Sulzer Dowding & Mills
GasTurbine Conference , Brisbane, October 2013
Graeme Robertson – Head of Operations UK

Sulzer Tur...
LARGE HV MACHINE REPAIR OPTIONS

Sulzer Turbo Services

 Repair to coil lead
 Cutting coils out of circuit
 Splicing in...
FACTORS TO BE CONSIDERED

 Machine Specific
 Secondary damage, core
loss or impact
 Impregnation system
 Type of windi...
REPAIR TO COIL LEAD OR CONNECTIONS - 1

Sulzer Turbo Services

 Simplest repair option if only one coil leg or connection...
2.5MVA, 2 MW, 8 Pole, 11KV

Sulzer Turbo Services

Global VPI Impregnation

Lead Arc Flash Damage

| slide 5
CUTTING COILS OUT OF CIRCUIT - 2

Sulzer Turbo Services

 Will affect machine performance
 Likelihood of reduced output
...
12 MW 4 Pole 11KV Compressor Motor

Sulzer Turbo Services

Failed with multiple failed coils and earths

Stator Winding Ea...
ORIGINAL COIL CIRCUIT

Sulzer Turbo Services

| slide 8
CUTTING COILS OUT OF CIRCUIT

Sulzer Turbo Services

 Coils reduced from 72 to 66
 1 coil splice repair
 STAR connected...
REDESIGNED COIL CIRCUIT

Sulzer Turbo Services

| slide 10
REDESIGN MODIFICATIONS TO CONNECTION RING

New Coil to Coil
Connections
@ Conn Ring

Sulzer Turbo Services

Connections of...
MODIFICATION TO NON CONNECTION END COIL

Sulzer Turbo Services

Cut Coil Knuckle
@ Non Conn End

Cut Coil Isolated & Insul...
SPLICE IN COIL SIDE - 3

Sulzer Turbo Services

 Straight forward with top coil side, can be achieved on bottoms legs
 M...
SPLICE IN COIL SIDE

Sulzer Turbo Services

 Slot Cleaning is critical
 Care taken to avoid damage to
adjacent coils

 ...
STAGES OF SPLICING IN COIL

Sulzer Turbo Services

| slide 15
REPLACE A FAILED COIL / BARS - 4

Sulzer Turbo Services

 No change in performance
 Easier with half bars, diamond coil ...
120 MW 2 Pole 13.8KV Gen

Sulzer Turbo Services

 Connections un-brazed to allow
bar testing and subsequent
removal

 St...
120 MW 2 Pole 13.8KV Gen

Sulzer Turbo Services

| slide 18
Replace Failed Coil

Sulzer Turbo Services

Secondary Epoxy Injected



| slide 19
120 MW 2 Pole 13.8KV Gen

Sulzer Turbo Services

 Significant number of top bars
[25] which had to be removed

 Finished...
REPLACE FAILED COIL

Sulzer Turbo Services

 Stator bar being
jacked out of slot,
note the use of
multi point
jacking, th...
FULL STATOR REWIND - 5

Sulzer Turbo Services

 Performance maintained or Increased
 If possible engineer out the previo...
Production Platform – Generation Problems

Sulzer Dowding & Mills

Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slid...
Overview

Sulzer Dowding & Mills

 Total generation capacity of 35MW
 GT 4 was to be returned to Service after period of...
Bringing back to service…

Sulzer Dowding & Mills

 Pre-commission checks identified very low IR and no PI.
 1000v DC Te...
Investigating the problem

Sulzer Dowding & Mills

 Our Service Engineers then carried out a methodical check:




open...
The Defective Coil

Sulzer Dowding & Mills

 The defective coil was identified by a process of elimination,
and located a...
The Turbo Generator

Sulzer Dowding & Mills

Generator
with end
covers
partially
removed
to expose
Stator
Winding

Sulzer ...
Source of the Problem

Sulzer Dowding & Mills

Generator
Stator Coils
ready for
splitting to
locate
defective
coil

Sulzer...
Winding Modification

Sulzer Dowding & Mills

4 pole 3 Phase Generator
66 Slots & 66 Coils
2 Parallel Circuit Star
12 Coil...
Winding Modification

Sulzer Dowding & Mills

4 pole 3 Phase Generator
66 Slots & 60 Coils
2 Parallel Circuit Star
12 Coil...
Our Solution..

