Gek103566_j Creating An Effective Generator Maintenance Program 6x136m
This document was ed by and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this report form. Report 3i3n4
Overview 26281t
& View Gek103566_j Creating An Effective Generator Maintenance Program as PDF for free.
More details 6y5l6z
- Words: 5,795
- Pages: 12
DWG Number GEK103566
Rev J
GE Power & Water
Released 11/14/2014
Page 1 of 12
GEK 103566 Revised, November 2014
Creating an Effective Generator Maintenance Program
These instructions do not purport to cover all details or variations in equipment nor to provide for every possible contingency to be met in connection with installation, operation or maintenance. Should further information be desired or should particular problems arise which are not covered sufficiently for the purchaser’s purposes the matter should be referred to General Electric Company. These instructions contain proprietary information of General Electric Company, and are furnished to its customer solely to assist that customer in the installation, testing, operation, and/or maintenance of the equipment described. This document shall not be reproduced in whole or in part nor shall its contents be disclosed to any third party without the written approval of General Electric Company. © 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
GEK 103566
2
Rev J
Released 11/14/2014
Page 2 of 12
Creating an Effective Generator Maintenance Program
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 3 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Contents Part 1 – Maintenance Outage Planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Background – Part 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Maintenance Planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Maintenance Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Visual Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. MAGIC* (Miniature Air Gap Inspection Crawler) Robot Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.
Rotor Life Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Part 2 – Other Maintenance Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8. Other Maintenance Considerations – Part 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
List of Tables Table 1. Recommended Initial Maintenance Interval in Absence of Operational Experience. . . . . . . . . . . . . . . . . 5 Table 2. Recommended Stator and Core Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7 Table 3. Recommended Water Cooled Stator Leak Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 4. Recommended Field Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9 Table 5. Summary of Generator Field Inspection Recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 3 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 4 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
Part 1 – Maintenance Outage Planning
A few examples of the primary factors that affect the maintenance planning process are shown as follows and should be integrated into the overall maintenance program: • O&M manual • Manufacturer’s recommended maintenance program • Technical Information Letters • Operational history • Monitoring trends • Previous inspections • Design features • Duty cycle • Ambient and environmental conditions • Risk tolerance • Reliability/availability needs
1. Background – Part 1 A thorough maintenance program is recommended to retain generator reliability and avoid major failure expenses. The three important elements of a thorough program are maintenance frequency, testing and visual inspection. It is the intent of this document to provide information on each of these elements, which will aid the owner/operator to establish a thorough and cost effective maintenance program.
2. Maintenance Planning Advanced planning for maintenance is necessary for generator operators in order to maintain reliability and availability. The correct implementation of planned maintenance and inspection provides direct benefits in the avoidance of forced outages, unscheduled repairs, and downtime. The basic design and recommended maintenance of GE heavy-duty thermal generators are oriented toward: • Maximum periods of operation between inspections • In-place, on-site inspection and maintenance • Use of local trade skills to disassemble, inspect, and re-assemble generator mechanical components
4
In addition to maintenance of the basic thermal generator, other auxiliaries require periodic servicing including the control devices, downstream electrical components, and other auxiliaries. This document is focused on maintenance planning for the basic thermal generator, which includes the field, stator core, and frame. Other systems, while outside the scope of this document, also need to be considered for successful plant maintenance. The inspection and repair requirements, outlined in the O&M Manual provided to each owner, lend themselves to establishing a pattern of inspections. These inspection patterns will vary from site to site due to numerous factors such as duty cycle and ambient conditions. GE monitors operating experience, inspection results, and in-service operating issues of the installed base to the degree that the information is available. This is used to analyze and identify potential issues specific to similar units across the fleet with subsequent recommendations to owners on specific matters forwarded by means of Technical Information Letters (TIL) so applicable action can be taken to obtain maximum reliability, availability, and maintainability. The recommendations contained in TILs should be reviewed and factored into the overall maintenance planning program.
The operational log should include the type of duty and any known abnormal operating incidents. Operational events which should be carefully noted are: a. Errors in synchronizing b. Under or over frequency operation c. Lightning surges or other transients d. Faults (such as short circuits) on system or adjacent machines e. Unbalanced load, including single phase operation (Negative Sequence and Motoring events) f. Overload g. Over voltage or under voltage h. Loss of field i. Loss of cooling water without load run-back j. Asynchronous operation Each of these events would have a different impact on the necessary planning for maintenance and inspection. Depending on the circumstances, some of these events might dictate that the machine be shut down for immediate inspection, whereas other events may allow a reasonable wait for the next scheduled inspection. The maintenance program should reflect the level of acceptable risk for the unit. This will vary from unit to unit and plant to plant, and will change over time as the
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 5 of 12
Creating an Effective Generator Maintenance Program importance of the unit to the power system changes. In addition, new technologies are constantly being developed to improve unit reliability, performance, and monitoring and inspection equipment, to provide a cost–effective means for maintaining the generator. The MAGIC* Robot In-Situ Generator Inspection System is one example of a technology developed by GE to provide a more cost-effective means of performing a major inspection. Other examples include advanced continous monitors such as stator partial discharge, field shorted turns, and collector health. The owner/operator should be aware of these developments and modify the maintenance program accordingly. While this should be a continuous process, the “maintenance outage planning review” is an appropriate checkpoint. Planned maintenance outages are usually scheduled well in advance of the actual outage date, and preparation for the outage should begin early. Materials that might be needed for the inspection should be ordered in advance so that they will be available at the start of the outage to avoid the risk of a costly delay.
The frequency and level of inspection can be dependent upon service duty, system demands, age of the unit, and risk tolerance, among many other individual plant considerations. These factors were discussed in Section 2 Maintenance Planning. The owner must balance performance, reliability and cost when planning maintenance outages and setting maintenance intervals. Many of the factors related to the timing of inspections are determinable by the owner/operator; other factors draw from empirical knowledge and fleet experience.
maintenance experiences are accumulated. While reductions in the recommended intervals could result from abnormal operational events described previously or unfavorable operating experience, increases in the recommended intervals may also be considered where operating experience has been favorable. Historical operation and machine conditions can be used to tailor maintenance programs such as optimized inspection intervals to specific sites/machines. GE can assist operators in determining the appropriate maintenance intervals for their particular application.
