• Published: 19 Dec 2011
  • Incident ID: 3405

Pressure Relief Valve Sprays Dilute Acid Across Location on a Frac Job

Cause & Consequence

  • Release of a harmful substance
Incident Consequence

Incident Location

Drilling unit

Incident Activity

Drilling, workover

Lessons Identified


The pressure relief valve that was used during this incident had been used in the past, but had been replaced with a newer design because the newer design relieves into a tank instead of to the atmosphere. However, the new design was unavailable at this location so the contractor used the older valve that relieves to atmosphere. The hazards associated with potential atmospheric release by this older pressure relief valve were recognized during the Job Safety Analysis; and injuries were avoided by restricting worker access to the area in which the relief valve might affect if it were to release.

The pressure relief valve activated unexpectedly because the diesel engine that provides the hydraulic pressure ran out of fuel. The diesel engine ran out of fuel because the crew changed in mid-stage and during the handover the fuel status was not communicated. This failure would have caused either the old or new pressure relief valves to release. The difference between the old and new pressure relief valve is that the newer design would have relieved into a tank whereas the older valve relieved to atmosphere.

Incident Recommendations

CORRECTIVE ACTIONS: To address this incident, this company did the following:

1) Pre-Job Safety Analyses should continue to be standard operating procedure.

2) In the future, shift changes will not take place mid-stage of a frac without extraordinary consideration and handover discussion.

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