Creating a Safe and Sustainable Environment for Science 1 Lesson Learned: PVC Pipe Explosion Presented at Accelerator Safety Conference August 12, 2008

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Creating a Safe and Sustainable Environment for Science

Lesson Learned:PVC Pipe Explosion

Presented atAccelerator Safety Conference

August 12, 2008

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Stanford Linear Accelerator Center• SLAC is a U.S. DOE-SLAC is a U.S. DOE-

funded, National funded, National Laboratory, operated Laboratory, operated by Stanford Universityby Stanford University

• Est. in 1962Est. in 1962• Main Linear Main Linear

Accelerator is 3 km in Accelerator is 3 km in lengthlength

• ~1,300 employees + ~1,300 employees + 3,000 visiting 3,000 visiting scientists and scientists and students per yearstudents per year

• Particle Physics & Particle Physics & Astrophysics and Astrophysics and Photon SciencesPhoton Sciences

• Work here has Work here has resulted in 4 Nobel resulted in 4 Nobel Prizes in PhysicsPrizes 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

Cooling Water main

Flange blank

8” dia., Sch. 80 PVC

8” dia., carbon steel

Hot Tap point for gauge

trench

LINAC alcove wall

Isolation valve to exchanger (closed)

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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 CalculationPipe Vol. = 17.4 ftPipe Vol. = 17.4 ft33 (0.5 m (0.5 m33))Pipe Vol. = 17.4 ftPipe Vol. = 17.4 ft33 (0.5 m (0.5 m33))

AssumptionAssumption:: THF only (~60% v/v)THF only (~60% v/v)AssumptionAssumption:: Stoichiometric mix:Stoichiometric mix:

CC44HH88O + 5.5 OO + 5.5 O22 + 20.68 N + 20.68 N22 4 CO 4 CO22 + 4 H + 4 H22O + 20.68 NO + 20.68 N22

Volume of THF = 0.018 mVolume of THF = 0.018 m33 (0.64 ft (0.64 ft33))Mass = 54 gm (0.119 lb)Mass = 54 gm (0.119 lb)

Energy = 4,188 kJ vs. 4,500 kJ/kg TNT = Energy = 4,188 kJ vs. 4,500 kJ/kg TNT = 0.93 kg (2.05 lb) TNT equivalent0.93 kg (2.05 lb) TNT equivalent

AssumptionAssumption:: THF only (~60% v/v)THF only (~60% v/v)AssumptionAssumption:: Stoichiometric mix:Stoichiometric mix:

CC44HH88O + 5.5 OO + 5.5 O22 + 20.68 N + 20.68 N22 4 CO 4 CO22 + 4 H + 4 H22O + 20.68 NO + 20.68 N22

Volume of THF = 0.018 mVolume of THF = 0.018 m33 (0.64 ft (0.64 ft33))Mass = 54 gm (0.119 lb)Mass = 54 gm (0.119 lb)

Energy = 4,188 kJ vs. 4,500 kJ/kg TNT = Energy = 4,188 kJ vs. 4,500 kJ/kg TNT = 0.93 kg (2.05 lb) TNT equivalent0.93 kg (2.05 lb) TNT equivalent

Estimated terminal Pressure in the Pipe = 175.4 atm = 2,579 psiEstimated terminal Pressure in the Pipe = 175.4 atm = 2,579 psiPipe Rating = 250 psi; 4 x safety factor = 1,000 psiPipe Rating = 250 psi; 4 x safety factor = 1,000 psi

2,579 psi > 1,000 psi 2,579 psi > 1,000 psi Failure Failure

Estimated terminal Pressure in the Pipe = 175.4 atm = 2,579 psiEstimated terminal Pressure in the Pipe = 175.4 atm = 2,579 psiPipe Rating = 250 psi; 4 x safety factor = 1,000 psiPipe Rating = 250 psi; 4 x safety factor = 1,000 psi

2,579 psi > 1,000 psi 2,579 psi > 1,000 psi Failure Failure

Overpressure Calculation:Overpressure Calculation:2.05 lb TNT2.05 lb TNTee yields: yields:

• 0.5 psi (window breakage) at 38 feet 0.5 psi (window breakage) at 38 feet • 1.0 psi (knockdown) at 23 feet 1.0 psi (knockdown) at 23 feet

Overpressure Calculation:Overpressure Calculation:2.05 lb TNT2.05 lb TNTee yields: yields:

• 0.5 psi (window breakage) at 38 feet 0.5 psi (window breakage) at 38 feet • 1.0 psi (knockdown) at 23 feet 1.0 psi (knockdown) at 23 feet

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Incident Analysis Board

Wall of Stickies in “War Wall of Stickies in “War Room”Room”

• 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

eventevent.

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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 (web-based)

• 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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Documents

Creating a Safe and Sustainable Environment for Science 1 Lesson Learned: PVC Pipe Explosion Presented at Accelerator Safety Conference August 12, 2008