Gu i d e l i n e s f o r g o o d w o r k i n g p r a c t i c e i n h i g h p r e s s u r e c o m p r e s s e d a i r ITA Working Group N°5 Health & Safety in Works

N° ISBN: 978-2-9700776-4-0 ITA REPORT n°010 / FEV 2012 ITA Report n°010 - Guidelines for good working practice in high compressed air - N°ISBN: 978-2-9700776-4-0 / FEV 2012 Layout : Longrine – Avignon – France – www.longrine.fr

The International Tunnelling and Underground Space Association/Association Internationale des Tunnels et de l’Espace Souterrain (ITA/AITES) publishes this report to, in accordance with its statutes, facilitate the exchange of information, in order: to encourage planning of the subsurface for the benefit of the public, environment and sustainable development to promote advances in planning, design, construction, maintenance and safety of tunnels and underground space, by bringing together information thereon and by studying questions related thereto. This report has been prepared by professionals with expertise within the actual subjects. The opinions and statements are based on sources believed to be reliable and in good faith. However, ITA/AITES accepts no responsibility or liability whatsoever with regard to the material published in this report. This material is: information of a general nature only which is not intended to address the specific circumstances of any particular individual or entity; not necessarily comprehensive, complete, accurate or up to date; This material is not professional or legal advice (if you need specific advice, you should always consult a suitably qualified professional). Gu i d e l i n e s f o r g o o d w o r k i n g p r a c t i c e i n h i g h p r e s s u r e c o m p r e s s e d a i r ITA Working Group N°5 Health & Safety in Works

PREPARED JOINTLY BY

INTERNATIONAL TUNNELLING ASSOCIATION WORKING GROUP N°5 - “HEALTH & SAFETY IN WORKS”

AND

BRITISH TUNNELLING SOCIETY COMPRESSED AIR WORKING GROUP >> Fo r e w o r d

At its meeting in Vancouver in 2010, International Tunnelling Association Working Group N°5, identified the need for guidance on the use of high pressure compressed air. WG5 defined this as “work in compressed air at above historical statutory limits, which in most countries are between 3 and 4 bar (gauge), and which involves the use of mixtures other than compressed natural air and can involve the use of saturation techniques”.

High pressure compressed air working was a topic of interest which had previously been addressed by the British Tunnelling Society Compressed Air Working Group and which BTS CAWG had identified as a significant development in the use of hyperbaric techniques on site for which no guidance existed.

Consequently the two organisations have come together to jointly produce the first edition of these guidelines for use by the international tunnelling community.

This document will be reviewed and revised as necessary in the light of practical experience of HPCA work on site. Comment and feedback is welcomed and should be made to the ITA Secretariat through the website www/ita-aites.org.

4 Guidelines for good working practice in high pressure compressed air >> Ta b l e o f c o n t e n t s

FOREWORD...... 4

1. INTRODUCTION...... 6

2. lEGISlation, standards, guidance etc...... 7

3. nOTIFIcations, exemptions and approvals...... 8

4. Organisation of works in HPCA...... 10

5. Safe system of work and operational procedures...... 12

6. Plant, equipment and gas supply...... 13

7. Occupational health...... 18

8. hyperbaric procedures...... 19

9. Record keeping...... 22

10. Emergency procedures...... 22

11. INFORMATION, INSTRUCTION AND TRAINING...... 23

12. acknowledgements...... 24

GLOSSARY OF TERMS AND ABBREVIATIONS...... 25

ITA Working Group n°5 – Health & Safety in Works 5 21 >> SInat fre ot dy u r c et qi o u n i r e m e n t s in a l l s t a g e s o f c o n s t r u c t i o n

1.1 Background 1.3 Minimising hyperbaric 1.5 Choice of hyperbaric exposure technique In recent years several tunnels have been built which required the application of It is implicit when undertaking HPCA High pressure, non-sat exposures only high pressure compressed air (HPCA) for work in accordance with these guidelines, permit short working periods because interventions in the head of the Tunnel that all reasonably practicable measures of the relatively lengthy Boring Machine (TBM). This is a significant should be taken to minimise the number requirements required from such development in hyperbaric activity in of persons exposed along with the pressures. Hence for exposures at tunnelling and has required the transfer pressure and duration of each exposure, pressures in excess of 5 bar, saturation of hyperbaric technology, from the diving commensurate with minimising the overall working should be considered. See Cl 8.1 industry to tunnelling. risk to the health and safety of those for further guidance. exposed. 1.2 Scope Note: there are measures such as remote 1.6 Existing statutory limits on wear detection and the use of CCTV which pressure These guidelines apply to the use of HPCA can be used alone or in conjunction with in tunnelling (including shaft sinking). other ground stabilisation techniques In many countries existing limits on To date, such work has been mainly (see Cl 1.7) to further reduce the need for exposure pressure do not appear to have associated with TBM interventions for HPCA interventions. changed since work in compressed air maintenance and repair. However it is was first regulated. Although there may not foreseeable that conventional tunnelling 1.4 Balancing medium be evidence to show how statutory limits operations may have to be undertaken in were derived, there is ample evidence that HPCA. In the HPCA work covered by these they were adequate for the requirements The guidelines are intended for use by guidelines, the pressurising medium of the tunnelling industry of the day as regulatory authorities, clients, designers, envisaged in the working chamber is records show very few exposures to contractors, insurers and others involved in compressed natural air except where pressures close to the limit. The inference HPCA work. stated otherwise. Non-air mixtures used is therefore that they were based on a Whilst this guidance is intended to for breathing are fed through a mask and degree of empiricism which reflected both apply to HPCA work as defined above, unbilical. the state of knowledge and the practical the guidance is equally applicable to working limits which could be achieved intermediate pressure exposures above with air breathing in the early to mid 20th 3.5 bar. century when most countries with statutory limits set these limits. The pressures now being considered for HPCA work are well within the range of pressures routinely experienced in offshore . Consequently it is concluded that there is nothing inherently unsafe about exposure to higher pressures per se, provided appropriate safe systems of work are adopted.

1.7 Other ground stabilisation techniques

Other ground stabilisation techniques which are utilised in tunnelling include grouting, ground treatment, ground freezing and dewatering. These guidelines deliberately give no guidance on the often complex issues around selection of an appropriate ground stabilisation technique. The guidelines apply to the use of HPCA once the decision has been made to use it.

6 Guidelines for good working practice in high pressure compressed air 32 >> PLel ga ni s n l i a nt gi o f no, rs temergenciesa n d a r d s , g u i d a n c e e t c

