FRick compressor slide valve issue

[namihabib]

The compressor was commisioned in 2015, the slide valve of the compressor is stuck at less than 4%. the compressor doesn't start and trips. The slide valve had the double acting actuator that is gas stream at one side and oil at other. previously a locknut breakage issue happened on the compressor due to which OEM said that the slide valve should be operated as single acting with only gas stream and the oil system was blocked. what can be the cause of this stucking issue?

 

[zdas04]

I've followed Frick's advice of single acting the slide valve and driving it with process gas, and it is half a good idea (and half a horrible idea). I had good success single acting the slide valve against a spring, but never got the pneumatics to work properly. They always overshot the desired point and caused the machine to hunt. I changed them to operate under hydraulic pressure (using compressor oil) and those problems went away.

To me a bigger issue is why you are relying on the slide valve for capacity control. I don't know what your speed control method is (remember, more information leads to better responses), but if you have speed control like you should have, then your control algorithm should only take the slide valve off the shut stop at maximum or minimum rpm. If you don't have speed control then the algorithm should only activate the slide valve at max power.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist