW England Avenue, Blackpool 315230241 764 PC 4 NW St Aldwyns Road, Withington 313339640 767 PC 4 NW Egerton Road, Whitefield 311324767 768 PC 4 NW Fir Road, Swinton 313550759 774 PC 4 NW Dale Road, New Mills 314291134 777 PC 4 NW Kelvin Street, Darwen P 3.12E+08 778 PC 3 NW Gregg Street, Reddish 3140801095 779 PC 4 NW Branksome Road, Stockport 314047460 783 PC 4 NW Wilson Road, Stockport 314057319 784 PC 4 NW Daniel Fold, Rochdale NW 44R 786 SC 4 NW Scott Park Road, Burnley 311993635 788 PC 4 NW Moreton Avenue, Bramhall, Stockport 314182807 790 PC 4 NW Lydgate Drive, Oldham 311737458 793 PC 4 NW Larch Street, Nelson 312062880 797 PC 6 NW 1-19, Delamere Avenue, Stretford 313646900 802 PC 6 NW 293-321, Park Road, Oldham 311746066 803 PC 6 NW Infirmary Street, Blackburn 311861175 807 PC 6 NW Malvern Road, St Helens 314748664 808 SC 6 NW Westbourne Road, Lancaster 314469731 811 PC 6 NW Nairne Street, Burnley 311998852 813 PC 8 NW Crumpsall Lane, Manchester 8 3123232689 814 PC 8 NW Towerlands Street, Liverpool 312595664 817 PC 8 NW 10-46, Dialstone Lane, Stockport 314130222 818 PC 8 NW 2a-24, Walverden Road Nelson 312090909 822 PC 8 NW 114-128,Barkerhouse Road Nelson 312060975 827 PC 12 NW Newbridge Lane Stockport 0314084437 831 PC 5 NW Blackfriars Road Salford 3 313473059 832 PC 12

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NW Freckleton Street Blackburn 311869970 834 PC 12 NW Whitworth Street Manchester 1 313106824 835 PC 12 NW Falkirk Avenue, Blackpool 315235084 841 PC 3 NW Foxfield Road, Manchester 23 313691618 843 SC 6 NW Harlyn Close, Liverpool 312527036 845 SC 3 NW Holbeach Close, Bury 311346047 850 DI 4 NW Mile Lane, Bury 311359818 851 SC 4 NW Earlsway, Euxton 315450647 854 DI 4 NW Glenham Court, Manchester 15 0313591814 859 DI 4 NW 1-27 Ribble Road, Wigan 315064799 863 DI 6 NW The Uplands, Runcorn 315098578 866 DI 6 NW Standish Walk, Denton 314313833 867 DI 6 NW Scroggins Lane, Partington 3.14E+08 873 ST 3 NW Coppull Moore Lane, Coppul, Chorley NW199T 874 ST 3 NW St Francis Road, Blackburn 311874098 876 PC 3 NW Highfield Road,Grange-Over-Sands 314598845 877 SC 4 NW Long Lane Chapel-En-Le-Frith 314277076 878 ST 4 NW Wheatley Road Swinton 313544176 880 PE 4 NW 4-18 Moira Crescent, Ribbleton, Preston 0315337200 881 PE 3 NW Clifton Avenue, Manchester 14 313291266 883 PE 5 NW 11-19, Albert Road, Cheadle Hulme 313415867 885 PE 10 NW 9-19 & 22a-34, Windsor Road, Chorley 315494277 886 PE 4 NW Patterdale Crescent, Maghull 312274194 891 PE 4 NW Broad Oak Road, St Helens 314748878 1266 PC 6 NW Grasmere Avenue, Thornton Cleveleys 315258133 1272 SC 3 NW Dovedale Road, Bolton 3.11E+08 1274 SC 3 NW Garswood Road, Ashton In Makerfield 314775879 1281 ST 3 NW Anchorite Fields, Kendal 314572227 1285 ST 6 NW Washburn Close, Westhoughton, Bolton 311273008 1286 PE 0 NW Roundthorn Road, Oldham 311739835 1288 PE 3 NW Chatterton Close, Withington, Manchester 313341572 1289 PE 3 NW Brook Avenue, Shavington, Crewe 313945538 1290 PE 3 NW Larches Avenue, Preston 605430345 1293 PE 3 NW Calder Drive, Catterall, Preston 315532261 1294 PE 3 NW Belvoir Road, Allerton, Liverpool 312482323 1302 PC 3 NW Minster Road, Bolton 311063625 1303 ST 3 NW Sowerby Avenue, Blackpool 315182374 1306 PC 3 NW Belgrave Road, Manchester 10 313220338 1622 PC 4 NW Billington Gardens, Clitheroe 311953761 1639 SC 4 NW Old Broadway, Manchester 20 313341047 1641 PC 4 NW Brantingham Road, Manchester 21 313303876 1648 PC 8 NW Castle View, Clitheroe 311964805 1650 PC 8 NW Adair Street, Manchester 1 313106242 1654 PC 12 NW Barnes Street, Clayton Le Moors 311937750 1655 PC 12 NW Granville Park, Aughton, Ormskirk 312266889 1663 PE 4 NW Lower House Lane Burnley 312010859 1908 PC 12 NW Burnley Close Blackburn 311838081 1909 PC 12 NW Tottleworth Great Harwood 311939201 1910 PC 12 NW Chapeltown Road Bromley Cross 311077328 1911 PC 12 NW Chorley New Road Lostock Bolton 311135586 1912 PC 12 NW Queens Road Blackburn 311847959 2093 PC 3 NW Tockholes Road Darwen 311770521 2094 PC 4 NW Sough Road Darwen 510908725 2096 PC 4 NW Ford Lane, Didsbury, M20 313361056 2150 PC 4 NW Doncaster Avenue, Manchester 20 313333597 2153 PC 4 NW Longlands Ave Heysham 314528717 2275 PC 3 NW Blackburn Road Bolton 311087638 2277 PC 12 NW East Mount Wigan 315029452 2280 DI 4 NW Ox Hey Lane, Lostock, Bolton 311136461 2281 DI 4 NW Lower Rosegrove Burnley 312005282 2282 DI 6 NW Billington Road Burnley 312603171 2283 DI 6 NW Borth Avenue, Offerton 314133665 2288 PC 4 NW Stenner Lane, Didsbury 313361031 2289 PC 4 NW Heyscroft Road, Withington 313345330 2290 PC 4 NW Buckingham Road, Manchester 21 313314143 2291 PC 4 NW Church Road, New Mills 314290852 2292 PC 4 NW Reynolds Road, Whalley Range 313597010 2293 PC 4 NW Kings Road, Whalley Range 313600860 2294 PC 4

