e atomizer explosion 2013.10.26

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, firebird.one@alum.mit.edu

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?