thermmech
Mechanical
- Dec 13, 2004
- 103
We are experiencing a vibration / noise in a stretch of 38" piping downstream from compressor to the first heat exchanger. In this stretch of piping there is a conical strainer with fine mesh. Recently we have removed the fine mesh from the strainer perforated plate (basket). There was no noise while mesh was installed.
The noise levels are extremely high (up to 120 dBA), dominant vibration frequency range is from 500 - 100 Hz, vibration velocity and amplitude = 0.040 mm/s and 0.01 mm max. We have shut down the compressor to prevent high-frequency fatigue of piping and SBCs.
A number of hypotheses for the noise cause has been proposed (high probability listed first):
1. Improper strainer installation (strainer "spiders" not fully engaged into the pipe ID allowing front strainer end to move - not possible to verify until basket pulled out)
2. Vortex shedding through perforated plate (recently removed fine mesh)
3. A foreign body lodged upstream into pipe reducer (not likely, pipe ID very large)
4. Fluid oscillations caused by compressor (not likely, examined compressor vibration and operation data and no indications)
Q-1:
Till we get more data and open the strainer, I would like to understand which hypotheses above are reasonable? Is it reasonable to expect to create vortex shedding or some sort of fluid-elastic vibration of strainer basket (perforated plate) when fine mesh is removed?
Q-2:
Our strainer philosophy was only to provide 200% "open area" through the fine mesh. No other criteria was set (CFD, stiffness, Rho-v2 threshold, etc. Could anyone give me some pointers to proper strainer selection and design? Our plant is a clean gas plant with mostly T (basket in a Tee) and C-type (conical) strainers ranging in size from 12 to 80".
The noise levels are extremely high (up to 120 dBA), dominant vibration frequency range is from 500 - 100 Hz, vibration velocity and amplitude = 0.040 mm/s and 0.01 mm max. We have shut down the compressor to prevent high-frequency fatigue of piping and SBCs.
A number of hypotheses for the noise cause has been proposed (high probability listed first):
1. Improper strainer installation (strainer "spiders" not fully engaged into the pipe ID allowing front strainer end to move - not possible to verify until basket pulled out)
2. Vortex shedding through perforated plate (recently removed fine mesh)
3. A foreign body lodged upstream into pipe reducer (not likely, pipe ID very large)
4. Fluid oscillations caused by compressor (not likely, examined compressor vibration and operation data and no indications)
Q-1:
Till we get more data and open the strainer, I would like to understand which hypotheses above are reasonable? Is it reasonable to expect to create vortex shedding or some sort of fluid-elastic vibration of strainer basket (perforated plate) when fine mesh is removed?
Q-2:
Our strainer philosophy was only to provide 200% "open area" through the fine mesh. No other criteria was set (CFD, stiffness, Rho-v2 threshold, etc. Could anyone give me some pointers to proper strainer selection and design? Our plant is a clean gas plant with mostly T (basket in a Tee) and C-type (conical) strainers ranging in size from 12 to 80".