In the absence of operating experience and resulting condition assessments, Table 1 lists the recommended inspection intervals for GE thermal generators. Generally speaking, GE generators can be inspected commensurate with the associated turbine inspection outage with the exception of a “first” inspection defined as 8000 fired hours, 4000 turning gear hours, or 250 starts whichever comes first. These initial intervals should be reviewed and adjusted as operating and
During the first several months or several thousand hours of operation, some generator components experience a break-in period. The first year inspection will detect and correct for this period of potentially increased wear. Additionally, it should be noted wear can accumulate during turning gear operation. During turning gear operation, relative motion may occur in the field winding components potentially causing fretting wear. It is advised to the operator to minimize turning
Table 1. Recommended Initial Maintenance Interval in Absence of Operational Experience1
The local GE Field Service Office can assist in maintenance planning, and review of the overall maintenance program, incorporating any appropriate new maintenance and upgrade available technologies.
3. Maintenance Frequency There are a number of components which require routine maintenance or inspections between scheduled outages. The operator will find these recommendations in various equipment manuals, and should also include additional maintenance tasks as operating experience indicates. Results of this routine maintenance should be retained in well-organized files readily available for reference. These routine maintenance records coupled with the information from the monitored operating data are a good indicator of pending service or operating problems that should be addressed at the next scheduled outage. The monitored information alone is usually not sufficient for tracking or highlighting trends.
GEK 103566
Model
1st Major
Minor
Major
7FH2, 7FH2B, 6A2, 6A3, 6A6, 6FA, 7A3, 7A6, 9A3, 9A5
8,000 Fired Hours, 4,000 Turning Gear Hours, or 250 starts, whichever comes first
24,000 to 32,000 Factored Turbine Hours or 900 to 1,250 Factored Turbine Starts 30,000 to 32,000 Turning Gear Hours
48,000 to 64,000 Actual Turbine Hours or 1,800 to 2,400 Actual Turbine Starts 60,000 to 64,000 Turning Gear Hours
Liquid Cooled
8,000 Fired Hours, 24,000 to 32,000 4,000 Turning Gear Turbine Hours or 900 Hours, or 250 starts, to 1,200 Turbine Starts whichever comes first
48,000 to 64,000 Actual Turbine Hours or 1,800 to 2,400 Actual Turbine Starts
All Other Models
8,000 Fired Hours, 4,000 Turning Gear Hours, or 250 starts, whichever comes first
20,000 to 24,000 Factored Turbine Hours or 750 to 900 Factored Turbine Starts
40,000 to 48,000 Actual Turbine Hours or 1,800 to 2,400 Actual Turbine Starts
12,000 to 15,000 Factored Turbine Hours or 400 to 600 Factored Starts
24,000 to 30,000 Actual Turbine Hours or 800 to 1,200 Actual Starts
Asphalt Stator Bar Windings for Core Does not apply Lengths Over 150 Inches Note: 1
These initial recommendations assume GE approved repairs, field services, and full compliance to GE’s technical recommendations.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 5 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 6 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
gear operation to the extent possible without violating limits on the other rotor train components. It is recognized that some power generation plants may run in an operational regime which could produce extended turbine inspection outage intervals in the 6 to 10 year range. Regardless of plant operating regime, GE can help the owner define a customized cost effective maintenance plan. During a minor inspection, upper end shields or end plates are removed to permit
inspection of the end winding area, but the field remains in place. A major outage includes removing the field from the stator or using the MAGIC* robot (Miniature Air Gap Inspection Crawler) to permit a thorough inspection of the core section of the stator and field. Inspection of the field and stator using the MAGIC* robot may require the removal of a few entrance gap baffles to allow access to the air gap with the field in place. The inspection includes a series of tests and a visual inspection.
Each has their particular advantage and neither alone is sufficient. See Section 6 for a brief description of the capabilities of the MAGIC* robot. Note that the MAGIC* robot inspection technique for performing a major inspection may not eliminate the need to remove the rotor if an issue is discovered that requires rotor removal to correct, such as loose stator core wedges. Tables 2 through 4 display recommended test and inspections.
Table 2. Recommended Stator Tests and Inspections Stator and Core
Major Rotor Major In with LCSW Minor Rotor MAGIC* Out Robot / RAC
AIR
HYD
Checks for calibration and poor connections.
X
X
X
X
X
X
Stator Winding RTD’s
Insulation condition of RTD.
X
X
X
X
X
X
Stator Winding
Checks for poor connections and breaks.
X
X
X
X
X
X
CE Bearing
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
Hydrogen Seal Casing
Contamination and/or deterioration of insulation.
X
X
X
X
X
Polarization Index
Stator Winding
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
DC Leakage Current
Stator Winding
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
Over Potential/Hipot
Stator Winding
Ground wall insulation integrity
X
X
X
X
X
X
Stator Wedges
Detect wedge tightness deterioration
X
X
X
X
X
All Visible Components
Cleanliness, foreign material, loose or displaced parts, damage, wear, corrosion, deterioration
X
X
X
X
X
Core Laminations
Foreign Object Damage, surface condition and wear, cracks, burning
X
X
X
X
X
Core End
Surface condition and wear, cracks, burning, blocked ventilation, bar sparking
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Test
Component
Inspection Objectives and Assessment
RTD Element Resistance
Gas and Winding RTD’s
RTD Ground Insulation Winding Copper Resistance Insulation Resistance (aka Megger)
Wedge Tightness Map1
Visual Inspections
Core Ventilation Ducts Blocked ventilation Space Blocks
6
Migration, cooling age blockage
X
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 7 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Stator and Core
Major Rotor Major In with LCSW Minor Rotor MAGIC* Out Robot / RAC
AIR
HYD
Cracked welds, looseness
X
X
X
X
X
Stator Wedges, Top and Side Ripple Springs
Evidence of abrasion or looseness
X
X
X
X
X
Stator Bars
Cracks, worn parts, burning, bar sparking, tape migration, water leaks if applicable
X
X
X
X
X
End Winding System
Cracks, worn or loose parts, blocked ventilation, broken ties, dusting and or greasing
X
X
X
X
X
Connection Rings and Lower Leads
Cracks, worn parts, burning, tape migration, broken ties, dusting and or greasing, and water leaks if applicable
X
X
X
X
X
High Voltage Bushings
Cracks, worn parts, burning, blocked ventilation, water leaks if applicable
X
X
X
X
X
Copper Flux Shield
Overheating, hardware looseness
X
X
X
X
X
Frame
Corrosion, cracks, blocked ventilation
X
X
X
X
X
X
Bearings and Seals
Corrosion, cracks, worn parts, burning
X
X
X
X
X
X
Coolers
Corrosion, cracks, water leaks
X
X
X
X
X
Key Bars and Core Compression Bands
Cracks, burning, core tightness
X
X
X
X
X
Key Bar Nuts and Locking Tabs
Cracks, burning, core tightness
X
X
X
X
X
Partial Discharge Analysis
Stator Winding Insulation
Localized deterioration
X
X
X
R
R
Water Flow Verification
Water Cooled Stator Winding
Restrictions in hydraulic circuit
X
X
X
Magnetic Scalar Potential (EL CID)
Stator Core Insulation
Weak or damaged core enamel.
