e uptime m 11 1• gazine Hydro: Magnetic flux • A06 module • Field news Case study / Turbo-machinery diagnostics e uptime m 11 1• gazine

# 1/06 3 Technical News Effective Hydropower Monitoring Demands Magnetic Flux Monitoring of Hydro Generators oday’s global installed hydro- In this issue we also present the new 7 Product Update – Dedicated power capacity of approximately SM-610-A06 hydro monitoring mod- Hydro Monitoring Hardware T 780 GW, represents approximately ule to the VC-6000 data acquisition 8 Field News – Hydro Monitor- 20% of the world’s electricity or about system. The introduction of the SM- ing Projects in Southwestern 88% of electricity from all renewable A06 simplifies vibration monitoring of China sources. Despite rapid development medium sized units for both safety 9 Case Study – Early detection from other sources and condition monitoring applications of a compressor impeller crack such as wind, biomass and solar, using Compass 6000. In most cases 14 Field News – Hydro Monitor- hydropower capacity has grown in a single module is sufficient for moni- ing Projects in leaps and bounds over the years and toring an entire hydro unit! 15 Case Study – VC-1500 is still growing. Only 25% of the po- Selected for monitoring small tential capacity has been realized up Visit our web site for more informa- hydroelectric generating units to now! In this powerful sector of the tion on our hydro monitoring tech- in Norway energy market, what does this mean niques, applications and products. 20 Events 2011/12 in terms of hydro machine operation In addition to the hydro theme for this and maintenance? A lot; machine issue of Uptime, there is also a spe- uptime is more important now than cial feature section on turbo-ma- ever before! chinery diagnostics. Diagnostic services have always played an im- This issue of Uptime is dedicated to portant role in the expertise we offer hydropower generating unit monitor- our customers, and we are including ing. Brüel & Kjær Vibro have been a case story on this particular sub- monitoring hydropower turbines for ject. This demonstrates how we can Uptime Megazine is a newsletter pub- turn measurement data into action- lished by Brüel & Kjær Vibro to keep you over 15 years worldwide. With signifi- up-to-date with new machine monitoring cant experience in monitoring all types able information that provides the trends and technologies. This issue fo- of machines in all types of hydroelec- longest lead time to failure, enabling cuses on hydroelectric tric configurations, ranging from under you to be proactive in machine main- monitoring. 1 MW to 700 MW, Brüel & Kjær Vibro tenance activities so they can be If you have comments, ideas or case have developed and implemented undertaken in a planned manner. I stories, please contact: monitoring strategies ranging from am delighted to launch this special The Editor, Uptime Megazine, Brüel & Kjær Vibro, simple safety installations to compre- edition of Up- DK-2850 Naerum, Denmark. hensive safety/condition monitoring time, and hope Tel.: +45 7741 2500 applications involving advanced you enjoy read- Fax: +45 4580 2937 measurement techniques for the gen- ing it! E-mail: [email protected] Copyright 2011, all rights reserved erator, shaft/bearings, turbine and Editor-in-chief: Shohan Seneviratne auxiliaries. Read more about this in Managing Editor: Mike Hastings the case story and technical article in Alfred Schübl Design&Production: Gitte Blå Design Cover photo: Ermenek , monitored by this issue of Uptime. Hydro key VC-6000 Compact Monitor. account manager

2 uptime megazine • 01/11 focus gazine 3 technical e 01/11 • uptime m 01/11 Purpose for Purpose for monitoring the magnetic flux The magnetic flux monitoring technique is primarily intended for detecting shorted rotor turns and incipient ground faults on rotor salient pole windings. short generally occurs if the winding A insulation is damaged or degrades shorted turn on a rotor A over time. pole will not necessarily require the machine to be immediately shut down for service but it will degrade perfor- mance. It can cause hot spots and force the field current to increase. It can also create an unbalance that results in excessive vibrations and overheating. There are several factors that affect the magnetic flux density; namely the physical air gap between the stator and poles, temperature of the wind-

turbo-generators used in other utilities turbo-generators used in other utilities The slow rotate at 3000/3600 rpm. rotation of the hydro generators ne- cessitates many rotor poles in order to generate power at line frequency. An enormous rotor is therefore need- ed to accommodate the large number of poles, sometimes exceeding 12 m Such a large generator, in diameter. with a relatively small air gap, is sus- ceptible to small deformations that can create enormous imbalance forc- The resulting vibration can cause es. premature failure of bearings and other components. The massive area of the generator also makes it susceptible to hot spots, looseness, and other irregu- There are several specialized larities. measurement techniques to detect and diagnose these problems, but this article will focus on one such technique; the magnetic flux meas- urement.

n order to extract the maximum n order to extract the maximum energy available from a particular

Hydro Generators Monitoring of Magnetic Flux design of hydro generators. are needed to monitor the unique are needed to monitor the unique Special monitoring techniques Special monitoring techniques This makes the hydro generators This makes the hydro generators unique as electrical machines, since water head, the hydrogenerating water head, the hydrogenerating units at a hydroelectric power station have to rotate at relatively slow speeds; 50-300 rpm. I ings and the exciter field current and Figure 1. Prepa- voltage. Therefore to more accu- ration of a hydro rately monitor to alarm limits and to generating unit simplify trending, magnetic flux stator (prior to should be correlated to these pro- installing the cess parameters. The most important magnetic flux correlation for a magnetic flux meas- sensor). urement, however, is with the air gap measurements. This helps to deter- mine if a generator unbalance is due to physical reasons (change in air gap) or electrical reasons (a shorted channels or between the ends of the pared to alarm limits in the Compass pole turn). windings. The sensor measures the monitoring system and then stored in magnetic flux of each passing rotor the database. Variations in the magnetic flux meas- pole face. The signal from the condi- urements can be small, so an accu- tioning unit is referenced to a phase/ The magnetic flux sensor resembles rate measurement is required for speed tacho, so the signal from each an air gap sensor (e.g. Brüel & Kjær each pole. As an example, on a 72- individual pole can be identified. Vibro EQ 2431) and in fact both are pole machine with 20 turns/pole, a These signals are conditioned, com- installed in the same way, but this is single shorted turn will reduce the magnetic flux measured by only 5%.