2.1 National legislation, 2.3.2 EN 12110 – Tunnelling Machines – 2.3.4 BS 6164:2011 – “CoP for standards and guidance Air Locks – Safety Requirements health and safety in tunnelling in the CEN/TC151/WG4 has confirmed that construction industry” These Guidelines are intended to EN 12110 would apply only to work in This British Standard has a section complement existing national legislation, compressed air within national statutory giving guidance on work in compressed standards and guidance as appropriate. limits, assumed to be between 3 and air. It complements the BTS “Guide” by 4 bar. However WG4 recognised that addressing the design of the tunnel/ground As HPCA work is still a rarely used but EN 12110 could be used to inform interface, effects of compressed air on the developing technique, few countries are requirements for air locks for use in HPCA. ground and air loss. It also gives guidance likely to have altered existing legislation Where reference is made to EN 12110, it is on a range of emergency situations which and guidance to accomodate it. the version of the standard which could arise. The principles covered are should be used. relevant to HPCA work. These guidelines should be read in Note: CEN/TC151/WG4 “Tunnelling conjunction with the current version of the Machinery” is a working group of the 2.4 Relevant guidance sources guidance documents listed in 2.3 and 2.4 European Standard technical committee – diving (and 2.5 where relevant). CEN/TC151 “Construction Machinery – Safety”. WG4 is responsible for EN 12336 The hyperbaric techniques required 2.2 ILO Convention C167 “Tunnelling machines - Shield machines, for HPCA are very similar to those for thrust boring machines, auger boring diving at similar pressures but without The International Labour Organisation machines, lining erection equipment being immersed in water. From the convention C167 on Health and Safety – Safety requirements” and EN 12110 1970s onwards, diving technology and in Construction has been ratified by 24 “Tunnelling machines — Air locks — Safety hyperbaric safety advanced greatly with countries and requires through Article 21 requirements”. EN 12336 is currently the exploitation of oil in the relatively deep “Work in compressed air”: being revised and will be harmonised as waters of the North Sea. Consequently • Work in compressed air shall be carried EN 16191” Tunnelling machinery - Safety there is much relevant guidance to be had out only in accordance with measures requirements”. from diving sources. prescribed by national laws or regulations. • Work in compressed air shall be 2.3.3 British Tunnelling Society “Guide 2.4.1 Classification societies carried out only by workers whose to the Work in Compressed Air “Classification societies” are the major physical aptitude for such work has been Regulations 1996”. international insurance companies established by a medical examination and The British Tunnelling Society (BTS) which set detailed rules for the design, when a competent person is present to document “Guide to the Work in construction and testing of equipment supervise the conduct of the operations. Compressed Air Regulations 1996” for use in the marine environment. This which was published in 2012, is a revised includes the hyperbaric systems used in 2.3 Relevant guidance sources - and updated version of the guidance diving and other underwater hyperbaric tunnelling which was formerly published by the activity. At least one classification society Health and Safety Executive (HSE) as has already developed specific rules for Although no comprehensive guidance publication L96. The BTS Guide primarily the tunnelling environment. Care should on HPCA has been identified, a number covers work in compressed air within the be taken to ensure their application is of organisations provide highly relevant existing UK statutory limit of 3.45 bar. appropriate, when transposing rules background guidance and information. However the possibility of HPCA work intended for the marine environment to the These Guidelines build extensively on the had been foreseen when the Regulations underground environment. The Contractor information which they provide. were drafted in 1996. Consequently the in Charge should be aware that these “Guide to the Work in Compressed Air rules will most likely be applied to plant 2.3.1 ITA Report N°001 Regulations 1996” recognises the use of and equipment used in HPCA work as a The International Tunnelling Association HPCA and provides extensive information condition of the insurance of the works. Report N°001 “Guidelines for good of fundamental relevance to HPCA work. Reference is made to classification society occupational health and safety practice rules in these guidelines. in tunnel construction” was published in 2008 and has a section covering work in compressed air. The report was drafted to apply within national statutory limits and consequently does not have specific requirements for HPCA work.

ITA Working Group n°5 – Health & Safety in Works 7 2 >> Le g i s l a t i o n , s t a n d a r d s , g u i d a n c e e t c

2.4.2 Diving Medical Advisory 2.6 Guidance from other Committee countries The Diving Medical Advisory Committee (DMAC) (see www.dmac-diving-org) is a 2.6.1 Germany European organisation comprising diving For non-saturation exposures, the and hyperbaric medical experts from “Druckluftverordnung” (Technical regulation civilian, military and clinical backgrounds for compressed air application) applies. which provides guidance on a range of This should be referred to along with the issues relating to the medical aspects of RAB 25 (“Regeln zum Arbeitsschutz auf hyperbaric exposure in diving. Even though Baustellen” – Rules for occupational health the much of its guidance is not relevant to and safety on construction sites). the environments in which the hyperbaric exposure occurs, some DMAC guidance is 2.6.2 Canada equally applicable to HPCA exposure. Canadian Standard Z275 .1-05 “Hyperbaric Facilities” provides 2.4.3 HSE diving guidance comprehensive guidance on requirements HSE publishes extensive guidance on for hyperbaric chambers including those commercial diving, some of which is for saturation systems. Canadian Standard equally relevant to HPCA work. Z275.3-09 provides guidance on work in compressed air. 2.5 ASME PVHO Standards

The American Society of Mechanical Engineers produces standards for pressure vessels for human occupancy (PVHO). Although reference can be made to them as an alternative to EN 12110 or Classification Society rules as a source of guidance, any tunnelling specific requirements in EN 12110 should be adopted in addition to the ASME requirements.

8 Guidelines for good working practice in high pressure compressed air 3 >> XNxxxxotifica xxxxxtions, e x e m pt i o n s a n d a pp r o v a l s

3.1 Notification of regulatory 3.2.2 Exemption 3.2.4 Variances authority The supporting evidence for an application for In some countries, the regulatory authority an exemption from regulations should include: grants variances. These are formal In some countries it is a statutory requirement • A description of the exemption sought; permissions to depart from or vary statutory to notify the regulatory authority for • A robust technical and/or medical requirements. Where there is no guidance occupational health and safety or labour justification of why the exemption is on how to apply for and issue a variance, inspection of the intention to work in considered necessary; the regulatory authority should treat them as compressed air. Whether this is a requirement • Submissions from expert advisers, if any, exemptions and/or approvals as appropriate. or not, it is strongly recommended that the supporting the exemption. relevant authority is notified and their advice • Proposals for alternatives to the matter 3.3 Demonstration of sought. exempted effectiveness of decompression regimes 3.2 Exemptions, variances and 3.2.3 Approval of alternative hyperbaric approvals procedures On completion of all HPCA work, the The package of supporting evidence for Contractor in Charge should prepare a report In countries where there are statutory limits approval of alternative hyperbaric procedures on the effectiveness of the decompression on hyperbaric exposure, and/or prescribed decompression regime should include regimes used on the project. This should be decompression procedures, it is likely that a description of the compression and based on the statistical analysis of exposure HPCA work will require formal exemption decompression procedures, exposure limits data and post-decompression physiological from or a variation in statutory requirements and breathing mixtures. Where an alternative monitoring of workers. probably accompanied by a formal approval decompression regime is proposed, the of part or all of the exposure procedures package of evidence should include: 3.3.1 Derivation of the tables to be used proposed. Similarly the use of non-air • A description of the tables to be When relevant the submission should include breathing mixtures may require exemption, approved; details of the proposed compression and variance or formal approval. As part of the • Relevant theoretical derivations; decompression regime along with information application process a robust safety case • Reports of any relevant on how the decompression tables were should be prepared and submitted to the evaluation or hyperbaric trials of the tables; derived and validated. This is not required for regulatory authorities setting out the technical • Details of relevant experience of long-term nationally recognised tables. However the reasons dictating the need for HPCA use using recognised measures of DCI choice of such tables should be justified. interventions and justification of the hyperbaric incidence where available; procedures being proposed. • A robust technical justification of the likely 3.3.2 Mathematical modelling of benefits of the proposals; decompression tables In countries where there is no statutory power • Submissions from expert advisers, if any, Physiological mathematical models of the of exemption etc, the advice of the national supporting the application; human response to pressure exist and can be regulatory authority on how to proceed, • A scheme for monitoring the overall used as part of the process of demonstrating should be sought at an early stage in planning effectiveness of the hyperbaric the effectiveness of decompression regimes. the project. procedures throughout their use on site. The models can be used to predict gas in Such a scheme should allow for post- blood levels and as part of the retrospective 3.2.1 Technical justification decompression physiological monitoring at analysis of exposure data. A relevant reference A full technical justification of the proposed the level of individual exposed persons. is HSE Contract Research Report 201/1998 use of HPCA should be made including • An assessment of the likely risks of “Decompression risk factors in compressed information on likely ground and ground water and osteonecrosis air tunnelling: options for health risk reduction”, conditions (see also Cl 5.2). It should include using the proposed procedures and a Unimed Scientific Ltd, available from www.hse. information on proposed tunnel excavation comparison of these risks with those gov.uk. and lining techniques along with information occurring from the use of the existing on the and other plant and equipment decompression tables currently used in the required for the hyperbaric interventions country concerned.