X
X
X
X
X
Core Ring Test
Stator Core Insulation
Weak or damaged core enamel
X
X
X
X
Dynamic Frequency Response
Stator End Winding
Potentially damaging resonance.
X
X
X
X
Test
Component
Inspection Objectives and Assessment
Gas Gap Baffles
Visual Inspections
X
Optional Tests
Air – Air Cooled Generator
R
HYD – Hydrogen Cooled Generator
LCSW – Hydrogen Cooled Generator with Liquid Cooled Stator Winding
X - Pertains only to type of unit selected
R - These tests are performed while the unit is running.
Note: For inner gas cooled stator bars use the hydrogen column. 1
This test does not apply to units with asphalt stator windings or units with the “camelback” wedge system.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 7 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 8 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
Table 3. Recommended Water Cooled Stator Leak Tests† Clip-Strand Braze: Phos Containing
Stator
Orig SLMS, Bagged Vent, or No Monitoring
H2 Leak Monitoring Method
Global Epoxy Injection or Clip-Strand Braze: Phos-Free Orig SLMS, Bagged Vent, or No Monitoring
SLMS HP Installed
Test
Inspection Objectives and Assessment
Minor
Major
Vacuum Decay
Checks the hydraulic integrity of the entire winding.
X
Pressure Decay
Checks the hydraulic integrity of the entire winding.
X
Helium Tracer Gas
Detects minute leaks in the hydraulic circuit.
X
X
X
Capacitance Mapping
Wet ground wall bar insulation
X
X
X
WIM – Wet Insulation Measurement
Wet ground wall bar insulation
X
X
X
Electrical Testing
Ensure the electrical insulation integrity of the system
X
Minor
Minor
Major
X
X
X
X
X
X
X
Major
X
X
X
X
SLMS HP Installed Minor
Major
X
X
† These tests are required to detect hydrogen leaks in water cooled stator windings only and should be performed in conjunction with the recommended tests
in Table 1
Table 4. Recommended Field Tests Field AIR
HYD
Major Rotor In with LCSW Minor MAGIC* Robot / RAC
Major Rotor Out
Test
Component
Inspection Objectives and Assessment
Winding Copper Resistance
Field Winding
Checks for poor connections and breaks.
X
X
X
X
X
X
Polarization Index
Field Winding
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
Shorted Turn Test1
Field Inter-Turn Insulation
Turn shorts
X
X
X
R
R
R
Incremental Winding Copper Resistance
Main lead, Gooseneck, and Bore Copper
Checks for looseness of the main lead and orientation dependent connectivity issues
X
X
X
All Visible Components
Cleanliness, foreign material, loose or displaced parts, damage, wear, corrosion, deterioration
X
X
X
X
X
Field Surface
Heating, arcing, foreign object damage
X
X
X
X
X
Body Weights
Looseness, staking
X
X
X
X
X
Visual Inspection
8
X
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 9 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Field AIR
HYD
Major Rotor In with LCSW Minor MAGIC* Robot / RAC
Major Rotor Out
Component
Inspection Objectives and Assessment
Body Wedges
Arcing, migration, cracking, blocked ventilation
X
X
X
X
X
Retaining Ring “Nose”
Wedge , arcing, foreign object damage
X
X
X
X
X
Retaining Rings
Cracks and burning
X
X
X
X
X
Coil End Turns
Blocked ventilation, damaged insulation, coil distortion
X
X
X
X
X
Fans
Cracks
X
X
X
X
X
Spindles
Cracks
X
X
X
X
X
Winding
Cracks, burning, blocked ventilation, worn parts
X
X
X
X
X
Collectors
Cracks, burning, blocked ventilation, worn parts
X
X
X
X
X
X
Journals
Cracks, burning, worn parts
X
X
X
X
X
X
Over Potential/Hipot
Field Winding
Ground wall insulation integrity.
X
X
X
X
X
X
Bore Pressure Test
Chevron Seals
Sealing capability of the Chevron seals.
X
X
X
X
X
Test
Visual Inspection
Optional Tests
Air – Air Cooled Generator
1
HYD – Hydrogen Cooled Generator
LCSW – Hydrogen Cooled Generator with Liquid Cooled Stator Winding
X - Pertains only to type of unit selected
R - These tests are performed while the unit is running.
The preferred method for shorted turn testing is the flux probe. Another method is AC Impedance testing.
4. Testing
5. Visual Inspection
Generator electrical testing is focused on the insulation systems. There are other tests used to monitor for degradation in other components. A list of the typical tests recommended and the test purpose is shown in Tables 2, 3, and 4. Historical records of test results should be maintained and compared to the new test results. Changes between outage test results may point to needed repairs/rework that may not be evident from the absolute test values themselves.
A visual inspection, performed at every inspection by an experienced individual, can disclose unit conditions not detected by monitoring equipment or tests. In some instances, electrical testing will only detect issues when the stator and field insulation systems have been significantly compromised. Also, for example, there is no definitive test for contamination, rust or oil, and water leaks, and yet the presence of any of these could adversely affect reliability and operation. A typical visual inspection should include those items listed in Tables 2 and 4.
Many of the tests require special equipment that has been properly maintained and calibrated to assure accurate results.