Sensor The magnetic flux sensor system (e.g. Brüel & Kjær Vibro EQ 2430) includes a long thin sensor that is permanently glued to the inner wall of the stator. It is attached to a signal conditioning box/ power source a few meters away by signal wires that pass though the stator ventilation

Figure 2. Magnetic flux sensor shown on the left, air gap sensor shown on the right.

4 uptime megazine • 01/11 focus gazine 5 technical e will be will be H, 01/11 • uptime m 01/11 Figure 5. No magnetic field present. Figure directly proportional to directly proportional to the strength of the mag- netic field of each passing rotor pole. The magnetic flux sensor measures the the flux sensor measures The magnetic using the Hall ef- magnetic flux density by Dr. This principle was discovered fect. but has only been Edwin Hall in 1879 30 years since the used within the last state electronics. development of solid conductor or Imagine a thin rectangular has current flowing semi-conductor that of a magnetic through it. In the absence no voltage across the field, there would be the to perpendicular conductor the of width The Figure 5. as shown in current flow, occurs if a magnetic field cuts Hall effect perpendicular through the rectangular This produces a potential conductor. that is across the width of the conductor, proportional to the current and the flux density of the magnetic field perpendicular in Figure 6. as shown to the conductor, similar to element Hall effect A that shown in the figures below is built into the mag- Assum- netic flux sensor. ing the sensor current is constant, the output sensor voltage of the i.e. the Hall sensor, V voltage effect Hall Effect – The theory behind Effect Hall of the magnetic the operation flux sensor Figure 6. Hall effect principle, magnetic field present. 6. Hall effect Figure

Figure 3. Com- pass 6000 plot above showing the raw time signal that is saved in the database for diagnostic pur- poses. Figure 4. Maxi- mum peak value extracted for each pole (single val- ue) to be used for monitoring, trend- ing and alarming purposes. The magnetic flux signal is used in The magnetic flux signal is used in an automatic monitoring capacity to detect a possible shorted turn. It is also used in a diagnostic capacity as a plot display to distinguish, for ex- Data Monitoring and Data Monitoring and Diagnostics where the similarity ends. The air gap The air gap where the similarity ends. sensor operates on a capacitive prin- ciple for measuring distance between the stator wall and the passing rotor The capacitive current pole face. measured between the sensor plate and the passing rotor pole is propor- tional to the dielectric value between these surfaces, which in turn is pro- portional to the physical distance (i.e. magnetic flux sensor A the air gap). measures the magnetic field between the stator and the passing rotor pole face and operates on an entirely principle, namely the Hall different (see the inset describing the effect theory behind the Hall effect). Figure 7. Com- pass 6000 multi-trend plot showing the maximum peaks for each ample, between rotor/stator deforma- pole, trended tion and a shorted turn. over time. These values The raw time signal for one rotation of are monitored the rotor shows the magnetic flux for to alarm limits. each pole, as seen in Figure 3. This signal provides valuable diagnostic information, but it is not monitored to alarm limits. For this purpose the signal is conditioned as shown in Figure 4. A single maximum peak Figure 8. Com- value for each pole is extracted and is pass 6000 plot monitored to alarm limits and trended showing the over time as shown in Figure 7. magnetic flux These values, corresponding to a maximum peak specific pole, can be correlated to the value for each values from other poles, or correlated pole for one to process conditions such as winding rotation in a temperature, exciter current and volt- circular plot. age, and air gap measurements. The

Magnetic Flux Measurements

Only 1 sensor needed

Top view of generator Hall effect Sensors

Profile ⠳⡄⡒⡋⡀ meas. Magnetic flux Speed/Reference

Tacho Rotation

Stator

Faults Detected Rotor poles n Shorted rotor turns. These can generate hot spots, higher field current and unbalance. Unbal- ance can create excessive vibrations and over-heating. n Often correlated with air gap and excitation voltage and Figure 9. Overview of magnetic flux current monitoring strategy

6 uptime megazine • 01/11 news

product gazine 7 e 01/11 • uptime m 01/11 Machine states – 6 user-de- 8 fined machines states (up to for safety monitoring applica- tions) Hot swappable module

and condition monitoring to be to be and condition monitoring undertaken with corresponding This limits. Alert and Danger alarm early and reli- provides accurate, capability. able fault detection Contact your local Brüel & Kjær Contact your local Brüel & Kjær sales representative for more Vibro information! n n (VC- TM Up to 11x vibration, up to vibration, up to Inputs Up to 11x 2x axial position, 3x binary in- puts and up to 2x speed inputs (for machine state definition) and a 1x master trigger input signal (for other modules) Outputs – Up to 8x DC outputs and 2x relays (with user-defined voting logic)

