Gas was detected by a maintenance technician working near the VVP of an adjacent compressor. The investigation revealed that gas was passing the o-ring on the cylinder head arrangement. A small blister on the o-ring indicated where the gas was released. Checks of the bolt torques indicated a slight under tension on some of the bolts.
• O-ring was not properly installed but the system passed a pressure test
• Installation in congested area may have caused problems
• Bolt under tensioning allowed gas to pass at discrete location on the o-ring
• Torque wrench was in certification but calibration was suspected as incorrect
• Care needed when installing o-rings in congested areas as they may be misaligned or become damaged.
• Check calibration of torque wrenches regularly
Variable Volume Pocket o-ring seal