Causes of Cylinder Vibration in Vertical Reciprocating Labyrinth Piston Compressor

[JoeFission]

Hello there,

New to the forum, but was hoping I could draw on some of the extensive knowledge I've seen here reading through old and new threads.

My plant recently ran into some issues with one of our 2-stage vertical reciprocating labyrinth piston seal compressors. 1st stage is 3 cylinders, 2nd stage is 1 cylinder. Process gas is high purity hydrogen. Some observations:
-Rising interstage pressure
-Rising stage 1 and stage 2 discharge temperatures
-2nd stage cylinder vibration picked up by monitoring software... audible knock could be heard at suction side of 2nd stage cylinder.
-2nd stage piston rod packing gland wear (ring dust seen collecting inside the distance piece below the packing rings)

What typically can cause piston cylinder wall contact in a vertical reciprocating labyrinth compressor? Can ovality of the cylinder or irregular wear of the cylinder wall cause unbalanced radial forces on the piston and lead to contact between the piston and cylinder?

Thanks for any information any of you can provide to help me out with this problem!

-Joe

 

[georgeverghese]

Observations 1 and 2 seem to indicate leaking suction or discharge valves on either or both stage 1 and 2. Check also the clearance between cylinder wall and piston for all throws to see if clearances all round the piston perimeter are within limits.
Observations 3 and 4 are clearly caused by some mechanical issues - my guess would be misalignment between motor shaft and compressor shaft at the shaft coupling?

 

[quadtracker]

I would check for rod runout problem caused by crosshead guides worn, cylinder - oval Inside diameter, piston wear, improper piston clearances to cylinder for 2nd stage problem. For 1st stage problem I would check discharge valves and second stage suction valve condition. Possible improper valve lift clearance in suction and discharge in second stage.