VIBROCONTROL 6000 VIBROCONTROL 6000), Brüel & Kjær Vibro’s data data Vibro’s 6000), Brüel & Kjær as a rack acquisition unit (used or in conjunc- based safety monitor 6000 for inte- tion with Compass offers grated condition monitoring), module; monitoring hydro-specific a This module, tailored SM-610-A06. to meet the monitoring require- ena- ments of the hydro industry, bles vibration monitoring of an entire hydroelectric machine in a The module is de- single module! signed as a flexible, user-defined platform for all kinds of hydro in- stallations, and includes a wide range of user-defined measure- unique machine state A ments. function allows safety n n Features: Dedicated Hydro Hydro Dedicated Hardware Monitoring Conclusion Magnetic flux monitoring enables accurate detection of shorted turns in a rotor pole, that if left uncorrected, reduce the performance of the gen- flux measure- The magnetic erator. to Vibro Kjær & Brüel by used is ment complement its integrated monitoring strategy for hydropower turbines. Due to its sensitivity to process con- ditions, it is not suitable as a stand- alone technique and should be cor- related to process conditions and air gap measurements as well. Compass enables magnetic flux flux Compass enables magnetic on the monitoring to be categorized basis of specific machines states, which can be the above mentioned process parameters, or the generat- ing unit loading or operational re- gimes such as pumping, generating, This allows compensating, etc. “cleaner” trending, earlier and more reliable automatic fault detection and simplified plot comparison for diag- nostic purposes. same peak values are also displayed also displayed same peak values are a single rotation in a circular plot for process class, of the rotor at a given from earlier rota- or overlapping data 8. tions as shown in Figure Figure 1. View of the Xiaowan hydroelectric power station, 6 x 700 MW field

Massive hydro expansion news Hydro Monitoring Projects The hydro projects mentioned in Southwestern China are only a few of the total num- ber to be built as part of China’s plan to expand its installed hy- Brüel & Kjær Vibro has won a boosted China’s hydropower ca- dropower capacity from a current bid to install monitoring systems pacity to being the world’s largest. 200 GW to 300 GW by 2015. on three large hydroelectric power This is in response to a con- stations in the Yunnan province; the n Jinghong Hydropower Station certed effort to cut carbon diox- Ruilijiang hydro plant on the Ruili (景洪水电站) – The fourth hydro- ide emissions. China has long River, and the Xiaowan and Jinhong station downstream relied on coal to fuel its economic hydro plants on the Lancang (Me- from Xiaowan in the enormous growth with about 83 percent of kong) river. The latter two are part of Lancang river cascade scheme. its electricity produced by coal- an enormous eight cascade hydro- Jinghong has 1750 MW generat- fired stations, but this is rapidly power station scheme on the Lan- ing capacity and a 108 m high changing. China plans to cut its cang River that will have the capacity dam. Construction began in 2003, carbon emissions per unit of to generate 16 GW. and was completed in 2008. Part gross domestic product (GDP) by of the power generated will be 40 to 45 percent by 2020. China Highlights of the sold to Thailand under an agree- also undertook a commitment to hydroelectric power stations ment with China. generate 15 percent of its power n Xiaowan Hydropower Station from non-fossil sources by 2020, (小湾水电站) - With 6 installed n Ruilijiang Hydropower Station up from the current 7.8 percent. hydro turbine generator units of (瑞丽江水电站) – Located on the Brüel & Kjær Vibro are proud to 700 MW each, Xiaowan Hydro- Ruili River in Dehong County, take part in this ambitious renew- power Station is the largest single- close to the Myanmar border. It able energy expansion project. unit capacity presently available in has 600 MW generating capacity. the world for such a water head segment. The Xiaowan Dam is also the world’s highest arch dam Monitoring Strategy (300 m) and the second largest Hydro Power All 17 hydro-generating units are Units MW/Unit hydroelectric power station in Station monitored for safety using the Brüel China after the Three Gorges & Kjær Vibro VC-6000 data acquisi- Ruilijiang 6 100 Dam. The Xiaowan Hydropower tion unit (except for Ruilijiang, which Station also holds a special status Jinhong 5 350 is monitored by the VC-4000). The in the sense that the operation of new SM-610-A06 hydro module is Xiaowan 6 700 its last generating units in 2010 being used in the Xiaowan project!

8 uptime megazine • 01/11 Early detection of a compressor impeller crack

casestudy Turbo-machinery, unlike hydro Performance Callcs generating units, operate at high Compressor speeds and have their own Gearbox unique set of potential failure Figure 1. Com- Motor modes. Fortunately most of these pressor train can be readily detected using an (top) and in- board and out- advanced condition monitoring board vibration Imported Data system such as Compass 6000. Compressor measurement points (bottom). There are, however, some turbo- machinery faults that require di- 0.8362 bar(q) 8.533 mbar(q) agnostic expertise to both detect 2.073 bar(q) 0.8647 bar(q) 4.564 bar(a) 2.029 bar(q) 20.77 deg.C 6.404 deg.C and diagnose. This case story 74.06 deg.C 85.27 deg.C 20.14 deg.C 74.92 deg.C 74.34 deg.C 62.38 deg.C

addresses exactly such an in- 62.66 62.38 57.43 11.40 stance and demonstrates the fact

that advanced diagnostic tools Stage 4 Stage 3 Stage 2 Stage 1 such as ADVISOR can greatly assist monitoring specialists. But

these tools can in no way replace Inboard (left) and outboard bearing (right) sensor locations for monitoring X-Y radial vibration them. Brüel & Kjær Vibro offers diagnostic expertise as a service