ITA Working Group n°5 – Health & Safety in Works 9 3 >> Notifications, e x e m p t i o n s a n d a p p r o v a l s / 4 >> Or g a n i s a t i o n o f w o r k s in HPCA

3.3.3 Statistical analysis 4.2 Notification of public 4.5 Expert hyperbaric advice A number of recognised parameters for emergency services reporting the results of statistical analysis of The Contractor in Charge should have exposure data are available. Where sufficient The Contractor in Charge should notify the access to expert hyperbaric advice. Likely data exists it is recommended that single public emergency services for the area of topics with which the hyperbaric expert(s) exposure risk factors are used to calculate the works, of the HPCA work. In addition should be familiar include international the incidence of decompression illness and any off-site facility operating a hyperbaric practice in hyperbaric exposure, plant and the standardised bends ratio is used for chamber to which HPCA workers might equipment, the availability and selection comparison between datasets. Both measures be taken in an emergency should be of appropriate decompression regimes, are described by Lamont and Booth in “Acute notified of the typical exposure regimes gas and breathing mixtures, saturation decompression illness in UK tunnelling”, Proc being operated on site, the decompression and TUP techniques if appropriate and Inst of Civil Engineers, London, Paper 14384, being undertaken along with the breathing human physiology relevant to hyperbaric Nov 2006. mixtures and gases used. There should be exposure. discussions between the CMA along with 3.3.4 Details of personnel, expert advisers the contractor’s hyperbaric experts and 4.6 Roles to be discharged by etc the hyperbaric facility over the maximum personnel The submission should include details of pressure capability of the facility and the qualifications and expertise of the main possible treatment regimes which that It is essential for the execution of HPCA work personnel to be used in overseeing HPCA facility could/should provide, to reflect in a healthy and safe manner that a number work along with similar details for expert the exposures being undertaken on site. of personnel are nominated by the Contractor advisers to the project The facility should have contact details of in Charge to take on various roles relating to a responsible person on site with whom the management or undertaking of the work. 3.4 Prohibition on the use of contact can be made at any time. All those nominated should be competent and non-air breathing and have had relevant previous experience mixtures 4.3 Emergency planning as appropriate, of managing, overseeing or undertaking work in compressed air or other Where national regulations do not allow Given the relative rarity of any compressed high pressure hyperbaric exposure along the use of oxygen and/or non-air breathing air tunnelling work, the local emergency with knowledge of the tunnel environment. mixtures, additional exemptions, approvals or services may have had no experience Given the rarity of HPCA work, it is likely variances should be sought to cover their use. of dealing with hyperbaric emergencies. (and could be desirable) that for those The principles for such applications, set out Therefore the Contractor in Charge managing or overseeing the work, part of elsewhere in this clause should be followed. should assist the services in planning their that experience would have been gained response to an on-site emergency. That from a diving support role in the offshore 4.1 Contractor in charge assistance should extend to the provision industry. Those managing or of equipment and training facilities as overseeing HPCA work do not need to hold Experience has shown that there should necessary. Where the emergency services diving qualifications but should hold relevant be a contractor with overall responsibility are unable to respond, and this is likely hyperbaric support qualifications (see the BTS for the HPCA work – the Contractor in to be the norm, the Contractor in Charge «guide»). Charge. The Contractor in Charge should should make provision for emergency It is recommended that the personnel and the be able to provide the senior personnel response from within his own resources. roles set out in the BTS «guide» are adopted to manage the HPCA work from his own for HPCA work but with the changes noted resources. The Contractor in Charge 4.4 Emergency exercises below. should be responsible for ensuring that all plant and equipment necessary for HPCA The Contractor in Charge should work with 4.6.1 Hyperbaric supervisor work along with the personnel to operate the emergency services to allow them to For HPCA work the role of the hyperbaric and maintain that plant and equipment, undertake simulations and joint exercises supervisor as described in the BTS «guide» are immediately available on site. The to improve their ability to respond to should be extended to overall control and recommendations in the BTS “Guide”, emergencies. Such exercises should be coordination of both the hyperbaric and on personnel required and management undertaken early in the works period and tunnelling aspects of each intervention. The of work in compressed air, should be at intervals of not more than 12 months hyperbaric supervisor would effectively be a followed. thereafter. deputy to the “person in charge”. The person filling this demanding role should have had experience of HPCA work and also extensive experience of the tunnelling environment.

10 Guidelines for good working practice in high pressure compressed air 4 >> Organisation o f w o r k s in HPCA

4.6.2 Gas attendant 4.6.5 HPCA worker selection 4.6.6 Saturation workers When deemed necessary by the Those being exposed to HPCA should be Because of the nature of saturation hyperbaric supervisor, there should be a medically fit. In addition they should be working, its psychological and social person responsible for the organisation of instructed in and have sufficient knowledge impact requires special qualities in those gas supplies on site. Such a person should of the risks of hyperbaric exposure to doing the work. No-one should be have had experience of the management be able to work safely in a hyperbaric considered for saturation working unless of gas supplies in saturation diving as tunnelling environment using non-air they can demonstrate having successfully well as an appreciation of the tunnel breathing mixtures. They should preferably undertaken such work previously in either environment. have had previous experience of working the diving or tunnelling industry or have in hyperbaric environments in tunnelling. undergone specific training and been 4.6.3 Lock attendant Inevitably however, because of the rarity of assessed as suitable. HPCA workers The lock attendants should have had HPCA work, they may come from a diving should ideally hold an offshore commercial previous experience of lock keeping at background. If so they should demonstrate diving qualification in saturation similar pressures to those to be used their ability to transfer their skills to HPCA techniques. Appropriate internationally on site. They should also have had in the tunnelling environment. There are recognised qualifications are listed on the experience of using exposure techniques likely to be benefits in HPCA work from HSE website at http://www.hse.gov.uk/ and breathing mixtures similar to those to building a team of workers made up from diving/qualifications/approved-list.pdf. be used on site. This experience may have both diving and tunnelling backgrounds. been gained in the diving industry however familiarity with the tunnelling environment is also necessary. Lock attendants should also control the hyperbaric aspects of TUP shuttle use.

4.6.4 Umbilical tender When using line fed masks, there should be a person in the manlock or intermediate chamber (see Cl 6.9) to tend the umbilicals of those in the working chamber. One person can tend no more than two umbilicals simultaneously.

ITA Working Group n°5 – Health & Safety in Works 11 5 >> Sa f e s y s t e m o f w o r k a n d o p e r a t i o n a l p r o c e d u r e s

5.1 Safe systems of work 5.4 Face intervention 5.5 Refilling head with slurry procedures whilst decompression still The requirements for safe systems of work going on set out in the BTS “Guide” are generally Before any face intervention takes applicable to HPCA and should be place, the stability of the ground and the 5.5.1 Slurry TBM adopted with modifications as necessary availability of suitable protective measures On a slurry TBM, the cutterhead should be to reflect the higher pressures. No work necessary to enhance stability should be refilled with slurry as soon as possible after should be carried out on the TBM which confirmed. HPCA work has been completed and the could endanger those undergoing HPCA Before anyone enters the manlock to be HPCA workers are sealed in the manlock, exposures whilst work in HPCA is being compressed, the working chamber should to maintain face support. This requirement undertaken. Additional requirements are have been pressurised and air pressure may conflict slightly with requirements in set out in these guidelines. maintained for at least one hour. All valves documents such as the BTS “Guide” or EN should have been shown to be functionally 12336 regarding energising of equipment on 5.2 Face support and air loss operative. the TBM during hyperbaric interventions, but it is an essential precaution for HPCA work. It is of fundamental importance to the 5.4.1 Slurry TBM safe execution of HPCA work that the On a slurry TBM, slurry in the excavation 5.5.2 EPB TBM stability of the ground is maintained along chamber should be allowed to seal the Restarting an EPB in a controlled manner with the structural integrity of the tunnel face to minimise air leakage, before an after an intervention is a highly critical lining. Calculations should be prepared intervention takes place. Ensuring that the activity especially for larger diameter to demonstrate that these requirements bentonite slurry, used prior to or for refilling machines. Depending on the face are being met. Independent checking the excavation chamber during an permeability two different procedures (Category 3) of the calculations should intervention, has the correct properties and are possible. If the face is permeable, be undertaken. In addition, it is important is subject to strict quality control of the bentonite suspension should be to ensure that the correct air pressure is bentonite slurry is an essential aspect of pumped into the excavation chamber maintained in the working chamber without the overall safety of the HPCA work. before restarting the advance. In less excessive air loss. The design input data permeable soils, it is assumed that the should be updated as actual data on water 5.4.2 EPB TBM TBM will restart without the need to refill table and the geological strata become In permeable ground the excavated the excavation chamber with bentonite available from site (see also Cl 1.3). The material in the excavation chamber should suspension. calculations should be submitted as part be mixed with bentonite slurry during the Note: Filling the chamber with bentonite of the technical justification required under last advance cycle before entry to the may produce a chamber fill that its too Cl 3.2.1. excavation chamber takes place. liquid to be discharged via the screw Additional sources of air loss such as In cohesive ground the conditioned conveyor whilst maintaining full pressure around the tailskin of the TBM should muck in the excavation chamber can be control. The restarting procedure be considered and appropriate remedial lowered without prior injection of additional eliminates any information about volume action taken if required. bentonite suspension. loss or mass balance for a significant amount of time and needs very stable face 5.3 Duty lock attendants conditions.