As important as it is, visual inspection is limited to areas that can be accessed for view either directly or with mirrors, borescopes, cameras, etc., and therefore, it must be combined with testing to give a complete picture of generator condition.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 9 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 10 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
6. MAGIC* Robot Inspection GE’s MAGIC* (miniature air gap inspection crawler) robots provide a thorough visual inspection of the stator and field using the robot’s on-board high-resolution video cameras. Additionally, it is capable of providing quantitative wedge tightness and Electromagnetic Core Imperfection Detection (ELCID) assessments. Coupled with the Remote Access Camera (RAC), the MAGIC* robot inspection can provide a comprehensive stator and field inspection. The customer may utilize the MAGIC* robot to perform the recommended inspection tasks that normally require the removal of the rotor. As a result, the customer may substitute a MAGIC* robot inspection for a major inspection providing the major inspection tasks outlined in Tables 2, 3, and 4, that don’t require the removal of the rotor, are performed during the outage as well. In order to use a MAGIC* robot, the generator must meet the following minimum radial entrance gap dimensions: MAGIC* (Senior)
MAGIC* (Junior)
• Retaining ring to core minimum radial gap 1.13 inches [28.7 mm]
• Retaining ring to core minimum radial gap 0.5 inches [12.7 mm]
• Field to core minimum radial gap of 2.0 inches [50.8 mm]
• Field to core minimum radial gap 0.75 inches [19.05 mm]
7. Rotor Life Management Generator rotor structural components are designed for normal transient events including 10,000 start/stop cycles for combined cycle power plants. However, with proper maintenance and inspections, generators can last much longer than that. Common issues with aged rotor forgings are typically related to the number of start/stop cycles. Several Technical Information Letters (TILs) have been
10
written on the subject. Particularly when performing rotor rewinds, those TILs should be reviewed and the inspections performed. These inspections are mostly focused on cracks in the wedge loading face, in the slot and in the bore if the rotor forging has one. Rotor forgings, retaining rings and wedges should be inspected as given in Table 5, and according to applicable TILs.
2,000 starts interval being the maximum. If the rotor has not been inspected within the last 20 years or the rotor has operated greater than the re-inspect interval, then the rotor should be inspected at the earliest opportunity.
Bored Rotors
Rotors being Rewound
Ultrasonic volumetric testing, including bore sonic (bored rotors only), axial UT and periphery UT, should be performed within 20 service years of initial operation. Recommendations for subsequent re-inspections will be made on the basis of the test results and associated structural integrity, with a 20 year and a
Magnetic particle testing of the external surfaces of the rotor should be performed at outages that expose the bottom of the rotor slot. Magnetic fields in both the axial and circumferential directions should be used. Note that the axial direction may not be possible unless copper windings are removed.
Magnetic particle testing of the rotor bore surface (bored rotors only) should be performed concurrent with ultrasonic volumetric testing.
Table 5. Summary of Generator Field Inspection Recommendations Generator Field Characteristics
Outage Type
Ultrasonic Volumetric
Mag Particle of all shaft diameters and slots
In service and has a main body bore
Maintenance
Notes 1 and 2
Note 3
In service more than 20 years with no main body bore
Maintenance Note 1
In service and has a main body bore
Rewind
Notes 1 and 2
Note 4
In service more than 20 years with no main body bore
Rewind
Note 1
Note 4
Note 3
Note: [1] Ultrasonic volumetric testing includes boresonic tests (bored rotors only), axial UT and periphery UT tests. The recommendations for subsequent re-inspections will be made on the basis of the test results and associated structural integrity, with a 2000 start-stops or 20 year (whichever occurs first) re-inspect interval being the maximum. If the rotor has not been inspected within the last 20 years or the rotor has operated higher than the re-inspect interval, then the rotor should be inspected at the earliest opportunity. [2] Magnetic particle testing of the rotor bore surface (bored rotor only) should be performed concurrent with ultrasonic volumetric testing. [3] The turbine end of the generator field from the coupling face to the fan ring should also receive a magnetic particle inspection concurrent with ultrasonic volumetric testing. Extreme caution should be exercised during magnetic particle testing to prevent foreign particles from entering the field windings. [4] During full rewinds, perform mag particle testing of all accessible surfaces including axial and circumferential magnetization.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 11 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Part 2 – Other Maintenance Considerations 8. Other Maintenance Considerations – Part 2 Part 1 includes general guidance and recommendations in connection with generator maintenance. As technology is continually evolving, additional methods that aid the owner/operator in maintaining generator reliability at lower lifecycle costs become available. Non-invasive inspection, monitoring, and diagnostic technologies are a few recent examples.
Non-invasive visual inspections: Additional inspections can be performed with borescopes, cameras, etc., by removing access covers not requiring the removal of the end shields or field. These inspections can be performed during short duration planned outages such as balance of plant or heat recovery steam generator inspections. These non-invasive, short inspections can provide early critical insight into developing problems.
Monitoring & diagnostics: Between periods of planned offline maintenance, there are a number of parameters an operator can monitor to detect changes in equipment condition. Analysis of this operating data can be used to understand the overall condition of the unit and enables prediction of possible equipment failures in advance. Advances in partial discharge monitoring of the stator insulation system aim to detect numerous aging or wear mechanisms within the stator before significant damage can occur. Advances in shorted turn monitoring allow early detection of the number and location of coil to coil shorts within the field. Advances in collector monitoring allow early detection of electrical arcing/sparking of the collector system in order to avoid possible flashovers. Connection ring displacement monitoring allows early detection of relative movement of the connection rings before significant
insulation abrasion occurs. These tools can be integrated into a comprehensive maintenance program. Should further information be desired or should particular problems arise which are not covered sufficiently for the owner/operators purposes the matter should be referred to the local GE Service Office.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 11 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 12 of 12
Imagination at work
*Trademark of General Electric Company.
GEK 103566 (11/2014)
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
Rev J
GE Power & Water
Released 11/14/2014
Page 1 of 12
GEK 103566 Revised, November 2014
Creating an Effective Generator Maintenance Program
These instructions do not purport to cover all details or variations in equipment nor to provide for every possible contingency to be met in connection with installation, operation or maintenance. Should further information be desired or should particular problems arise which are not covered sufficiently for the purchaser’s purposes the matter should be referred to General Electric Company. These instructions contain proprietary information of General Electric Company, and are furnished to its customer solely to assist that customer in the installation, testing, operation, and/or maintenance of the equipment described. This document shall not be reproduced in whole or in part nor shall its contents be disclosed to any third party without the written approval of General Electric Company. © 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
GEK 103566
2
Rev J
Released 11/14/2014
Page 2 of 12
Creating an Effective Generator Maintenance Program
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 3 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Contents Part 1 – Maintenance Outage Planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Background – Part 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Maintenance Planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Maintenance Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Visual Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. MAGIC* (Miniature Air Gap Inspection Crawler) Robot Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.
Rotor Life Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Part 2 – Other Maintenance Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8. Other Maintenance Considerations – Part 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
List of Tables Table 1. Recommended Initial Maintenance Interval in Absence of Operational Experience. . . . . . . . . . . . . . . . . 5 Table 2. Recommended Stator and Core Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7 Table 3. Recommended Water Cooled Stator Leak Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 4. Recommended Field Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9 Table 5. Summary of Generator Field Inspection Recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 3 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 4 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
Part 1 – Maintenance Outage Planning
A few examples of the primary factors that affect the maintenance planning process are shown as follows and should be integrated into the overall maintenance program: • O&M manual • Manufacturer’s recommended maintenance program • Technical Information Letters • Operational history • Monitoring trends • Previous inspections • Design features • Duty cycle • Ambient and environmental conditions • Risk tolerance • Reliability/availability needs
1. Background – Part 1 A thorough maintenance program is recommended to retain generator reliability and avoid major failure expenses. The three important elements of a thorough program are maintenance frequency, testing and visual inspection. It is the intent of this document to provide information on each of these elements, which will aid the owner/operator to establish a thorough and cost effective maintenance program.
2. Maintenance Planning Advanced planning for maintenance is necessary for generator operators in order to maintain reliability and availability. The correct implementation of planned maintenance and inspection provides direct benefits in the avoidance of forced outages, unscheduled repairs, and downtime. The basic design and recommended maintenance of GE heavy-duty thermal generators are oriented toward: • Maximum periods of operation between inspections • In-place, on-site inspection and maintenance • Use of local trade skills to disassemble, inspect, and re-assemble generator mechanical components
4
In addition to maintenance of the basic thermal generator, other auxiliaries require periodic servicing including the control devices, downstream electrical components, and other auxiliaries. This document is focused on maintenance planning for the basic thermal generator, which includes the field, stator core, and frame. Other systems, while outside the scope of this document, also need to be considered for successful plant maintenance. The inspection and repair requirements, outlined in the O&M Manual provided to each owner, lend themselves to establishing a pattern of inspections. These inspection patterns will vary from site to site due to numerous factors such as duty cycle and ambient conditions. GE monitors operating experience, inspection results, and in-service operating issues of the installed base to the degree that the information is available. This is used to analyze and identify potential issues specific to similar units across the fleet with subsequent recommendations to owners on specific matters forwarded by means of Technical Information Letters (TIL) so applicable action can be taken to obtain maximum reliability, availability, and maintainability. The recommendations contained in TILs should be reviewed and factored into the overall maintenance planning program.
The operational log should include the type of duty and any known abnormal operating incidents. Operational events which should be carefully noted are: a. Errors in synchronizing b. Under or over frequency operation c. Lightning surges or other transients d. Faults (such as short circuits) on system or adjacent machines e. Unbalanced load, including single phase operation (Negative Sequence and Motoring events) f. Overload g. Over voltage or under voltage h. Loss of field i. Loss of cooling water without load run-back j. Asynchronous operation Each of these events would have a different impact on the necessary planning for maintenance and inspection. Depending on the circumstances, some of these events might dictate that the machine be shut down for immediate inspection, whereas other events may allow a reasonable wait for the next scheduled inspection. The maintenance program should reflect the level of acceptable risk for the unit. This will vary from unit to unit and plant to plant, and will change over time as the
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 5 of 12
Creating an Effective Generator Maintenance Program importance of the unit to the power system changes. In addition, new technologies are constantly being developed to improve unit reliability, performance, and monitoring and inspection equipment, to provide a cost–effective means for maintaining the generator. The MAGIC* Robot In-Situ Generator Inspection System is one example of a technology developed by GE to provide a more cost-effective means of performing a major inspection. Other examples include advanced continous monitors such as stator partial discharge, field shorted turns, and collector health. The owner/operator should be aware of these developments and modify the maintenance program accordingly. While this should be a continuous process, the “maintenance outage planning review” is an appropriate checkpoint. Planned maintenance outages are usually scheduled well in advance of the actual outage date, and preparation for the outage should begin early. Materials that might be needed for the inspection should be ordered in advance so that they will be available at the start of the outage to avoid the risk of a costly delay.
The frequency and level of inspection can be dependent upon service duty, system demands, age of the unit, and risk tolerance, among many other individual plant considerations. These factors were discussed in Section 2 Maintenance Planning. The owner must balance performance, reliability and cost when planning maintenance outages and setting maintenance intervals. Many of the factors related to the timing of inspections are determinable by the owner/operator; other factors draw from empirical knowledge and fleet experience.
maintenance experiences are accumulated. While reductions in the recommended intervals could result from abnormal operational events described previously or unfavorable operating experience, increases in the recommended intervals may also be considered where operating experience has been favorable. Historical operation and machine conditions can be used to tailor maintenance programs such as optimized inspection intervals to specific sites/machines. GE can assist operators in determining the appropriate maintenance intervals for their particular application.
In the absence of operating experience and resulting condition assessments, Table 1 lists the recommended inspection intervals for GE thermal generators. Generally speaking, GE generators can be inspected commensurate with the associated turbine inspection outage with the exception of a “first” inspection defined as 8000 fired hours, 4000 turning gear hours, or 250 starts whichever comes first. These initial intervals should be reviewed and adjusted as operating and
During the first several months or several thousand hours of operation, some generator components experience a break-in period. The first year inspection will detect and correct for this period of potentially increased wear. Additionally, it should be noted wear can accumulate during turning gear operation. During turning gear operation, relative motion may occur in the field winding components potentially causing fretting wear. It is advised to the operator to minimize turning
Table 1. Recommended Initial Maintenance Interval in Absence of Operational Experience1
The local GE Field Service Office can assist in maintenance planning, and review of the overall maintenance program, incorporating any appropriate new maintenance and upgrade available technologies.