Sulzer Dowding & Mills

 We calculated what would be the effect of cutting out 6 coils, 2 per
phase, on t...
The Completion..

Sulzer Dowding & Mills

 Work was completed in 14 Days utilising 24 hr working :







The gener...
Conclusion

Sulzer Dowding & Mills

 Drilling Program was at risk due to lack of generation capacity
 Failure to complet...
BEST PRACTICES – SITE WORKING

Sulzer Turbo Services

 LOCAL SITE CONDITIONS REQUIRE

 MITIGATING FACTORS

 Simple encl...
BEST PRACTICES - STATOR WORKS

Sulzer Turbo Services

 Stator core fit for 20-30 years
 Fit of coil in slot
 Resistance...
BEST PRACTICES – STATOR SLOT FILL

Sulzer Turbo Services

Wedge
Top Packing
Top
Coil Side
Conducting Vetronite
Conducting
...
BEST PRACTICES - STATOR CORE

Sulzer Turbo Services

 Test by power flux test or El-Cid method
 Ensure tightness of lami...
BEST PRACTICES – STATOR WEDGING

Sulzer Turbo Services

 For tight fitting wedges max length 8”
 Staggered under wedge p...
BEST PRACTICES – STATOR SCARFING

Sulzer Turbo Services

 Good scarfing of joints and staggering of scarfs
 Avoid local ...
BEST PRACTICES – STATOR BRACING / BLOCKING

Sulzer Turbo Services

 Maintain end winding blocking &
bracing, maintain coi...
BEST PRACTICES – STATOR TESTING

Sulzer Turbo Services

 Winding Tests
 DC resistance
 Insulation resistance
 Polarisa...
BEST PRACTICES – ROTOR REWINDING ON SITE

Sulzer Turbo Services

Two Options



New Rotor Copper



Utilising Original C...
BEST PRACTICES – ROTOR REWINDING ON SITE

Sulzer Turbo Services

 When rewinding Rotor >100MW we would recommend high spe...
HIGH SPEED BALANCING FACILITY

Sulzer Turbo Services

| slide 45
Questions ?

Sulzer Dowding & Mills

Thank you for your attention,

Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | sli...
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Graeme Robertson, Sulzer Downing and Mills: Generator repair and rewind

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Graeme Robertson, Head of Operations – UK, Sulzer Dowding & Mills delivered this presentation at the 2013 Gas Turbines conference. The event is designed as a platform for discussion on the latest technologies & developments in gas power generation. For more information on the annual event, please visit the conference website: http://www.informa.com.au/gasturbinesconference

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Graeme Robertson, Sulzer Downing and Mills: Generator repair and rewind