There should be two lock attendants 5.6 Inching of cutter head on duty at a hyperbaric control panel whenever the health and safety of anyone When designing a TBM for HPCA use, in saturation or undergoing HPCA due account should be taken to ensure exposure is dependent on that panel. the requirements in EN 12336 relating to access to the cutter head or excavation chamber and rotation of the cutter head in jog mode can be complied with when access is by means of a manlock.

12 Guidelines for good working practice in high pressure compressed air 5 >> Sa f e s y s t e m o f w o r k a n d o p e r a t i o n a l p r o c e d u r e s / 6 >> Pl a n t , e q u i p m e n t a n d g a s s u p p l y

5.7 Access in cutter head In the absence of national requirements, Electrical power to essential services in the the plant and equipment shall meet the working chamber should be supplied from The increased difficulty in moving requirements of these guidelines along appropriate low voltage sources situated around the cutter head and excavation with the requirements in the BTS “Guide”, outside the working chamber. chamber when wearing an umbilical EN 12110 and relevant classification fed mask should be recognised during society rules. 6.3 Access and working space machine design and construction so that on TBM appropriate access can be provided. Assisting the Contractor in Charge in complying with this requirement is The TBM should be designed and 5.8 Welding, cutting and other an important part of the hyperbaric constructed to provide adequate working hot work supervisor’s duties. space to access and operate the manlock safely. When HPCA operations are being Welding, burning and other hot work shall 6.1.2 Saturation operations undertaken a working platform should only be carried out in HPCA in accordance In addition to the requirements above, extend for at least 2m on the free air side with a permit to work system. Those for saturation exposures a transfer under of the manlock door to provide working undertaking such work should normally pressure shuttle, a saturation living space and to facilitate the removal of a wear outer garments made from a highly complex on the surface for storage of casualty from the manlocks. The working flame resistant material such as Nomex personnel under pressure and handling platform should also accommodate the or equivalent. These garments should equipment for the TUP shuttle shall be workstation for the lock attendant and the completely cover the head, neck and torso provided. air lock control panel. as well as covering the shoes. Note: if space on the TBM is limited, the Notes: There should be a person 6.2 Restrictions on HPCA due to working platform may be a temporary immediately available and capable of tunnelling considerations structure which is set up only for the responding to an outbreak of fire during duration of the HPCA work. hot work. In order to undertake HPCA work safely a It is important to ensure the correct considerable amount of space is required Likewise there should be a clear path to dimensioning and installation of welding on the TBM. This is particularly relevant permit the passage of the TUP shuttle from supply cables as there have been incidents to TUP operations and hence saturation its transport vehicle to the manlock. This in the past in which hot cables have been exposure. The geometrical constraints this area should be adequately lit. a source of ignition. presents have a significant bearing on the minimum diameter and type of TBM on 6.4 Minimum lock dimensions 5.9 Use of explosives which HPCA work can be undertaken. The dimensions of the manlocks should Explosives should not be used under It is suggested that geometrical constraints not be less than those set out in HPCA. Non-explosive techniques for rock make TUP using the TBM , and EN 12110. bursting should be used instead. hence saturation working, impractical on EPB machines below 6 m in diameter 6.5 Location of living habitat 5.10 Clamping of bulkhead because of conflict with the screw doors conveyor and erector and on slurry TBMs The saturation living habitat should be below 5 m in diameter because of conflict located on the surface in a purpose built It should be possible to clamp shut the with the erector. structure and fully protected from adverse door between a manlock chamber and the weather and fluctuations. working chamber. In smaller tunnels where it may not be There should be a workstation for the lock possible to use a TBM airlock, it will be attendants and the hyperbaric control 6.1 Plant and equipment necessary to install one or more bulkheads panel. in the tunnel. As much of the TBM backup 6.1.1 All HPCA work equipment as possible should be moved The structure should be lit and heated/ The Contractor in Charge should ensure suitable back to allow the bulkhead(s) to be cooled as necessary. The structure should and sufficient plant and equipment is available positioned close to the rear of the TBM be protected by a water spray or high on site, whenever needed, to undertake safely shield. In particular all hydraulic fluid tanks pressure water mist fire extinguishing and without risk to health, both the HPCA work, and grease injection stations should be system. and any action which may be necessary in the removed. Major electrical installations event of a reasonably foreseeable emergency should be de-energised. connected with the HPCA work.

ITA Working Group n°5 – Health & Safety in Works 13 6 >> Pl a n t , e q u i p m e n t a n d g a s s u pp l y

6.6 Suitability of plant and 6.9 Umbilicals 6.10 Communications equipment Each person in the working chamber All masks or helmets for use in the All plant and equipment should be suitable should have a single multiline umbilical working chamber should be fitted with for the maximum foreseeable working supplying breathing mixture and an appropriate two way communications pressure taking into account seasonal communication lines to that person. The system. For non-sat exposures, an integral ground water variations or tidal variations umbilical casing should protect the lines communications system is required as appropriate. from damage. Where there is a need whenever the mask or helmet has the for an emergency supply of breathing potential to interfere with normal verbal 6.7 Inspection maintenance and mixture, a second breathing mixture communication. testing supply line should be provided in the umbilical. To permit rapid evacuation of 6.11 TUP shuttle The Contractor in Charge should ensure the working chamber in an emergency, there are formal inspection maintenance all umbilicals should originate in a place The transfer under pressure shuttle and testing procedures for the plant of relative safety outside the working should be designed and constructed and equipment, taking account of the chamber. This can be in the manlock or in accordance with relevant standards maximum foreseeable working pressure. in an intermediate chamber which can e.g. classification society rules and This should also take account of national be securely isolated from the working relevant principles for airlocks. Its size requirements for the inspection and testing chamber. This intermediate chamber should reflect the guidance on minimum of pressure systems. They should take (motor chamber in the illustration below) dimensions in EN 12110. The TUP shuttle account of the requirements of the BTS can be considered as first point of escape should be of double chamber construction “Guide”, EN 12110, relevant classification or safe area but should not be considered as for manlocks. The shuttle should society rules or the requirements of the as manlock chamber for compression or be fitted with all necessary life support insurers of the Contractor in Charge decompression purposes. There should systems including appropriate backup should be adopted. Full records should be then be provision for transfer to the capacity. kept of all inspection, maintenance and manlock chamber whilst still breathing the testing. appropriate breathing mixture. 6.12 Coupling

6.8 Emergency breathing supply There should also be an on-board system Pressurised systems should be fitted to supply breathing mixtures to those in with safety interlocks where necessary, to Where the working pressure is above the TUP shuttle. It should be set up in a prevent any unintentional pressurisation 5 bar, there should be the immediate way which will not impair the operation of or de-pressurisation, or uncontrolled loss capability to supply an emergency the access door(s) between the man lock of pressure. Particular attention should be breathing mixture to each person under and the transfer shuttle. paid to chamber mating systems, and food pressure in the working chamber. It should comprise a suitable mask or helmet and independent source of breathing mixture. The quantity of emergency breathing mixture available shall be at least sufficient to allow all persons under pressure to return to the manlock and to remain on the emergency supply until breathing from the masks in the manlock or from the manlock atmosphere itself, can be established with a reserve of at least 10 minutes (see Cl 6.24).

