STEAM TURBINE ENGINEERING AND MAINTENANCE, INC. HP/RH/LP Steam Path Audit and Repair Recommendations March/April 2007 Fall Outage TB#, HP/RH/LP General Electric HP/RH/LP Sections 200 MW Cross Compound 2 nd Stage HP Bucket as Found Foreign Object Damage. 891 Nissen Drive 32034 Phone: 904-321-1946 PO Box 15010 32035-3101 Fax: 904-321-2701 Fernandina Beach, FL Cell: 904-535-4330
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STEAM TURBINE ENGINEERING AND MAINTENANCE, INC.
HP/RH/LP Steam Path Audit and Repair Recommendations
March/April 2007 Fall Outage TB#, HP/RH/LP General Electric HP/RH/LP Sections 200 MW Cross Compound
2nd Stage HP Bucket as Found Foreign Object Damage.
891 Nissen Drive 32034 Phone: 904-321-1946 PO Box 15010 32035-3101 Fax: 904-321-2701 Fernandina Beach, FL Cell: 904-535-4330
STEAM TURBINE ENGINEERING AND MAINTENANCE, INC.
EXECUTIVE SUMMARY March 31, 2007 Steam Turbine Engineering And Maintenance, Inc. was engaged to perform a Steam Path Audit on unit #4 during the March/April 2007 scheduled outage. We arrived on-site the morning of March 16 to start the Audit. The Audit was completed on March 22. This 200 MW, 1050/1000 °F, 2400 psi General Electric cross compound unit is in fairly good condition for the years of reliable service that it has seen. During this outage the HP, RH and LP sections of the machine are scheduled for the outage. High Pressure Section The High-pressure section, in the as found condition, is estimated to have an efficiency loss of approximately 11.9%. A large part of the efficiency losses are due to heavy coating buildup on the diaphragm partitions and bucket vanes. Other factors include damaged and rubbed bucket tip spill strips and packing. Moderate losses from flow path damage and surface roughness also contributed to the HP efficiency losses. The damaged N2 packing also contributed to efficiency losses allowing a significant amount of leakage into the reheat section. In general the buckets on the HP rotor and all of the associated hardware suffer from heavy to light FOD, Foreign Object Damage. The 2nd, 3rd 4th and 5th stage buckets should be replaced during the next scheduled outage. Diaphragm stages 1-7 have all been previously majored. The 2nd through 7 stage diaphragms suffer from heavy to moderate FOD and will require major repairs during the next scheduled outage. Stages 8 and 9 have also been majored previously and are still in relatively good condition. The 9th stage diaphragm partition edges were cut back .030” during this outage. The 1st stage nozzle may also require major repairs during the next scheduled outage. The HP bucket tip spill strips will be replaced during this outage except on stages 2 and 9. The N2 packing will be replaced during this outage. The inter-stage packing on stages 2-6 in the HP will also be replaced during this outage. The HP section is estimated to have a 3 - 3.5% efficiency loss from design after completion of the 2007 outage. Reheat Section The Reheat section, in the as found condition, is estimated to have an efficiency loss of approximately 3.6%. The majority of the RH section losses are due to excessive packing and spill strip clearances, heavy coating deposits on the bucket cover ID’s and minor FOD. All reheat buckets, covers and tenons are in reasonably good condition and should perform well for a good number of years. The 10th stage diaphragm will probably require major repairs during the next scheduled outage. The remaining RH diaphragms, stages 11-13, will be repaired as minors during this outage. During the next scheduled outage RH diaphragm stages 11-13 will probably will require only minor repairs. The RH bucket tip spill strips on stages 10 and 13 will be replaced during this outage. The RH section inter-stage packing was found in good condition and will be re-used. The RH section is estimated to have a 1.0 to 1.5% efficiency loss from design after completion of the 2007 outage.
Low Pressure Section The LP section, in the as found condition, is estimated to have an efficiency loss of approximately 2.0%. Approximately 25% of the LP section losses are due to excessive packing and spill strip clearances. Approximately 50% of the losses are due to coating buildup and surface roughness. The remaining LP losses are due to minor FOD and general wear. The 1st stage LP bucket tenons were found severely eroded on the leading edges. The 1st stage LP tenons were weld repaired during this outage. The last stage LP buckets were previously under-shroud brazed. The silver was found loose on the bucket tips. The silver was ground off and the tips re-soldered during this outage. The remaining LP buckets, covers and tenons are in reasonably good condition. All LP diaphragms will be repaired as minors during this outage. The LP diaphragms should be able to be repaired as minors again at the next scheduled outage. The LP spill strips on stages 1,4,5,6 and 7 will be changed during this outage. The LP packing was found in relatively good condition and will not be replaced during this outage. The LP section is estimated to have a .5 - .75% efficiency loss from design after completion of the 2007 outage. In the as found condition, unit #4 is estimated to have an efficiency loss of 5.33%. New spill strips and packing will be installed in most of the HP section. New spill strips will be installed on stages 10 and 13 in the RH section. And new spill strips will be installed in the LP section on stages 1,4,5,6 and 7 during this outage. The RH and LP packing was found to be in relatively good condition. With these improvements, along with the diaphragm repairs and bucket repairs planned to be completed this outage the unit should come back up no more than 1.5-2.0% off of the original design. If you have any questions or wish to discuss any of the above in greater detail, please feel free to contact us at your convenience. And we would like to thank the outage personnel for their timely support and cooperation during the time we were on-site. Dan McCarthy
HP Diaphragms 1st Stage Nozzle 35 Openings per half R.H. = 1.000 I.W. Dia. ≈ 35.125 T @ Y ≈ .360
1. The partitions in the upper and lower nozzle plate have moderate FOD, Foreign Object Damage, on the partition convex surface.
2. 2-3 partitions in the upper half and 1-2 partitions in the lower half are eroded and will require weld repairs.
3. The bucket cover spill strip is rubbed and has pieces broken out. 4. The nozzle bolt cover plate and welds appear to be in good condition. 5. There is a .010” coating buildup on the convex surface of the partitions.
Repair Recommendations: Minor Repair
1. Weld repair partitions in the U.H. and L.H. as required including any indications found during N.D.E.
2. Weld repair NDE indications and heavy FOD as required. 3. Replace bucket cover spill strip.
2nd Stage 35 Openings per half R.H. = 1.150 I.W. Dia. ≈ 31.125 T @ Y ≈ .320
1. All partitions are intact. There is some moderate FOD on the partition convex surface.
2. The inner and outer sidewalls are in good condition. 3. The admission sides of the partitions are in good condition. 4. There are 6-8 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face has some fretting and galling. 6. The crush pins appear to be worn. 7. There is a .060” coating buildup in the throat area and a .020” coating
buildup on the remaining convex surface. There is a .010 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition. Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots.
24. Polish steam seal face, check crush pin fit areas in the shell and replace
crush pins 1” from current location if required.
3rd Stage 22 Openings per half R.H. = 1.225 I.W. Dia. ≈ 31.500 T @ Y ≈ .560
1. All partitions are intact. There is some moderate FOD on the partition convex surface.
2. The inner and outer sidewalls are in good condition. 3. The admission sides of the partitions are in good condition. 4. There are 3-4 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face has some fretting and galling. 6. The crush pins appear to be worn. 7. There is a .060” coating buildup in the throat area and a .025” coating
buildup on the remaining convex surface. There is a .005 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition. Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots. 4. Polish steam seal face, check crush pin fit areas in the shell and replace
crush pins 1” from current location if required. 4th Stage 34 Openings per half R.H. = 1.400 I.W. Dia. ≈ 32.125 T @ Y ≈ .370
1. All partitions are intact. There is some minor FOD on the partition convex surface.
2. The inner and outer sidewalls are in good condition. 3. The admission sides of the partitions are in good condition. 4. There are 5-6 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face has some fretting and galling. 6. The crush pins appear to be worn. 7. There is a .060” coating buildup in the throat area and a .015” coating
buildup on the remaining convex surface. There is a .005 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition. Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots. 4. Polish steam seal face, check crush pin fit areas in the shell and replace
crush pins 1” from current location if required.
