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7/27/2019 Hrs g Operating and Maintenance Issues
1/21
HRSG Maintenance &
Operating Issues
David Buzza
Region 7 Engineering
August 6, 2012
7/27/2019 Hrs g Operating and Maintenance Issues
2/21
Lawrenceburg Primary Reheat Tube Failures
Looking Up
Tubes bowed at header ends
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Lawrenceburg Primary Reheat Failures & Cracks
Four HRSG Units
From Feb 2009 toAug 2011 - 9 forcedrepairs and 5
unforced repairs. 37 of 45 tube repairs
are near header ends
versus over drainlines.
Panel Top Header
Crack at toe of fillet
weld (tube side)
7/27/2019 Hrs g Operating and Maintenance Issues
4/21
Reducing Lawrenceburg Primary Reheat Failures
Condensate in bottom headercreates preferential steam path for
tubes over drains. Tubes over drains are cooler.
Tubes at ends are hotter.
Found attemperator water leakingthrough between starts.
Corrective Action Manually closed all attemperator
water between starts.
Increased manual drain to 2 inchand drained header prior to each
start.
7/27/2019 Hrs g Operating and Maintenance Issues
5/21
Lawrenceburg LP FW Heater / Economizer Deposits
Deposit may be corrosion and/or ammonium sulfate /bisulfate deposit. Need sample to verify.
7/27/2019 Hrs g Operating and Maintenance Issues
6/21
LP Economizer ProtectionMaintain FW inlet temperature 15F above fluegas dew point with FW recirculation system.
7/27/2019 Hrs g Operating and Maintenance Issues
7/21
Lawrenceburg Distribution Grid Failure
Turbine to HRSGexpansion joint
GridStart of TubePanels
Duct
Burner
SCR
7/27/2019 Hrs g Operating and Maintenance Issues
8/21
Distribution Grid
Supports
Guides
(7/8 overlap)
Guides
(1 overlap)
54feet
25 feet
HRSG Casing
Distribution Grid
Top = SS
Bottom = P11
7/27/2019 Hrs g Operating and Maintenance Issues
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Lawrenceburg Failed Distribution Grid
Failure
GasFlow
DistributionGrid
Tube Bundledownstream
of Grid
7/27/2019 Hrs g Operating and Maintenance Issues
10/21
Turbine Exhaust Gas Velocity at Turbine Exhaust
25 m/s
83 m/s
33 m/s
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Turbine Exhaust Gas Velocity at the SCR
With Distribution Grid No Distribution Grid
5 m/s
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Turbine Exhaust Gas Velocity at the Duct Burners
With Distribution Grid No Distribution Grid
9 m/s
6 m/s
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Turbine Exhaust Gas Velocity at First Tube Bundle
With Distribution Grid No Distribution Grid
16 m/s
8 m/s
8 m/s
26 m/s
32 m/s
Concern Gas & acoustic baffles and/or tube ties may fail with nodistribution grid because of higher gas velocity / higher tube vibration.
7/27/2019 Hrs g Operating and Maintenance Issues
14/21
Eliminating Single Point Trips / Runbacks
Lawrenceburg Plant DCS
Event Single Points Resolution
Gas Turbine
trip
high HRSG duct P Remove trip, already protected
by GT exhaust P trip
Gas Turbinerunback
high HP or HRH steamT
Add 2 XMTRs for 2/3 medianselect for each
Boiler Feed
Pump trip
High vibration or high
bearing T
Remove trip, allow operator to
decide
Boiler FeedPump trip
Low NPSH (P&T) Add 2 XMTRs for each for 2/3median select
Condensate
Pump trip
Low condenser level Add 2 XMTRs for 2/3 median
select
Duct Burnertrip
High HP 2ndary P
High HP 1st or 2nd T
High RH 1
st
or 2
nd
T
Add 2 XMTRs for 2/3 medianselect for each
7/27/2019 Hrs g Operating and Maintenance Issues
15/21
Waterford HP Pipe Support Cracking
Crack
Crack
Pipe Movement
Stanchion
7/27/2019 Hrs g Operating and Maintenance Issues
16/21
Waterford HP Pipe Support Repair
Shortened stanchion
from 27 to 9 longto reduce moment
arm
Added plateto bottom ofstanchion toimprovesliding
7/27/2019 Hrs g Operating and Maintenance Issues
17/21
Waterford HRSG Drain Line Pipe Buckling andSupport Failures
Buckled
DrainLine
BentSupport
7/27/2019 Hrs g Operating and Maintenance Issues
18/21
Waterford HRSG Drain Line Repair
Re-ran thepipe withexpansion
loops
7/27/2019 Hrs g Operating and Maintenance Issues
19/21
Lawrenceburg Boiler Feed Pump Piping Support
To BFP
Suction
ExistingSupport
Existing
Support
ExistingSupport
NewSupport
7/27/2019 Hrs g Operating and Maintenance Issues
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Lawrenceburg Boiler Feedwater Pump Vibration
Time
PumpDriv
eEnd&Non
DriveEndVib
ration,mils
BFP 1
BFP 2
0
9
0
9
0
0
9
9
BFP 3
BFP 4
Before After
7/27/2019 Hrs g Operating and Maintenance Issues
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Improving Reliability of Gas Regulating Station for Duct Burners
Need PM that includes replacement of regulator soft goods. Verify that all regulator valves have proper set points. Add vortex heater to prevent freeze up of regulator orifice & distillate drop out in pilot
gas.
Lawrenceburg Plant