Diesel Building Fire Damper Failing

Closed Mike Walker

TVA

Diesel Generator HVAC

SQN has 4 diesel generators Each Diesel generator has 2 fans for

cooling Cooling utilizes outside air Once through system

Diesel Generator Building Air flow

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

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

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

CO2 Blow OFF Clip

Installed CO2 Blow Off Clip and Nozzle

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

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!!!!

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.

?????????

Observation of installed CO2 Blow Off Clip

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

Conduit Nut on One Side Vendor recommended installation

Final Modified Installation Vendor Manual revision was made to allow

2 conduit nuts

Load on the Blow Off ClipLoad angle must be within + 5 degrees

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

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

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

Root Cause Conclusion The old spacers impede the blow off clip

from being fully engaged with the CO2 release nozzle.

Questions or Comments?