35th Stage 35 Openings per half R.H. = 1.600 I.W. Dia. ≈ 33.000 T @ Y ≈ .360
1. All partitions are intact. There is some minor FOD on the partition convex surface.
2. The inner and outer sidewalls are in good condition. 3. The admission sides of the partitions are in good condition. 4. There are 5-6 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face has some fretting and galling. 6. The crush pins appear to be worn. 7. There is a .050” coating buildup in the throat area and a .025” coating
buildup on the remaining convex surface. There is a .005 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition. Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots. 4. Polish steam seal face, check crush pin fit areas in the shell and replace
crush pins 1” from current location if required. 6th Stage 35 Openings per half R.H. = 1.825 I.W. Dia. ≈ 33.000 T @ Y ≈ .400
1. All partitions are intact. There is some minor FOD on the partition convex surface.
2. The inner and outer sidewalls are in good condition. 3. The admission sides of the partitions are in good condition. 4. There are 1-2 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face has some fretting and galling. 6. The crush pins appear to be worn. 7. There is a .050” coating buildup in the throat area and a .025” coating
buildup on the remaining convex surface. There is a .005 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition. Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots. 4. Polish steam seal face, check crush pin fit areas in the shell and replace
crush pins 1” from current location if required. 7th Stage 36 Openings per half R.H. = 1.900 I.W. Dia. ≈ 33.563 T @ Y ≈ .370
1. All partitions are intact. There is some very minor FOD on the partition convex surface.
42. The inner and outer sidewalls are in good condition. 3. The admission side of the partitions is in good condition. 4. There are 1-2 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face appears to be in good condition. 6. The crush pins appear to be in good condition. 7. There is a .050” coating buildup in the throat area and a .020” coating
buildup on the remaining convex surface. There is a .005 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition. Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots.
8th Stage 37 Openings per half R.H. = 2.000 I.W. Dia. ≈ 34.063 T @ Y ≈ .400
1. All partitions are intact. There is some very minor FOD on the partition convex surface.
2. The inner and outer sidewalls are in good condition. 3. The admission sides of the partitions are in good condition. 4. There are 1-2 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face appears to be in good condition. 6. The crush pins appear to be in good condition. 7. There is a .050” coating buildup in the throat area and a .020” coating
buildup on the remaining convex surface. There is a .005 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition. Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots.
9th Stage 37 Openings per half R.H. = 2.375 I.W. Dia. ≈ 34.375 T @ Y ≈ .430
1. All partitions are intact. There is some very minor FOD on the partition convex surface.
2. The inner and outer sidewalls are in good condition. 3. The admission sides of the partitions are in good condition. 4. There are 1-2 partitions in each half with bent and dinged exhaust edges. 5. The steam seal face appears to be in good condition. 6. The crush pins appear to be in good condition. 7. There is a .050” coating buildup in the throat area and a .020” coating
buildup on the remaining convex surface. There is a .005 coating buildup on the concave surface of the partitions.
8. The horizontal joint faces appear to be in good condition.
5Repair Recommendations: Minor Repair
1. Straighten exhaust edges as required. 2. Weld repair any indications found during N.D.E. 3. Polish FOD high spots.
Future HP Diaphragm Repairs
The 2nd, 3rd, 4th, 5th, 6th, and 7th Stage diaphragms will require major repairs during the next scheduled turbine outage. The above stage diaphragms are structurally in acceptable condition, however the partitions suffer from heavy FOD resulting in significant efficiency losses.
HP/RH Rotor HP Single Flow Stages 1-9 1st Stage HP Buckets 108 spaces, Notch Block. A.L. ≈ 1.025” Cover Dia. 38.692” Throat @Y≈ .400”
1. The admission sides of the vane sections have minor FOD. The bucket vanes have a S.P.E. resistant coating. There are a few vanes that have small areas where the coating has been knocked off by impact of foreign objects.
2. The exhaust sides of the vane sections are in good condition. 3. The outer covers are down tight on the vane tips. There is some minor FOD on the cover
OD’s. 4. The tenons have some minor FOD on the leading edges. 5. The notch block is down tight. 6. The vane exhaust edge thickness is ≈ .050”. 7. A coating buildup of ≈ .025” was found on the convex surface.
1. The admission sides of the vane sections have heavy FOD. The vane admission edges are thin and there are a few bent admission edges.
2. The exhaust sides of the vane sections have some minor FOD and a few bent exhaust edges
3. The bucket covers, fox-hole construction, are down tight on the vane tips. There is moderate FOD on the cover OD’s.
4. The tenons have moderate FOD all over. 5. The notch bucket is down tight. 6. The vane exhaust edge thickness is ≈ .015”. 7. The bucket root radial spill strip is in good condition. 8. A coating buildup of ≈ .015” was found on the convex surface.
Repair recommendations:
1. Straighten the admission and exhaust edges as required. 2. Cut back admission edges .060” to thicken and stabilize. 3. Cut back the exhaust edges .040” to thicken and stabilize. 4. Polish FOD high spots on the admission side of the vane sections.
1. The admission sides of the vane sections have moderate FOD. There are a few bent
admission edges. 2. The exhaust sides of the vane sections have some minor FOD and a few bent exhaust
edges 3. The bucket covers, fox-hole construction, are down tight on the vane tips. There is minor
FOD on the cover OD’s and admission edges. 4. The tenons have moderate FOD all over. 5. The notch bucket is down tight. 6. The vane exhaust edge thickness is ≈ .015”. 7. The bucket root radial spill strip has a minor rub. 8. A coating buildup of ≈ .035” was found on the convex surface and ≈ .005” on the
concave surface. Repair recommendations:
1. Straighten the admission and exhaust edges as required. 2. Polish FOD high spots on the admission side of the vane sections. 3. Sharpen bucket root radial spill strip.
1. The admission sides of the vane sections have moderate FOD. There are a few bent admission edges.
2. The exhaust sides of the vane sections have some minor FOD and a few bent exhaust edges
3. The bucket covers are down tight on the vane tips. There is heavy FOD on the cover OD’s and admission edges.
4. The tenons have heavy FOD all over. 5. The notch bucket is down tight. 6. The vane exhaust edge thickness is ≈ .015”. 7. The bucket root radial spill strip has a minor rub. 8. A coating buildup of ≈ .035” was found on the convex surface and ≈ .005” on the
concave surface.
Repair recommendations:
1. Straighten the admission and exhaust edges as required. 2. Polish FOD high spots on the admission side of the vane sections. 3. Sharpen bucket root radial spill strip.
1. The admission sides of the vane sections have moderate FOD.
2. The exhaust sides of the vane sections have some minor FOD and a few bent exhaust edges
3. The bucket covers are down tight on the vane tips. There is heavy FOD on the cover OD’s and admission edges.
4. The tenons have heavy FOD on the leading edges. 5. The notch bucket is down tight. 6. The vane exhaust edge thickness is ≈ .015”. 7. The bucket root radial spill strip has a minor rub. 8. A coating buildup of ≈ .030” was found on the convex surface and ≈ .005” on the
concave surface. Repair recommendations:
1. Straighten the exhaust edges as required. 2. Polish FOD high spots on the admission side of the vane sections. 3. Sharpen bucket root radial spill strip.
1. The admission sides of the vane sections have light to moderate FOD. 2. The exhaust sides of the vane sections have some very minor FOD. 3. The bucket covers are down tight on the vane tips. There is light to moderate FOD on the
cover OD’s and admission edges. 4. The tenons have moderate to heavy FOD on the leading edges. 5. The notch bucket is down tight. 6. The vane exhaust edge thickness is ≈ .040”. 7. The bucket root radial spill strip has a minor rub. 8. A coating buildup of ≈ .025” was found on the convex surface and ≈ .005” on the
concave surface. Repair recommendations:
1. Polish FOD high spots on the admission side of the vane sections. 2. Sharpen bucket root radial spill strip.
1. The admission sides of the vane sections have light to moderate FOD. 2. The exhaust sides of the vane sections have some very minor FOD. 3. The bucket covers are down tight on the vane tips. There is light FOD on the cover OD’s
and admission edges. 4. The tenons have moderate FOD on the leading edges. 5. The notch bucket is down tight.
6. The vane exhaust edge thickness is ≈ .040”. 7. The bucket root radial spill strip has a heavy rub. 8. A coating buildup of ≈ .025” was found on the convex surface and ≈ .005” on the
concave surface. Repair recommendations:
