Hydrocarbon release from flanged joint

Cause & Consequence

• Uncontrolled release of a flammable gas or liquid

Incident Location

Fixed Installation

Incident Activity

Production operations

Specific Incident Equipment

Control valve on a HP gas system (molecular sieves)

Lessons Identified

• Thermal expansion together with fixed supports on the control valve resulted in high compression and bending across the leaked flange. The bending moment was deemed to have induced a considerable tension force on some of the flange bolts, resulting in the effective bolting loads decreasing at these bolts allowing the gas to escape.
• Consideration should be given to alternatives to fixed supports for pipes and/or valves on equipment which is subject to large pressure and temperature variations during normal operation.

Incident Recommendations

• Assess pipe and valve support arrangements against design intent on all equipment that is subject to large pressure and temperature variations during normal operation.
• If applicable change fixed supports to rest supports.
• If applicable use alternative arrangements where supports are bolted directly onto the flanges with flange bolts.