Oil loss while idle - York HTK Hermetic TurboPak Chillers
Hello Everyone,
I am a new member to the HVAC community. I work for a power generation plant, and I've been tasked with solving an oil loss issue on a handful of our old York Hermetic TurboPak Chillers designed in the late 1970s. The oil loss occurs during idle periods (2 weeks +). We have eleven York HTK Hermetic TurboPak Chillers that experience this issue. The eleven chillers consist of two different models listed below.
6 Units - 500 Ton Model: HTK3E2-EDCS
5 Units - 550 Ton Model: HTK4E2-EDCS
Both models have the MTD-120 Compressor with upper and lower sight glass.
Normal Conditions
Hot Gas Bypass: Closed
PRV: ~50%
Evaporator: 15 - 18 in. Hg
Condenser: 0-7psig
Oil Pressure: 28-35 psig
I have been in touch with our vendor (Johnson Controls, Inc.) for support on this issue and they have provided their input; however, I am reaching out to look for any other information I can get a hold of. I am new to chillers and trying to soak up all the professional wisdom anyone is willing to provide. Also, with these units being so old and not many professionals still around who designed them, there seems to be limited knowledge when I ask questions about them.
These chillers have the Upper and Lower oil sump in the compressor with the Aux Pump and Jet pump suction coming off the Upper sump and the Oil Return line from the Evaporator dumping into the lower sump. Just before the Oil Return line connects to the lower sump, there is an inverted trap to prevent back-flow when the unit is idle (per my understanding from discussions with JCI). The vendor recommended I raise this inverted trap to be above the upper sight glass on the compressor to prevent the oil from draining down or back flowing into the evaporator when the chiller is shutdown.
To test this before modifying the tubing, we simply closed the isolation valve on this line just below the inverted trap. We closed it immediately after shutting down the chiller to see if we would have missing oil the next time we started the chiller (2-4 week idle time).
We tested this on two chillers that give the most trouble as it relates to oil loss. We notice the oil loss by how much oil is reclaimed from the system after starting the chillers from sitting idle for weeks at a time. Both chillers we tested normally required the addition of 5 gallons of fresh oil to get them to start. This is believed to be partly due to losing oil from the oil loss issue I’m describing as well as an oil foaming issue experienced with the units due to refrigerant saturated oil. It’s understood that the fresh dense oil helps maintain the proper pressure to keep from tripping on Low Oil Pressure. (Note: I have a modification for the oil foaming I will be implementing but I’m wanting to solve the oil loss issue first.)
550 Ton Model: HTK4E2-EDCS: The first chiller (Chiller A) we tested the valve closure test on was promising. We chiller ran for over 2 weeks prior to the test where we drained over 12 gallons of excess oil from the system as the Oil Return system kept raising the oil level in the upper sight glass. After oil level stabilization, the chiller was secured, and isolation valve was closed. After 2 weeks idle, we started the chiller without adding any oil and the level was stable at normal level. Periodically checking oil level over the next two weeks, the oil level remained stable. No oil was being returned from the evaporator raising the level in the compressor sight glass. This told me that by closing that valve, we had no oil migrating to the evaporator/condenser during the idle period through the oil return line.
500 Ton Model: HTK3E2-EDCS: The second chiller (Chiller B) we tested the valve closure test on was different. We ran the chiller for over 2 weeks prior to the test where we drained over 12 gallons of excess oil from the system as the Oil Return system kept raising the oil level in the upper sight glass. After oil level stabilization, the chiller was secured, and isolation valve was closed. After 2 weeks idle, we had to add 5 gallons of oil to the chiller to get it started (as usual). I expected this to potentially be due to it needing the fresh oil to hold pressure due to foaming. Then when it started, I expected to see a very high oil level in the upper sight glass). After starting and stabilizing, oil level in the upper sight glass was normal level. It has been running now for approximately 2 weeks and we have drained close to 5 gallons from the system as the oil return system reclaims it from the evaporator. It appears we are still losing oil from the compressor sumps to the evaporator during idle periods on this chiller.
For this chiller, and others, where we find this issue, what are other ways that the oil can be draining to the evaporator/condenser while the unit is sitting idle? Do we need to tear into the compressors and replace specific gaskets/O-rings/seals to get to the bottom of this issue?
Been a while, so having a brain fart.. so assuming …would have to review parts diagram to match model numbers.
solenoid ventura pump in the external piping on the side of the compressor. If the diaphragm dries out or fails it can cause oil loss.
Sump vent line solenoids, have drilled orifice in the seat and time delay on the solenoid.
Check the solenoid valves, some powered to open some powered to close. Keep oil close to 140-150 F at start up.
Valve should open when aux. pump starts stays open while running.
All the piping feeds oil in and out of the oil pumps that are driven by the high and low speed shafts.
I don’t have a book anymore but the original O and M had a good drawn of the oil path.
1. Solenoid ventura pump in the external piping on the side of the compressor. If the diaphragm dries out or fails it can cause oil loss.
2. Sump vent line solenoids, have drilled orifice in the seat and time delay on the solenoid
3. Check the solenoid valves, some powered to open some powered to close.
I'm having trouble seeing how these potential issues could result in oil migrating into the evaporator/condenser? The only solenoid valves we have on our systems are the ventura pump (jet pump) solenoid, the vent relief on top of the purge unit, and the 3-way solenoid on the bottom of the purge unit for the oil to enter and exit. The solenoid on the oil return float system was removed from our systems years ago and they have the inverted trap mentioned previously.
I've attached the O&M with the drawing of oil supply system (with my additions that tie into the evaporator and condenser).
