Could a ‘dead-leg’ be stopping your plant from running at full flow
Flow-Induced Pulsation in Pipework
The Asset Integrity Division at AVT Reliability recently came across a puzzling pipework vibration problem at a customer site in the North East.
An 8 inch bypass line off a 16 inch gas mainline was showing high levels of vibration. That alone was not unusual, but even when the bypass actuator valve was closed and the line was not in use, the vibration continued.
Armed with Machine Sentry® Fixed (MSF 2) sensors and a range of vibration analysis techniques, the team set to work capturing natural frequencies and mode shapes, monitoring how the pipe behaved under different flow conditions.
A likely suspect? Flow induced pulsation (FIP), possibly caused by a dead leg, a section of pipework with no flow that can cause pressure pulsations under the right conditions. Think of blowing across the top of a bottle and hearing it whistle. If that acoustic resonance matches the pipe’s mechanical frequency, it can lead to structural resonance.
But just when the team thought they had cracked it, things changed. With the bypass open again, under certain conditions the vibration returned.
The real breakthrough came when the team took a step back and looked at the wider system. A second dead leg was identified. Further analysis confirmed a perfect frequency match with the vibration data and a mechanical natural frequency.
Mystery solved. Root cause found. The client? Very impressed, not just by the investigative work, but by the clear, practical steps AVT provided to address it.
