YORK Chiller Air Ingress on Shutdown

[imranmd]

Hi,

We are facing air ingress problem on one of our Centrifugal York chillers Model No. YTH3J3E35COG, 500 Tons with R123. Last time we found some leakage in the solenoid purge valve on the purge unit which was afterwards rectified. The purge unit was separated from other system and Vacuum was held for 24 Hours in both systems. After this satisfaction the gas was charged and chiller taken in service. After purging air from the system during the operation, the chiller worked fine at 0 purges/hour for the last 40 days. however when it was turned off, the condenser and evaporator pressures started to increase gradually and after 2-3 days time the condenser pressure reached 14.7 PSIA. Which shows an air ingress in the system.
The problem is that the air ingress problem comes only when the chiller in non-functional (in off state). While running there in no air ingress and no purges. Can someone identify the root cause of this problem? Please let us know the efficient and quick way to detect the leakage. :o

[Grizzly]

Have you looked at the shaft seal ?

Just a thought!

Grizzly

[Brian_UK]

Is it air leakage or refrigerant leaking through somewhere ?

[nike123]

What are the ambient temperatures?

[imranmd]

I dont think its the shaft seal as the unit was pressure tested the last time air leakage was rectified. Can anybody suggest an effective method/procedure for leak detection???

[GHAZ]

Hello imran the exhaust valve might be faulty or the pressure transducer , just a thought

[imranmd]

Please let me know the efficient way to detect the leak in the system. We have waisted a lot of time in detecting the leak but still experiencing the same problem. During operation the gas may leak from condensor side therefore chiller runs on zero purges and on shutdown it losses vacuum, just a thought. Please help.

[imranmd]

Can anybody reply me earlier?

[nike123]

Do you have any isolation valves on that system, If not, install few and isolate system parts, vacuum every part of system until 300 microns and look in rise of pressure. That way you should be able to locate part of system that is leaking. Then, depending of system components in that section of system refit any possible leaking part one by one and every time make this test. First start with devices who are sensitive at negative pressure (Schraeder valves and similar).
You didn't answered what are the ambient temperatures there.

[imranmd]

Thanks for your reply. Now a days the ambient temperature varies in between 27 to 33 C

[Mr. Boon]

recover the refrigerant, blank off the rupture disk, pressurize the chiller at about 20psig with r22 traceand dry nitrogen, drain the chiller and condenser and isolate just to see if may be you have a tube leaking, also what type of detector are you using, usually suction elbow gaskets are leakers and check that shaft seal is the drain cup full? do you get an indication at the shaft, check all flared connections for oil recovery eductors

[Pooh]

Imranmd
I do not think it is only leaking when it is shut down I beleive it is leaking all of the time but as the air purger only works when the plant is running you are not noticing the problem when running as the air is being removed which is quite normal. However when the plant is shut down a large amount of air is being drawn in and then when you start the plant that has to be got rid of which makes the small problem look worse. I am trying to remember what the acceptable number of air purges is, one every 5 or 6 minutes rings a bell.

It may be worth letting the plant run and check the oil pressure as if that is not high enough the purger will not work correctly either, 20PSI rings a bell.

Long time since I worked on centrifs but still love them.

Ian

[imranmd]

If the leakage is at evaporator side (suction Elbow)then purges should be observed during running also. If the condensor or evaporator tubes are leaking then water should be mixed in refrigerant gas, please let me know the way to detect the leakage in tubes if any.

Please let me know the gasket material and type at suction elbow.

[centrifs]

imranmd,when the chiller is running the condenser is above atmospheric pressure 50 -60 kpa . it is leaking r123 out when it is running. when it cycles off both sides of system are in a vacuum and it starts sucking in air. it will need to be purged.
i suggest first trying an ultra sonic leak detector, it will listen to the air sucking in. purge the chiller, run on a low load and continue purge till it is free of air, then shut it down and concentrate on hi-side of system start listening for leaks. if that fails , pull the charge out and blank the rupture, pressure up to 20 psig and do the same . failing that you may have a tube leak.....

[Toosh]

Hi Centrifs, you dont need to blank out the ruputure disc you can run a line to its outlet if it has a threaded coupling on it from the vessel and it will be eqauliazed the same pressure both sides have done it many times

Regards Norm

[Taffy]

We once had the same problem when I worked for York, working on a 1000 Tonner in IBM Portsmouth. We Isolated the main Condenser and Chilled water Valves and introduced warm water into the Evap and Condenser slowly raising the pressure until we achieved a positive, then we took our time and found lots of leaks all told, on flare nuts, the casing, old capillary lines etc, we replaced all the lines and flares for new and re-pressure tested then ran the machine with no further problems. The Kit we used was basically a Shower unit and a pump and a pressure switch to cut it of at whatever pressure desire. :) Took away all the fun tho no more surging!! :eek:

[Superheatman]

We once had the same problem when I worked for York, working on a 1000 Tonner in IBM Portsmouth. We Isolated the main Condenser and Chilled water Valves and introduced warm water into the Evap and Condenser slowly raising the pressure until we achieved a positive, then we took our time and found lots of leaks all told, on flare nuts, the casing, old capillary lines etc, we replaced all the lines and flares for new and re-pressure tested then ran the machine with no further problems. The Kit we used was basically a Shower unit and a pump and a pressure switch to cut it of at whatever pressure desire. :) Took away all the fun tho no more surging!! :eek:

Was that in Portsmouth itself or in Cosham taffy....brings back memories....anyway...good suggestion...we used to carry out a service/change filters etc in R11 centrifs (Yorks/Carrier etc) by utilising the building hot water supplies (with clients permission)....just had to take a hose and connect it to a tap in the boiler room..valve off the unishell and allow a drain flow at the same rate as the water flow in...saved all that hefting heavy drums and getting your brain buzzing and your nose running when working on units in basements and having to remove the complete charge...although it sure did clear your head when you had a cold lol :D

[dbobo]

York YT chillers had 2 purge units options: The Turboguard and the Skyguard. The turboguard cannot remove condensables when the chillers is idle but the skyguard can. Based on your description of the problem I think you probably have the turboguard version so it might be better for you to upgrade to the skyguard version. At least it will remove the non-condensables when the chiller is off.