noisy compressor

[engeltech]

a problem with a Bitzer two stage compressor,7.5HP: emits a very loud, high pitch noise when operating full capacity but runs normal at 50%.lubricating the solenoid valve initially helped,so did changing it-but the sound returned after some time.the capacity solenoid valve on the compressor head is definitively involved.any thoughts?

[centrecipew]

Hi, I believe the capacity control is acheived by Hot Gas Pressure being exerted on a piston, ie unloader valve.
There is a "Teflon" seal on the piston and almost certainly a piston ring too. Should these be worn then I believe that possibly " Hot Gas " passing through a faulty seal or ring might cause the noise described by you. You will need to remove the unloader head and physically inspect the piston and cylinder of the unloader valve assembly. Good Luck.

[centrecipew]

Hi Again, I would also recommend you carry out an efficiency test on the compressor as you may find that the valve plate on the "Loader" cylinders has excessive wear causing the suction valves to "let by" discharge gas.

[icecube51]

hey centrecipew, would you discribe an efficienty test for comps pls.
thnx, Ice

[mrfrze]

I may be wrong here but you cannot "unload" a Bitzer two stage compressor. You can false load it - which is not a good to stage design practice. Additionally, the "7.5" is a S4N-8.2 (aka 8HP) 4 cylinder. Two low stage cylinders pumping into the high stage side of which are smaller pistons. In my humble opinion, your high stage reeds are broke.

To check - go to the BitzerUS site and download the software. Put in your conditions and check to see what you INTERSTAGE pressure is (shut off you subcooler feed). If its higher than the "modeled" interstage - its a high side issue..if its lower, it a low side issue.

Good luck.

[benji]

From what you guys are saying yes, that is correct, also because your teflon seal is leaking past you will have a hike in suction pressure as well....