Vilter Cool Compression Mono Screw

[Steve Mackie]

We have one customer with a Vilter Cool Comression mono screw. During their 5000 hour check, they've notcied the gaterotor edges are chipped and the ends look as though they are delaminating.

I've read a couple of threads talking about possible backspin and possible passing too much liquid.

Any updates on causes and/or solutions? The "solution" from Vilter is that it's normal wear and tear. They've buttoned it back up and put it back in service as is.

I'll post images later.

Steve

[US Iceman]

Will they supply new gate rotors when the compressor is out of warranty?

[nh3wizard]

You figure with only 5000 hours on a machine it would be covered....but I think I live in a fantasy world sometimes.

[Josip]

You figure with only 5000 hours on a machine it would be covered....but I think I live in a fantasy world sometimes.

Hardly, if one year warranty is behind

Best regards, Josip

[US Iceman]

Some of the Vilter compressors have a 5 year warranty if you do certain tasks (oil analysis, buy Vilter oil, etc.).

Personally, I am a little surprised with the rotors delaminating, but this Cool Compression stuff was "invented" after my time.

[Andy]

We have one customer with a Vilter Cool Comression mono screw. During their 5000 hour check, they've notcied the gaterotor edges are chipped and the ends look as though they are delaminating.

I've read a couple of threads talking about possible backspin and possible passing too much liquid.

Any updates on causes and/or solutions? The "solution" from Vilter is that it's normal wear and tear. They've buttoned it back up and put it back in service as is.

I'll post images later.

Steve

Steve

delamination usually comes with bigger hours than that and also comes with overheating

A small amount of what can be called micro delamination comes simply with the running in of the compressor.

If you can post some photos we maybe able to help you with that.

Kind Regards Andy

all the same I would be talking about it with them and insisting in a new set of gate rotors sitting on the shelf free of charge.

[refteach]

Please post pictures, I agree with andy on the delaminating, usually normal for a small amount, if there are large chunks taken out of the tips and delamination then there is a system problem. With a cool compression unit the separator is kept at discharge pressure when the unit is shut down. It is not equalized to suction like other screw compressors. Reverse rotation is caused by a sticking suction check, if it sticks the contents of the separator will be dumped into the suction line and there would be nothing in the separator. A single screw compressor can tolerate a large amount of reverse rotation due to the design. The discharge gas will press the gate rotor to the support and not allow it to be pinched when it is rotating backwards, however you will eventually run out of the lubricating medium because the separator is now located up stream of the comrpessor and not down stream.

[Steve Mackie]

Here are some pictures.

[nh3wizard]

What does Vilter have to say?

[Andy]

Hi Steve

to me those star wheels ae fine at the moment and have life in them yet. BUT they have been overheated and need at check again within the year.

PS is that rust and moisture we see in the photograps

Kind Regards Andy

[US Iceman]

The gate rotors seem to be OK from what I can see.

What were the discharge temperatures you were running and what are you compressing?

I also agree with Andy on the red oxide color. It does look like rust? Is this a ***** application?

[refteach]

The cool compression is ammonia only, the rust and moisture are not good the oil is ammonia rich and when you pump down to open it up, it distills out the water, the blades have definately expanded due to heat. The delaminating will not hurt the capacity or the efficiency, the chunks are only on the upper surface and not really effecting the sealing portion of the blade. Have the pictures been sent to Vilter's service department?

[IceMan_4000]

I would agree with the rest

1. Get Vilter involved
2. The liquid injection line is the biggest problem I have run into with the Kool Compression. and could be causing your heat issues, since this is the method in which oil heat is removed.

With the kool compression you must insure that there is a solid column of liquid at the valve. If the line is tight or undersized as soon as the valve opens you have flash gas which reaks havok on the oil charge and the temp.

With that said, are you or the customer adding lots of oil to this machine. These compressors have a extremely small oil charge heat issues happen so quick if the liquid injection line is flashing.
I now install 3" x 24" drop leg before the kool compression inlet to ensure even when the liquid valve opens I have not flashing going on.

I do not think you should be seeing that kind of wear on the gates at 5,000hr. I would certianly address the system these compressors are so picky on installation. good machine but a little piping gone wrong and it will self-destruct. When installed right these compressors seem to run issue free for ever.

IceMan_4000

[I LUV NH3]

I have seen this happen before. It was basically due to the compressor overheating. The cause was the home made pilot receiver piped between the condenser and the high pressure receiver. This little home made vessel was nothing more than an 8" diameter pipe 30" long with end caps on both ends. THe bottom endcap had a hole torched in it and is the liquid injection connection for these screws. Guess what? There was no connection for an oil drain on this little contraption. So as the oil level rose in the vessel it eventually passes straight to the compressors causing them to over heat.

Make sure that you are getting liquid NH3 in your liquid injection lines.

Crappy install.