3. Maintenance Frequency There are a number of components which require routine maintenance or inspections between scheduled outages. The operator will find these recommendations in various equipment manuals, and should also include additional maintenance tasks as operating experience indicates. Results of this routine maintenance should be retained in well-organized files readily available for reference. These routine maintenance records coupled with the information from the monitored operating data are a good indicator of pending service or operating problems that should be addressed at the next scheduled outage. The monitored information alone is usually not sufficient for tracking or highlighting trends.
GEK 103566
Model
1st Major
Minor
Major
7FH2, 7FH2B, 6A2, 6A3, 6A6, 6FA, 7A3, 7A6, 9A3, 9A5
8,000 Fired Hours, 4,000 Turning Gear Hours, or 250 starts, whichever comes first
24,000 to 32,000 Factored Turbine Hours or 900 to 1,250 Factored Turbine Starts 30,000 to 32,000 Turning Gear Hours
48,000 to 64,000 Actual Turbine Hours or 1,800 to 2,400 Actual Turbine Starts 60,000 to 64,000 Turning Gear Hours
Liquid Cooled
8,000 Fired Hours, 24,000 to 32,000 4,000 Turning Gear Turbine Hours or 900 Hours, or 250 starts, to 1,200 Turbine Starts whichever comes first
48,000 to 64,000 Actual Turbine Hours or 1,800 to 2,400 Actual Turbine Starts
All Other Models
8,000 Fired Hours, 4,000 Turning Gear Hours, or 250 starts, whichever comes first
20,000 to 24,000 Factored Turbine Hours or 750 to 900 Factored Turbine Starts
40,000 to 48,000 Actual Turbine Hours or 1,800 to 2,400 Actual Turbine Starts
12,000 to 15,000 Factored Turbine Hours or 400 to 600 Factored Starts
24,000 to 30,000 Actual Turbine Hours or 800 to 1,200 Actual Starts
Asphalt Stator Bar Windings for Core Does not apply Lengths Over 150 Inches Note: 1
These initial recommendations assume GE approved repairs, field services, and full compliance to GE’s technical recommendations.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 5 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 6 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
gear operation to the extent possible without violating limits on the other rotor train components. It is recognized that some power generation plants may run in an operational regime which could produce extended turbine inspection outage intervals in the 6 to 10 year range. Regardless of plant operating regime, GE can help the owner define a customized cost effective maintenance plan. During a minor inspection, upper end shields or end plates are removed to permit
inspection of the end winding area, but the field remains in place. A major outage includes removing the field from the stator or using the MAGIC* robot (Miniature Air Gap Inspection Crawler) to permit a thorough inspection of the core section of the stator and field. Inspection of the field and stator using the MAGIC* robot may require the removal of a few entrance gap baffles to allow access to the air gap with the field in place. The inspection includes a series of tests and a visual inspection.
Each has their particular advantage and neither alone is sufficient. See Section 6 for a brief description of the capabilities of the MAGIC* robot. Note that the MAGIC* robot inspection technique for performing a major inspection may not eliminate the need to remove the rotor if an issue is discovered that requires rotor removal to correct, such as loose stator core wedges. Tables 2 through 4 display recommended test and inspections.
Table 2. Recommended Stator Tests and Inspections Stator and Core
Major Rotor Major In with LCSW Minor Rotor MAGIC* Out Robot / RAC
AIR
HYD
Checks for calibration and poor connections.
X
X
X
X
X
X
Stator Winding RTD’s
Insulation condition of RTD.
X
X
X
X
X
X
Stator Winding
Checks for poor connections and breaks.
X
X
X
X
X
X
CE Bearing
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
Hydrogen Seal Casing
Contamination and/or deterioration of insulation.
X
X
X
X
X
Polarization Index
Stator Winding
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
DC Leakage Current
Stator Winding
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
Over Potential/Hipot
Stator Winding
Ground wall insulation integrity
X
X
X
X
X
X
Stator Wedges
Detect wedge tightness deterioration
X
X
X
X
X
All Visible Components
Cleanliness, foreign material, loose or displaced parts, damage, wear, corrosion, deterioration
X
X
X
X
X
Core Laminations
Foreign Object Damage, surface condition and wear, cracks, burning
X
X
X
X
X
Core End
Surface condition and wear, cracks, burning, blocked ventilation, bar sparking
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Test
Component
Inspection Objectives and Assessment
RTD Element Resistance
Gas and Winding RTD’s
RTD Ground Insulation Winding Copper Resistance Insulation Resistance (aka Megger)
Wedge Tightness Map1
Visual Inspections
Core Ventilation Ducts Blocked ventilation Space Blocks
6
Migration, cooling age blockage
X
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 7 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Stator and Core
Major Rotor Major In with LCSW Minor Rotor MAGIC* Out Robot / RAC
AIR
HYD
Cracked welds, looseness
X
X
X
X
X
Stator Wedges, Top and Side Ripple Springs
Evidence of abrasion or looseness
X
X
X
X
X
Stator Bars
Cracks, worn parts, burning, bar sparking, tape migration, water leaks if applicable
X
X
X
X
X
End Winding System
Cracks, worn or loose parts, blocked ventilation, broken ties, dusting and or greasing
X
X
X
X
X
Connection Rings and Lower Leads
Cracks, worn parts, burning, tape migration, broken ties, dusting and or greasing, and water leaks if applicable
X
X
X
X
X
High Voltage Bushings
Cracks, worn parts, burning, blocked ventilation, water leaks if applicable
X
X
X
X
X
Copper Flux Shield
Overheating, hardware looseness
X
X
X
X
X
Frame
Corrosion, cracks, blocked ventilation
X
X
X
X
X
X
Bearings and Seals
Corrosion, cracks, worn parts, burning
X
X
X
X
X
X
Coolers
Corrosion, cracks, water leaks
X
X
X
X
X
Key Bars and Core Compression Bands
Cracks, burning, core tightness
X
X
X
X
X
Key Bar Nuts and Locking Tabs
Cracks, burning, core tightness
X
X
X
X
X
Partial Discharge Analysis
Stator Winding Insulation
Localized deterioration
X
X
X
R
R
Water Flow Verification
Water Cooled Stator Winding
Restrictions in hydraulic circuit
X
X
X
Magnetic Scalar Potential (EL CID)
Stator Core Insulation
Weak or damaged core enamel.
