Mycom 250VLD

Gentlemen,

One of my facility's has a Mycom 250VLD with approx. 12,000 hours and is less than 2 years old, from the initial start up this machine has made a noise like it was taking on liquid (Nh3), the compressor was taken off and sent back to the company that the package was purchased from and they supposedly tore the machine apart and found nothing wrong, and was reinstalled.

Within the last month this machine has continued to sound worse, same kind of noises but worse,
I had a vibration analysis done and the end play checked;
The end play was off approx. 3 thousandths, and the anaylsis shows some rubbing or contact on the suction end.

Has anyone else expeianced any of these problems on a Mycom with such low hours?

Are you seeing a fair amount of vibration on the oil injection lines?

No, Mike Ill send you the analysis (if you like) via email, these reports are Greek to me. Maybe you can understand it better.

nh3wizard;
Afraid I have never seen anything like this. It seems strange that the machine would run that long with mechanical problems that severe.
At the expense of sounding silly, is it possible that the machine could be getting liquid? Are the discharge temperatures normal? I once had a Frick driving me to drink with Frostback, reduced capacity and low oil temperature, until a friend came by and followed the suction line. We found a cool room coil had been piped to the suction line where it was out of sight. I had always assumed that it was on the same compressor as the other cool rooms.
The solenoid valve on that coil was stuck.
Felt stupid.
I do know that Dunham Bush rotors will bang if the oil injection flow is low.

Hi, nh3wizard :)

About Mycom screws all the best. No problem at all, very reliable machines.

But this can be a source of some big noise.

Quote:

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Originally Posted by US Iceman

Are you seeing a fair amount of vibration on the oil injection lines?

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Many years ago we had a similar problem with STAL compressor, oil injection into screws (bottom connection).
If there is not a regulating valve you can have to much oil injected in between screws causing overheating and strange noise, but very similar is if there is not enough oil too;)

Quote:

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Originally Posted by nh3wizard

The end play was off approx. 3 thousandths

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it must be in inches;) , what is 0,0762mm. Seems too small

In Mycom manual I found this values for discharge end clearance:
High stage 250V** L=0.08-0.11mm
Booster 250V** L-B=0.50-0.54mm

Best regards, Josip :)

The one instance I've seen something like this was were the oil injection port was placed on a single screw compressor.

The rotor tip was causing a high frequency noise that created vibration. This sounded very similar to a screw ingesting a steady stream of liquid. A small amount, not large.

Are you running an oil analysis program for wear metals, etc? If the rotors are starting to cut into the end plates the metal has to go somewhere (oil filters and coalescers).

What about oil pressure? Is it too high, too low, or just right? If the oil pressure is too high, it could be causing the slide valve to lift into the rotors. This depends on the adjustment of the guide block or slide valve wear.

Did the shop provide any pictures of the internals?

Ill be at that plant on Tuesday, and Ill advise what I find.

Thanks All

Hi, :)

Quote:

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Originally Posted by US Iceman

Are you running an oil analysis program for wear metals, etc? If the rotors are starting to cut into the end plates the metal has to go somewheree (oil filters and coalescers).

Did the shop provide any pictures of the internals?

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Are you sure they did open compressor and maybe made some;)

Yes, I know we should believe, I am optimist, but having a lot of experience put you close to be pessimist.

Best regards, Josip :)

Here are some possible causes of noise in addition to the ones mentioned above.
1. High oil pressure. What is your oil pressure and what type of oil pump system is in use, Full lube or differential feed. What type of oil cooling system is used, oil cooler or liquid injection.
2. Excessive oil through the oil injection port ( as mentioned by Josip). If there is a regulating valve on the oil injection line, this should be adjusted until you have the correct discharge temperature. If you provide the suction and discharge pressure I can provide you with the correct discharge temp.
3. VI is not set correctly if it is has an adjustable VI.
4. If the compressor runs long periods unloaded the loading slides tend to wear and can start to " rattle" in the compressor. This is particularly more noticable as the compressor unloads. However this does not explain your noise from new.
5. Sometimes excessive side load through the economiser port can create noise.
I hope this has been useful.

Regards

Mike W

Hy friends, I'm from Brazil and listenning critical informations about base PAO. Is it true that PAO go away? The problem will be done at march 2009? Sorry about my english...I'm at school yet. Best Regards.

I am surprised that someone would take down a screw, tear it down and not replace the bearings while it is on the bench. I hope you got internal pictures.

Sorry, I just saw the original post dates.:o

Sorry guys, thanks to keepitcool he jogged my memory on this,the cause was " Excessive oil through the oil injection port ( as mentioned by Josip and Mike W). If there is a regulating valve on the oil injection line. Mycom came in and made the adjustments and she is purring like a kitten.