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NW Armadale Road, Bolton 311132680 2517 DI 4 NW Carry Lane Colne 312095549 2518 PC 3 NW Hill Lane Colne 312112591 2520 PC 4 NW Skipton Road Colne 312107680 2521 PC 8 NW Nuttall Road, Ramsbottom 311438444 2736 ST 3 NW Manchester Road, Walmesley, Bury 311438196 2737 ST 3 NW Heaton Road Hraton Bolton 311133792 2756 DI 4 NW Ashbourne Road, Salford 6 313522963 3106 PC 4 NW Ashbourne Grove, Salford 7 313447158 3257 PC 4 NW Enfield Road, Monton, Eccles 313560457 3258 PC 4 NW Park Road, Walkden, Worsley 0311184199 3259 PC 3 NW Stretford Road, Man 15 0313591536 3358 PC 8 NW Dickenson Road, Manchester 13 313269116 3570 PC 8 NW Harwood Lane, Great Harwood, Blackburn 311951924 3630 PC 6 NW Hougoumont Ave., Crosby 0312250958 3631 PC 12 NW Audley Lane, Blackburn 311846409 3654 PC 6 NW Milton Street, Nelson 312081408 3693 PC 12 NW Clarence Street, Bolton 311107254 3874 DI 18 SC Balmossie Street North, Barnhill, Dundee 466717484 186 PC 3 SC Stevenson Street, Clydebank 465392062 194 PC 3 Montrose, Murray, Leslie Pl. Lauriston G, SC 466591012 202 SC 4 Selkirk SC Balmoral Gardens, Dundee 466652781 204 SC 4 SC Riggs Place, Cupar, Fife 466888911 222 SC 4 SC Lawhead Road West, St Andrews, Fife 466914518 224 SC 4 SC Main Street, West Lothian 466571376 226 SC 4 SC Garth Avenue, Perth 466946148 232 SC 8 SC Holehouse Drive, Glasgow 465305099 1068 PC 4 SC Fairfax Avnue, Glasgow 465201025 1071 PC 4 SC Cardonald Place , Glasgow sc64t 1072 PC 4 SC Thornley Avenue, Glasgow 465310115 1073 PC 4 SC Fishescoates Avenue, Rutherglen 465424510 1074 PC 4 SC Moredun Park Road, Edinburgh 466401852 1082 SC 4 SC Danes Drive, Glasgow 465313532 1086 PC 6 SC Park Road, Bishopbriggs 465354317 1088 PC 6 SC Wallace Avenue, Elderslie 0465787415 1089 SC 6 SC Broompark Road, Wishaw 466158238 1090 SC 6 SC Needless Road, Perth 466951631 1092 PC 6 SC Kilbowie Road, Clydebank 465401964 1097 PC 10 SC Caskieberran Road, Glenrothes 466835016 1098 SC 10 SC Sutherland Street, Dundee 466703361 1104 ST 4 SC Kerrystone Court, Dundee 466669735 1106 ST 4 SC Craigfern Drive, Glasgow SC 101T 1109 PE 3 SC Thomson Grove, Glasgow 4.66E+08 1110 PE 3 SC Channonry Wynd, Brechin 4666737513 1111 PE 3 SC Hospital Road, Montrose 466752440 1112 PE 3 SC Lawers Place, Aberfeldy 4.67E+08 1113 PE 3 SC Victoria Street, Portessie / Buckie 0467090262 1114 PE 3 SC Admiralty Street, Buckie 0467088911 1115 PE 3 SC Oxgangs Crescent, Edinburgh 466482603 1511 PC 9 SC Glengarry Road, Perth 466947145 1512 SC 8 SC Northfield Broadway, Edingburgh 466376670 1514 PC 9 SC Strathaven Road, Hamilton 466052483 1690 ST 3 SC Doon Terrace, Dundee 466656866 1693 ST 3 SC Rowantree Crescent, Dundee 466665140 1694 ST 3 SC Morningside St, Glasgow 465093299 1919 PC 4 SC Lochlea Rd, Glasgow 465194846 1920 PC 4 SC Arisaig Drive, Glasgow 465242414 1921 PC 4 SC Selborne Rd, Glasgow 465308850 1922 PC 4 SC Earn Avenue, Bearsden 465340498 1923 PC 4 SC Ardencaple Quadrant, Helensborough 465509156 1924 PC 4 SC Gilmourton Cresc, Newton Mearns 465411547 1925 PC 4 SC Pentland View, Currie (Dolphin Road) 466503483 1929 PE 4 SC Park Road, Dundee 466683052 1930 PC 4 SC Springburn Avenue, Glasgow 465119079 1931 PC 6 SC Drum Brae Drive, Edinburgh 466312087 1944 SC 12 SC Seagate, Prestwick 465489894 2364 SC 3 SC Forsyth Street, Greenock 465544334 2365 PC 3

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SC Whitehaugh Drive, Paisley 465720967 2372 PC 4 SC Stirling Drive, Johnstone 465758100 2374 PC 4 SC Grange Road, Edinburgh 2574 PC 12 SC Longhill Gardens, Dalgety Bay 466828975 2582 DI 4 SC The Beeches, Dalgety Bay 466829214 2857 DI 4 SC Oldhall Road, Paisley 465712743 3712 PC 3 SC Off Inverness Street, Glasgow 465230743 3714 PC 4 SC Daviot Street, Glasgow 465230055 3715 PC 4 SC Kincraig Street, Glasgow 46523442 3718 PC 6 SC Laburnum Road, Kilmarnock 0465666742 3840 PC 12 SC Mill Street, Dunfermline 466784070 3843 DI 4 SC Calderglen Road, East Kilbride 0466100551 3845 DI 8 SC Cedar Road, Kilmarnock 0465646530 3949 PC 12 SC Burleigh Crescent, Inverkeithing 0466806617 3950 DI 4 SC Milton Crecent, Inverness 0467141930 3951 DI 8 SC Park Road, Dundee 0466683058 4031 PC 4 SC Royston Road, Glasgow 0465117084 4036 PC 8 SC Mosspark Boulevard, Glasgow 0465252568 4040 PC 12 SC Baldwin Avenue, Glasgow 0465299659 4041 PC 12 SC Craighead Way, Barrhead 0465737685 4045 PE 12 SE Wellington Parade, Kingsdown, Deal, Kent 115029285 1249 PC 3 SE Gorse Crescent, Maidstone, Kent Me20 1.14E+08 1250 SC 4 SE Tainter Road / Twyford Road, Hadlow, Kent 115567849 1251 PC 4 SE Crockham Way, London Se9 114724857 1253 PC 5 SE Kingsdown Close, Maidstone, Kent Me16 1.14E+08 1254 PC 4 Highfield Road, Minster-On-Sea, Sheerness, SE 1.14E+08 1257 SC 3 Kent SE Foxwarren, Claygate, Esher, Surrey Kt10 25714 1258 SC 4 Grasmere Way, West Byfleet, Woking, SE 1.14E+08 1262 SC 6 Surrey SE Waterside Road, Guildford, Surrey Gu1 1.14E+08 1264 SC 10 SE Cobham Close, Canterbury 115002004 1542 SC 4 SE Kent Avenue, Sittingbourne Kent 114489148 1546 SC 4 SE Kings Drive Eastbourne 0114556948 1547 SC 4 SE Church Road Woking 0115677144 1548 SC 0 SE Martin Dene, Bexleyheath, Kent 115132718 1549 PC 4 SE The Vale Croydon 114154110 1551 PC 4 SE Tavistock Crescent, Mitcham 114175083 1552 SC 4 SE Granville Avenue, Ramsgate 115093824 1554 PC 4 SE Timberlane Road Pevensey 114625281 1555 SC 4 SE Columbia Avenue, Whitstable Kent 115108469 1556 SC 4 SE Lloyd Road, Worcester Park 115643277 1557 PC 4 SE Queens Road Eastbourne ( Test 1 ) 114561445 1558 SC 4 SE Kings Close Lancing, West Sussex 114597763 1560 PC 4 SE Arlington Drive, Carshalton 0115420548 1562 PC 6 SE Noel Rise, Burgess Hill, Rh15 115208215 1565 SC 4 SE Stone Wood, Dartford 115151732 1567 SC 4 SE Azelea Drive Swanley ( Test 1 ) 114983159 1568 SC 4 SE Mill Lane, Rustlington, West Sussex Bn16 114615301 1572 ST 3 SE Pett Road , Hastings, East Sussex Tn35 0115515769 1573 ST 6 SE Cherry Drive, Canterbury, Kent Ct2 115001778 1574 PE 5 SE Roman Close, Chatham, Kent Me5 115896819 1575 PE 3 SE Teazlewood Park, Leatherhead, Surrey Kt22 0115907684 1576 PE 3 SE Brittenden Lane, Heathfield, East Sussex 1.16E + 08 1577 PE 4 SE Azalea Drive, Swanley 114983150 1599 SC 6 SE Northend Road Erith 0115663915 1606 PC 4 SE Arthurdon Road, London 114672993 1607 PC 4 SE Sidewood Road, London Se9 114871104 1608 PC 4 SE Edison Road, Welling, Kent Da 16 115198539 1609 PC 4 SE Westmoat Close, Beckenham 114931446 1610 PC 4 SE Plane Street, London Se26 114847120 1611 SC 4 SE Fendyke Road, Belvedere, Kent Da17 115119794 1612 PC 4 SE Hadley Road, Mitcham, Surrey Cr4 114168680 1613 PC 8 SE Kiln Meadows, Guidford, Surrey 0114217435 1615 PE 4 SE Woodward Close, Eastbourne, East Sussex 115842550 1616 PE 3 SE Tormead, Guildford, Surrey 0114223505 1621 SC 4 SE Francemary Road, London ( Test 1 ) 114756881 1675 PC 4 SE Sladebrook Road, London Se3 114872051 1677 SC 4 SE Ferrers Road, London Sw16 115339544 1679 PC 4 Page 57 of 64

Report R6303 :