Example of typical intermediate chamber arrangement on slurry TBM

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and equipment locks. The requirements in and tyres as relevant. A “double shot” hyperbaric operations for at least the time the BTS “Guide” and EN 12110 regarding system may be required to cover the tyres taken to perform decompression or to the opening of doors should be observed. of rubber tyred vehicles to counter re- remove those under pressure from the ignition of the tyres. tunnel. Such equipment includes lighting It should be possible to pressurise the and communications systems for the lock trunking with either air or breathing Movement of the shuttle should preferably attendant’s station. mixture. be by sliding or jacking. The movement path should be designed avoid the need to 6.16 Air and gas supply to TUP It is imperative that it should be impossible lift the shuttle by crane whenever possible. shuttle to open the mating clamp when the Where craneage for TUP handling, is trunking between the TUP shuttle and required, the crane must fully meet The TUP shuttle should be mounted on a the PVHO with which it is being mated, recognised standards for personnel lifting. support frame. The frame should have the remains under pressure. The clamping In the absence of national requirements at capability to carry an appropriate quantity mechanism should be equipped with an the place of use, a factor of safety of 10 of compressed air and breathing mixture interlock which makes it impossible to should be applied to the hoist ropes. to maintain pressure in and life support to release a clamping mechanism in the event the shuttle for at least 12 hours longer than that an undesirable drop in pressure would All mechanized equipment for TUP the predicted journey time. The quantity then take place. handling should be considered to be an of compressed air should as a minimum essential service and meet the relevant be sufficient to pressurise the shuttle to Appropriate performance criteria for requirements for continuity of power working pressure twice, from atmospheric coupling systems including mating flanges supply in EN 12336. pressure. There should be additional non- can be found in classification society rules. return valved fittings on to which additional Germanischer Lloyd has a set of rules During all these movements, the life air and/or breathing mixture supplies can specifically covering HPCA work. support system for the shuttle should be connected in an emergency. Note: the term “NATO flange” seems to be remain under the direct control of a lock used to denote a flange to STANAG 1079. attendant . This can temporarily be the 6.17 Shuttle doors There is no European or international team leader inside the capsule provided standard for mating flanges and clamps. he is competent to do so and the internal Internal communicating doors in the TUP equipment of the capsule is properly shuttle should be shut, and a seal should The person operating the clamping designed to allow control to be exercised be obtained when mating or unmating mechanism must make sure that opening from inside the capsule. At any time, a to a manlock or the transfer of personnel it will not cause an undesirable drop in lock attendant outside the shuttle should or equipment is taking place. These pressure. There should be a clearly defined be able to take over full control of the life doors should not be opened again until method for incrementally increasing or support system. the internal door between the transfer decreasing trunking pressure as part of chamber and the connecting tunnel has clamping procedures. 6.14 Emergency transfer from been shut. lock to dedicated vehicle 6.13 Movement of TUP shuttle 6.18 Colour coding of gas to/from and around the TBM There should be sufficient cylinders and pipework and/or diversity in the handling system, Transport of the TUP shuttle in the that a failure of one part of the system Gas cylinders and pipework should be tunnel should be by a dedicated vehicle. does not prevent transfer of the TUP colour coded in accordance with national There should also be a standby vehicle shuttle to the dedicated vehicle. standards in the country of use or where available in the tunnel to move the shuttle no such standards exist, in accordance in the event of breakdown. There should Tunnel workers involved in the shuttle with an internationally recognised colour be appropriate mechanical handling transfer should have ready access to self coding scheme such as EN 1089-3: 1997 equipment to facilitate the transfer of the rescuers. “Transportable gas cylinders . shuttle between vehicles. identification (excluding LPG). Colour 6.15 Emergency power coding” using the colours for set out for All vehicles involved in TUP transport continuity “gases used in diving”. An alternative should have a fixed, manually operated, standard is ISO 32:1977 “gas cylinders for on-board fire protection system covering All necessary steps should be taken medical use – marking for identification of motor compartments, fuel tanks, to ensure continuity of power to safety content” . switchgear, transmission systems, wheels critical equipment associated with the

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6.19 Man lock control panel to enable the lock attendant(s) on duty, to 6.24 Gas or breathing mixture continue to operate the panel even when quantity The TBM should be designed to the tunnel atmosphere is irrespirable. The incorporate a panel from which all air supply should have a minimum duration 6.24.1. Primary gas supply hyperbaric operations on the TBM can of 3 hours. In addition, there should be a The quantity of each breathing mixture be controlled. It should be remembered self rescuers for each attendant on duty. required in the tunnel for the HPCA work that unlike in intermediate pressure including decompression, along with compressed air working, it may not When not in use, the panel should be an allowance for leakage, wastage and be safe to breath the high pressure protected from dirt ingress and damage contingencies should be calculated. compressed air used as the pressurising either by a lockable cover or by removing medium because of the risk from nitrogen the panel. If the panel is removed all 6.24.2. Secondary gas supply narcosis or . Accordingly, services to the panel should be securely A secondary gas supply of at least the gas control of the HPCA work is a safety- capped. volume required for decompression plus critical operation. 1/3 the primary gas supply for the working 6.20 Face pieces - masks or phase of the exposure should be provided During HPCA work, this panel, the helmets in the tunnel. manlocks and all services necessary for their safe operation should be considered The most suitable mask for purpose, 6.24.3. Emergency gas supply “essential services” (term as used in EN should be used, taking account of For HPCA work at pressures above 5 12336), on the TBM . It should be located the need to provide security of fit and bar, an emergency gas supply equivalent close to the manlocks on the TBM. The to minimise inward leakage. Full face in volume to the secondary supply panel should be laid out according to masks or helmets should be used in should also be provided in the tunnel. good ergonomic principles and should the working chamber for sat exposures The emergency gas supply should be incorporate the following: where the pressurising gas is different connected to the spare gas line in the • All necessary pressure gauges and to the breathing mixture. The breathing umbilical. valves; resistance should meet diving industry • A digital clock with both real time and standards. 6.25 Separation of oxygen stopwatch facilities; supply from breathing mixture • A mimic diagram showing the layout, 6.21 Voice scrambling due to supply direction of operation and function of all use of helium valves and gauges; There should be separate supply lines • Results of analysis of gas and breathing Some voice distortion can be expected for oxygen and breathing mixtures along mixtures; from helium based breathing mixtures and with separate masks, umbilicals and • Pressure of gas in the supply cylinders; appropriate equipment should be provided connection manifolds. • Computing facilities for recording and to compensate for that distortion. storing exposure and decompression data; • Essential communication links; 6.22 Excavation chamber • CCTV display of the inside of each temperature manlock compartment; • Temperature gauge for each Steps should be taken to ensure that no compartment and the working chamber ; one should enter the excavation chamber when the TBM has just stopped and The control panel should be provided with the temperature in it exceeds 28°C. The an un-interruptible power supply. Seating excavation chamber temperature should for the lock attendant at the panel should be displayed on the hyperbaric control be provided. The area should be lit to a panel. minimum standard of 100 lux at working Note: a water spray cooling system for the surface level. Emergency lighting with a cutterhead can reduce waiting time. minimum duration of 12 hours should be provided. 6.23 Oxygen safety

The hyperbaric control panel should be This is extensively covered in the BTS fitted with sufficient air-line fed full face “Guide”. masks to provide a supply of respirable air