X
X
X
X
X
Core Ring Test
Stator Core Insulation
Weak or damaged core enamel
X
X
X
X
Dynamic Frequency Response
Stator End Winding
Potentially damaging resonance.
X
X
X
X
Test
Component
Inspection Objectives and Assessment
Gas Gap Baffles
Visual Inspections
X
Optional Tests
Air – Air Cooled Generator
R
HYD – Hydrogen Cooled Generator
LCSW – Hydrogen Cooled Generator with Liquid Cooled Stator Winding
X - Pertains only to type of unit selected
R - These tests are performed while the unit is running.
Note: For inner gas cooled stator bars use the hydrogen column. 1
This test does not apply to units with asphalt stator windings or units with the “camelback” wedge system.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 7 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 8 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
Table 3. Recommended Water Cooled Stator Leak Tests† Clip-Strand Braze: Phos Containing
Stator
Orig SLMS, Bagged Vent, or No Monitoring
H2 Leak Monitoring Method
Global Epoxy Injection or Clip-Strand Braze: Phos-Free Orig SLMS, Bagged Vent, or No Monitoring
SLMS HP Installed
Test
Inspection Objectives and Assessment
Minor
Major
Vacuum Decay
Checks the hydraulic integrity of the entire winding.
X
Pressure Decay
Checks the hydraulic integrity of the entire winding.
X
Helium Tracer Gas
Detects minute leaks in the hydraulic circuit.
X
X
X
Capacitance Mapping
Wet ground wall bar insulation
X
X
X
WIM – Wet Insulation Measurement
Wet ground wall bar insulation
X
X
X
Electrical Testing
Ensure the electrical insulation integrity of the system
X
Minor
Minor
Major
X
X
X
X
X
X
X
Major
X
X
X
X
SLMS HP Installed Minor
Major
X
X
† These tests are required to detect hydrogen leaks in water cooled stator windings only and should be performed in conjunction with the recommended tests
in Table 1
Table 4. Recommended Field Tests Field AIR
HYD
Major Rotor In with LCSW Minor MAGIC* Robot / RAC
Major Rotor Out
Test
Component
Inspection Objectives and Assessment
Winding Copper Resistance
Field Winding
Checks for poor connections and breaks.
X
X
X
X
X
X
Polarization Index
Field Winding
Contamination and/or deterioration of insulation.
X
X
X
X
X
X
Shorted Turn Test1
Field Inter-Turn Insulation
Turn shorts
X
X
X
R
R
R
Incremental Winding Copper Resistance
Main lead, Gooseneck, and Bore Copper
Checks for looseness of the main lead and orientation dependent connectivity issues
X
X
X
All Visible Components
Cleanliness, foreign material, loose or displaced parts, damage, wear, corrosion, deterioration
X
X
X
X
X
Field Surface
Heating, arcing, foreign object damage
X
X
X
X
X
Body Weights
Looseness, staking
X
X
X
X
X
Visual Inspection
8
X
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 9 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Field AIR
HYD
Major Rotor In with LCSW Minor MAGIC* Robot / RAC
Major Rotor Out
Component
Inspection Objectives and Assessment
Body Wedges
Arcing, migration, cracking, blocked ventilation
X
X
X
X
X
Retaining Ring “Nose”
Wedge , arcing, foreign object damage
X
X
X
X
X
Retaining Rings
Cracks and burning
X
X
X
X
X
Coil End Turns
Blocked ventilation, damaged insulation, coil distortion
X
X
X
X
X
Fans
Cracks
X
X
X
X
X
Spindles
Cracks
X
X
X
X
X
Winding
Cracks, burning, blocked ventilation, worn parts
X
X
X
X
X
Collectors
Cracks, burning, blocked ventilation, worn parts
X
X
X
X
X
X
Journals
Cracks, burning, worn parts
X
X
X
X
X
X
Over Potential/Hipot
Field Winding
Ground wall insulation integrity.
X
X
X
X
X
X
Bore Pressure Test
Chevron Seals
Sealing capability of the Chevron seals.
X
X
X
X
X
Test
Visual Inspection
Optional Tests
Air – Air Cooled Generator
1
HYD – Hydrogen Cooled Generator
LCSW – Hydrogen Cooled Generator with Liquid Cooled Stator Winding
X - Pertains only to type of unit selected
R - These tests are performed while the unit is running.
The preferred method for shorted turn testing is the flux probe. Another method is AC Impedance testing.
4. Testing
5. Visual Inspection
Generator electrical testing is focused on the insulation systems. There are other tests used to monitor for degradation in other components. A list of the typical tests recommended and the test purpose is shown in Tables 2, 3, and 4. Historical records of test results should be maintained and compared to the new test results. Changes between outage test results may point to needed repairs/rework that may not be evident from the absolute test values themselves.
A visual inspection, performed at every inspection by an experienced individual, can disclose unit conditions not detected by monitoring equipment or tests. In some instances, electrical testing will only detect issues when the stator and field insulation systems have been significantly compromised. Also, for example, there is no definitive test for contamination, rust or oil, and water leaks, and yet the presence of any of these could adversely affect reliability and operation. A typical visual inspection should include those items listed in Tables 2 and 4.
Many of the tests require special equipment that has been properly maintained and calibrated to assure accurate results.