SE Stoneyfield Road Coulsdon Surrey 114127388 1713 SC 4 SE Ewell Court Avenue, Epsom Surrey 114261976 1714 PC 4 SE Raglan Road Belvedere Kent Da 17 115121510 1715 PC 4 SE Clarendon Road, Shoreham West Sussex 114634762 1717 SC 4 SE Eltham Green Road, London, Se9 114745952 1718 PE 4 SE Wellington Road Belvedere Kent BA17 115122630 1734 PC 4 SE Halls Hole Road Tunbridge Wells 115580105 1746 PC 3 SE Greenacres Crawley West Sussex 0115218421 1747 SC 4 SE Maberley Road Beckenham Kent 114927975 1749 PE 5 SE Keynsham Road London Se9 0114793015 1750 PE 4 SE Westmeads Road, Whitstable 115117080 1785 DI 4 SE Mereworth Drive London Se18 114822420- 1789 PC 4 SE Brightling Road London 114695243 1816 PC 12 SE Littlehampton Road Worthing 0114661361 1870 SC 12 SE Mount Road, Canterbury, Kent Ct01 115006116 1872 SC 4 SE Sea Lane Goring By Sea West Sussex 114661867 1951 PC 12 SE Kent Gate Way, Croydon Surrey 0114141763 1952 PC 12 SE Worthing Road, Rustlington Bn16 0115702709 1994 SC 12 SE Middle Park Avenue Elthamlondon SE9 114823385 1995 PC 9 SE Bexley Road Eltham London Se9 114686014 1996 PC 9 SE Birdbrook Road London Se3 114687064 2033 PC 4 SE Weigall Road London Se12 114907079 2034 PC 7 SE Holme Lacy Road London Se12 114783664 2035 PC 5 SE Chalcroft Road Lewisham, London Se12 114709346 2036 PC 4 SE Thornwood Road Lewisham, London Se 12 114891804 2037 PC 4 SE Rochdale Road, London Se2 11485811 2038 PC 4 SE Glendown Road, Abbey Wood London SE2 114762624 2039 PC 4 SE Shallons Road New Eltham London Se9 0114868670 2040 PC 4 SE Crouch Croft, New Eltham, London Se9 114725856 2041 PC 4 SE Dallinger Road London Se12 011472910 2042 PC 4 SE Court Farm Road London Se9 114721710 2043 PC 9 SE Beaconsfield Road Chislehurst Kent Br07 114907079 2046 PC 5 SE Shieldhall Street Abbey Wood London Se2 0114869827 2098 PC 4 SE Chancelot Road Abbey Wood London 114709913 2099 PC 4 SE Lavidge Road Eltham London Se9 114801590 2263 PC 4 SE Keedonwood Road Downham 114943833 2264 PC 5 SE Strathaven Road Abbey Wood London Se2 114882626 2266 PC 5 SE Hafton Road Catford London Se6 114772252 2268 PC 4 SE Dickson Road, London Se9 114734014 2313 PC 9 SE Indus Road London Se7 114787568 2314 PC 7 SE Rochester Way London Se3 114858734 2315 PC 12 SE 27 Kelbrook Road London Se3 0114791229 2331 PC 7 SE 28 Kimmeridge Road London Se9 114794226 2338 PC 9 SE Wayside Grove/Marston Gardens London 114906751 2340 PC 7 SE Highbrook Road, London 114780453 2348 PC 7 SE Nigeria Road London Se7 114832677 2389 PC 5 SE Dunvegan Road London 114738452 2390 PC 9 SE Mottingham Lane London Se9 114827874 2391 PC 7 SE Goffers Road Blackheath London Se3 114764566 2402 PC 7 SE Partridge Green Eltham London Se9 114841826 2403 PC 9 SE Tilbrook Road, London Se3 114892540 2407 PC 4 SE Molescroft, Eltham, London Se9 114825774 2409 PC 5 SE Heather Road Lewisham Se12 114777502 2410 PC 4 SE Arran Road, London Se6 114672830 2421 PC 4 SE Newquay Road London Se6 114832427 2422 PC 5 SE Verdun Road, Plumstead London Se18 114902029 2427 PC 4 SE Ashwater Road, Lewisham, London Se12 114673700 2428 PC 4 SE Grassdene Road, Plumstead, London Se18 115654692 2429 PC 4 SE Bourne Park Close, Kenley 114162155 2493 DI 6 SE Woodcote Valley Road, Woodcote, Purley 114180315 2494 PC 6 SE Penerley Road, Catford, London Se6 114844405 2570 PC 9 SE Commonside East, Mitcham 114165991 2611 PC 12 SE Watneys Road, Coulsden 115673547 2614 PC 12 SE Brigstock Road Coulsdon 114124326 2796 PC 6 SE Bodley Road New Malden Surrey 115615681 2797 PC 6 SE Crossways Road Mitcham 114166377 2798 DI 4 SE 8 & 26 Grassmere Gardens, Folkstone 115051643 2858 DI 4 SE Speldhurst Road Tunbridge Wells Tn4 115585605 3076 ST 6