to companies that either lack Conference on Compressors and crack before failure. This could have Their Systems”, in London, UK, 10- resulted in destroying both the rotor these monitoring specialists or 12 September 2007. and casing. Later investigation re- have over-burdened diagnostic vealed that the shaft crack could Summary have been detected even earlier if groups. Rotor vibration and phase condition the automatic machine diagnosis monitoring limits were exceeded for a program ADVISOR, running on the 25 MW centrifugal compressor. Al- Compass platform, was being uti- his case story was adapted from though the vibration levels were still lised. of a paper written by Erik van 60% below the safety system alarm TDeursen from Hoek Loos/Linde Gas limits, the Rotating Equipment Engi- Introduction Benelux (Netherlands), Gert Hoefak- neer decided to shut down the ma- The 4-stage, 25 MW centrifugal com- ker, Brüel & Kjær Vibro (Nether- chine for inspection. A 25 cm crack pressor is used in an air separation lands), and Peter Surland and Mike was found on the impeller. If the process. The 5-year old compressor Hastings, Brüel & Kjær Vibro (Den- Compass condition monitoring sys- is a critical machine to the process, mark). It was presented at The Insti- tem had not been monitoring this and has no spares. The machine has tution Of Mechanical Engineers (Im- machine, it is possible the safety been monitored since it was commis- echE) conference “International system could not have detected the sioned.

01/11 • uptime megazine 9 Figure 2. Vector Shutdown radial vibrations on the inboard Alert alarm bearing: Alert alarm limits 1x Phase exceeded by 1x vector magni- 1x Vibration tude vibration at running speed. Danger Alarm Danger alarm exceeded by 1x vector phase. 1x Vibration 1x Phase

Monitoring Strategy Figure 3. Spec- A combined Compass condition mon- trum radial vibra- itoring and diagnosis system and tions on the safety monitoring system is used at 1x Alert limits inboard bearing: the air-separation plant for monitor- exceeded Alert alarm limits ing three machines. The condition- exceeded by 6% monitoring portion of the system is constant per- used in a predictive maintenance centage band- strategy for detecting faults at an width spectrum early stage of development. Both (CPB6%) at 6% Constant running speed. vibration and process parameters Percentage (many of these are imported from the Bandwidth distributed control system) are auto- Spectrum matically monitored at periodic inter- vals. Brüel & Kjær Vibro also pro- vides remote and on-site diagnostic services on request from the cus- Fault Detection partly due to the 1x phase shift of 65° tomer for analyzing faults. In January 2004 several condition- from the normal value for over a year monitoring alarms were abruptly (alert level is 85°), while the 1x vibra- The Compass system installation on generated, primarily on the inboard tion level has been gradually increas- the compressor includes X-Y dis- X-Y displacement sensors on the ing from around 30 μm to over 50 μm placement sensors on the inboard compressor rotor: for a period of around 3 years (see and outboard bearings, as shown in n CPB6% exceeded its 54.38 μm Figure 2). Figure 1. alert limits at running frequency The Engineer initially suspected the (61.30 Hz) problem was mechanical unbalance Measurements at each sensor point n 1x vector radial vibration level caused by fouling, so a camera in- include: exceeded the 60 μm alert limits spection was ordered. n DC (25 μm is normal) n Bandpass (10-1000 Hz, RMS n 1x phase exceeded the 90° dan- Machine Inspection and peak-peak) ger limits. Repair n 1x, 2x vector measurements (RMS The first thing noticed during inspec- peak-peak magnitude and phase), The alert-alarm levels were well be- tion was crackling of the cooling wa- ½x magnitude (RMS peak-peak) low the safety monitoring system trip ter piping with parts of the pipe miss- n 6% Constant Percentage Band- level of 130 μm overall vibration level ing. When the compressor was width (10.3 to 1030 Hz, RMS peak- (phase is not monitored for trip), but opened, there was no evidence of peak), 23% Constant Percentage they caught the attention of the Ro- fouling as previously thought, but a Bandwidth (2 to 1000 Hz, RMS) tating Equipment Engineer. This was large crack was found on the base of

10 uptime megazine • 01/11 Abrupt Increase Gradual Increase 1x Vibration Figure 4. 1x vibra- Post Fault Analysis and tion magnitude 1st Abrupt 2st Abrupt Diagnosis increased gradu- Increase Increase Looking back at the data in Figure 2, ally from 2001 to the changing 1X vibration and phase 2004, where there is an indication of a shaft/rotor crack1. was an abrupt Shutdown It is interesting to note that the vibra- increase in Janu- 1x Phase tion was higher at the inboard bear- ary 2004. 1x vec- ing position (stage 4) than the out- tor phase in- board (stage 1) position where the creased abruptly impeller crack appeared (see Figures first after the shut- 1 and 2). The compressor manufac- down in June turer confirmed this to be consistent

2002, and then nd for this type of machine. The effects 2 Major Phase Change again in January (Danger alarm - shutdown) of the mass balance between the first 2004. and fourth stage can influence the 1st Major Phase location where the first stage 1X Change vibration will be evident.

Compass had averted a catastrophic failure of the machine, but there was little lead-time to cost-effectively plan maintenance. Moreover, the initial 1x Vector Meas. (Normal Phase) diagnosis was incorrect as it was based on the premise of unbalance due to fouling, which is quite different from a rotor crack. The compressor had to be shut down quickly which resulted in unplanned downtime. Could the fault have been detected automatically? Maybe earlier? Could it have been correctly and automati- cally diagnosed as an impeller crack?

1 There is a lot of literature on rotor crack detection using vibration analysis. There are also a number of different vibration one of the first stage impeller blades. the system could not have tripped the analysis techniques used. References The damaged impeller could be re- machine in time to prevent a cata- [1-6] give an overview of some of these paired but it was quicker to install a strophic failure. Such a failure could techniques and [7] gives a description of a new one, which resulted in a 12-week have destroyed both the rotor and crack detection technique using 1X mag- shutdown. If Compass had not been casing, which would have resulted in nitude and phase measurements for monitoring this machine, it is possible 12 months of downtime. detecting cracks in gas turbine blades and the protective monitoring portion of rotors.

01/11 • uptime megazine 11 Looking at Figure 5, there were obvi- ous symptoms already back in Sep- tember 2002 that indicated the begin- ning of a phase change. There had been a shutdown in June the same year but the compressor was never opened for inspection at that time. For this reason it is doubtful that this shutdown could have aggravated the Figure 5. ADVISOR lists all likely and unlikely diagnoses for problem. There were also indications a given database scan. The diagnosis with the highest even further back to September 2001 certainty after 21 November 2002 is the “shaft change” (i.e. where the vibration levels began to a rotor dynamic change, such as a change in stiffness, gradually increase. But it is unlikely which can result when there is a rotor crack). Other ma- these symptoms would have ever chine faults can be seen listed below this one. been noticed since they were below the alarm levels. The phase in- creased in October 2002 but it quick- Figure 6. ADVI- ly leveled off and remained stable for SOR description a year and a half. Therefore, no real explaining the concern would have been raised. The rules and symp- gradually increasing vibration level toms used in the was still below alarm limits right up diagnosis. until the last moment. When both the magnitude and phase suddenly in- creased, the machine had to be man- ually shut down.

The problem is that no one had no- ticed these early indications of a developing fault.

Brüel & Kjær Vibro offers ADVISOR, Automatic machine tion. It is not necessary to set up an automatic machine diagnostic diagnosis system alarm limits to diagnose a fault. program that can be installed as an ADVISOR, the neural network-based add-on to Compass. ADVISOR was automatic machine diagnostic pro- ADVISOR evaluates the complete not installed at the time of the impel- gram that runs on Compass, classi- database on a regular basis (e.g. ler crack, so the customer asked fies measurements recorded by look- hourly) or it starts when it is triggered Brüel & Kjær Vibro to retroactively ing at the pattern of the levels at by an event. The results of the evalu- scan the compressor database with machine characteristic frequencies ation are: the ADVISOR diagnostic program. (correlated to potential failure modes n List of calculated certainty of diag- The Rotating Equipment Engineer of the machine) in the vibration spec- nosis of potential faults wanted to know if the developing trum. As soon as a machine shows n Description of the diagnoses of the impeller crack could have been de- “non standard” behavior, this is auto- potential faults (rules, symptoms) tected earlier using this automatic matically identified and converted into n Plots showing a trend of the cer- diagnosis technique. a machine problem. This means auto- tainty of the diagnosis over time matically diagnosing a fault requires only some initial data where the ma- chine is assumed to be in good condi-

12 uptime megazine • 01/11 Figure 7. This plot shows the calcu- lated certainty of the shaft crack diag- nosis by ADVISOR. Already by 21 November 2002 the certainty of diag- nosis was up to 80% (the highest certainty level of the system). Even though the certainty levels of the rotor crack diagnosis are relatively low prior to this date, the diagnostic trend has been increasing in terms of probability (certainty) the entire time.

Conclusion tion since it would look at several Vibration Digest, Vol. 36, No. 4, Safety systems are not always effec- symptoms at the same time when pp. 287-296, 2004 tive in protecting a machine against making a diagnosis – not just one. As 2. Green, I., Casey, C. “Crack Detec- faults such as blade or rotor cracks. It described in the preceding case sto- tion in a Rotor Dynamic System by is difficult to detect the minute energy ry, ADVISOR can be used at any time Vibration Monitoring – Part I: Anal- changes caused by a slowly develop- to search the entire monitoring sys- ysis”, Paper GT2003-38659 pre- ing crack using overall vibration tem database for symptoms. As the sented at ASME Turbo Expo 2003, measurements. Once a crack has symptoms begin to develop over time June 16–19, 2003, Atlanta, Geor- reached critical proportions, the rotor to fulfill the criteria established in the gia, USA could conceivably fail before high diagnostic rules, the certainty of the 3. Imam, I. et al, ”Development of an vibrations are detected by a safety diagnosis also increases. The calcu- On-line Rotor Crack Detection and system. lated diagnosis certainty can then be Monitoring System”, Journal of plotted and trended to give advance Vibration, Acoustics, Stress and There is a greater likelihood that rotor warning of a fault. The diagnoses Reliability in Design, Vol. 111, 1989 cracks can be detected at a relatively created by ADVISOR can also be 4. Grabowski B, The Vibrational Be- early stage of development by using automatically sent as a file to a main- haviour of a Turbine Rotor Con- any number of transient or steady- tenance management system or taining a Transverse Crack, Jour- state vibration analysis techniques. operator. nal of Mechanical Design, Trans. 1X and/or 2X vector measurements ASME, Vol 102, 1980 are one possible technique. The Using such a system can significantly 5. Wauer J, “On the Dynamics of changes, however, can be subtle and reduce the workload of the system Cracked Rotors”: A literature Sur- below the defined alarm limits, mak- user while simultaneously providing vey, ASME Book No AMR067, ing it necessary to trend the values earlier warning of a developing fault. Applied Mechanics Reviews, Vol over time. This can be exhausting The program can also be used to 43, No 1, 1990 work for a diagnostician to look at all fine-tune diagnosis rules and symp- 6. Sekhar et al, Crack Detection and data even before they exceed alarm toms and to “verify” the diagnoses Vibration Characteristics of limits. An automatic trend alarm func- done by others. Cracked Shafts, Journal of Sound tion for each measurement would be and Vibration, Vol 157, 1992 more useful, but this would have to References 7. Sonnichsen, H.E., “Real-time De- be set up individually for each meas- 1. Sabnavis, G., Kirk, R.G., Kasarda, tection of Developing Cracks in Jet urement. M., Quinn, D., ”Cracked Shaft Engine Rotors”, Aerospace Con- An automatic expert system such as Detection and Diagnostics: A Lit- ference proceedings, 2000 IEEE, ADVISOR provides the optimal solu- erature Review”, The Shock and Vol. 6, pp. 173-183, 2000

01/11 • uptime megazine 13 field Hydro Monitoring Projects news in Turkey Brüel & Kjær Vibro deep and narrow gorge, having a has recently won a bid width of less than 150 m at its top, Massive hydro expansion to install monitoring and as little as 5 m at its bottom. Turkey’s energy needs are growing systems on five hydroelec- n Büyügdüz – A small 2 x 30 MW at 6-8% annually, which equates to tric power stations in Turkey. installation. around 1,5 GW to 2 GW of new These include the and Erme- n Sarihidir – A small run-of-the-river generation capacity that is needed nek hydro plants in the installation near the town of each year up until 2017. Much of basin, part of the strategically impor- Nevsehir. this will be provided by greenfield tant Southeastern Anatolia Project coal plants and gas-fired plants in (Güneydoğu Anadolu Projesi, GAP) Hydro Power the short term, but Turkey has a for developing this rural part of the Units MW/Unit Station vast hydroelectric potential of 128 country. Birecik 6 110 billion kWh, of which only 35% is Highlights of the being used. Currently Turkey has hydroelectric power stations Boyabat 3 170 142 hydroelectric power stations with an installed capacity of 13 GW n Birecik – One of 19 hydroelectric Ermenek 2 150 generating 46 billion kWh/year of the Southeastern Anatolia Büyügdüz 2 30 (2007). In an effort to increase re- Project of Turkey, Birecik is located newable energy utilization, there are on the Euphrates near the town of Sarihidir 2 6.4 plans to develop 60 −100 billion Birecik 80 km west of the Sanliurfa kWh of hydropower potential by Province in the southeastern re- 2023. gion of Turkey. The Birecik dam is Monitoring Strategy a structure constituted of a con- All hydrogenating units are monitored One of the largest regional develop- crete gravity and clay core sand- for safety using the Brüel & Kjær ment projects in Turkey is the gravel fill with a height of 62.5 m Vibro VC-6000 data acquisition sys- Southeastern Anatolia Project from the foundation. The power tem (except for Büyügdüz, which is (Güneydoğu Anadolu Projesi, or station has 6 vertical axis Francis monitored by VC-920’s, and the two GAP). This vast project includes units, each of 112 MW, With a units at Ermenek, which are moni- hydroelectric power development, 317 m3/s flow from a 42 m head, tored by the VC-6000 Compact Moni- where it is planned to build 22 dams these units will generate an aver- tor). in the area. The Birecik and Erme- age of 2.5 billion kWh per year. nek hydro plants, to be monitored n Boyabat – Located in Sinop prov- by VC-6000, are part of this impor- ince in the country’s Black Sea tant project, and will help bring eco- region, 15 km southwest of Ermenek hydroelectric power station. nomic livelihood to the region. Durağan, on the Kızılırmak River. It has a 195 m high concrete dam, and includes three vertical shaft Francis turbines of 170 MW each with 157 m3/s flow. Upon commis- sioning the dam will generate 1.5 billion kWh/year. n Ermenek – The double curvature, asymmetrical, thin concrete arch dam body, which will have a height of 210 m, is among the two high- est dams in Turkey and the 6th highest in Europe. The dam is being constructed in an extremely

14 uptime megazine • 01/11 casestudy

VIBROCONTROL 1500 selected for Aunfoss Facts: monitoring small hydroelectric Catchment area 3000 km2 generating units in Norway Power 2x18 MVA Annual production 199 GWh

The VIBROCONTROL 1500 (VC-1500) vibration monitor was installed Head 30 m in the Aunfoss hydroelectric power station as a protective monitor for Flow 76 m3/s their 18 MVA hydro generating units. This vibration monitor proved to be well suited to this application not only because of its user-friendly capacity of 820 MW, which ranks them eighth among Norway’s biggest operability, but also because of its extra functionality. power producers in a country where 99% of all electricity is produced from hydroelectric power. Most of the Aunfoss Hydro Power Plant energy company Nord-Trøndelag NTE’s capacity is produced in small The Aunfoss plant, built in 1959, is Elektrisitetsverk (NTE) to install the and medium-small hydro power one of several hydro power stations Brüel & Kjær Vibro VC-1500 monitor plants equipped with 1 to 4 turbines. regulating the water flow on the Nam- for vibration monitoring. Over the last two decades, NTE and sen River, known for its salmon. It the other Norwegian hydroelectric consists of 2 x 18 MVA generating NTE is a 92 year old Norwegian local power stations have changed from units equipped with vertical-shaft energy utility with 16 main hydroelec- continuous operation to more partial Francis turbines. Aunfoss was the tric power stations north of the city of load and periodic operation to better first hydroelectric power station in the Trondheim. NTE has an installed adapt to seasonal changes in water

01/11 • uptime megazine 15 on the productivity of the downstream turbines.

