Cause & Consequence
- Uncontrolled release of a flammable gas or liquid
Specific Incident Equipment
Control valve on a HP gas system (molecular sieves)
- 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.
- 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.