york 400 ton yt mystery leak

[jlp32040]

I take care of this machine and have for seven years since start up. It is a low pressure machine using r-123. The first five years of running 3 shaft seals were replaced , the first one was the regular type seal , 2nd and 3rd were bellows type. When each of the previous seals went bad there was no guess work : when it was leak checked the leak detectors would scream on the large setting and the halide torch would be purple. Now when the machine runs I get less than 10 purges per month but when it is shut down for 10 days or more it will fill up with air to the point where it will not run = 25 degree difference in leaving water temp vs. saturated evap temp with machine off and with chilled water flow. I have spent probably 40 hrs over the past 2 years leak checking (paying special attention to the seal) and I come up with nothing each time. I have had other mechanics perform leak checks on it just to have another set of eyes on it and they come up with the same thing ....nothing. It has got to the point now if it gets air in it I dont even leak check it , I pull the air off of the top of the evaporator and condenser , start the machine , put the liquid back in , let it purge for a couple of days and it will be back to running like a million dollars , and all I can do is hope that it is not shut down for any extended periods of time. One would think that it would be a high side leak with only 10 purges per month while running and it fills up when it is off but I cant find a leak. Any thoughts or suggestions would be greatly appreciated. Thanks.

[KnewYork]

Not sure I agree with the previous diagnosis of shaft seal leaks by the method you describe, but that's neither here nor there.

When you say leak check just how extensive are you checking? Are you removing the insulation at the suction elbow and checking there with soap bubbles after taping the flange? Is the rotor support to volute a gasket or o-ring? Another place I have found leaks is the bearing head to rotor support o-ring. That one is a little harder to detect. I have also seen the return line from the oil cooler to the evaporator rust out a pin hole under the insulation. I'm pretty sure you have a leak you aren't finding. If you take the charge out and evacuate it you should see this in a proper vacuum hold test.

[jayguy]

we had a very similar issue...turns out it was in the purge. YT purge leaks are really hard to find because they use oil in the purge so soap doesn't work. when the chiller shuts down, valve off the purge. after a week or so, when you go to start it up, open the valves to the purge. if the chiller runs great then you know.

[tcy612]

Good point Jay... I've ran into the same problem in the past...

[SteveBelcher]

What jayguy said

[tcy612]

As far as the shaft seal is concerned... I should tell you that York does NOT recommend that you determine if the shaft seal leaking with a refrigerant leak detector. This is because there is more than one potential leak source of the seal assembly and may not require entire seal replacement... I also believe this because since the seal surfaces of the YT seal (like most seals) relies on oil to create the seal, if the machine does not run for an extended period and seal goes dry, it WILL leak... IMO

York recommends troubleshooting a "leaky" shaft seal based on oil leakrate AS WELL AS where the oil is leaking...

This should help...

[jlp32040]

Thank you for your reply Knewyork. After reading your reply I will be a little clearer with my wording. The shaft seal diagnosis = I never described a method on how they were diagnosed I simply made reference to 2 tools that were used in the diagnosis. After each seal was replaced the machine did pass the proper vacuum hold test each time, and after each of the seal replacements the machine ran with no purges while running and did not collect any air when it was off until the seal in use at the time started to fail. All seals that were replaced showed signs of excess heat and even though there was no indication of seal pressure regulator problems a new one was installed during each of the seal installations and the oil supply to them was verified. All regulators were set in accordance to OEM recommendations. As you probably know the recommendation for this setting has changed several times in the past. Just how extensive am I checking = 100% of my ability which seems inadequate(every gasket, o-ring, packing, threaded connection, flare connection, rupture disk, tubing etc.) Suction elbow = I have indeed removed the insulation each time. I have not taped and soaped, because I can not even pick up a trace with the leak detectors set to their highest sensitivity. Rotor support to volute is an o-ring. I have leak checked every piece of tubing on this machine, because I too have found pin holes due to pitting. I KNOW I HAVE A LEAK and am not finding it , but what do you do right? Thanks again for taking the time to reply.

[jlp32040]

Thanks for your input Jay. I have pressure tested the purge numerous times and replaced the solenoid and check. I have not isolated it by valving it off for a prolonged shut down. I will try that.......... Also thankyou tcy612 for the literature I did not have that document.

[KnewYork]

I went out to assist one of our techs today on a YT chiller that has a small leak that was not found during the annual service. I found it within ten minutes of being there. It was on the evaporator return from the oil cooler piping. I kept getting these "hits" and ruled out the insulation. Soaped pipe and found two tiny pinholes near where the steel tubing is inserted and brazed into the steel pipe coming out of the evaporator. My assumption is that as the pipe sweated under the insulation water would "stack up" on the lip made where the tubing inserts into the pipe. Eventually (12 years) the pipe started to rust through. The tough part is going to be fixing it.

Double check the where the bolts go through the bearing head to the rotor support (as previously mentioned). Also if the seal is running hot you could be affecting the ability of the seal to "travel" on the "nose piece". I know with the old six spring seals, replacing the o-ring in the carbon and polishing the "nose piece" would allow the seal to move. Without movement of the seal you could have a leak. I would suspect you would leak oil as well. Can't imagine it would suck air and not leak oil.

[jlp32040]

I hear you buddy Ive been there and done that , Good luck.

[sargent york]

Curious, what was found to have failed on 2 shaft seals that were changed? faces chipped or worn? O rings brittle, cut etc? Was low speed axial thrust checked?

[Nuclrchiller]

And I'm curious as to whether the leak has been found....

[chilbrig]

Had a leak on a York one time that no one could find. Went on for a couple of months and no one could find it. Then one day another guy was having a go at it with out much luck. He laid his leak detector down on the top of the condenser, and the probe was hanging down on the side of the barrel. The detector went wild. The leak was a small hair line crack in the shell about halfway down. Wasn't near any welds or fittings.