Transcript Stanford Linear Accelerator Center (SLAC)

Lesson Learned:
PVC Pipe Explosion
Presented at
Accelerator Safety Conference
August 12, 2008
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Stanford Linear Accelerator Center
• SLAC is a U.S. DOEfunded, National
Laboratory, operated
by Stanford University
• Est. in 1962
• Main Linear
Accelerator is 3 km in
length
• ~1,300 employees +
3,000 visiting
scientists and
students per year
• Particle Physics &
Astrophysics and
Photon Sciences
• Work here has
resulted in 4 Nobel
Prizes in Physics
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What Happened?
• Safety & Operational Reliability Improvements (S&ORI) Project
– Upgrades of identified critical sections of failing systems for the
underground mechanical utilities throughout the site, and
seismic/structural upgrades of identified critical experimental and
laboratory buildings
• Cooling water piping replacement for the Linac
– Replacement of old transite piping with 8” dia., Sch. 80 PVC,
connected to 8” dia. carbon steel piping
• September 12, 2007:
– PVC pipe (~35’) installed, connected to flange on main at one end
and to steel pipe flange at other end
– Pressure testing was going to need to be performed next day, so
flange on main was blanked and the butterfly valve on steel pipe
was closed
• September 13, 2007:
– Contractor realized they forgot to pre-install a “threadlet” on the
steel pipe to attach the pressure gauge.
– Initiated cutting operation on steel pipe to cut a hole for threadlet
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Installation Configuration
Isolation valve to
exchanger (closed)
Cooling
Water main
8” dia.,
carbon steel
Hot Tap point
for gauge
Flange
blank
LINAC
alcove wall
8” dia., Sch.
80 PVC
trench
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Pipe Explosion
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Pipe Disintegration
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Shrapnel
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Injuries
• One nearby (~25’) worker was almost
knocked down by the force
• One suffered temporary hearing loss,
and due to elevated pulse and blood
pressure was taken to Stanford Medical
Center
• Three others went back to work after
going to SLAC medical for hearing
evaluation
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Fuel
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Force Calculation
Pipe Vol. = 17.4 ft3 (0.5 m3)
Assumption: THF only (~60% v/v)
Assumption: Stoichiometric mix:
C4H8O + 5.5 O2 + 20.68 N2  4 CO2 + 4 H2O + 20.68 N2
Volume of THF = 0.018 m3 (0.64 ft3)
Mass = 54 gm (0.119 lb)
Energy = 4,188 kJ vs. 4,500 kJ/kg TNT = 0.93 kg (2.05 lb) TNT equivalent
Estimated terminal Pressure in the Pipe = 175.4 atm = 2,579 psi
Pipe Rating = 250 psi; 4 x safety factor = 1,000 psi
2,579 psi > 1,000 psi  Failure
Overpressure Calculation:
2.05 lb TNTe yields:
• 0.5 psi (window breakage) at 38 feet
• 1.0 psi (knockdown) at 23 feet
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Incident Analysis Board
• Appointed by Lab Director
–
–
–
–
Chair: Steve Williams, Special Asst. to Director
Representatives from Accelerator, Facilities, ES&H
Facilitation by Bob Crowley, McCallum-Turner (former DOE)
Observation by DOE Stanford Site Office
• Scope:
– Development of a timeline of events
– Identification of relevant facts
– Analysis of the facts to determine causal factors including a
systemic root cause and contributing causes
– Identification of organizational weaknesses
– Recommendations to promote prevention of recurrence of a similar
event.
Wall of Stickies in “War Room”
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Causal Factor 5:
Over-reliance on “Skill of Craft”
• Work was considered routine and low hazard;
line drawings only. Not enough detail.
• Contractor and sub did not provide sufficient
job steps/sequence in JSAs
• Details left to foreman to determine
• No pressure testing plan
• All previous experience with Sub contractor at
SLAC was good.
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Causal Factor 4:
Project Management
• LINAC downtime planning began June, 2007.
Bid package not introduced until August 15.
• University Technical Representative (UTR)
assigned August 31 (Labor Day Friday) with
project to start Tuesday September 4
– Forced UTR to work the holiday to try to do his
planning
• Set up time pressure which was reflected in
rushing the UTR
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Causal Factor 3:
ISMS Req’ts not integrated into Proj. Mgmt.
• Incomplete flow down of ISMS to
subcontractor per DOE O 413.3
• UTR stated he “should have stopped
the job because he did not have time to
do a thorough analysis of the job.” He
understood his R2’s but not his A2’s. He
didn’t want to “get flak for slowing down
the project.”
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Causal Factor 2:
Expectations Poorly Communicated
• Site Specific Safety Plan (SSSP)
inadequate
– But approved by PM
• Safety related documents (IIPP, SSSP,
JSAs, MSDSs) not always thorough,
available or communicated to all
contractors
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Causal Factor 1 (Root Cause):
Inadequate Work Planning & Control Process
• Construction PM process buried in UTR Manual
• Inadequate JSA help section in the UTR training
materials for PMs/UTRs, purchasing and construction
safety people
• Hazard recognition.
• Walkdown of the job site inadequate
• Ineffective Lessons Learned integration with work
planning
• Both SLAC and Sub Contractor using Google and trade
databases found numerous examples of this type of accident –
after the event.
• Hot work permit system deficiencies
• Training of staff on management expectations is not
comprehensive
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Corrective Actions
• Immediate
– Stopped work; subs re-worked their safety policies and
procedures; review by Facilities Dept. and ES&H
– Increased oversight of Hot Work Permit Process and JSAs
• Near-term
– Revisions to hot work permit program
– Project planning
– Revisions to program documentation (SSSP, JSA)
• Developed guidelines for project managers/UTRs and improved
forms
– Implementation of Lessons Learned (DOE O 210.2)
• Note: was not in SLACs contract prior to this year
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Corrective Actions
• Long-term
– ISEMS Communications and Training of Subcontractors and
UTRs
• Implementation of a Construction Safety at SLAC course (webbased)
• Developing R2A2s for UTRs and personnel overseeing
subcontracted work
• Work Planning & Control
– Already a pre-existing CAP from a DOE OIO Review in 2006
• A WPC Program Manager was hired in May 2008
• WPC Manager has assumed responsibility for the OIO WPC
CAP.
– Although the OIO findings and CAP specifically did not include
subcontractor work, SLAC has incorporated subcontractor work
into its draft WPC process.
• Beta testing of new WPC process to commence at the end of
August and run through October 2008. Full roll out of the
program will occur beginning February 2009.
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OE Investigation Report
• Received July 23, 2008
• Enforcement conference TBD
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