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 position AH 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 Clip Load angle must be within + 5 degrees

Bench Test Results  Testing with old spacer installed 0 degree angleClip released at 65 lbs 5 degree angleClip released at 50 lbs 10 degree angleClip released at 10 lbs

Bench Test Results  Bench testing with spacer removed and conduit nuts installed 0 degree angleClip did not release, measured > 100 lbs 5 degree angleClip did not release, measured > 100 lbs 10 degree angleClip did not release, measured > 100 lbs 20 degree angleClip did not release, measured > 100 lbs 30 degree angleClip 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?