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SE Manton Road London Se2 114816832 3084 PC 12 SE King Alfred Avenue London Se6 115659204 3085 PC 12 SE Midfield Way Orpington Kent Br6 114974598 3086 PC 12 SE Dahlia Gardens, Mitcham 114166414 3109 PC 6 SE 15 & 45 Beech Grove, Mitcham 114163848 3124 PC 6 SE Hallford Way Dartford Kent 115141791 3359 PC 12 SE Firhill Close, London Se 18 114753654 3439 PC 8 SE Collyers Lane, Erith, Kent Da8 114753654 3477 PC 12 SE Woodcourt Close, Sittingbourne 114492535 3478 DI 4 SE 6 & 24 Latham Road, Bexleyheath 1151131869 3670 PC 12 SE 44 & 58 Eltham Hill, London Se9 11476177 3691 PC 12 SE Coniston Rd / Eltham Road, London Se9 114746339 3705 PC 12 SE The Silvers, Broadstairs, Kent 11499308 3729 DI 6 SO Newbarn Rd, Havant Hants 160496175 16 SC 6 SO Hazel Rd, Bognor Regis W. Sussex 160556892 19 PC 10 SO Southdown Rd, Portsmouth 160489830 22 PC 12 SO Valley Close, Caversham Reading 160707612 27 SC 4 SO Pansy Rd, Swaythling Southampton 0160252527 1049 ST 3 SO Linden Rd, Reading Berks 160692802 1053 ST 4 SO Victena Rd, Eastleigh Hants 160319221 1054 ST 4 SO Queens Rd, Bournemouth 016115966 1059 PE 3 SO Abbey Rd, Basingstoke Hants 0600726840 1060 PE 4 SO Parklands Rd, Chichester W.Sussex 0060078436 1062 PE 5 SO Lark Vale, Aylesbury Bucks 0160914941 1065 PE 5 SO Littlecote Drive, Reading 0160681066 1198 SC 3 SO Kingsway, Aldershot 160826914 1202 PC 4 SO Diamond Ridge, Camberley 0160859512 1203 PC 4 SO Burnham Drive, Bournemouth 0160061400 1206 St 4 SO Kingsway, Chandlers Ford 0160281252 1209 SC 6 SO Fairoak Road, Eastleigh 0160356842 1212 PC 8 SO Winchester Road, Chilworth, Soton 160251322 1215 SC 12 SO Maple Drive, Waterlooville 160523908 1216 SC 6 SO Commons Road, Wokingham 0016071613 1217 SC 4 SO Rex Lane, Chickerell 0160140733 1223 SC 4 SO Dumbarton Way, Caversham 0160705953 1229 DI 4 SO The Hyde, Abingdon 0160976012 1232 SC 4 SO Pound Road, Lymington 1233 ST 4 SO Rempstone Road, Merley 0160114573 1237 SC 6 SO Maldon Road, Southampton 0160270427 1238 St 3 SO Alton Road, Poole 0160018595 1241 SC 6 SO Velmore Road, Chandlers Ford 0160278261 1245 ST 4 SO Underwood Place, Milton Keynes 161099183 1528 PE 3 SO Battery End, Newbury 1709 DI 4 SO Kilnsea Drive, Lower Earley 0160740720 1711 DI 8 SO St Johns Road, Grove 0160981430 1712 PE 7 SO Park Road, Abingdon 0160975498 1791 PC 12 SO Coleridge Drive, Abingdon 0160976135 1792 PE 4 SO The Warren Caversham 0160768540 1917 PC 4 SO Virginia Way, Abingdon 0160977194 1959 DI 4 SO Three Gates Road, Cowes, Iow 0160615176 2005 St 6 SO Taunton Drive, Bitterne, Southampton 160264452 2006 ST 4 SO Rownhams Road North Southampton 0160364776 2024 DI 8 SO Elvetham Road Fleet Gu13 0160870865 2026 PC 10 SO Camp Road, Freshwater 0160645476 2106 PC 3 SO Tarn Road, Hindhead 160847778 2107 PC 3 SO Cromer Road, Portsmouth 0160484670 2108 PC 4 SO Colchester Road, Portsmouth 0160484678 2109 PC 4 SO Sudbury Road, Portsmouth 160484498 2110 PC 4 SO Eastfield Avenue Basingstoke 160723486 2143 St 4 SO Beechwood Road, Portsmouth 160411132 2205 PC 4 SO Oakwood Road, Portsmouth 160411132 2206 PC 4 SO Harding Road, Ryde, Isle Of Wight 0160630994 2209 PC 6 SO Mill Road, Yarmouth, Isle Of Wight 0160644511 2211 PC 4 SO 15 St Peter's Crescent, Bicester 0161007534 2309 DI 4 SO Reading Road Farnborough 0160830728 2318 PC 12 SO 83 Salisbury Road, Farnborough 0160831582 2328 PC 6 SO Thursley Road Elstead 0160084993 2412 PC 6 SO Eastwood Road Portsmouth 01604 2432 PC 4

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Report R6303 :