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6.26 Gas or breathing mixture 6.28 Gas mixing 6.30 Provision of gas in the sourcing tunnel For sat exposures, it may be preferable Gas and breathing mixtures should be to have a gas mixing and reclaim plant on The Hyperbaric Supervisor should confirm sourced from a reputable supplier normally site when the quantity being processed that the volume of breathing mixture supplying the medical or diving sectors. is sufficiently large to make it reasonable required for each supply is available in The supplier should be able to demonstrate to do so. The gas mixing and reclaim the tunnel and on the TUP shuttle, if that control of gas purity and blending of operation should be set up as a stand- being used, before HPCA work begins. breathing mixtures conforms to a quality alone operation separate from any HPCA Immediately before use he should satisfy assurance scheme complying with an activity and preferably run by a reputable himself that the composition of each internationally recognised standard such gas supplier. The plant should operate cylinder of breathing mixture is correct. as ISO 9001. Gas purity should comply in accordance with a quality assurance He should do the same for any oxygen with national standards in the country scheme certified as conforming with ISO required for decompression purposes. of use or where there are none, with a 9001. recognised standard such as the current 6.31 Loss of flow version of BS 8478 “Breathing gases for Cylinders of gas to replenish the stocks on diving and hyperbaric applications” or EN site should have their purity confirmed on Where more than one person is being 12021 “Respiratory protective devices. arrival at the gaz mixing and reclaim plant. supplied by umbilical from a single Compressed air for breathing apparatus”. panel, severance or disconnection of Before leaving the plant for re-use in HPCA one umbilical should not result in loss or It is essential that all gas including that work, every cylinder should be tested to deprivation of supply to the others being used to form breathing mixtures, should check its composition and purity meet the fed from that panel. be of medical or diving quality. For routine data marked on the cylinder. HPCA operations only pre-mixed breathing 6.32 Cleaning and disinfection mixtures should be used. All gas or breathing mixture supplied from of masks the plant should be treated as being from 6.27 Sampling and testing an off-site supplier and subject to the The cleaning and routine disinfection of sampling and testing in Cl 6.25. the person masks is important to prevent the growth The Contractor in Charge should ensure all testing the gas or breathing mixture on of micro-organisms including fungi, gas or breathing mixtures are sampled on delivery to the HPCA work should not be yeasts, bacteria and viruses. Fungi are delivery to site and again immediately prior the same person as tested that cylinder one of the most likely contaminants and to use to confirm their composition is as prior to dispatch from the mixing plant. these can produce large quantities of intended. The Contractor in Charge should spores. Inhalation of these spores can ensure that on delivery to site, all gas or The Contractor in Charge should not cause an allergic reaction in the lungs, breathing mixture cylinders are properly permit the piecemeal mixing of small producing potentially life-threatening colour coded. Where more than one gas quantities of breathing mixture on an ad- conditions, particularly in those individuals or breathing mixture is used on site, the hoc basis for use in HPCA exposures. who may be predisposed to allergy. Contractor in Charge should ensure that The recommendations of HSE Diving proper arrangements are in place for the 6.29 Oxygen sampling Information sheet N° 12 “Cleaning of diving separate identification, marking, storage equipment” should be followed. and handling of each to prevent accidental For all exposures where the breathing misuse. mixture is supplied from cylinders, there 6.33 Storage of masks should be direct sampling of the supply to the masks immediately downstream After cleaning, masks and helmets of the control panel to permit analysis of should be bagged and stored in a clean the oxygen content. Analysis should be environment. to an accuracy of +/- 0.1% by volume. An audible alarm should sound when the oxygen deviates by more than +/- 1% by volume from the required oxygen content.

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7.1 Provision of occupational 7.3 Heat strain in the is an acceptable substitute. health advice hyperbaric environment A minimum of two trained diver medics should be at pressure in the chamber The Contractor in Charge should appoint Those undertaking heavy physical work system. Fewer than two could result in an occupational health doctor, the in the hyperbaric environment are at risk the situation where the only trained diver “Contract Medical Adviser” (CMA), to from heat strain. Wearing the full face medic is the casualty. advise on all aspects of occupational masks required for efficient breathing health arising from the HPCA work. That purposes can further increase the risk. 7.6 Biological infections doctor should hold a recognised specialist The risk arises from the reduction in professional qualification in occupational body cooling from sweat evaporation, Bacterial and fungal infections can readily health and be familiar with the tunnel due to the pressurised atmosphere. The occur in saturation living. The guidance environment and competent in current normal indices by which heat strain risk from the DMAC should be observed. No good practice in is assessed, such as wet bulb globe one suffering from such infections or the for the pressures anticipated along with temperature are for normobaric conditions ear, nose or throat infections which are the medical, social and psychological only (including exposure to sunlight) normally a bar to entry into compressed air problems of saturation working where and should not be applied to hyperbaric should undertake saturation exposures. appropriate. The doctor should act as the exposure without first seeking expert professional leader for the medical aspects advice. 7.7 Physiological monitoring of the HPCA work throughout its duration. The CMA needs to be on call whenever an 7.4 General health care for 7.7.1 Use of physiological monitoring HPCA operation is in progress. those living in saturation It is recommended that physiological monitoring of tunnel workers post- 7.2 Health assessment In addition to normal occupational decompression, should be adopted as a health provision, for saturation working technique for assessing the effectiveness All those undergoing HPCA work should the Contractor in Charge has to make of decompression regimes in real time. be subject to a health assessment regime provision for the general physical and The monitoring should be undertaken by appropriate to the pressures being used. mental healthcare and dental healthcare of recognised specialists using standard Where appropriate national requirements those living in saturation. The CMA should protocols. Techniques available include do not exist, the regime should take be able to advise on this matter also. Doppler monitoring and ultrasonic the form of a stringent annual medical scanning. Research is ongoing to exanimation to establish fitness for 7.5 improve the interpretation of the results HPCA work coupled with periodic health in the context of tunnelling exposure. checks throughout its duration, to ensure 7.5.1 General requirements The Contract Medical Adviser should be continuing fitness for such work. The CMA The Contractor in Charge should ensure competent to advise on the use of should advise on the form and content of there is adequate availability of emergency these techniques and other indicators of the examination and should undertake the medical and first aid facilities for those clinical decompression stress. examinations unless national requirements under pressure. This should cover the dictate otherwise. Reference can be made working chamber, airlocks, any TUP 7.7.2 Monitoring frequency to the BTS « guide «. The results of the facilities and the living accommodation if in For tables with no history of satisfactory examinations should be recorded. Clinical saturation. use, all persons exposed should be records should be retained by the CMA in subject to physiological monitoring after his archive in a secure fashion complying 7.5.2 Non-sat exposures each exposure, until the effectiveness of with recognised professional standards. All persons undergoing non-sat exposures the tables has been established. Thereafter should have had basic first aid training. a representative sample of exposures Anyone intending to enter saturation should be checked to confirm the ongoing conditions should have a medical check 7.5.3 Sat exposures effectiveness of the tables within the 24 hours before entering All personnel undergoing saturation saturation, to confirm their fitness. exposure should have had basic 7.7.3 Doppler monitoring hyperbaric first aid training. This training Relationships exist between bubble score should cover the use of common items and what is considered an unacceptably of first aid equipment including oxygen high risk of DCI. Because of inter and administration systems. In the absence intra-individual variation, no indication of of an appropriate hyperbaric first aid the absolute risk to the individual can be qualification, a diving first aid qualification inferred from personal Doppler scores.

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Based on the Kisman Masurel scale, it is recommended that continued use of a particular decompression schedule be assessed if more than 20% of individuals monitored routinely have Doppler scores of grade III or above. Whilst any grade IV score is considered an unacceptably high risk of DCI, it is not per se a reason to give that person a prophylactic recompression treatment.

7.8 Medical equipment to be held at the site

It should always be possible to undertake emergency recompression on site with suitable supporting medical equipment available. In addition it should be possible to monitor blood pressure, pulse rate along with the mood and state of confusion of a casualty. Blood pressure and pulse rate can easily be monitored automatically.

Where sat exposures are being undertaken in a location without ready access to public emergency medical services, the medical equipment and supplies set out in the current edition of “Medical Equipment to be Held at the Site of an Offshore Diving Operation” DMAC 15 should be available on site.

7.9 Assessing fitness to return to HPCA work after decompression illness

No one should be exposed to HPCA following a decompression illness event until declared fit by the CMA.

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8.1 Choice of routine exposure dose (OTD) or oxygen toxicity unit (OTU)). 8.4 technique Limits should be placed on maximum daily and weekly UPTD arising from hyperbaric Trimix may be considered as an alternative Routine non-sat exposures at high exposure. Hyperbaric oxygen dose should to or for saturation exposures. pressure allow for only short working be kept as low as possible consistent with Trimix is probably the breathing mixture of periods (typically 45 minutes at 6 bar (g)). good hyperbaric practice. Recommended choice for non-sat exposures at pressures Such exposures permit inspection and maximum limits for routine exposure are above 3.5 bar because it reduces gas limited maintenance only to be undertaken. 400 UPTD daily and 2000 UPTD over density and the narcotic effects of Where significant working periods are any period of seven consecutive days. It nitrogen. required for major maintenance, saturation should be noted that additional oxygen working should be undertaken. When exposure will be incurred if therapeutic 8.5 Nitrox the exposure pressure exceeds 6 bar recompression becomes necessary. The the useful working period available with ongoing risk of oxygen toxicity should be Nitrox may be use for exposures around non-sat exposures but still adhering to reviewed regularly by the contract medical the interface between the intermediate and the 2 hour decompression limit (see Cl advisor. high pressure exposure range but is of little 8.8) becomes impracticably short and use in normal HPCA work because of the saturation exposure should be considered. 8.3.2 Nitrogen relatively limited range of pressures over For safety reasons, saturation exposure Nitrogen is a narcotic gas at high partial which it can be used should always be undertaken at pressures pressures. It also has a high gas density of 7 bar and over. which makes the more 8.6 Basic principles in selecting strenuous. Exposure to compressed breathing mixtures 8.2 Minimum oxygen content in natural air at up to 5 bar is accepted cylinders in some diving legislation. However There is considerable flexibility when the narcotic effect of nitrogen at such selecting the proportions of each gas in All gas cylinders delivered to site should pressures is considered to create an the mix but the following principles should contain at least a sufficient concentration unsafe and inefficient working situation. be adhered to: of oxygen to support life were they to be • The oxygen content of the mix for non- used in error. Helium cylinders should Compressed air or any breathing mixture sat exposures should never be less than contain a minimum of 2% oxygen by in routine use containing nitrogen, should 16% and the PO2 in the mix should never volume. Nitrogen cylinders should contain provide the user with a of exceed 1.6 bar in use. For sat exposures a minimum of 16% oxygen by volume. nitrogen (PN2) not exceeding 3.6 bar. This the PO2 in storage should be between limit is equivalent to breathing air at 3.5 0.35 and 0.45 bar. 8.3 Gas properties and limits of bar (gauge). Due to the narcotic effects of • The nitrogen content should not give a exposure nitrogen, caution should be exercised in PN2 of more then 3.6 bar in use. breathing air giving a partial pressure of • It is preferable to select a breathing

