Fuel Gas Screw Compressor with axial high vibration

[sjpark]

Hi all,

I have a screw compressor, which is fuel gas compressor. It has 4 female/6male screws no timing gear. The customer want to reduce vibration because they had to welding cracked pipe and structure caused by high vibration.

The highest vibration freq. is 4x rpm, it could be screw mesh freq. I guess. And, the direction is axial.
Hor. and ver. vibratin is about 4mm/sec but axial is 17mm/sec. Not to mention, dominant freq. is 4x rpm.
I also checked the structure vibration, exactly this 4x rpm is main vibration on the structure and pipe.

I suspect that the high vibration would be main cause for pipe crack. I checked vibration data from several points, on both side of Compressor and some points of pipe lines. Whole machine including structure is rattling. The source of that is 4x rpm(14325cpm). The running speed of Compressor is 3550 rpm.

Highest vibration is 5.411 G, Peak to peak on that freq.
It is equal to 23.588 um(PtP), 0.929 mils.
Autally, We had to fix the crack of some pipe lines and structure frames until now.


I also suspect the resonance in the pipe.
But, I would like to reduce the source of vibration. That is best way to avoid the resonance.


I need your help for reducing this vibration.
If you have any information and experience, Please tell me about anything.

 

[crjones]

Typically the air end motor assembly is isolated from the framing structure by vibration mounts and soft pipe joints. The other route is to make a torsionally rigid base again with soft pipe joints. The next area to look at is the coupling alignment your TIR should be no greater than 0.002 in/in of coupling diameter.