The selection process for the ideal vibration monitoring system was not trivial. A typical rack-based safety and condition monitoring system has all the necessary functionality and remote monitoring capability for this type of application, but such a sys- tem would be too expensive for moni- toring only one or two smaller hydro Figure 2. Aunfoss generator hall. generating units. On the other hand there are many inexpensive vibration supply and spot energy prices. The mented such monitoring systems with monitors available in the market, but periodic operation, while more cost- over half of NTE’s hydro power sta- they lack important functionality for effective, has placed a higher load on tions being monitored using Brüel & effectively monitoring critical ma- the machines due to the increased Kjær Vibro vibration monitoring chines. After careful consideration number of starts and stops of the equipment! Over the years, Brüel & and market research, Aunfoss se- generating units. Kjær Vibro has delivered a range of lected the 2-channel VC-1500 moni- different monitoring solutions to NTE Previous Monitoring encompassing the VC-2000 and Experience VC-4000. These systems monitor Historically, NTE’s monitoring has hydro generating units ranging from 4 been restricted to the lubricating oil to 75 MW. In fact, Brüel & Kjær Vibro temperature, pressure and levels on monitoring systems are currently their hydroelectric generating units. being used to monitor over 150 hydro More recently, some of the plants turbines in Norway. have extended their monitoring capa- bility by adding vibration monitoring. Monitoring System Firstly, vibration monitoring gives Requirements at Aunfoss earlier warning of most of the impor- As in the case of most other NTE tant developing faults in the bearings power stations, Aunfoss requires that and shafts than other techniques. any new vibration monitoring system Secondly, effective asset manage- must complement the existing lubri- ment has become more important - cation system monitoring, not replace not only with respect to machine it. The vibration monitoring system protection but also for more effective should be used primarily for protec- Figure 3. VC-1500 vibration monitor operation and maintenance schedul- tive monitoring of the thrust bearing, ing. two guide bearings and the shaft, with the provision for seamless ex- For these reasons, Aunfoss decided pansion to implement condition moni- to add vibration monitoring capability toring, either immediately or at a later in 2011. While NTE operate some time to mitigate the enormous cost of hydro power stations that have not downtime. This downtime cost is not implemented a vibration monitoring limited to lost production, but extends solution, most facilities have already to reduced flow during the downtime, embraced the technique and imple- resulting in negative chain-reactions

16 uptime megazine • 01/11 Figure 4. Generator bearing bolt dam- age (left). Damage to the generator bearing housing weld (right).

Case story – Undetected for implementing vibration monitoring. been avoided, with Failures At Aunfoss, as shown in Figure 4, the the problem de- Prior to installing the Brüel & Kjær generator bearing bolts failed as a tected with suf- Vibro vibration monitoring system, result of excessively high vibrations. ficient lead time for Aunfoss, like other power stations at A similar vibration related failure is evi- service action, by the study NTE, have seen failures that were not dent in the weld of the generator bear- operation of a vibra- case detected by their existing monitoring ing housing shown in the same figure. tion monitoring system. systems. This was one of the drivers Both of these faults could have easily

tor, because it proved to be the opti- The VC-1500 monitor is a two-chan- alarms, resetting relays and changing mal solution offering reliable absolute nel absolute vibration monitor with measurement setups. There is also vibration safety monitoring with some two user-defined alarms and relays. condition monitoring functionality that key condition monitoring functionality A 4-20mA output is also available for enables remote post mortem, trend- and an interface bus for exporting each channel. Additionally, the VC- ing and frequency analysis of the data. 1500 enables temperatures to be data. monitored from the same two chan- VC 1500 Compact Monitor nels but these are not currently being Several VC-1500 devices can be The VC-1500 acquires vibration sig- used at Aunfoss since the bearing integrated into a single network, nals via accelerometers mounted on temperature is being monitored by thereby enabling effective monitoring the bearing casing to monitor the the existing instrumentation. and diagnostics of several machines. condition of the shaft, radial sleeve Two individually adjustable data bearings and the axial thrust bearing. Data display, trending and system transmission rates enable the user to The absolute radial vibration is inte- control of the VC-1500 is undertaken respond flexibly over any distance grated to a velocity signal that actu- by a PC server via a USB/CAN bus within a plant. ally provides more complete vibration interface. The VC-1500 unit itself has data on the components than what a local display for data trending and Monitoring System can be provided by a displacement analysis. Configuration sensor. The accelerometer does not Two VC-1500 monitors are used for have as wide a dynamic range as a Although the functionality is currently each turbine at Aunfoss (see Figure 5 displacement sensor at very low not being fully utilised at Aunfoss, on the next page). One monitor is speeds, but this is not a problem in one of the special features of the used for the turbine guide bearing, many applications, and it is much VC-1500 is remote operation via the which is equipped with two radial X-Y easier to install and maintain. Internet for acknowledging incoming accelerometers installed 90 degrees

01/11 • uptime megazine 17 Generator Bearing Relays Thrust Bearing

Data/Contro l

Turbine Bearing X Relays Turbine Bearing Y

Upper Generator Bearing

Lower Generator Bearing

Thrust Bearing

Turbine Bearing

Figure 5. Top, the monitoring system apart. The second unit is used to plier function in the VC-1500 pre- configuration at Aunfoss. Bottom, a monitor the generator bearing, with vents tripping the machine when high typical installation configuration for a one accelerometer in a radial direc- vibrations occur due to start-up/syn- 3-bearing hydro generating unit con- tion and the other for the thrust bear- chronization. Data display and sys- struction, of which NTE has several ing in an axial direction. The acceler- tem control can be undertaken locally (this is shown for illustrative purpos- ometer installation is shown in Fig. 6. or by a PC server via a USB/CAN es). bus interface. The two VC-1500 mon- Relay signals are wired to the DCS itors are typically installed in a cabi- and emergency shutdown system for net close to the generator in the pow- tripping the machine if the vibrations er station, as shown in Figure 7. indicate an impending failure (which could be catastrophic). A trip multi-

Figure 6. Examples showing the accelerom- eter installation, highlighting the ease of installation and maintainability on the tur- bine bearing (Brüel & Kjær Vibro AS 0070/02 accelerometers are used). The accelerometers are shown mounted on the turbine bearing casing, with one in the X direction (right) and one in the Y direction (left). The generator bearing (not shown) is mounted with one X radial and one Z direc- tion axial accelerometer, 90 degrees apart.

