York YK Teardown Issues
We have just completed a YK teardown in our shop and this being my first one I have a few questions. The compressor was torndown for a number of reasons......excessive excelleration time on startup, oil loss and very difficult to spin the compressor coupling with the motor disconnected.
The excelleration issue was obvious.....one of the vanes was open and the ball joint had come out of the ring. Any thoughts on how this may have happened....the slot is not deformed and the ball joint went back in with no issues.
My next question has to do with the laby seal areas on the impeller. The seal area on the impeller inlet is not smooth but it is grooved as though the floating laby seal has ground itself into the impeller. The laby does float but the grooves in the laby are ground down and this part of the system needs replacing. The seal area on the balancing piston looks very much like the impeller eye but it is so perfect it looks like the grooves were machined into the impeller. Again the actual balancing piston does float and the grooves are worn out. I am having trouble determining the reason for the impeller issues because the bearings are not that bad......of course York info does not give bearing clearances so my observations are based on teardowns of other manufacturers chillers. The impeller shows no other signs of extreme wear except the two seal areas.
Oil loss occured without the chiller even running ( this chiller has periodic seal lube). The oil cooler is refrigerant cooled and is under test.....any other thoughts where to look.....nothing obvious in the compressor.
All thoughts are appreciated.........................wayne
All the YK's suffer from the impeller eye ring & the balance piston digging into the impeller...
Although I have not seen your compressor, I will bet a dollar to a hole in a do-nut that the Impeller Labyrinth as well as the balance piston is showing severe wear @ the 10-11 O'clock position.
For years I have pondered this problem & now I do believe that I not only know the reason...but I know of a cure as well....
Each and every one I have seen, and it has been more than a few, showed severe wear on the seals in question at the position mentioned earlier..
Some claim it is the weight of the Labyrinth & the Balance Piston, or even some claim it was done in shipment as the "Free-Floating" seals bank into the Impeller....Poppycock sez' I....
My theory is that a minute amount of oil/refrigerant gathers in the very deep cut Labyrinth grooves,then, upon start up this area goes into an extremely low pressure(Vanes closed-Impeller pumping) and as the oil/refrigerant is pulled CCW(facing impeller) the oil expands at a VERY rapid rate(fraction of a second on X-Line compressors) That diff.pressure between the Labyrinth & the impeller drives the "Free-Floating Labyrinth" towards the 4-5 O-Clock direction and thereby pulling the seals into the impeller @ the10-11 O'clock position.
That....my friend is the sole reason that the YK's without a VSD, (slowwwww acceleration) suffer from this problem.
The cure is extremely simple.....
When installing a new eye seal or balance piston, drill a teeny little hole thru the labyrinth grooves @ the 6 O'clock position to drain any oil/refrigerant from settling into the grooves in the first place,(A 1/16" hole is plenty big enough)
The PRV blade that jumped out of it's Lil' hole needs to be reshimmed to remove "ANY" clearance @ the 50% vane opening on all the ball end connectors. If you can move the blade arm at all @ the 50% opening into the blade ring...You needs a shim or 2 under that Ball end...
Don't expect the factory to agree with me on this wear on the impeller, but hey... I'm just a half witted semi-retired Greaseball with an opinion....
Ain't "None" of us as smart as "All" of us..
Thanks for your excellent response Richard, I was hoping you in particular would chime in. I will inspect the labys tomorrow to determine the clock position of the most wear on each laby. In your opinion would this be cause to replace the impeller or just the labys? I would say that the impeller is grooved down about .050 on the EYE and .020 on the balancing piston seal areas. This chiller is 4160V auto-transformer start, sooo it comes to speed very quickly which would carrobrate your theory.........wayne.
In a warranty condition, I would never hesitate in relacing both the Impeller eye seal as well as the balance piston and yes...even the impeller.
But to go to a customer and lay the price of that impeller on him is never a pretty picture.
I have re-used plenty of the "Grooved" impellers but always with new eye seals & balance pistons without any detectable problems at all. Granted the thrust equalization will be somewhat altered as the balance piston sealing area is somewhat reduced, but I have never...not once seen even a degree difference in the thrust oil drain temperature even though the Thrust equalization performed by the balance piston has been compromised with the grooving of the balance piston sealing area.
