View Full Version : Vilter Blues

30-01-2008, 08:19 AM
Hello, I have a compressor that isn't functioning properly. I would like to give out some info and if you could give me some feed back with a recommendation or a possible solution.

Vilter 150hp 450XLcompressor w/440 safety plates. Half of them “4 of 8” of these have been replaced. Water jackets have been cleaned and good H2o flow and head cooling. The main problem is high discharge temperature, when compared with past logs at same or like operating conditions. This particular unit has three un-loaders, when this unit unloads on the 1-5 and 3-7 cylinders there is a delay before you hear an audible pitch change but both solenoids show energized. When coils are removed you can hear the plunger switching “clicking” action accruing. Un-loading 25% 95Amp+/-, 50% 80Amp+/-, 75% 80Amp+/- after a 45 Second delay 65Amp+/-.... Loading 75% 65Amp, 50% 65Amp, 25% 80Amp fully loaded only 95Amp "this is probably due to the low head pressure/lower comp ratios".

Suction press 33#
Suction Temp. 33f
Discharge press 85#
Discharge Temp 235/250f
Oil temp 130/150f
Oil inlet 90#+/-
Oil diff 2#/3#
“this info is from pressure gauges and computer readouts.”
The internal pressure relief was replaced.

30-01-2008, 11:49 AM
There was a similar post about this problem a while back go back through the posts under industrial / compressors I think it is there.
The high discharge temp could be caused by the valve assemblies not seating on the liners properly allowing bypass, safety head springs under length allowing the valve assemblies to lift slightly on compression, internal relief valve passing, discharge valves not sealing or possibly air in the system.
Also the unload piston on the 75% could be sticking
or there is a problem with the lift pins.
Hope this helps, let us know what you find.

30-01-2008, 03:39 PM
Is this the same Compressor Joshieboy was writing about?

30-01-2008, 08:51 PM
Yes, this is the same comp that joshieboy has posted, with just a little more data to present after the IPR replacement. I’ve read through all the postings.. Just picking at things slowly.

US Iceman
30-01-2008, 10:18 PM
Are you sure the oil temperature is 130-150°F?! The maximum allowable oil temperature for a 450XL is 130°. It should be around 115-120°F during full load operation in the summer.

That sounds like a dirty oil cooler, warm supply water, or insufficient cool water flowing to the oil cooler.

You also have about 13° of suction superheat. Is the system operating with TXV's or flooded evaporators?

The main problem is high discharge temperature, when compared with past logs at same or like operating conditions.

What was the discharge temperature before? And why did it only affect 4 of the 8 compressors?

01-02-2008, 07:38 AM
Ice Man, yes the oil temp does rise to very high levels and yes we shut the machine down before any high oil or high discharge temp limits/safety’s trip.
On compressor cooling all of the water jackets have recently been cleaned and the same with the oil cooler. The water source is a common condenser sump/ defrost tank. I don't think high water temp is an issue. This is a large NH3 flooded coil plant.
I think there might be a miss understanding, there is only one 450xl but when we removed the heads we only replaced half "4" of the "8" safety head assemblies. The ones with visible problems like pieces of the discharge valve plate missing. In the past maintenance logs from the previous operator this was due to running high discharge/ head pressures. “We have had this facility less than a year”
Both the responses from joshieboy and this one are indicating recirculation of discharge gases. This is now with a new IPR valve. Do we look into suction/discharge valves? With a little humble pie the compressor worked within proper temps/pressure ranges before the new discharge safety plates were installed. Now we’re left scratching our.........

01-02-2008, 03:51 PM
A quick and dirty way to check for a bad valve is to open the discharge check valve and shut the machine off.
If you can hear gas leaking back throug the machine you have a valve problem. Or, you can shut off the suction and see how fast the pressure rises in the crankcase.
(I do not like to let the crankcase pressure go up to full head pressure, but I am a coward)
I am assuming that the sealing surfaces are in good shape. The one thing I do not like about Vilters is that a bad spot on the head or liner can cause a leak. Unlike Mycoms where you can lap the discharge valves into the machine.

US Iceman
01-02-2008, 05:36 PM
The water source is a common condenser sump/ defrost tank. I don't think high water temp is an issue.

Have you checked the water temperature in the sump?

I have seen remote sump temperatures reach warm temperatures during the winter, since sometimes the water pumps are not ran very often because someone is running the condenser dry (or worse, cycling the water pumps on & off).

What was the discharge temperature before?

Core4 Guy
17-02-2008, 08:25 PM
The Reply is going to look alot like my other reply to Joshieboy. The facility has multiple compressors on a common suction. All the conditions would then dictate to be some what the same. Yet, the compressor is either over compressing or the dischage gas is bypassing into the suction and recompressing.

I ran this system on a Ph chart to see what the discharge temp range thearetically would be. I came up with no less than 170f at 50 psia and 124 psia.

I dont think there's much difference between the 440 and 450XL machines (except that they took off all the sharp edges inside, my fingers thank them). Everyone else came up with great suggestions. I would look at two things. Compression and Inefficiency creates high dischage temps, high oil temps and well problems. I would look for a true Crank Case suction presure vs Discharge Preasure and make sure the gauges calibrated and are not before (suction) and after (discharge) of any valves. I think these machines are suction unloading so this really would only increase the cyclinder temp not the dischage temp.

Also "a trick" I would do is get a IR temp meter, turn off the water to the heads (temporally) and check the top and sides of the cyclinders any cyclinder that is loaded will be doing work thus warmer head, any cyclinder with bad discharge valves will be really hot, any suction valves bad will be warmer on the casing wall, any unloaded cyclinder will be the simular as the bad suction valve. Play with the unloaders and watch them work with temperature. Get to know your machines, love your machines.:eek:

The reason I would check the pressures is because I once had a lunch bag located before the isolation valve on the suction side of a machine causing a pressure drop into the crankcase. I failed to notice the issue on start up and had high dischage temp issues. What a pain to repair. Say thanks to the welders...