SO Littleworth Road Seale Farnham 0160850282 2434 PC 4 SW Reids Piece, Toothill, Wilts 363119207 257 SC 4 SW Dixon Way, Calne, Wilts 362264450 260 DI 4 SW Elm Road, Colern, Wilts 362377486 261 DI 4 SW North Road, Thornbury, Bristol 362051687 262 SC 4 SW Berrells Road, Tetbury, Glos 363181586 263 SC 4 SW Westfield, Shepton Mallet, Somerset 362962804 265 St 4 SW Addison Road, Newton Abbott, Devon 362723849 268 PC 4 SW Withymead Road, Marshfield, Glos 362377289 271 SC 4 SW The Butts, Westbury, Wilts 363294895 276 SC 4 SW Firbank Crescent, Warminster, Wilts SW 25T 277 PC 4 SW Willow Bank Rd, Winchcombe, Glos 605354179 280 SC 6 SW Rayens Cross Rd, Long Ashton, Bristol 362021925 285 PC 6 SW Gill Avenue, Bristol 361942476 287 PC 8 SW Welshmill Lane, Frome , Somerset 362556505 289 PC 8 SW Groundwell Road, Swindon, Wilts 363069661 290 SC 8 SW Park Street, Hungerford, Berkshire 362644764 292 PC 10 SW Trym Side, Bristol 361992546 298 PC 12 SW Sylvian Way, Shirehampton, Bristol 361988395 299 PC 12 SW Oldfield Rd ,Bath, Somerset 361822962 301 PC 12 SW Kenlem Rise, Winchcombe, Glos 0362360396 313 SC 6 SW Delamere Road, Trowbridge, Wilts 363241256 314 SC 8 SW Allington Gardens, Nailsea, Somerset 362026197 316 DI 4 SW The Uplands, Nailsea, Somerset 363392282 322 DI 4 SW Dowding Way, Bowerhill, Melksham, Wilts 362701177 326 DI 4 SW Redhill Close, Lacock, Chippenham, Wilts 362269967 328 DI 4 SW Broadmead, Trowbridge, Wilts 363239278 330 SC 6 SW Hooper Avenue, Wells, Somerset 363286573 333 DI 8 SW Hazel Lane, Almondsbury, South Glos 0363918916 347 PE 3 Brewers Lane, Badsey, Hereford & SW 568567602 348 PE 3 Worcester SW Westfield Chase, Aldbourne, Wilts 362689449 351 PE 4 SW Main Street, Clutton, Somerset 0363928250 353 PE 5 SW Manor House Road, Glastonbury, Somerset 362560073 355 PE 7 SW Cheapside, Bampton, Oxon 362754144 356 PE 7 SW Golden Close, Brixham, Devon 362235658 361 ST 3 SW Drake Rd, Newton Abbot, Devon 362727111 364 ST 3 SW Nupend, Stonehouse, Glos 363004758 368 SC 3 SW Benson Rd, Truro, Cornwall 0363255239 370 ST 3 SW Corn Gaston &Parklands, Malmesbury, Wilts 362684800 375 SC 4 SW Rue St Pierre, Ivybridge, Devon 0363550952 378 DI 6 SW Glyn Way, Truro, Cornwall. 0363263838 394 ST 3 SW St Rylands Beckington 363392049 2245 SC 4 King Edwards Avenue, Gloucester, SW 0362592245 2701 PC 6 Glocestershire Littledean Hill Road, Cinderford, SW 362380576 2716 PC 4 Gloucestershire Shakespear Road, Cheltenham, SW 362331639 2717 St 4 Gloucestershire SW Downsview Road, Swindon 363059839 2908 PC 4 SW Hawthorn Ave, Swindon 363071143 2909 PC 4 SW Weymouth Road, Frome 362556828 2915 PC 4 SW Northumbria Drive, Bristol 361968979 2988 PC 12 SW Brunel Way, Frome 036592985 2993 DI 8 SW Cropthorne Road South, Bristol 363963108 3081 PC 4 SW Filton Avenue, Bristol 361938176 3082 PC 4 SW Macauley Road, Bristol 362207919 3126 PC 4 SW St Whytes Road, Bristol 362144209 4162 PC 4 SW Shaftesbury Road, Weston-Super-Mare 363326685 4188 PC 4 SW Portway, Bristol 361974627 4189 PC 12 WA Bendow Close,Swansea 0210098603 110 SC 4 WA Brookfield Road,Bridgend 0210088588 114 SC 4 WA Ffordd Gwynedd,Wrexham 210163122 117 PC 3 WA Llandennis Ave,Cardiff 210013563 127 PC 6 WA Birchfield Cres,Cardiff WA 72T 128 PC 6 WA Lower Leigh Road,Pontypool 210071050 133 PC 8 WA Auckland Road,Newport gtrr021005 145 SC 4 WA Berkley Close,Bassaleg 0210059888 152 SC 4 WA Pine Close,Newport 210062004 156 DI 4 Page 60 of 64

Report R6303 :

WA Coeden Dal,Pentwyn 210013103 157 DI 4 WA Bryncoed Tce,Hengoed 210079789 165 ST 3 WA Glan-Ddu Tce,Tir Y Berth 210080032 166 ST 3 WA Llanedeyrn Road,Llanedeyrn 210012373 168 ST 8 WA De Breos Drive,Porthcawl 210082089 171 DI 4 WA Groves Road, Newport 210057354 174 PE 3 WA Kirrlach Close, Caldicot 210051631 175 PE 3 WA Joslin Terrace, Bridgend 210086968 176 PE 3 WA Woodland Road, Newport 210054956 178 PE 5 WA Roberts Close,Rogerstone WA 69T 183 PE 4 WA Ellis Ave, Rhyl 210144875 2015 SC 8 WA Hoel Bathafarn, Coedpoeth 210159422 2017 SC 4 WA De Muir Road, Cardiff 0210009741 2353 PC 4 WA Smith's Road, Swansea 2100104255 2354 DI 4 WA Blaen-Y-Maes Drive Swansea 210102018 2416 SC 6 WA Coed Celyn Rd, Swnasea 0210098792 2622 PC 4 WA King Street, Neath 0210095624 2627 PC 6 WA Woodside Avenue, Neath 210095185 2634 St 4 WA Queens Road Sketty 210097500 3016 PC 4 WA Heol Croes Faen, Nottage 210083246 3199 DI 8 WA Everswell Road, Cardiff 210019243 4108 ST 4 WA Heol Carne, Cardiff 210016105 4114 PC 4 WA Wordsworth Ave, Penarth 210008437 4119 PC 6 WA Greenwood Rd, Cardiff 210018683 4120 PC 6 WA Wilson Rd, Cardiff 210019770 4121 PC 6 WA Cwmbach Rd, Swansea 210101374 4127 PC 8 WA Bardsey Crescent, Cardiff 210015470 4130 PC 12 WA Canal Bank, Behind Ty Coch Way, Cwmbran 210074850 4140 DI 6 WA Off Wheatley Road, Neath 210095962 4144 St 3 WA Whitehall Road, Cardiff 210018681 4178 PC 4 WM The Ring Yardley 561441627 1308 PC 3 WM Durley Rd B'ham 561432542 1312 PC 3 WM Fleming Rd Quinton 561398406 1314 PC 3 WM Elsma Rd Oldbury 0561334450 1318 PC 4 WM Chaffcombe Rd B'ham 561437229 1323 PC 4 WM East Bank Rise Forsbrook 561147162 1324 SC 4 WM Parton Grove Weston Coyney 561176077 1329 St 6 WM Quilletts Close Coventry 561526695 1332 PC 4 WM Beanfield Av Coventry 0561544196 1334 PC 4 WM Lingard Rd Sutton Coldfield 561464210 1335 SC 4 WM Farm Av Oldbury 561336411 1338 St 4 WM Chestnut Rd Bedworth 561532474 1339 SC 4 WM Woodlands Rd Binley Wood 561519396 1341 PC 4 WM Beanfield Av Coventry 561544195 1371 PC 6 WM Ambleside Dr Worcester WM 46S 1373 SC 6 WM Old Hawne Ln H/Owen 0561328378 1374 SC 6 WM Woodside Ave South Coventry 0561544129 1377 SC 6 WM Woodlands Rd Binley Wood 561519396 1378 PC 6 WM Duncroft Ave Coventry 561536370 1379 PC 6 WM Worlds End La Quinton 561397836 1386 PC 10 WM Chaffcombe Rd B'ham 561437228 1389 PC 8 WM Rotherham Rd Coventry 561533909 1393 PC 8 WM Sandon Rd Stoke 561176589 1399 PC 8 WM Clermont Rd Stoke 561183105 1400 St 8 WM Arden Rd Saltley WM 161T 1418 PC 12 WM Malthouse La B/Ham 561445998 1421 PC 12 WM Bromford La Erdington 561457344 1422 PC 12 WM Waddington Ave B'ham 561376474 1428 SC 6 WM Slater Rd Solihull 0561479012 1431 SC 4 WM Redlands Rd Solihull 0561435023 1435 SC 7 WM Redlands Rd Solihull 0561435024 1437 SC 4 WM Lydate Rd H/Owen 561329884 1438 SC 4 WM Ronaldsway Dr Newcastle 561157254 1454 DI 4 WM Off Kingsbury Rd B/Ham 561475428 1463 SC 10 WM Woden Rd East Wednesbury 561351931 1464 PC 12 WM Birch House Rd 561160751 1473 St 6 WM Newcastle Lane 561186327 1475 St 6 WM Talbot Fields Telford 561192081 1479 PE 3

