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Lesson Learned: PVC Pipe Explosion

Lesson Learned: PVC Pipe Explosion. Presented at Accelerator Safety Conference August 12, 2008. Stanford Linear Accelerator Center. SLAC is a U.S. DOE-funded, National Laboratory, operated by Stanford University Est. in 1962 Main Linear Accelerator is 3 km in length

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Lesson Learned: PVC Pipe Explosion

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  1. Lesson Learned:PVC Pipe Explosion Presented at Accelerator Safety Conference August 12, 2008

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

  3. 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

  4. Installation Configuration Isolation valve to exchanger (closed) 8” dia., carbon steel Cooling Water main Hot Tap point for gauge Flange blank LINAC alcove wall 8” dia., Sch. 80 PVC trench

  5. Pipe Explosion

  6. Pipe Disintegration

  7. Shrapnel

  8. 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

  9. Fuel

  10. 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

  11. Wall of Stickies in “War Room” 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.

  12. 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.

  13. 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

  14. 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.”

  15. 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

  16. 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

  17. 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

  18. 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.

  19. OE Investigation Report • Received July 23, 2008 • Enforcement conference TBD

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