Recip compressor crosshead vibration

[Wkcoo]

Hi, just checking with the community if anyone has any experience with random crosshead vibration for recip compressor.

It's a two stage machine, however the first stage crosshead vibration will randomly spike above 20m/s^2 then come back down again.
It's just been overhauled last year but the issue started once startup.
There seems no correlation with other process trend. Rule out mechanical issue as well as it is random and not constantly high. However the machine does run at conditions different from design, and simulation show the rod load is different on both sides. I am suspecting the deviation of operating condition from design condition causes unbalance thus high vibration but again, it is random and kind of defeat my suspicion.

 

[Strong]

Check that sensor and monitor/meter/analyzer are working properly.
Check/test for resonant structure that is close to dominant frequency and direction of motion.
Check/test for torsional vibration and inspect condition of shaft coupling.

Specific recommendations cannot be made without a lot more information!

Walt

 

[JJPellin]

I would get additional data to correlate the crosshead event with crank angle. This could help you differentiate if is is likely:

A spun crosshead pin bushing
Excess clearance in crosshead pin bushing
Excess crosshead shoe clearance
Loose piston rod jam nut / super-nut / flange bolting
Liquids carryover to compressor cylinder
Etc.

What is the sensor? Where is it mounted? Which direction is it oriented?

Johnny Pellin

 

[Strong]

Since your vibration level is in Acceleration, I assume you are using an accelerometer on the crosshead casing. Adding to Johnny's comments, I would also check lubrication. Check you accelerometer and and cable mounting for poor (loose) contact. Consider replacing sensor, cable, and analog input or at lease making independent measurements with another system or data channel on monitor. View unfiltered waveform synchronized to shaft position to help locate source of impacting (assumed type of vibration).

Walt

 

[Jone k]

check the foundation for compressor . We faced this issue in our plant.

 

[georgeverghese]

Random condensate - liquid slugs getting into compressor from pocketed suction line ?