We have Dresser Rand make 2 stage 4 cylinder double acting Reciprocating compressor. It runs on 0%,25%,50%,75% and 100% load. It is equipped with plate type valve 4 suction and 4 discharge in each cylinder. Variation of load done by diaphragm type unloader on suction valve.
When we start compressor from 0% load and step wise increase to 100% load everything runs smoothly. when we decrease the load from 100% to 25% (Stepwise)everything runs smoothly. But when we further decrease the load from 25% to 0% heavy abnormal sound comes from one of HP cylinder.
On opening the end cover and removing the piston it has been observed that both the rider ring has been damaged in corner.
we have replaced the rider ring and after trial this thing again happened.
Today we have taken trial third times and problem still exists.
Please send us your information regarding this problem.
pawan
Original Post
Hi pawan,
It's really intresting.

Could you give the following information.
During startup you mentioned that the compressor is running smoothly at 0% load.
Pls note down all the parameters including the motor amps and compare with that readings while you decrease the load from 25% to 0%.

Which parameter is varying.

Something is going wrong while you decrease the load from 25% to 0%

Check from operation point of view.

We faced one similar problem in one centrifugal compressor but there the vibration is high during decrease in load ( from 100 % to 50%).

There the problem was from the operation. The control valve was havong problem.

Regards
Selva
Dear Pawanlng,
I have gone through the various communications you have had. I wish to only know is whether the vent line on the clearance pocket outer head is open once the clearance pocket outer head unloads from 25% to No Load condition. If this is blanked due to some reason, then the chattering may occur in clearance pocket outer head. The OEM(Original Equipment Manufacturer) generally mention this in the compressor maintenance manual.

Another aspect is to be checked is whether Road Reversal exists at 25% loading condition? This is a must for the healthy operation of the compressor.

By the way what are the cylinder sizes and the stroke of the machine? At what speed the compressor runs? Is this Gas Engine Driven OR direct Motor Driven?
If you send me the performance of the compressor, probably I would be able to say something on Rod Reversal.
samrat

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