  1. 1. Sulzer Dowding & Mills GasTurbine Conference , Brisbane, October 2013 Graeme Robertson – Head of Operations UK Sulzer Turbo Services
  2. 2. LARGE HV MACHINE REPAIR OPTIONS Sulzer Turbo Services  Repair to coil lead  Cutting coils out of circuit  Splicing in a coil side  Replace a failed coil [s] / bars  Complete rewind | slide 2
  3. 3. FACTORS TO BE CONSIDERED  Machine Specific  Secondary damage, core loss or impact  Impregnation system  Type of winding Sulzer Turbo Services  General Factors  Physical size & access  Impact on other operations  Production loss and outage cost / Budget Availability  Age of winding | slide 3
  4. 4. REPAIR TO COIL LEAD OR CONNECTIONS - 1 Sulzer Turbo Services  Simplest repair option if only one coil leg or connection is affected  Damage to adjacent coils increases the risk of repair escalating  Likely that secondary arc flash damage will be evident  Global VPI makes this process more difficult | slide 4
  5. 5. 2.5MVA, 2 MW, 8 Pole, 11KV Sulzer Turbo Services Global VPI Impregnation Lead Arc Flash Damage | slide 5
  6. 6. CUTTING COILS OUT OF CIRCUIT - 2 Sulzer Turbo Services  Will affect machine performance  Likelihood of reduced output  Excitation current will change  Out of circuit coils need to be isolated and insulated to prevent circulating currents  Minimise air gap harmonics to minimise, noise, vibration, increased losses  In all cases Stator core requires to be fit for service as a result of failure | slide 6
  7. 7. 12 MW 4 Pole 11KV Compressor Motor Sulzer Turbo Services Failed with multiple failed coils and earths Stator Winding Earth Fault Damage to sidewall insulation | slide 7
  8. 8. ORIGINAL COIL CIRCUIT Sulzer Turbo Services | slide 8
  9. 9. CUTTING COILS OUT OF CIRCUIT Sulzer Turbo Services  Coils reduced from 72 to 66  1 coil splice repair  STAR connected with 2 parallel circuits.  Coils / Phase parallel path 12 to 11  10% increase in gap density  Rating reduced from 12MW to 9MW  Minimal outage time available, required for production | slide 9
  10. 10. REDESIGNED COIL CIRCUIT Sulzer Turbo Services | slide 10
  11. 11. REDESIGN MODIFICATIONS TO CONNECTION RING New Coil to Coil Connections @ Conn Ring Sulzer Turbo Services Connections of coils taken out of circuit | slide 11
  12. 12. MODIFICATION TO NON CONNECTION END COIL Sulzer Turbo Services Cut Coil Knuckle @ Non Conn End Cut Coil Isolated & Insulated | slide 12
  13. 13. SPLICE IN COIL SIDE - 3 Sulzer Turbo Services  Straight forward with top coil side, can be achieved on bottoms legs  Must maintain strand continuity  Must maintain strand, turn & ground insulation levels  Must maintain coil bracing, coil to coil, coil to support arm  Must not restrict airflow – staggered scarfing | slide 13
  14. 14. SPLICE IN COIL SIDE Sulzer Turbo Services  Slot Cleaning is critical  Care taken to avoid damage to adjacent coils  Lift Centre strip packing  Vacuum to remove all debris before, repacking and wedging | slide 14
  15. 15. STAGES OF SPLICING IN COIL Sulzer Turbo Services | slide 15
  16. 16. REPLACE A FAILED COIL / BARS - 4 Sulzer Turbo Services  No change in performance  Easier with half bars, diamond coil requires care / process  Must lift all coils in coil pitch [Diamond]  More coils lifted for WAVE winding  Depends upon condition of original winding, evolute / nose stress  Very difficult for global VPI windings, hard coil cells, prone to cracking during removal | slide 16
  17. 17. 120 MW 2 Pole 13.8KV Gen Sulzer Turbo Services  Connections un-brazed to allow bar testing and subsequent removal  Stator bar being jacked out of slot | slide 17
  18. 18. 120 MW 2 Pole 13.8KV Gen Sulzer Turbo Services | slide 18
  19. 19. Replace Failed Coil Sulzer Turbo Services Secondary Epoxy Injected  | slide 19
  20. 20. 120 MW 2 Pole 13.8KV Gen Sulzer Turbo Services  Significant number of top bars [25] which had to be removed  Finished stator with bracing and blocking all restored, new connection caps fitted | slide 20
  21. 21. REPLACE FAILED COIL Sulzer Turbo Services  Stator bar being jacked out of slot, note the use of multi point jacking, the fit of coil and VPI system meant that the coil had to be drilled and tapped to facilitate removal without damage to core | slide 21