If the jet pump solenoid valve leaks by when off it should just drain down the upper sump to the lower. Once this happens there is no oil for the aux pump to start the oil pressure build up for start up.
Oil foaming at start up is due to low oil temperature.
Gaskets and o-rings between the dumps and diaphragm plate that don’t seal can let oil get to the discharge volute. At start up the oil can get pumped out to condenser.
Running oil loss can be to low of head pressure, oil return educator needs that higher pressure to pull oil rich gas up to sump. Check valve on foul gas line not seating , you will see fast oil loss. Eye seals on impeller worn , oil can come off out board high speed bearing to back of impeller and thrown down discharge line.
Might be time for an internal inspection of compressor.
Seriously doubt you can get a code kit and change to a YT compressor.
Check the jet pump diaphragm. Common they would fail.
Thank you ehsx. I will investigate the diaphragm concern with the chiller crew at the plant. Not sure if we inspect/replace regularly with a PM or not.
If the jet pump solenoid valve leaks by when off it should just drain down the upper sump to the lower. Once this happens there is no oil for the aux pump to start the oil pressure build up for start up.
Oil foaming at start up is due to low oil temperature.
Gaskets and o-rings between the dumps and diaphragm plate that don’t seal can let oil get to the discharge volute. At start up the oil can get pumped out to condenser.
Running oil loss can be to low of head pressure, oil return educator needs that higher pressure to pull oil rich gas up to sump. Check valve on foul gas line not seating , you will see fast oil loss. Eye seals on impeller worn , oil can come off out board high speed bearing to back of impeller and thrown down discharge line.
Might be time for an internal inspection of compressor.
Seriously doubt you can get a code kit and change to a YT compressor.
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Chev5372,
If it were the jet pump solenoid leaking, I believe we would still capture that oil from the lower sump prior to start up since we perform an oil reclaim with the Aux Oil Pump. After reclaiming, we see the oil level rising in the lower sight glass and we typically achieve proper start up oil pressure.
The gaskets and O-rings between sumps and diaphragm plate leaking to discharge sounds reasonable given what we have been seeing (oil loss while it's been sitting shut down for a few weeks).
I'm curious if the foul gas line check valve could be leaking slightly after a unit is shut down and the internal pressures equalize? We have history with these Henry 119 - 1/4" check valves sticking open on some other units and causing the quick loss of oil issue you explain. I'm just curious that if they have that defect there, maybe they could leak by while it's shutdown and be leaking oil into the Condenser from the purge unit. I may isolate that line upstream after shutdown and see if that helps.
I'm going to try and do some digging into our work history on these chillers today, but I'm fairly certain they have never had any kind of compressor internal inspection performed during their life at the plant (~30 yrs). So it may very well be time to open one up and inspect and replace worn items. I'm sure you wouldn't make things worse by doing something like that (I would hope not).
This has been a long standing issue at our plant and it's been a very slow process understanding how these machines behave. I'll try and keep any new developments posted here to close the loop if we find our smoking gun.
I greatly appreciate the input from both you and ehsx.
If you have a slow leak on the foul gas line check valve the most oil you would lose is 2.5 gallon , the amount of oil the purge pot could hold. If you still have the old panel pull the fuse before you shut down to drain all the oil out of the purge pot. Wire 61 on the Opti-view panel.
The two candy cane looking lines that let lower sump oil back to the upper sump may not be tight anymore. They are like a compression fitting on the pipe to a male fitting screwed to the casting. They might be coming loose letting oil drain down.
If you have a slow leak on the foul gas line check valve the most oil you would lose is 2.5 gallon , the amount of oil the purge pot could hold. If you still have the old panel pull the fuse before you shut down to drain all the oil out of the purge pot. Wire 61 on the Opti-view panel.
The two candy cane looking lines that let lower sump oil back to the upper sump may not be tight anymore. They are like a compression fitting on the pipe to a male fitting screwed to the casting. They might be coming loose letting oil drain down.
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Well, I question that foul gas line check valve because of its history and in our manual it states that the 3-way solenoid valve opens up to the lower sump in the de-energized state. So I understood that to mean when the chiller was shut down. And also, the compressor is at a higher elevation to the purge pot so gravity would allow it to flow down from the compressor to the purge pot and then leak past the check valve (if leaking) and into the condenser.
The manual states ....
N.O. contact 22R (54) energizes the purge oil solenoid vaive 2SOL (54) allowing oil
to flow into the purge cylinder, opening switch BFS (56). The non-condensable gases ·
also flow into the cylinder and are compressed by the rising oil level. When the pressure
in the cylinder reaches 35 psig, the purge high pressure PHP (53) closes, energizing
the purge air exhaust solenoid valve 3SOL (53). The non-condensable gases are discharged
to the atmosphere until the pressure is reduced to 30 psig and switch PHP
(53) opens, de-energizing valve 3SOL (53). This cycle continues until the oil level
opens the top float switch TFS (56) and de-energizes relay 22R (56). N.O. contact
22R (54) opens, de-energizing solenoid 2SO L (54) which drains the oil from the purge
cylinder. When the oil level falls, the bottom float switch BFS (56) closes and the
purge cycle repeats.
I verified my understanding with an electrical engineer in our group and he said it the solenoid will open up to the lower sump to purge flow path.
If we check this idea and we still find we have oil draining down, we will most likely be scheduling an internal compressor inspection/rebuild to check the gaskets, O-rings, candy cane fittings, etc.
I assume they do. I've been in communications with them about these units and they have never directly told me they have no parts for repairs/overhauls. It's a good question to ask though. Thanks.
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Originally Posted by ehsx
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