Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
(OP)
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".





RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
dominant vibration frequency range is from 500 - 1,000 Hz, vib
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
We have opened the strainer, removed the basket and reinstated the piping. The high noise accompanied by low amplitude vibration is gone.
However, we have now detected another strainer basket where noise level is somewhat increased:
105 dBA, 3.36 RMS mm/s velocity, 826 Hz
Is there any danger of operating
1. long term (2years)
2. 1 month?
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
If the sensor is slid around the pipe does the amplitude vary?
I'm kind of expecting the vibration is a phenomenon related to a mode of the pipe wall -\http://www.betamachinery.com/uploadedImages/001_-_...
not the bending etc that piping system support calculations generally worry about.
http://jolisfukyu.tokai-sc.jaea.go.jp/fukyu/mirai-...
In either case petty detailed stress "calculations" would be necessary to determine what is harmful.
If resonance is involved I'd expect there are ways to re-tune or damp the system to reduce the vibration and the concerns.
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
I do not believe that there can be 200% open area when the entire area is 100%; perhaps you mean 50% open or something else?
Walt
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
200% strainer open area is correct, strainer cone is long
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
why not just put some less fine mesh back in if that was the issues? Or just remove it. What is it protecting downstream from a compressor??
In line strainers like this are not the best solution long term because, as you say there are no real specifications. I once used 3mm stl steel with punched holes and it was just as well - it took 20 bar differential (yes twenty bar) during commissioning and only bent a bit. The very thin commissioning strainer we refused to put in would have broken long before that and deposited all manner of stuff into the compressor...
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
op parameters and all else is as before the problem started
except that the mesh was removed in the meantime
vortex shedding?
RE: Pipin Acoustic Vibration caused by strainer? | Strainer Design Philosophy
Basket was damaged by vibration, upon its removal vibration and noise disappeared.