Knocking in Diaphragm Compressor

Gosh...! Don't take me for granted but I do believe that having the PRV set up with N2 within controlled pressurized with a good gage compatible for N2 purpose should be good for a test. The setting should stay the same value as is was oil pressure testing but will be more accurate by using the oil media better with an oil gage thougth because I believe the oil (Hydraulic Properties) will not give or yield much cushioning being more steady state pressure for the testing. Otherwise will be good to go for a new PRV and be on the safe side instead. 2) The PRV range are supposed to protect within equipment specifications for it safe operation. Most of the time it balanced between two forces (Spring and System Loop Media) acting oppositional against each other (Balancing) in order to sustain the safe operating conditions for the equipment. I believe that by cracking the vent you will be trying to simulate system pressures as far as there are real good set of operating gages in system loop to keep it in the safe range will provide some clues. 3) The knocking cause may be few things but check out for loops valves which can get jammed or bad and hopefuly not, something is loose or damage in compressor itself. And check propel rotation just in case.

I'm not an expert on such puppies and that's just my little suggestion and probably it will help you out somehow there. Alrigth buddy, work safe always and ' Lock Out and Tag Out ' energy source as safety measured and it doesn't feel sure, get a good contractor for such piece of equipment over there. And Don't rush into nothing and take it on downtime better instead.

Work Safe,

MC

#3. Lack of an accumulator?

No

we are having accumulator bottles in the suction as well as in the discharge. Moreover, accumulator helps in removing pulsations in the gas being compressed. But the problem of knocking is observed in the hydraulic system... the crank and the piston compressing the oil to oscillte the diaphragm

Only with respect to the PRV function. Most of hydraulic PRV have an integrated damper which uses the oil viscosity for damping. If you use N you obtain same cracking pressure but an unstable poppet movement with jerks and this can lead to a too abrupt pressure rise or fall. This damper is required to damp during the transient period of the poppet movement its tendency to oscillate with its own frequency (its mass and the spring stiffness). The flow through the seat in an open position generates also jet reaction forces which have the tendency to close the poppet.

I would NOT recommend to set the valve with N2 since the N2 viscosity is much less than oil's one and the dynamics of the poppet are strongly disturbed.

"I would NOT recommend to set the valve with N2 since the N2 viscosity is much less than oil's one and the dynamics of the poppet are strongly disturbed."

I strongly agree!

Yes sir chief.. in that case then I would agree here with you on this one having that condition then. Good deal then, good advice Boss, you have the technology. I was thinking that it can happen that probably there are a solenoid hunting opening and closing or something like that interfering the normal loop flow. But, yes, if the condition of viscosity will alter the testing then, I will go with the oil media to perform such test better accurate instead. Good feedback buddy. Have a nice one ....!

Allset Chief...

MC