Screw Compressor Thrust Bearing Frequent Sudden Failure

What does the manufacture have to say? Have you contacted them about this condition.? The reason I ask, is it is very hard to trouble shoot this kind of problem using the written word. You need someone on site who can touch feel and suggest.

Is there a way it could be getting liquid in the suction?

since the suction line is set to higher pressure than atmosphere and evaporator side pressure and temperature is carefully controlled there is no way for liquids to exist in the circuit the same results came from oil analysis

as i mentioned before all vibration and temperature logs and observations shown no abnormal condition , the thrust bearing oil temperature logs also was normal that one may conceive no alignment issue , but the last thing is what happens really and im suspicious about. what causes a sudden overload on a thrust bearing while there is no leakage and the separator oil level logs show normal , can you explain what can cause oil path blockage, i was more thinking of balance piston malfunction but had no idea how and why

Get the manufacturer's representative in to have a look at it right now. These individuals may have seen the problem elsewhere and will be in the best position to help fix it. After all, these people have a commercial reputation to maintain; CR4 readers don't.

I do notice that you have compared two like compressors. The one on which you have stated as less the full load works fine. The one that is used at full load fails. Possibility is that what you have is an over load on the one that fails.

since the full output power of drive system is less than full load power draw of comp. its nonsense to have compressor to go under excessive load

the sys dont need to exceed it's specified load to start failing -- if it's utilized 24-7 ... you start to notice where manufacturer's specs don't hold

Just check the quality of propyle both at the inlet and out let if there any diferrences compared to other compressor you have. Could also be liquification of the same.

both compressors work parallel in a single circuit

Please check for failure in the large-diameter balance piston labyrinth. This may cause the thrust bearing failure you describe.

http://books.google.com.au/books?id=ePBZJiy1qBEC&pg=PA261&lpg=PA261&dq=propylene+compressor+bearing+failure&source=bl&ots=dQ2tSNfhM-&sig=bf3XNMT8-fPhQiPs8VTjMFTd_-U&hl=en&sa=X&ei=hErJUPqJIIXtiAf-poE4&ved=0CDEQ6AEwAQ#v=onepage&q=propylene%20compressor%20bearing%20failure&f=false

Mark Bingham
Relativity PL

this link is filtered by my ISP, im trying to bypass the filteration to see inside , itd be helpful to give some mirrors or proxy server address

What are the findings on the failed bearing, balance piston and screws? Any major deviation of operating parameters? Oil quality. Is it beyond doubt ok? What type of bearing it is? Are you using same make bearing in both compressors?

the thrust on the male shaft is burnt dark blue and nearly melt but no significant problem on balance piston but the head of screw badly rubbed to the casing to produce deep grooves that i can say for sure it occurred just after thrust bearing failure , the bearing used were not same make but fully satisfied manufacturer specifications and approved by them

(1) Check with manufacturer of the machine as they have much more combined experience with their product.

(2) After repair trend the machine with ultra sound for the simple reason ultra sound signature is predominately the first indication of things going wrong.

(3) Since you have a sister machine you may as well trend that machine as well to try to ascertain any variations in the two machines. They should be similar but not necessarily identical.

i didnt get you in 2nd sugg. , what sort of test it is can you please give me more info or a link to find more about

There are three main indicators of problems. #1 is ultra sound , #2 is heat and # 3 is vibration unless the failure is catastrophic, ( sudden with no warning ) Ultrasound appears to be almost always the first signature of imminent failure or issues. Anything that moves makes sound and if inaudible then it is ultra sound usually under 20,000 in frequency. Your cat or dog may be able to hear it but humans do not. Companies such as UE and SDT make good ultra sound detectors that convert ultra sound into audible sound. Every owner of machinery should have this diagnostic tool along with thermal imaging and vibration testing if they are serious in preventing expensive damage.. Most managers are unfamiliar with ultra sound diagnostics and appear to write it off due to their ignorance. Trending is taking a reading at the same spot under similar conditions (temperature) and recording same for future reference,reading of monthly or weekly work well and if changes happen quickly then step up to daily or even hourly depending on equipment, as sound increases it should be a warning of imminent failure if taken seriously. Look up one of the companies mentioned ( not an endorsement ) they have all the information you need.

i'm not a production tech -- however

you never described the failed bearing (most bearings i know failed - and there are 2 or 3 - are due water or moist)

the abrupt failure may indicate constant overload - from the shaft side - 5deg from axes something ... may and not

speculation - the full load wears inequalities to roller path >> heat >> expansion >> blow

It sounds like you are getting a liquid slug.

what sort of slug may occur in the refrigerant circuit pipe line if its terrain slugging what would be that liquid to make a plug and after all how a periodic slug would cause a sudden over thrust on the comp. shaft

((((I dunno even what the machine looks like you're talking about))))

anyways certain oil metal can act as acid metal (why dont you use ®bearings)

Burnt bearings may be due to overloading or lack of lubrication. Compare it with the good running compressor. Are the bearings and balance piston identical in all respects? The rubbing of the screw with the casing may have occurred only after bearing failure.What is the sealing between bearing and system fluid? Any chances of failure of the seal. Is the balance piston able to take care of the thrust load?

there is no special sealing but accurate designed tolerances to let lub oil( that is pumped to higher pressure than discharge) to escape from bearing casing into screw area and mix with refrigerant