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Report R6303 :

WM Barnett Rd Willenhall 561292236 1480 PE 3 WM Tintern Rd B/Ham 561379403 1481 PE 3 WM Arden Vale Rd Knowle 561478417 1482 PE 3 WM Delius Grove 561582492 1484 PE 3 WM Elliot Drive, Warwick 561505938 1485 PE 4 WM Elgar Crescent, Pensnett 561303285 1755 ST 3 WM Thomas Lane St Coventry 561926684 1759 PC 4 WM Parkdale Rd Sheldon B/Ham 561437082 1760 PC 4 WM Berryfields Rd Sheldon B/Ham 561437096 1761 PC 4 WM Gayer Rd Coventry 561526689 1762 PC 6 WM Cranes Park Rd B/Ham 561437063 1763 PC 6 WM Parkdale Rd Sheldon B/Ham 561437085 1764 PC 6 WM Poffitt Av Coventry 561526655 1765 PC 8 WM Woodland Av Dudley 561304522 1766 DI 4 WM Rokholt Cr Cannock 561235949 1767 DI 4 WM Carriage Dr Biddulph Stoke 561138863 1768 SC 4 WM Wood Rd Gornal Dudley 561302745 1770 DI 8 WM Barlow Rd Wednesbury 0561350987 1838 PC 3 WM Hilderstone Rd B/Ham 561148092 1839 PC 4 WM Harvard Rd Solihull 561436255 1840 PC 4 WM Aldershaw Rd B/Ham 561433345 1841 PC 4 WM Knightsbridge Rd Solihull 561436080 1842 PC 4 WM Hardwick Rd Solihull 0561433762 1843 PC 4 WM Wichnor Rd Solihull 0561433449 1844 PC 4 WM Ulleries Rd Solihull 0561436197 1845 PC 6 WM Church Ave Brierley Hill 0561318100 1848 PC 12 WM Bluebell Rd Dudley 561304366 1849 DI 4 WM Stockwell Avenue, Brierly Hill 561321625 1899 DI 6 WM Hillfields Smethwick 561336780 1976 PC 4 WM Clark Street Coventry 0568629347 1977 PC 12 WM John Ward St Coventry 0561517165 1978 PC 4 WM Lincroft Cr Coventry not known 1979 PC 4 WM Grove Cr Brierley Hill 0561312665 1980 PC 4 WM Unketts Rd Smethwick 0561336770 1981 PC 4 WM Tennal Ln Harbourne 561398661 1982 PC 4 WM Lichfield Rd Covenrty 561517068 1983 PC 4 WM Headlands Covenrty not known 1984 PC 4 WM Earlsdon Av South Coventry 0561542817 1985 PC 12 WM Allesley Old Rd Covenrty not known 1986 PC 12 WM Holyhead Rd Coventry 561594984 1987 PC 12 WM Cressett Avenue Brockmoor 561316406 1989 PC 4 WM John Ward Coventry 561517163 2050 PC 6 WM Queen Isabels Av Coventry 561517080 2132 PC 6 WM Abbey Rd Smethwick 0561335342 2133 PC 10 WM Church Rd Malvern 561263845 2134 PC 12 WM Arden Av Telford 561206172 2135 DI 4 WM Cedar Road Dudley 056130437 2144 DI 4 WM 19 Botany Road, Wallsall 561354358 2165 PC 3 WM 35 Sandon Old Road, Stoke On Trent 561176724 2240 PC 8 WM 37 Firsby Rd., Quinton, Birmingham 561397849 2241 PC 12 WM 43 Ridgacre Lane, Quinton, Birmingham 561397907 2243 PC 12 WM 19 Oxford Road, Moseley, Birmingham 561420980 2252 PC 12 WM 56 Lower White Road, Quinton, Birmingham 561397881 2253 PC 4 WM 170 Lower Howsall Rd., Malvern 561263677 2257 PC 12 WM White Road, Quinton 561397804 2406 PC 4 WM Woden Road North, Wednesbury 561351185 2484 PC 4 YK Northallerton Road, Bradford 260144859 473 St 3 YK First Avenue, Horbury, Wakefield 260089489 487 SC 4 YK Grosvenor Road, Leeds 260066914 488 PC 4 YK Stainland Road, Halifax 260168958 507 PC 6 YK Lexington Drive, Hull 260046551 532 SC 4 YK Quarry Fields, Mirfield 260116460 539 DI 4 YK Vicar Lane, Ossett 260097333 548 DI 4 YK St Marys Walk, Mirfield 260117740 549 SC 4 YK Moor Close Lane, Queensbury, Bradford 260143964 552 DI 4 YK Lyndale Avenue, Cross Hills, Keighley 260156820 556 SC 4 YK Pyenot Gardens, Cleckheaton 260116409 558 SC 4 YK Waverley Avenue, Sandbeds, Keighley 260159119 561 DI 4