  22. 22. FULL STATOR REWIND - 5 Sulzer Turbo Services  Performance maintained or Increased  If possible engineer out the previous failure mechanism – [ increase interturn or sidewall insulation]  Restores Winding & Bracing system to new condition  Winding is a ‘consumable’ of a Motor or Generator, has a life span, which is determined by loading / cycling / starts /environmental conditions / maintenance procedures  New Windings will obviously extend the machine expected lifespan | slide 22
  23. 23. Production Platform – Generation Problems Sulzer Dowding & Mills Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 23
  24. 24. Overview Sulzer Dowding & Mills  Total generation capacity of 35MW  GT 4 was to be returned to Service after period of inactivity, this was a 15MW, 6.6kv, 4 pole Generator driven by an Avon Engine  Provided critical power for Sea Water Injection Pump motors  Platform required SWI Pump Motors running to support production  Module Roof was not watertight !  Generator Anti-Condensation Heaters were defective ! Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 24
  25. 25. Bringing back to service… Sulzer Dowding & Mills  Pre-commission checks identified very low IR and no PI.  1000v DC Test IR value 0.2MΩ & breaking down after 4 minutes  As our engineers were being mobilised to site, platform staff spun the turbine generator for a period of 4 hours unexcited to determine if dampness / condensation was the issue.  Retest did not show any difference in the IR or PI levels  Complete winding was wet with an earth fault present Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 25
  26. 26. Investigating the problem Sulzer Dowding & Mills  Our Service Engineers then carried out a methodical check:   opened alternator for internal inspection of rotor / stator for any evidence of ingress of contamination cables and all connections from the cubicle to the alternator terminal box, removed all clamps / post connections  disconnected the star point / split phase connections  split low reading phase coils to form 2 halves for inspection & test  continue to split until defective coil or coils were located  identify the defective area / coil section Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 26
  27. 27. The Defective Coil Sulzer Dowding & Mills  The defective coil was identified by a process of elimination, and located at 4 o'clock position when viewed from DE, fault was specific to one diamond coil.  The stator winding had 66 coils connected in 2 parallel circuits  The winding had 5 & 6 coil groups  We proposed an in-situ repair potentially saving 16 weeks on time scale and circa £700k on rewind costs  A primary objective was to minimise outage time to get SWI pumps operating ASAP. Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 27
  28. 28. The Turbo Generator Sulzer Dowding & Mills Generator with end covers partially removed to expose Stator Winding Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 28
  29. 29. Source of the Problem Sulzer Dowding & Mills Generator Stator Coils ready for splitting to locate defective coil Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 29
  30. 30. Winding Modification Sulzer Dowding & Mills 4 pole 3 Phase Generator 66 Slots & 66 Coils 2 Parallel Circuit Star 12 Coil Groups 5 coils & 6 Coils 2 Coil Groups in each parallel path 1 with 5 coils the other with 6 coils Failed coil 2nd in 6 coil group Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 30
  31. 31. Winding Modification Sulzer Dowding & Mills 4 pole 3 Phase Generator 66 Slots & 60 Coils 2 Parallel Circuit Star 12 Coil Groups all 5 coils Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 31
  32. 32. Our Solution.. Sulzer Dowding & Mills  We calculated what would be the effect of cutting out 6 coils, 2 per phase, on the performance of the Generator  It was necessary to take 2 coils from each phase, to prevent circulating currents and kept the winding balanced  We assessed that a maximum 10 % loss of output would result in changes  Results were relayed to Client who approved the process and methodology of repair. Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 32
