Incident Report

Subject:                Importance of Flange QA/QC - Loose Flange Bolts at PSV May Have Caused Big Fire     

Date of Email report:   Mon 01/11/2010

Report Detail:

Loose Flange Bolts at PSV May Have Caused Big Fire
A crude unit at our Chevron Pascagoula refinery experienced a big & costly fire back in August. (see attached pics). The official investigation report has not yet been issued, but the likely scenario of events leading up to this fire has been informally reported as follows:

• A  6 X 8" PSV  was removed for routine servicing at last TA but when it was reinstalled, the flange bolts were not properly tightened (maybe only hand tightened)
• The PSV was not easy to access; the loose PSV inlet flange probably leaked a small amount for quite some time, but the small leak was not detected due to the PSV's location
• Some time well after TA, the PSV started "simmering" due to system pressures getting close to the PSV set pressure.
• The simmering of the PSV was just the "right frequency" such that multiple of the loose stud nuts backed off the studs and some nuts fell off completely
• With missing and very loose nuts, the flange opened up enough to cause a significant release, and the fire pictured

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Additional Documentation: