Investigating Investigation Methodologies

Handout For IRIA2003 Presentation

Ludwig Benner Jr
Williamsburg VA 9/18/03

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Handout 1 accompanying Benner IRIA Presentation 9/18/03

This is a printout of remarks entered in Event Block on MES matrix.


Examples of ambiguous description disclosed by MES

? told lead operator extruder had been run with purge material

? scheduled restart for March 12

? raised extruder temperature to 315†C

? decided to close PCT without level detector

? called Maintenance ? to assist with extruder problem

? decided to divert process flow from PCT to RKP

? observed small fire in extruder and what did they see

? ignited residual purging material ?

? ? did what about fire in extruder

? observed vapor leak from RKP cover and what did they see

? left instructions for night shift to empty PCT and RKP of polymer

? purged extruder with purge material to clean screws

? extinguished remaining fire

? decided to not do recommended HAZOP after drawings finalized

? designated HAZOPS team for safety analyses of facility

? designated HAZOPS methodology for facility safety analysis

? observed thermal degradation in product performance tests

? tested unsuccessful alternative PCT level indicators

? isolated hot oil system to stop flow from tubing break

? recognized PCT was too small after overfilling

? repaired PCT relief valve fouled with polymer

? repaired PCT relief valve fouled with polymer (2nd time)

? repaired PCT relief valve fouled with polymer (third time)

? ignited hot oil vapor cloud

? submitted engineering request to redesign system

? shut down Amodel unit to repair equipment in extruder

? mechanical problem delayed startup of unit for 4 ? hours


Examples of questions raised by MES

  • Why didn't solvent clean out ash in extruder?
  • Timing of fire/solvent shutoff/fire out?
  • Was hot oil involved with PCT pressure rise?
  • Why did workers have to position themselves in harms way to remove the head?
  • Why did Maintenance Tech remove bolts in sequence he did, and would another sequence have changed the outcome?
  • Need to confirm that hot oil continued flowing to heat inlet line to PCT after shutdown
  • before and after head blew off - did that contribute to heading of contents?
  • Why didn't HAZOP recommendation successfully control hazard? (Methodologyical problem)
  • Why wasn't unsuccessful recommendation remedied when experience showed it was unsuccessful? (system problem)
  • Why did Operators position selves with Maintenance Technician at head of PCT (if they did)
  • What exactly created internal pressure -what were roles of hot oil, overfilling, and decomposition of stored material in PCT
  • What ignited fire in extruder? Why did it spread
  • Who told whom what and why about pre-run?
  • What was data and rationale for this decision? Who made it?
  • Find out what procedure is to learn from incidents ‚system breakdown or people problem?
  • Find out why air could get into the extruder,, providing oxygen for fire??
  • What was the impact trauma that killed 2 workers - tank cover or plastic from inside tank?