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YK Clarondale, Hull 260041455 562 DI 4 YK Valley View Close, Oakworth, Keighley 260159008 564 DI 4 YK Gilstead Lane, Bingley 260155439 569 DI 6 YK Oak Crescent, Leeds 260074154 577 ST 3 YK Cheltenham Gardens, Halifax 260161420 578 ST 3 YK Wellstone Drive, Leeds 260082888 581 SC 3 YK Chequerfield Lane, Pontefract 2.6E+08 582 SC 4 YK Lynwood Crescent, Pontefract 260103570 589 PE 5 YK Eaglesfield Drive, Bradford 26013748 591 PE 10 YK Golf Links Crescent, Tadcaster 260026863 593 PE 3 YK Milner Place, Bridlington 260032738 594 PE 3 YK Cross Road, Oakenshaw, Bradford 260136691 598 PE 3 YK Greenside, Oakenshaw, Bradford 260139341 599 PE 4 YK Beech Avenue, Willerby, Hull 260039673 1531 PC 3 YK Mill Lane, Otley 0260192197 1532 SC 6 YK Hookstone Road, Harrogate 260027626 1533 PC 8 YK Keighley Road, Bradford 0260141445 1535 PC 12 YK Low Lane, Clayton, Bradford 1211 1536 PC 12 YK Meanwood Road, Leeds 260072211 1537 PC 12 YK Palmer Avenue, Willerby, Hull 260048716 1538 SC 4 YK St Johns Avenue, Filey, North Yorkshire 260036845 2057 PC 3 YK Twentieth Avenue, Hull, Hu6 260052535 2060 PC 4 Burniston Road, Scarborough, North YK 260034024 2067 PC 6 Yorkshire YK Fixby Road, Huddersfield, West Yorkshire 260123357 2068 PC 6 Birchlands Avenue, Wilsden, Bradford, West YK 260154025 2074 DI 4 Yorkshire YK Furness Avenue, Halifax, West Yorkshire 260162990 2078 DI 4 YK Southmere Drive, , Bradford, West Yorkshire 260148283 2083 St 3 YK Leysholme Crescent, Leeds 260070792 2086 ST 4 YK Lea Avenue Halifax 260164963 2113 PC 4 YK Blackthorn Drive, York 260019108 3703 DI 6 YK Burnham Avenue, Bradford. 260135038 3758 PC 3 YK Leeds Road, Bradley, Huddersfield 260125064 3761 PC 9 YK Box Hill, Scarborough, North Yorkshire 260033956 3763 DI 4 YK Langdale Avenue, Bradford 260142033 3769 DI 6 YK Burnby Lane, Pocklington, North Yorkshire 260040635 3770 ST 3 YK The Fairway, Leeds, West Yorkshire 260081134 3771 ST 6 Leymoor Road, Broomroyd, Grange Road, YK 260125113 3814 PC 4 Huddersfield YK Astral Way, Sutton-On-Hull. 260131834 3861 DI 4 YK Oaken Grove, Haxby, York 260022716 3862 DI 8 YK Temple Walk, Leeds 260080752 3880 PC 4 YK Kirkstone Road, Hull 260046272 3886 PC 4 YK Scammonden, Road, Halifax, Barkisland 260190670 3891 PC 4 YK Long Ridge Lane, Upper Poppleton 617731777 3894 PC 5 YK Pudsey Road, Leeds 260181667 3908 PC 12 YK Coxwold Grove, Hull 260041932 3914 PC 4

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Appendix J Rejected Tests 13 tests (1.5% of the total number undertaken) produced results that were rejected for the following reasons: 2 were rejected due to services not being cut off at the appropriate times. These services were found after the end of the testing programme. 1 was rejected due to customer interference during test the disconnected gas supply was reconnected. 7 were rejected due to the main being of mixed material this prevented the leakage results from being assigned to one category. It is not plausible to allocate the proportion of leakage to the two categories that the site was in and as a result the data had to be rejected. 1 was rejected because the main was cement lined. This site was not felt to be representative of other mains of that material due to the cement lining. 1 was rejected due to faulty pressure data the equipment was not operating correctly during the test. 1 was rejected due to incorrect site preparation. During site preparation the plugs were not inserted correctly in the ends of the pipe.

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