diesel building fire damper failing closed mike walker tva
DESCRIPTION
Diesel Generator Building Air flowTRANSCRIPT
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Diesel Building Fire Damper Failing
Closed Mike Walker
TVA
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Diesel Generator HVAC
SQN has 4 diesel generators Each Diesel generator has 2 fans for
cooling Cooling utilizes outside air Once through system
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Diesel Generator Building Air flow
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Damper Configuration Diesel generator room inlet dampers
Fire damper and motor operated damper in series
Fire damper is normally open and is closed by a spring
Fire damper has a fusible link and a CO2 blow off clip
Motor operated damper is normally closed and opens on fan start signal
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Damper configuration Diesel generator room outlet damper
Fire damper only
Fire damper normally open, and is closed by a spring
Fire damper has a fusible link and a CO2 blow off clip
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Fire Damper Failure ON 6/6/08 the inlet fire damper for 2A-A DG failed closed
with 1 fan in operation
HIGH Crankcase Pressure HIGH alarm actuated on the DG
Also resulted in DG lockout and LCO entry.
Discovered CO2 blow off clip was dislodged from the CO2 nozzle
Previous failure of CO2 blow off clip happened on 8/7/07 on
fire damper for DG 1B-B
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CO2 Blow OFF Clip
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Installed CO2 Blow Off Clip and Nozzle
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Typical Cross Tied Fire Damper
Cross brace not at SQN
Cross brace not at SQN
To CO2 blow off clip
Fusible link
4 separate damper sections at SQN are tied together
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Troubleshooting All Fire dampers on the inlet side were
wired open to ensure DG operability Vendor drawing indicated maximum load
for CO2 clip was 25 lbs. Pull test was performed on the fire damper
assembly 31 pounds of force was required to hold
the damper in the open positionAH HA!!!!
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Troubleshooting (continued)
Ensured blow off clip was fully installed
Pull test on blow off clip determined that it would hold at > 50 lbs of force
????????? Also a history search determined that 2
similar failures have occurred on very small dampers.
?????????
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Observation of installed CO2 Blow Off Clip
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Discussions With Vendor Vendor did not have any idea where large
spacer came from
Normally the blow off clip body is bottomed out against the brace, and a conduit nut holds the device in place
Vendor agreed that a conduit nut could be used on both sides of the bracket to adjust the clip location
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Conduit Nut on One Side Vendor recommended installation
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Final Modified Installation Vendor Manual revision was made to allow
2 conduit nuts
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Load on the Blow Off ClipLoad angle must be within + 5 degrees
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Bench Test Results Testing with old spacer installed
0 degree angle Clip released at 65 lbs5 degree angle Clip released at 50 lbs10 degree angle Clip released at 10 lbs
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Bench Test Results Bench testing with spacer removed and conduit
nuts installed
0 degree angle Clip did not release, measured > 100 lbs
5 degree angle Clip did not release, measured > 100 lbs
10 degree angle Clip did not release, measured > 100 lbs
20 degree angle Clip did not release, measured > 100 lbs
30 degree angle Clip released at 50 lbs
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Conclusions Testing provided assurance that the
present clip should hold the damper open
The clip must be fully engaged
The old spacer can not be utilized
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Root Cause Conclusion The old spacers impede the blow off clip
from being fully engaged with the CO2 release nozzle.
Questions or Comments?