As important as it is, visual inspection is limited to areas that can be accessed for view either directly or with mirrors, borescopes, cameras, etc., and therefore, it must be combined with testing to give a complete picture of generator condition.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 9 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 10 of 12
GEK 103566
Creating an Effective Generator Maintenance Program
6. MAGIC* Robot Inspection GE’s MAGIC* (miniature air gap inspection crawler) robots provide a thorough visual inspection of the stator and field using the robot’s on-board high-resolution video cameras. Additionally, it is capable of providing quantitative wedge tightness and Electromagnetic Core Imperfection Detection (ELCID) assessments. Coupled with the Remote Access Camera (RAC), the MAGIC* robot inspection can provide a comprehensive stator and field inspection. The customer may utilize the MAGIC* robot to perform the recommended inspection tasks that normally require the removal of the rotor. As a result, the customer may substitute a MAGIC* robot inspection for a major inspection providing the major inspection tasks outlined in Tables 2, 3, and 4, that don’t require the removal of the rotor, are performed during the outage as well. In order to use a MAGIC* robot, the generator must meet the following minimum radial entrance gap dimensions: MAGIC* (Senior)
MAGIC* (Junior)
• Retaining ring to core minimum radial gap 1.13 inches [28.7 mm]
• Retaining ring to core minimum radial gap 0.5 inches [12.7 mm]
• Field to core minimum radial gap of 2.0 inches [50.8 mm]
• Field to core minimum radial gap 0.75 inches [19.05 mm]
7. Rotor Life Management Generator rotor structural components are designed for normal transient events including 10,000 start/stop cycles for combined cycle power plants. However, with proper maintenance and inspections, generators can last much longer than that. Common issues with aged rotor forgings are typically related to the number of start/stop cycles. Several Technical Information Letters (TILs) have been
10
written on the subject. Particularly when performing rotor rewinds, those TILs should be reviewed and the inspections performed. These inspections are mostly focused on cracks in the wedge loading face, in the slot and in the bore if the rotor forging has one. Rotor forgings, retaining rings and wedges should be inspected as given in Table 5, and according to applicable TILs.
2,000 starts interval being the maximum. If the rotor has not been inspected within the last 20 years or the rotor has operated greater than the re-inspect interval, then the rotor should be inspected at the earliest opportunity.
Bored Rotors
Rotors being Rewound
Ultrasonic volumetric testing, including bore sonic (bored rotors only), axial UT and periphery UT, should be performed within 20 service years of initial operation. Recommendations for subsequent re-inspections will be made on the basis of the test results and associated structural integrity, with a 20 year and a
Magnetic particle testing of the external surfaces of the rotor should be performed at outages that expose the bottom of the rotor slot. Magnetic fields in both the axial and circumferential directions should be used. Note that the axial direction may not be possible unless copper windings are removed.
Magnetic particle testing of the rotor bore surface (bored rotors only) should be performed concurrent with ultrasonic volumetric testing.
Table 5. Summary of Generator Field Inspection Recommendations Generator Field Characteristics
Outage Type
Ultrasonic Volumetric
Mag Particle of all shaft diameters and slots
In service and has a main body bore
Maintenance
Notes 1 and 2
Note 3
In service more than 20 years with no main body bore
Maintenance Note 1
In service and has a main body bore
Rewind
Notes 1 and 2
Note 4
In service more than 20 years with no main body bore
Rewind
Note 1
Note 4
Note 3
Note: [1] Ultrasonic volumetric testing includes boresonic tests (bored rotors only), axial UT and periphery UT tests. The recommendations for subsequent re-inspections will be made on the basis of the test results and associated structural integrity, with a 2000 start-stops or 20 year (whichever occurs first) re-inspect interval being the maximum. If the rotor has not been inspected within the last 20 years or the rotor has operated higher than the re-inspect interval, then the rotor should be inspected at the earliest opportunity. [2] Magnetic particle testing of the rotor bore surface (bored rotor only) should be performed concurrent with ultrasonic volumetric testing. [3] The turbine end of the generator field from the coupling face to the fan ring should also receive a magnetic particle inspection concurrent with ultrasonic volumetric testing. Extreme caution should be exercised during magnetic particle testing to prevent foreign particles from entering the field windings. [4] During full rewinds, perform mag particle testing of all accessible surfaces including axial and circumferential magnetization.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 11 of 12
Creating an Effective Generator Maintenance Program
GEK 103566
Part 2 – Other Maintenance Considerations 8. Other Maintenance Considerations – Part 2 Part 1 includes general guidance and recommendations in connection with generator maintenance. As technology is continually evolving, additional methods that aid the owner/operator in maintaining generator reliability at lower lifecycle costs become available. Non-invasive inspection, monitoring, and diagnostic technologies are a few recent examples.
Non-invasive visual inspections: Additional inspections can be performed with borescopes, cameras, etc., by removing access covers not requiring the removal of the end shields or field. These inspections can be performed during short duration planned outages such as balance of plant or heat recovery steam generator inspections. These non-invasive, short inspections can provide early critical insight into developing problems.
Monitoring & diagnostics: Between periods of planned offline maintenance, there are a number of parameters an operator can monitor to detect changes in equipment condition. Analysis of this operating data can be used to understand the overall condition of the unit and enables prediction of possible equipment failures in advance. Advances in partial discharge monitoring of the stator insulation system aim to detect numerous aging or wear mechanisms within the stator before significant damage can occur. Advances in shorted turn monitoring allow early detection of the number and location of coil to coil shorts within the field. Advances in collector monitoring allow early detection of electrical arcing/sparking of the collector system in order to avoid possible flashovers. Connection ring displacement monitoring allows early detection of relative movement of the connection rings before significant
insulation abrasion occurs. These tools can be integrated into a comprehensive maintenance program. Should further information be desired or should particular problems arise which are not covered sufficiently for the owner/operators purposes the matter should be referred to the local GE Service Office.
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, 11 without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
DWG Number GEK103566
Rev J
Released 11/14/2014
Page 12 of 12
Imagination at work
*Trademark of General Electric Company.
GEK 103566 (11/2014)
© 2014 General Electric Company. All Rights Reserved. This material may not be copied or distributed in whole or in part, without prior permission of the copyright owner. GE Proprietary Information - Class II (Internal) US EAR - NLR
Related Documents 3h463d
Gek103566_j Creating An Effective Generator Maintenance Program 6x136m
December 2020 0
Creating An Effective Online Syllabus 3f3c5h
November 2019 39
Creating An Effective Supply Chain 2l6e5x
November 2019 33
Developing An Effective Ethics Program q103t
December 2019 34
Effective Building Maintenance 385j5d
October 2020 0
Elements In An Effective Marketing Research Program 1hy
November 2021 0More Documents from "Manuel L Lombardero" 1w3q27
113 Snackshop Vending Manual Automatic Products 5o6i5q
November 2019 29
St5484e 2-wire Seismic Vibration Transmitter Installation Manual 5w5a6l
December 2019 16
4p345f
April 2020 30
Til 1886 Inspection Of Low Pressure Rotor Wheel Dovetails On Steam Turbines With Fossil Fueled Drum Boilers 135n4o
December 2019 27
Gaines Vm-750 Vending Machine Manual p3w68
December 2019 27