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jeffp1956
13-09-2015, 12:58 AM
I have a 160 series mycom screw compressor that has been modified with a variable frequency drive and a danfoss liquid cooling injection valve and I put a hand expansion valve at the point where the liquid is injected into the screw and it has a FES processor installed when the original McKormak panel puked. My problem is that when my head psi is over 140 - 150 the oil pressure starts to slowly decline as the compressor loads until it alarms out. I have installed a new oil pump, rebuilt the danfoss valve and verified its operation, had my screw guy pull it down till all i had was a case with rotors in it and he replaced all o-rings and gaskets. I have screwed around with the oil temperature (it was erroneously set to 130 deg.) and I have found that the problem gets better the colder the oil is the oil cooling is now set at 95 deg. I am also seeing foaming in the oil. I have 4 other mycoms though they are bigger machines are set up the same way and I am having no issues with them thanks in advance.
Jeff

RANGER1
13-09-2015, 09:07 AM
I have a 160 series mycom screw compressor that has been modified with a variable frequency drive and a danfoss liquid cooling injection valve and I put a hand expansion valve at the point where the liquid is injected into the screw and it has a FES processor installed when the original McKormak panel puked. My problem is that when my head psi is over 140 - 150 the oil pressure starts to slowly decline as the compressor loads until it alarms out. I have installed a new oil pump, rebuilt the danfoss valve and verified its operation, had my screw guy pull it down till all i had was a case with rotors in it and he replaced all o-rings and gaskets. I have screwed around with the oil temperature (it was erroneously set to 130 deg.) and I have found that the problem gets better the colder the oil is the oil cooling is now set at 95 deg. I am also seeing foaming in the oil. I have 4 other mycoms though they are bigger machines are set up the same way and I am having no issues with them thanks in advance.
Jeff

Jeff,
Have seen this occur over the years with a lot of different scenarios.
Oil temperature of 130F would be relatively normal to suit all conditions, 95 F pretty low.
Has the compressor worked in the past, if so what possible changes were made, if any.
Some helpful information could be
Current oil pressure & alarm as well as trip point.
Does it load quickly, dropping oil pressure, causing alarm?
Type of Danfoss injection valve ( reg valve not usually necessary).
suction & discharge pressures
are gauges or pressure transducers reading correctly
oil pump & type & model
oil pump motor speed
oil pressure regulator, maybe built into pump, is it bypassing.
any relief vales on oil circuit bypassing oil pressure
oil injection valve, is it open a bit, or a lot, or could be an orifice?
oil pump suction strainer blocked or changed to a finer mesh.
main oil filter, has it been changed, does it have pressure difference across it.
Describe oil circuit, valves strainers etc.

The bigger the pressure differential across the machine, it consumes more oil through pressure difference.

Some reasons compressor could need excessive oil are

Worn main bearings or rotor journals
bearings excessive clearance in housings (can happen in liquid injection compressors).
worn balance piston & sleeve (can lose a lot of oil through this if worn).
oil pump not big enough
oil injection open to much

If you can provide most of this It will be helpful to Solving problem.

Magoo
14-09-2015, 01:19 AM
To add to Ranger1 question list. Discharge temp.

RANGER1
16-09-2015, 09:53 PM
Jeff, any news or developments?
What clearances did your screw guy have on main bearings & journals?