1. Polish FOD high spots on the admission side of the vane sections. 2. Sharpen bucket root radial spill strip.
1. The admission sides of the vane sections have light to moderate FOD. 2. The exhaust sides of the vane sections have some very minor FOD. 3. The bucket covers are down tight on the vane tips. There is light FOD on the cover OD’s
and admission edges. 4. The tenons have light to moderate FOD on the leading edges. 5. The notch bucket is down tight. 6. The vane exhaust edge thickness is ≈ .040”. 7. The bucket root radial spill strip has a heavy rub. 8. A coating buildup of ≈ .025” was found on the convex surface and ≈ .005” on the
concave surface. Repair recommendations:
1. Polish FOD high spots on the admission side of the vane sections. 2. Sharpen bucket root radial spill strip.
1. The admission sides of the vane sections have light FOD. 2. The exhaust sides of the vane sections have some very minor FOD. 3. The bucket covers are down tight on the vane tips. There is light FOD on the cover OD’s
and admission edges. 4. The tenons have light FOD on the leading edges. 5. The notch bucket is down tight. 6. The vane exhaust edge thickness is ≈ .040”. 7. The bucket root radial spill strip has a heavy rub. 8. A coating buildup of ≈ .025” was found on the convex surface and ≈ .005” on the
concave surface. Repair recommendations:
1. Polish FOD high spots on the admission side of the vane sections.
1. The admission sides of the vane sections have some minor FOD. The bucket vanes have a S.P.E. resistant coating. There are a few vanes that have small areas where the coating has been knocked off by impact of foreign objects.
2. The exhaust sides of the vane sections are in good condition. 3. The covers, fox-holed construction, are down tight on the vane tips. There is some very
minor FOD on the cover OD’s. 4. The tenons have some minor erosion on the leading edges. 5. The notch block shows sign of some lifting, ≈ .025” on the admission side and ≈ .015” on
the exhaust side. 6. The vane exhaust edge thickness is ≈ .045”. No coating buildup was found on the vane
sections or cover ID’s. Repair recommendations:
1. Monitor the notch lifting during the next scheduled outage. 11th Stage RH Buckets 144 spaces, Notch Bkt. A.L. ≈ 3.100” Cover Dia. 47.660” Throat @Y≈ .380”
1. The admission sides of the vane sections have some minor FOD. 2. The exhaust sides of the vane sections are in good condition. 3. The covers are down tight on the vane tips. There is some very minor FOD on the cover
OD’s. 4. The tenons have some minor erosion on the leading edges. 5. The notch bucket shows sign of some lifting, ≈ .015” on the admission and exhaust sides. 6. The vane exhaust edge thickness is ≈ .050”. A .125 coating buildup was found on the ID
of the bucket covers. No coating buildup was found on the vane sections. Repair recommendations:
1. Monitor the notch lifting during the next scheduled outage.
1. The admission sides of the vane sections have some minor FOD. 2. The exhaust sides of the vane sections are in good condition. 3. The covers are down tight on the vane tips. There is some very minor FOD on the cover
OD’s.
4. The tenons have some very minor erosion on the leading edges. 5. The notch block is down tight. 6. The vane exhaust edge thickness is ≈ .040”. A .188 coating buildup was found on the ID
of the bucket covers. No coating buildup was found on the vane sections. Repair recommendations:
1. No repairs required.
HP/RH Rotor Body Journals
The #1 and #2 journals are in relatively good condition. There is only minor scoring on each. The journals will only require strap lapping prior to going back in service. The active and inactive faces on the thrust collar are in good condition and do not require any repairs.
Packing Lands
The end packing and inter-stage packing lands appear to be in good condition. Only some very light rubs were observed. Intermittent indications were found in the N2 heat groove adjacent to the first stage buckets on the admission side. In addition indications were found in the heat grooves between the 1st and 2nd stages and between the 2nd and 3rd stages. The indications were removed locally and the area polished.
Future HP/RH Rotor Repairs
During the next scheduled outage the 2nd, 3rd, 4th and 5th stage buckets should be replaced. The rest of stages on the HP/IP rotor should still be in relatively good condition at the next scheduled outage, approximately 7 years from now. The reheat section buckets, stages 10-13 are in good condition and probably will not require any repairs during the next scheduled outage.
Steam Turbine Performance Evaluation Program Unit 4 Opening Audit Results
Unit #4 Steam Path Audit Results 3-07 Audit Options :
Description : Unit #4 Steam Path Audit Results 3-07 Perform Ellipticity & Spring Clearance Corrections : Number of Tooth Height Measurements : 8 Surface Roughness Gradations : 3 Hand Calculations By : Stage Loss Values : Change In G.T.H.R. (Btu/kWh) First Year Fuel Cost ($)