York seal problem, now it seal, now it don't

[ga1279]

I have an 1980's York OT-K3-E3-OUC, I cant seem to keep a seal (sealed). It has a 3 piece seal 1 rotating hardface on the shaft and 1 stationary hardface with a spring mounted to the seal cover. There is a carbon disk between the hardfaces. The seals have been lapped to 1 light band each time they have been replaced. The problem is the seal cavity temperature will run up to 170*F. Oil sump temp runs 135-140*F. The seal pressure is set a 2#(at full load) as measured at a 1/4 angle valve installed on the bottom of the cavity. There is flow as pressure can be driven up or down by the regulator. (installed in place of original shim screw set-up) The regulator adjustment is York's replacement part. The oil from the seal cavity comes out black/ burnt. Once the oil gets into the cavity were does it go ? Net oil pressure generally runs at 43#s and filters are clean. There is a 12* delta T across the oil cooler in the base of the evaporator. The low speed bearing has been removed for inspection with no evidence of heat damage or wear. What about internal oil passages. I have seen general oil flow diagrams, but not so much for the seal cavity. What if a 1/4 copper line was installed from the angle valve and down to the bottom of the evaporator were the oil is educted out pulled through a drier and brought back up to the compressor. We have replaced too many seals. Alignment is as good as it gets with that shaft set-up, screwed into to the other side of the low speed gear, leaves the shaft to flex. Thanks in advance-GEO

[klove]

Are you lapping your own seals or buying new?

[ga1279]

We have them done professionally. There is no way I would try to do it. I could with precision glass, but why? The seals that were replacement were brand new York parts, but I still had them checked and two factory seals had to be lapped-GEO

[ga1279]

Actually what I'm more concerned about is the oil flow through the seal cavity and the amount of temperature rise generated by the seal itself. I know the oil can't just be allowed to just sit in the cavity and get hot because of the heat generated because by the friction being given off by the constant rubbing of the seal faces. This oil has to go somewhere other then the waste oil container and that is not that much, about one ounce per month. Like I said before I don't think I have a problem of oil pressure, alignment or seal surface condition when installed. my problem is more of the ability to remove heat away from the seal itself. I will admit I could be missing something that maybe quite obvious to the more experienced York people out there. I have been doing this for many years and am still learning thing everyday. Thank again guys-GEO

[ga1279]

In my thoroughness to supply information I neglected to tell you this is a York LTD-126 compressor using R-11 as the refrigerant and the oil is Mobil Gargoyle Artic 300 (York-C). Thanks again-GEO

[cperk]

Have you tried going up with the seal pressure to see if it lowers seal temp.? One ounce per month does'nt sound like much weapage. I have some that I have to dump the cup every week, but never had to replace the shaft seal, and they don't take-on any air neither. Are you sure that seal that your replacing it with is correct part? (not too much spring pressure).

[klove]

How long does it take to fill the seal drip container, and is the container a standard 750 ml (approx 1 quart) bottle? How many run hours and starts are in that period of time, generally? What's the criteria being used to determine the seal is defective?

I know these don't answer the specific question, but something ain't addin' up. One ounce per month is nothing, and nominal 170* on the cavity wall doesn't really throw up a red flag. You said the oil coming out of the angle valve is black and burned - what is its condition going into the seal? I'm not understanding the reasoning behind having the seal faces relapped before installation, either. Could you elaborate on why that's been necessary?

[ga1279]

The machine has had the seal replaced 4X in the last 2-1/2 years. All parts used are all York original parts. Inspection of the seal face (carbon) shows circular grooving and wear. Only 1 seal assembly was re used and it was out of tolerance in the light band test. They were able to save those parts by lapping them. When the machine is operating and the seal is beginning to fail refrigerant can be detected leaking from around the area of the input shaft and seal cover plate. During off cycle it will suck air in the vessel through the same opening. I'm from the old school and I was always told to at least have the sealing surfaces checked by light band equipment to eliminate guessing. The oil entering the seal cavity is a dark honey colored, at the seal oil pressure adjustment. At the 1/4" angle valve it comes out black (carbon) The oil in the waste bottle (also a York part) seems to be of a different viscosity then the oil in the circuit. We inspect this group of chillers once a month and the waste oil from the seal housing could be as much as 1/2 of the bottle or as little as 1 ounce. When we first took this account they were using a 5 gallon pale that would collect at least a gallon a month. This plant runs 16 hours a day 365 days a year, less hours during holidays. This is the oldest chiller in the group and the 2 other like chillers have been replaced 10 and 12 years ago. Basically because of repeated tube failure. We have done Eddy Current tests on this chiller with out any negative results. cperk all replacement parts are York replacement and the factory manual calls for 2# of seal cavity oil pressure at full load, 15-16"hg evaporator. I am also wondering about low speed shaft thrust that could allow the low speed shaft to float toward the seal. I am open to ideas or thoughts.-GEO

[Randy S.]

On the YT's I have under my care, I run them at about a half PSI positive. That gives more oil flow through the seal cavity, and keeps the seal cooler, but still a full cavity. Get the low speed thrust specs for your unit and check to see that you're within specs there, too.