18 uptime megazine • 01/11 Vibration Measurements and portant potential failure modes with station. The important functionality Alarm Setup sufficient lead time. includes: As shown in Figure 4, each VC-1500 n Two alarm levels and trip override monitor is set up for a specific moni- Aunfoss wanted to implement an n Absolute vibration measurements toring task. This is summarised in effective vibration monitoring strategy n Standard economical transducer Table 1. to avoid this downtime and after thor- configuration ough research and careful selection, n Simple connections and user inter- Conclusion decided on the VC-1500 vibration faces As a result of changes to operational monitor for this purpose. The n Condition monitoring strategy, many small generating units VC-1500 fulfils important market capability such as are subjected to extra loading which requirements, provides the necessary trending can lead to unpredictable and more functionality not present in inexpen- n Remote monitor- frequent downtime. The downtime of sive vibration monitors and meets the ing, data display a single unit can be costly because it economic requirements that expen- and control can lead to a cascading effect of sive rack-based monitoring systems reduced productivity in the down- cannot fulfil. This is important for Acknowledge- ments stream chain. As demonstrated in the monitoring and protecting critical casestudy case story at Aunfoss, the original hydroelectric generating units that We thank Oddvar monitoring systems were not neces- are relatively small, and installed in Lundseng from NTE sarily designed to detect all the im- sets of one or two units per power for his participation in making this article.

We also thank Thor Ivar Fjeld- heim from T.L Teknologi A/S for his contributions and Peter Surland, Application Engineer at Brüel & Kjær Vibro in Denmark, for his input into the article and monitoring strategy.

Figure 7. Cabinet installation for the two VC-1500 vibration monitors.

Table 1. Typical Accelerometer SETUP Fault detection VC-1500 setup Location Initial Alarm by absolute vibration from Measurement for monitoring (Orientation) limits any vibration source small hydro Generator bearing Loose bearing, Loose foundation, generating units Overall velocity (Radial, X) bearing damage, lack of lubrica- with two guide bandpass, RMS Alert limit = 2mm/s tion, overload, wear, misalignment, bearings. (ISO:1Hz - Trip limit = 4mm/s Turbine bearing unbalance and any other radial 1000Hz) (Radial, X-Y) vibration

Overall velocity Axial stator movement, Thrust bearing Alert limit = 2mm/s bandpass, RMS thrust bearing problems, (Axial, Z) Trip limit = 4mm/s (ISO:1Hz - 1000Hz) detection of any axial vibration

01/11 • uptime megazine 19 ev e nts 04 - 10 Oct. 2011 Smart 2011 Linz, Austria International Conference and Exhibition e www.smart-automation.at

The 7th Smart Automation Austria will be held at the Design Center in Linz. 23 - 27 April 2012 The international event is the infor- Hannover Fair 2012 2011-12 mation and communication platform Hannover, Germany of the Austrian automation industry. Power Transmission and Control Tech- Visitors of the automobile, chemical, nology – Automation – Energy – Sub- electronics, plastics, and other pro- contracting and Services – Cutting ducing industries will also be able to Edge Technologies benefit from an extensive conference www.hannovermesse.de program. Brüel & Kjær Vibro products will be presented at the booth of our It remains without rival as a show- Austrian sales team. case of industrial technology, with more than 65,000 exhibitors from 65 countries. Brüel & Kjær Vibro’s booth will be located in the Industrial Auto- mation section.

20 - 22 Sept. 2011 17 - 19 Oct. 2011 3 - 6 June 2012 HydroVision Brazil 2011 Hydro 2011 AWEA Wind Power 2012 Rio de Janeiro, Brazil Prague, Czech Republic Atlanta, USA International Conference International Conference International Conference and Exhibition and Exhibition and Exhibition www.hydrovisionbrazil.com www.hydropower-dams.com www.awea.org/events/

Latin America’s newest event focuses Hydro is an annual conference in The American Wind Energy Associa- on advancing the development of the different parts of the world. The trade tion’s annual WINDPOWER Confer- region’s hydroelectric power and fair with symposia are dealing with all ence & Exhibition is recognized as dams/civil structures sectors. Hydro- technical, environmental, social and one of the world’s premier wind en- Vision Brazil provides a strategic economic aspects of hydro plants ergy trade shows, bringing together platform for introducing the region’s and future projects for developing attendees and exhibitors from every development opportunities and ex- multipurpose water resources in or- aspect of the industry. Exhibitors pertise and features a practical, solu- der to cover the increasing demand display the latest industry products tions-oriented conference program for energy in times of climate change. and services from manufacturing and simultaneous exhibition focused Our Austrian sales team will be on leaders, component suppliers, and on new technologies, future trends site to answer visitors’ questions other wind energy organizations. In and business solutions. Visit Brüel & regarding monitoring technique of 2012, Brüel & Kjær Vibro will exhibit Kjær Vibro at booth no.128. hydro power machinery. as part of the Danish Pavilion.

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