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HRSG Maintenance &

Operating Issues

David Buzza

Region 7 Engineering

August 6, 2012

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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)

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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.

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Lawrenceburg LP FW Heater / Economizer Deposits

Deposit may be corrosion and/or ammonium sulfate /bisulfate deposit. Need sample to verify.

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LP Economizer ProtectionMaintain FW inlet temperature 15F above fluegas dew point with FW recirculation system.

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Lawrenceburg Distribution Grid Failure

Turbine to HRSGexpansion joint

GridStart of TubePanels

Duct

Burner

SCR

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Distribution Grid

Supports

Guides

(7/8 overlap)

Guides

(1 overlap)

54feet

25 feet

HRSG Casing

Distribution Grid

Top = SS

Bottom = P11

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Lawrenceburg Failed Distribution Grid

Failure

GasFlow

DistributionGrid

Tube Bundledownstream

of Grid

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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.

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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

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Waterford HP Pipe Support Cracking

Crack

Crack

Pipe Movement

Stanchion

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Waterford HP Pipe Support Repair

Shortened stanchion

from 27 to 9 longto reduce moment

arm

Added plateto bottom ofstanchion toimprovesliding

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Waterford HRSG Drain Line Pipe Buckling andSupport Failures

Buckled

DrainLine

BentSupport

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Waterford HRSG Drain Line Repair

Re-ran thepipe withexpansion

loops

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Lawrenceburg Boiler Feed Pump Piping Support

To BFP

Suction

ExistingSupport

Existing

Support

ExistingSupport

NewSupport

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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

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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