e atomizer explosion 2013.10.26
TRANSCRIPT
Electrical ExplosionElectrical Explosion
Near Miss to Personnel Injury
Luck is NOT a Robust Barrier
Fault Occurred Here
Fault Occurred Here
Simplified Schematic of Plant Electric System
Fault Occurred Here
Fault Occurred Here
FT 1.0Production Decrease 0955-1920
Plant Trip0955 Full Production
1920
No 4160-voltBlackout
No Rupture Disc Blow
See
FT 2.0
See FT 3.0
OperatorInitiative
END
Proper Operator Action
END
No Personnel Injury
See FT 4.0
SparesIncluding“Breaker”in Stock
END
Defect inCubicle
FT 2.0
Plant Trip0955
Contactors Closed
END
4160 Voltson Cubicle
CRO Starts Atomizer
Causes are unknown
Defect inCubicle Not Known
See FT 2.1
END
END
Inspections not capable
FT 2.1
Defect inCubicle Not Known
No test available
Instrumentation not capable
ENDENDEND
Fast Transfer to Start-up Transformer
FT 3.0No 4160-volt Blackout
Start-up Transformer Available
Fault on 4160 V Bus Cleared
SeeFT 3.1
Feeder Bkr Tripped
END
END
Aux XfmrMain BreakerOpens onUndervoltage
FT 3.1Fast Transfer to Start-up Transformer(Likely Scenario)
Aux XfmrDoes NotOpen onOvercurrent
4160-volt FeederBreaker Clears Fault
4160 FaultDrags Voltage down
Breaker Opens onTimed OvercurrentBefore SUT Main Bkr Shuts
Unknown
Unknown
Stand-off Distance of 22’
FT 4.0No Personnel Injury
Partial Shielding by Cubicle Stack
Fault on 4160 V Bus Cleared to Limit Energy
ENDENDEND
The next slide is a Factors-consequence Matrix
It shows how various factors would have affected the
consequences of the event.
Factors Actual Case
Case 1 IP enabled
Case 2 Anomaly detected
Case 3 Atomizer
not started.
Case 4 Combustible
s present.
Case 5 Operator
near cubicle.
Case 6 No fast transfer
Case 7No circ water
pump start
Instantaneous protection disabled
Yes No (not disabled)
Yes Yes Yes Yes Yes Yes
Undetected bkr abnormality
Yes Yes No Yes Yes Yes Yes Yes
Atomizer started Yes Yes Yes No Yes Yes Yes Yes
No combustibles nearby
Yes Yes Yes Yes No Yes Yes Yes
Operator protected by location
Yes Yes Yes Yes Yes No Yes Yes
Fast transfer Yes Yes Yes Yes Yes Yes No Yes
Circ water pump restarted
Yes Yes Yes Yes Yes Yes Yes No
Consequences
Personnel None Less severe
explosion.
None. Anomaly
fixed.
None right away. Latent
problem.
Worse fire.Potential
burns.
Severe injury or
death.
No change. No change.
Plant/Financial Explosion,Trip, Lost
Revenue, Equipment damage
No plant trip. Only
feeder bkr trip.
None None right away. Latent
problem.
Worse fire, etc..
Explosion, Trip, Lost Revenue,
Long outage for
investigation
Explosion,Trip, Lost Revenue,
Equipment damage. 4160v
blackout.
Longer outage due to
rupture disc(s) blown.
© 2000, William R. Corcoran, NSRC Corp., 860-285-8779, [email protected]
Eight Questions For Insight
Quality & Safety Impact What were the event consequences?
What was the event significance?
Vulnerability What set us up for the event?
What triggered the event?
What made the event as bad as it was?
What kept it from being a lot worse?
Learning: What should be learned from the event?
Doing: What should be done about it?
Consummation
Exacerbation
Mitigation
Corrective Action (closeout)
1. Consequences No personnel injuries. Explosion, fire, trip, lost revenue, etc.
2. Significance Saved by luck, lots of surprises, Arc Flash hazard underestimated, complex event
3. Set-up Bechtel wiring anomaly, latent defect in “breaker”
4. Trigger Starting an atomizer from Control Room
5. Exacerbation(what made it worse)
Feeder breaker didn’t trip on instantaneous. This caused plant trip.
6. Mitigation (what kept it from being even worse)
Operator location! Fast transfer malfunctioned in our favor! Good personnel actions. Spares on hand.
7. Lessons to be Learned
Energizing a circuit is a hazard. Distance and shielding work. Control combustibles.
8. Corrective Actions
Stand-off from energizations. Ring out protective circuits. Re-do Arc Flash Study. Re-do breaker co-ordination.
Now is the time for
• Questions?• Comments?• Recommendations?• Discussion?