Cracking in small bore piping due to vibration

Two events occurred at the same facility associated with small bore piping failures resulting in a loss of primary containment

Event 1 - an operator identified a gas leak from a bleed valve on a relief path from a natural gas booster compressor via visual observation during operator rounds. A leak clamp was installed on the cracked location and additional bracing installed to support the small bore piping. The adjacent natural gas booster relief valves with similar small bore piping were also braced.

Event 2 - one month later, an operator identified cracking on a different small bore piping connection, adjacent to the supporting gusset fillet weld. Work was stopped in the vicinity and plant rates reduced. Upon identification of the leak, the cold end of the plant was safely depressurised. Calculations confirmed the second event resulted in a Tier 2 gas release. The associated spool was removed from the location and a weld repair performed. Spool was installed with additional bracing.

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