[ga1279]

Thanks I've got the books for the LTD-126. I just haven't been sent back there as it is now dove season here in Texas and a lot of the ole' boys are swapping stories at the leases. So some of us remain behind to fill in were needed. If I reduce my seal cavity pressure am I not slowing down the oil flow rate? The adjustment sets the pressure feeding the cavity, right? It not that I'm saying your wrong, but I have been going round and round on this problem for 3 years now. Other techs from our shop have torn into it, only to have the same results. Now it seems I'll be back in the saddle this time. Thanks again-GEO

[Randy S.]

Well, I'm not familiar with that particular machine, but on the YTs its more like a bearing oil run off that flows through the seal cavity, and the regulator is like a drain regulator. You might want to take it apart and see that it isn't hanging up, or maybe even replace it if it shows any sign of wear. Or be cheap with a piece of crocus cloth and polish it up. The last bellows seal I replaced on an R-123 machine showed signs of overheating. It was set for about a PSIG and a half at 60HZ, Also have a couple 11 machines that haven't seen much surging and have seals in then that are 15 years old. One of my own harebrained theories is that the 123 hardens the o-rings on the shaft and binds the piece that has to move on the shaft with the older seals.

[ga1279]

The HT and OT are are similar machines except HT is hermetic and OT is open drive. I did not realize the oil to the seal came from the outer low speed bearing. I thought came the oil came through the casting located in the 2:00 o'clock position from the actual seal housing were the adjustment for seal cavity pressure adjustment is made. Maybe different on the HT's. The adjustment is working as I can float the pressure from a low of 0 to 10#'s, so that part is working. I could be wrong but thought the oil was fed through the wing casting direct to the seal cavity then through the low speed outer bearing to the sump, base of the rotor housing. York's oil flow diagrams aren't all that clear as they show oil to the bearings, but not he seal. as a matter of fact the diagram used is a HT with dash lines showing motor bearings for the hermetic motor. I have always been kind of the go to guy on this account but the powers that be have always had othern techs doing repairs. So I've been the source for information. (Thats a scarey thought) All our techs are of above average quality on workmanship and skill. It's just the way the work is shuffled out. With very little exception, mostly me, the next job goes to the next tech available. That means you work both industry extremes. Well Randy if you think of anything else let me know.-GEO: cheers:

[klove]

If low speed thrust hasn't been checked, now would be a good time to do it.

You could say that I, too, am from the old school (at least in comparison to the majority of folks in the field), but I've never had a new seal tested just for the sake of testing it, or had one lapped.

[Randy S.]

YTs are the only Yorkies I get to play around with, so I'm not up on the rest of 'em.

[ga1279]

I was thinking more about what you had mentioned concerning low speed thrust. This machine uses the York 4 piece coupling with 3 bolts 120* apart and once that unit is tightened down there can't be any movement fore and aft to stress the seal. Excuse me as I'm thinking online. One possibility does exist though. We haven't checked the motor for magnetic center, if it draws aft it adds pressure to the seal and if it draws forward it takes spring pressure off the seal. I worked on another OT that had this big (10") rubber flex coupling with an iron internal and external hub. Even though it was flexible you had to have it perfectly aligned or it wouldn't go together. If you put a strobe light on it you could watch it flex during start-up. Soft starter 45 seconds to come up to speed. I think I may have something else to look at.-GEO

[Randy S.]

Here again, my familiarity is solely with early 90's to 2000 YTs, and even with the coupling bolted up, you can set up the dial indicator and bar the shaft in and out. This is the coupling with the layers of flexible spring steel between both ends of the central "spool" piece, and the shaft flanges.

[heavymetaldad]

Yep, the shaft flanges, where the guy before you tightens the snot out of the bolts so you can't get it apart, leaving as a last resort cutting the bolts with a metabo............

[heavymetaldad]

I was thinking more about what you had mentioned concerning low speed thrust. This machine uses the York 4 piece coupling with 3 bolts 120* apart and once that unit is tightened down there can't be any movement fore and aft to stress the seal. Excuse me as I'm thinking online. One possibility does exist though. We haven't checked the motor for magnetic center, if it draws aft it adds pressure to the seal and if it draws forward it takes spring pressure off the seal. I worked on another OT that had this big (10") rubber flex coupling with an iron internal and external hub. Even though it was flexible you had to have it perfectly aligned or it wouldn't go together. If you put a strobe light on it you could watch it flex during start-up. Soft starter 45 seconds to come up to speed. I think I may have something else to look at.-GEO

The few OT's i've played with had ball bearing motors. I don't believe you'll find much movement. I do have a couple of sleeve bearing motors where you can visually see the motor find magnetic center, with it uncoupled, of course.They'll move 1/2'' from either thrust/counterthrust position to center. Kind of a cool sight the first couple of times.

[19C]

Yep, the shaft flanges, where the guy before you tightens the snot out of the bolts so you can't get it apart, leaving as a last resort cutting the bolts with a metabo............

SORRY !!! now I know not to over tighten them. I have paid dearly for my sins (torn rotator cuffs) ouch,ouch,ouch.
LOL,LOL,LOL. OUCH 19C

[ga1279]

Klove, excuse me as it has been a while since I updated this thread. Actually I have gone so far as to start another post. There was NO low speed thrust. No axial shaft movement. The high speed had min .010". We pulled the compressor out of the scroll housing. After separating all the oil plates on the impeller side the low speed oil pump has burnt oil through it. There is more information on my other post York oil seal, part deux, thanks again-GEO