  33. 33. The Completion.. Sulzer Dowding & Mills  Work was completed in 14 Days utilising 24 hr working :      The generator was part dismantled, rotor remained in position An environmental habitat was erected around the stator Stator winding configuration was changed and reconnected, the defective coil and 5 other coils removed from circuit. Stoving heaters were applied to dry the rest of winding The stator winding was cleaned, dried, and spray varnished The machine was fully built and prepared for test  Generator returned to service with slow increase of load from 2 MW to 7MW over a shift and then up to 13.8MW  Machine was handed back to client after successful commissioning test, with some alterations to protection relays and AVR settings. Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 33
  34. 34. Conclusion Sulzer Dowding & Mills  Drilling Program was at risk due to lack of generation capacity  Failure to complete the ‘well work-over’ in time put the complete well at risk, including future oil revenues  Failure to provide power for the SWI Motors would result in loss of oil production  Generator Repair saved 16 Weeks of down time and circa £700k  Generator operating satisfactorily 15months later  Sister 15MW generator rewound this year  Scheduled to return 2014 to rewind this generator Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 34
  35. 35. BEST PRACTICES – SITE WORKING Sulzer Turbo Services  LOCAL SITE CONDITIONS REQUIRE  MITIGATING FACTORS  Simple enclosure to create clean room  Remote Locations  Controlled environment with some or all of:-  Temperature & Humidity          Air Conditioning De-humidifiers Heaters Work platforms Positive pressure Air Filtration Lighting Power outlets Tool storage  Effects of high altitude  Hazardous Atmospheres  Noxious fumes  Political Situation (Risk) | slide 35
  36. 36. BEST PRACTICES - STATOR WORKS Sulzer Turbo Services  Stator core fit for 20-30 years  Fit of coil in slot  Resistance between coil & stator core  Tightness of wedging / size and position of ripple springs  Stress grading tape in correct position  Blocking & bracing of coil in endwinding  Continuity of sub-conductors  Insulation integrity / quality of coil / bar | slide 36
  37. 37. BEST PRACTICES – STATOR SLOT FILL Sulzer Turbo Services Wedge Top Packing Top Coil Side Conducting Vetronite Conducting Middle Strip Bottom Coil Side | slide 37
  38. 38. BEST PRACTICES - STATOR CORE Sulzer Turbo Services  Test by power flux test or El-Cid method  Ensure tightness of lamination packs and cleanliness  Condition of air vents and security of duct spacers | slide 38
  39. 39. BEST PRACTICES – STATOR WEDGING Sulzer Turbo Services  For tight fitting wedges max length 8”  Staggered under wedge packing | slide 39
  40. 40. BEST PRACTICES – STATOR SCARFING Sulzer Turbo Services  Good scarfing of joints and staggering of scarfs  Avoid local build ups of insulation which would restrict air flow paths Insulation Scarf Joint | slide 40
  41. 41. BEST PRACTICES – STATOR BRACING / BLOCKING Sulzer Turbo Services  Maintain end winding blocking & bracing, maintain coil spacing  Ensure adequate clearances;   between connections   between coils and to earth Ensure adequate separation between phase coils 6.6kV 5.5mm 0.22” 11.0kV 8.0mm 0.32” 13.8kV 10.0mm 0.40” | slide 41
  42. 42. BEST PRACTICES – STATOR TESTING Sulzer Turbo Services  Winding Tests  DC resistance  Insulation resistance  Polarisation Index  Voltage withstand AC or DC  Tan Delta  Partial Discharge | slide 42
  43. 43. BEST PRACTICES – ROTOR REWINDING ON SITE Sulzer Turbo Services Two Options  New Rotor Copper  Utilising Original Copper         Removal of old insulation Validate forging Renew all slot, end-winding and under retaining ring insulation Reinsulate and rewind Maintain all symmetry of blocking & bracing Refit all fan blades and auxiliaries in original position Balance weights all accurately recorded and refitted Minor trim balancing may be required | slide 43
  44. 44. BEST PRACTICES – ROTOR REWINDING ON SITE Sulzer Turbo Services  When rewinding Rotor >100MW we would recommend high speed balancing which usually cannot be achieved on site.  Similarly when fitting new retaining rings, we would also recommend high speed balancing to ensure the correct balance condition at speed and also to ensure settlement of the rings | slide 44
  45. 45. HIGH SPEED BALANCING FACILITY Sulzer Turbo Services | slide 45
  46. 46. Questions ? Sulzer Dowding & Mills Thank you for your attention, Sulzer Dowding & Mills 2013 <Copyright © Sulzer> | slide 46
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