Any losses on the impeller eye seal by using the now Grooved impeller along with a new eye seal has been totally undectable by me and even if a few tons of refrigeration are lost, I wonder how long it would take to offset the cost of the hi-dollar impeller you did'nt replace...Many years I would guess...
I would be upfront, forthrite & honest with the customer in the decision to replace the wheel myself, and see what comes from it. However...If it is a "Full-Maintenance" contract.....and you would have to absorb the high cost of replacing the wheel, well then...That my friend is totally different story.
I myself, personnaly, would bite the bullet and replace it...
Ain't "None" of us as smart as "All" of us..
richard - great theory on the laby wear. gonna have to give it more thought.
also had a yk last year, similar, cept lite grooving on the wheel,w/ flat laby grooves
This is a bit off topic but I have a question.
A few years ago I worked for a school system that had about 25 of the York chillers with external motors. All of these machines had a severe problem with the shaft seal where the motor entered the compressor. Has this problem been resolved so the shaft seal does not have to be replaced twice a year? This was about the time 11 was being replaced with 123.
Yes, they went to a bellows style seal.
Originally Posted by Mrduffin
To much work with too little time!!!!
Additional question as I was involved on this teardown from start to finish, what impact would it have if the compressor ran for a period of time with one vane stuck open and the rest fully closed? Would it throw the impeller off balance at all and increase the wear we saw on the impeller eye from the laby seal, and how much wear would be considered acceptable as the eye of the impeller is gouged in as deep as the grooves in the laby itself.
I do not see how one or more blades being open or partially open could throw the impeller out of balance at all. With it spinning @ approx. 10 grand and with the velocity being what it is between the PRV's & impeller, methinks there is no way that there could be any unequal loading on the wheel itself.
As far as how much wear would be allowable, the only thing published is the clearance between the impeller and it seal(s).
A pretty fair rule on labyrinths is .002" per inch bore being standard and anything greater than .004"/inch bore would have noticeable losses as well as a proportional increase in the discharge temperature.
The Balance piston would be compromised and a possible increase in oil drain temperature from the thrust bearing would be of much greater concern to this scribe...
Remember that the impeller is trying to pull its way to the suction ell on its way to Mecca as well as being pushed in that direction by the hydraulic piston effect of the oil pressure..That is the "Major-Thrust"..
To offset this "Thrust Loading", First off, the Seerbathe(spelling) are cut at a predetermed angle so as to "Pull" the impeller back from the suction ell while being assisted by the Balance Piston creating a lower pressure behind the wheel...
Ain't "None" of us as smart as "All" of us..
Thanks Richard, you wouldn't care to speculate how we might of lost 4 pails of oil to the tube bundles would you and I'll explain. This chiller has seen a lot of abuse by the owner and what we see inside is not a terrible surprise, however up until last year they had to keep 1 machine running all winter long to satisfy process loads. This past winter they no longer needed cooling and in order to avoid freezing of outside pipes ran 1 pump to keep constant circulation through this chiller and out to the various plant loops. Temperatures were often seen between 85-95 F, and during these times I saw higher oil levels in the sump sight glasses (assuming refrigerant condensing in the oil). We have a daily lube cycle to keep the seal wet and this chiller probably sat idle for 10 months since it last ran. At initial start-up this year we could not attain adequate oil pressure due to oil loss, I added 1 1/2 pails of oil to get it into the lower sight glass and generate normal oil pressures. That's when we found out it was drawing excessive current during acceleration and tripped out. Once we determined it had to come apart I recovered the entire charge as vapour in order to determine where the oil was, pressurized with N2 and collected 1 1/2 pails from the sump and 4 1/2 pails from the liquid feed line. The bulk of this oil loss was without the compressor ever running and I have confirmed the refrigerant cooled oil cooler is good. Any Suggestions as to how the oil was lost to the system??
Im no york expert but most hi speed machines the impelller will hit the seal the fist time it starts there is a certain amount of whip built into the hi speed shaft to keep it from breaking kind of like the flex in a golf club.Almost every impeller I have taken off will have a short marked area where it met the wheel but I like richard L therory
on 1 of mine there are 2 old yt's. forget which design, they have the hi & lo speed internal oil pumps, external ' aux' pump. they flow cold cdw (operator error?) & m-t the sumps every frikkin winter.gonna disable the heaters & pull the oil charge @ shutdown this year
Picture of our wheel.