The following properties of gases and nitrogen (PN2) of 3 bar and over. mixture which reduces the gas density. exposure limits should be taken into • It is preferable to select a single mixture account when designing a breathing 8.3.3 Helium which satisfies the above. mixture Helium is a relatively rare and hence expensive gas. It has a low gas density 8.3.1 Oxygen which facilitates breathing in HPCA at Oxygen is toxic at high partial pressures. high work rates. It also has a high thermal Consequently any breathing mixture in conductivity which can be beneficial in routine use should provide the user with countering the effects of heat strain. Some oxygen at a partial pressure of between voice distortion can be expected from 0.2 and 1.6 bar. helium based mixtures. Exposure to helium at high pressure can lead to high pressure Excessive chronic or repeated exposure nervous syndrome. The threshold at which to hyperbaric oxygen is harmful to health. this occurs is not clearly defined but can Such exposure can be measured in be around 15 bar. units of pulmonary toxicity dose (UPTD) (sometimes referred to as oxygen toxicity Heliox is an alternative to trimix or nitrox for saturation exposure.

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8.7 Air breathing during non-sat 8.10 Decompression tables 8.14 Living habitat decompression The Contractor in Charge should select The living habitat should meet the 8.7.1 Air breaks during oxygen the decompression tables to be used requirements of this document. decompression. taking account of the advice of his expert Appropriate air breaks should be hyperbaric advisers and the Contract It is recommended that there is a minimum incorporated in the oxygen stages of the Medical Adviser. vertical clearance of 2 metres above the decompression regime used. floor of the living chamber and a minimum The ratio should be around 20 to 30 Tables with a proven history of volume of at least 4 cubic metres per minutes oxygen breathing interspersed effectiveness are to be preferred. occupant. Some classification societies set with 5 minute breathing on air as required Un-proven tables should be subject to a additional requirements for living chambers by the decompression schedule being stringent verification process before they covering bed size and washing/toilet used. are put into routine site use. facilities.

8.11 Treatment tables, omitted The layout of the living chambers and 8.7.2 Period without use of masks. decompression tables, over system of work (team size, shift patterns, Tables which include periods where running permitted exposure etc) should allow occupants to have the a mask is not required to be worn period required periods of rest and not be woken may be advantageous as they permit up by other occupants going to/from the communication, rehydration, and As part of the safe system of work, the TUP shuttle. comfort breaks for the workers as well as Contractor in Charge should with the facilitating medical monitoring. advice of the CMA, identify appropriate 8.15 Living in saturation treatment tables for use in treating DCI. conditions 8.8 Exposure limits - Non-sat Similarly, the Contractor in Charge should exposure with the advice of the CMA identify For saturation working, the Contractor in procedures for dealing with omitted Charge has to extend the safe systems of For reasons of worker comfort and decompression and extended exposure work to cover the welfare and well-being control of hyperbaric exposure the more periods. of those in the living chambers between conservative of the following criteria should excursions. This includes the provision be adhered to: Additionally, procedures for dealing with of food and drink, the maintenance of • The exposure period should be such the use of incorrect breathing mixtures a comfortable living environment, the as to require a decompression time in during exposure if relevant should be provision of washing and toilet facilities, the manlock of not more than 2 hours. If drawn up. first aid and medical provision. The normal longer decompression is required it should standards of the saturation diving industry take place in a saturation habitat. 8.12 Loss of oxygen supply should be followed. • The total of exposure period and during decompression decompression time should not exceed 3 8.16 Saturation shift patterns hours There should be procedures in place including an appropriate air-only In order to ensure safe and efficient 8.9 Shift patterns – non-sat decompression table for use in the event operations, HPCA personnel should exposures the oxygen supply fails. work within a time routine which allows them to develop a regular work and sleep For non-sat exposures a shift pattern 8.13 Living habitat for pattern. The minimum rest period in the of five days on, two days off should be saturation living complex should be 12 hours (i.e. not adopted. working or carrying out pre or post-work In general the chambers in which workers checks). Therefore, when operations are live whilst in storage should satisfy the carried out on a 24/7 basis only one work relevant requirements of one of the period per 24-hour period is recommended. classification societies. They should normally be sited on the surface.

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8.17 Duration of Saturation 8.19 Hyperbaric operations Exposures and Surface Intervals During the transfer from shutle to chamber or living complex and back again every Where relevant national requirements do effort should be made to avoid changes not exist, it is recommended that no one in temperature, in the composition of the who is an experienced saturation worker mixture being breathed and physiological should experience a saturation exposure effects including isobaric counterdiffusion. exceeding 28 days under pressure. Otherwise the exposure should not exceed For tunnelling, it is normally desirable to 14 days. set the storage pressure to the working pressure and thus avoid the need for Thereafter that person should not undergo different breathing mixtures for excursions. any further exposure to HPCA until at least Where it is likely that excursions will be an equal interval of time at atmospheric required for operational reasons, storage pressure has elapsed. pressure should be selected to minimise A person’s cumulative saturation exposure pressure changes during excursions. The should not exceed 13 weeks in any 26 excursion procedure should be selected to week period. minimise undesireable physiological effects in those undertaking the excursion. Prior to decompression a person should have a 12 hour pressure stabilisation Final decompression to atmospheric period in the living complex. An excursion pressure should not be started with an at the pressure of the living complex can excursion to a lower pressure in the working be part of this 12 hour period. chamber. There should be a 12 hour stop in the habitat before final decompression 8.18 Working period begins unless there has been no excursion involving a working pressure different to The maximum working period is calculated storage pressure in the preceding 12 hours from initial lock-off until the final lock-on to the living complex and personnel are 8.20 Remaining on site after ready to transfer. No more than one decompression working period per day is recommended. The maximum working period away from Personnel undergoing HPCA exposures the living complex shall be 8 hours in a 24 should remain on site or its immediate hour period. The working periods set out in vicinity, for 2 hours after decompression these guidelines may need to be reduced from non-sat exposures and for 24 hours for very heavy work. following sat exposures. This will allow time for physiological monitoring to be As personnel are involved in tiring physical undertaken. work, the hyperbaric supervisor should appreciate that it may be appropriate for 8.21 Ascent to altitude them to return to the manlock periodically for a short rest and to take refreshment Personnel undergoing HPCA exposures before finishing their task. In any case, the should not fly or otherwise ascend to hyperbaric supervisor should ensure that altitude in excess of 150 metres or 500 the personnel have a refreshment break feet e.g. mountaineering or driving over hilly of at least 15 minutes, between 3 and 4 terrain, for 24 hours after decompression. hours into the working period. Where geographical or logistical conditions render this requirement un-acceptable restrictive, Contract Medical Advisers should produce local rules for travel involving ascent above this height.

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9.1 Record keeping

Exposure records should be made in the language of the jobsite on which the HPCA work is being undertaken. Records should be held in electronic format using one of the internationally available office software packages. Record keeping should generally be as described in the BTS “Guide” along with any additional requirements of the national regulatory authority. In addition a full record of the composition of all breathing mixtures and gases used along with the times and pressures at which they were used should be kept for each working exposure and subsequent decompression. Gas purity records should also be kept.

9.2 Records of saturation working

For saturation exposures, a full record for each person exposed should be kept starting at the point of initial compression until the end of the final decompression, including details of each excursion from the storage habitat.

9.3 Distribution of records

On completion of the work, in addition to copies of the records given to individuals and their employers, a copy of all records, in its official language, should be offered to the national regulatory authority for occupational health and safety in the country where the work was undertaken.

9.4 Retention of records

The Contractor in Charge should retain the records in the company archives for a period of 40 years from the end of HPCA work.

9.5 Individual records

On termination of employment, each person exposed should be given a full record of his exposures on the project, details of training received, results of medical surveillance, along with details of any decompression illness events experienced and their treatment

ITA Working Group n°5 – Health & Safety in Works 23 10 >> Em e r g e n c y p r o c e d u r e s

10.1 Emergency procedures and 10.2 Fire protection within and casualty evacuation around the TBM lock

The Contractor in Charge should draw The requirements of the BTS “Guide” and up a comprehensive set of emergency EN 12110 in respect of fire precautions procedures covering reasonably apply and should be supplemented by foreseeable emergencies including those the outcome of a project-specific fire risk which require the evacuation of personnel assessment of the HPCA work being and casualties to a place of safety on the undertaken and all relevant site conditions. surface. The Contractor in Charge should No productive work or maintenance work ensure that all necessary equipment and should be undertaken elsewhere on the personnel identified in the procedures TBM whilst HPCA work is underway. is immediately available for deployment and that a comprehensive test of the 10.3 Fire protection for evacuation procedures is undertaken surface facilities and recorded before any HPCA work begins. Procedures should be revised as The buildings housing the saturation necessary during the course of the works living complex should be fitted with a and further tests carried out. comprehensive sprinkler system. These buildings should be constructed from Typical emergencies include but are not incombustible materials whenever limited to: possible. • Medical emergency or injury to a person in the working chamber/manlock/TUP The control panel should be equipped with shuttle. at least one independent compressed air • Fire in working chamber, manlock of respirator for the lock attendant. other PVHO • Fire on TBM In addition, there should be sufficient • Fire elsewhere in tunnel oxygen self rescuers at the control panel • Fire on TUP shuttle transport vehicle for everyone normally working there • Breakdown of vehicle • Fire affecting saturation living complex 10.4 Hyperbaric self rescuers • Umbilical damage in the working chamber • Excessive air loss through tunnel face • Blow out A compressed oxygen self rescuer for use • Ground collapse in hyperbaric environments was shown • Lifting equipment failure to be feasible by HSE in the 1990s but • Lock attendant taken suddenly ill or its manufacturers never put it into mass otherwise no longer available production. The concept has been shown • Loss of air pressurisation supply to be technically feasible. There is no • Inability to dock TUP shuttle restriction by HSE, on others to develop • Loss of communications systems the concept further. • Loss of electrical power • Loss of gas supply to any PVHO 10.5 Fire protection for gas • Oxygen toxicity incident in PVHO cylinders • Mask malfunction or accidental removal Gas cylinders on the surface should be stored in a well ventilated and secure enclosure. It should be physically separated from other buildings or protected by a suitable fire wall. Cylinders in use should be protected by a sprinkler system.

24 Guidelines for good working practice in high pressure compressed air 11 >> In f o r m a t i o n , i n s t r u c t i o n a n d t r a i n i n g

11.1 Information, instruction and training

All those undergoing HPCA exposures should be given appropriate training in the risks from such work and how these risks should be mitigated. Reference should be made to the BTS “Guide” for a comprehensive list of topics. The training should take full account of site procedures. The theoretical training modules of internationally recognised qualifications give an indication of the level of hyperbaric knowledge required for non- sat and sat HPCA workers.

Most of the HPCA interventions to date have been undertaken by personnel with diving experience. However it is foreseeable that conventional tunnelling operations may have to be undertaken in HPCA. Personnel for such work would require experience as miners in conventional tunnelling techniques. The additional training required to make such persons competent to work under HPCA would be extensive and should reflect the risks associated with the work to be done.

ITA Working Group n°5 – Health & Safety in Works 25 12 >> Acknowledgemen t s

In addition to the contributions from their respective members, ITA WG5 and BTS CAWG acknowledge the direct or indirect contribution to the drafting of this document from Advanced Marine Pte Ltd, Babendererde Engineers, Ballard Diving and Salvage, Herrenknecht, Germanischer Lloyd, Health and Safety Executive, Hyperbaric and Tunnel Safety Ltd, IHC Hytech, JCLP Hyperbarie, Dr J King, Tony Ridley Hyperbaric Associates, CEN/TC151/WG4, Hyperbarie SARL, McNally Corporation, Dr W Sterk, Vinci and Washington State DoT.

26 Guidelines for good working practice in high pressure compressed air >> Gl o s s a r y o f t e r m s a n d a b b r e v i a t i o n s

Breathing mixture High Pressure Compressed Air (HPCA) Pressure Non-air respirable mixture, such as oxygen work Pressures in this document are stated in and nitrogen (nitrox); oxygen and helium Work in compressed air at pressures bar (gauge). (heliox) or oxygen, nitrogen and helium above historical statutory limits, which in (trimix) capable of supporting human life many countries are between 3 and 4 bar Pressure vessel for human occupancy under appropriate hyperbaric conditions. (gauge), and which involves the use of (PVHO) breathing mixtures other than compressed Manlocks and similar pressure vessels in BTS “Guide” natural air and can involve the use of which persons are exposed to pressure. The British Tunnelling Society’s document saturation techniques. “Guide to the Work in Compressed Air Note: In the past it was customary in some Quad Regulations 1996”. countries to describe exposure pressures Transportable gas storage consisting of from which stage decompression was multiple cylinder configurations connected Compressed air worker not required as “low pressure” and to to a common manifold, within a protective Person working in compressed air. describe exposure pressures from which frame. stage decompression was required as Contract Medical Adviser (CMA) “high pressure”. It is now proposed that Saturation exposure (“sat” exposure) Medical practitioner qualified in the latter be referred to as “intermediate A long duration exposure during which occupational health who is permitted pressure” i.e. pressure between “low the person exposed lives under pressure to practice in the location at which the pressure” and the statutory limit. and may make transfers into the working HPCA work is being undertaken and who chamber. is responsible for all medical aspects of Health and Safety Executive (HSE) HPCA work. The UK regulatory authority for Storage occupational health and safety. Maintenance of persons at pressure in a Contractor in Charge hyperbaric living complex. Contractor with overall responsibility for Isobaric counterdiffusion the HPCA work, and not necessarily the The of gases in different Transfer under pressure (TUP) main tunnel conractor. directions without decompression and The transfer of persons between without changes in the environmental pressurised habitats whilst maintaining Decompression illness (DCI) pressure which leads to the formation of those persons under pressure. A ill health conditions resulting from bubbles. decompression following exposure to Tunnel Boring Machine (TBM) pressure. Non-saturation exposure (“non-sat” A machine which in Europe would come exposure) within the scope of EN 12336 (references Diver medic A short duration exposure comprising to EN 12336 in this document to become An advanced hyperbaric first aid a compression, a working period under references to EN 16191 on harmonisation qualification endorsed by the International pressure, followed by a decompression. of EN 16191). Marine Contractors Association (IMCA) or It does not involve any storage time in a national equivalent. hyperbaric living complex. Tunnelling In this document tunnelling includes shaft Excursion Oxygen sinking and caisson work. A period in saturation away from the living Used in this document to mean oxygen of complex, spent in the working chamber medical or diving grade. Working period (sat exposures) normally at a different pressure to the The elapsed time from when a person storage pressure. Partial pressure (of a gas) leaves the living complex for the working The pressure of a gas in a gas mixture that chamber until that person arrives back in Gas the gas would have if it alone occupied the living complex. Used in this document to mean either the gas filled space (Dalton’s Law). It is oxygen or a breathing mixture. normally stated in bar and is the product of the absolute pressure of the mixture Gauge Pressure and the volume fraction of that gas in the Pressure above as mixture. In this document partial pressure in normal tunnel practice. of a gas (e.g. oxygen) is shown as PO2.

ITA Working Group n°5 – Health & Safety in Works 27 longrine 04 90 14 48 48 - (20282 - 11/11)

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