But, the oil is not supposed to do that?

[Grizzly]

Hi Guys,
I was called out yesterday to look at a York LCHHM Chiller.
Which had failed several times during the night with a "Low Oil Pressure" fault.
Looking at the history details showed that all the running parameters were normal.
Except for varying oil pressures below the preset 1.5 bar cut-out!

By the time I got to site the production shifts had changed.
The plant had been restarted and running for approx 1hr with no low oil trips?

So what I have found is.
Both compressors are 8 cylinder York "J" Style with identical refrigeration circuits, within 1 shell and tube evap.
When running on identical loads and temps etc.
The faulty system has an oil pressure (at LCD display) of between 1 to 1.5 bar less than the other.

This in itself is not unexpected as the better system is a newer compressor and has the new style "top hat " type oil pump fitted. (Approx 2 bar more output)
Whereas the faulty 1 has still got the old style oil pump.
So I would expect the oil pressures to differ.
SO.
Both comps are running, loads are balanced.
Comp 1 has 5bar oil pressure
Comp 2 has 3 to 3.5bar oil pressure.
Not brilliant but nowhere near the safety cut out of 1.5bar.
During operation C1 is relatively stable where C2 runs at a lower but stable pressure.
Then all of a sudden the oil pressure will drop and rise through sometimes 0.5bar diff and stabilise.
Other times pressure will fluctuate through 1 bar dif.
I fitted gauges to the oil pressure transducers of both systems and confirmed what the display was showing was indeed happening.

OK!
All the usual suspects were checked.
IE. capacity load, discharge and suction pressures.
This unit is also fitted with EEV's so I was able to monitor the superheat setting as well.
I even took superheat readings at the comp suction.
To check for liquid carry over.
Nothing unusual anywhere except for these random O.P. fluctuations.

Never seen this before guys, hence the post!
I have advised the customer that it may be a combination of wear within the comp and or oil pump?
So I have been authorised to purchase a new oil pump.
To be fitted next week subject to how the comp runs over the course of this weekend.
As a temporary measure I have raised the controlled discharge temp to 10bar from 9.5bar.
which has given a slightly higher O.P. at 4.0bar hopefully this has made it more stable for over the weekend. And informed our duty Eng. just in case!
Anyone seen anything similar?
Cheers Grizzly

[al]

Hi Grizzly

have seen this on the old j models, (2nd generation onwards), they fitted a pump which wore down the drive shaft, this led to intermittant failures on oil pressure!

also even after retrofitting the new style pump the oil levels had to be dramatically incresed, beyond top of the upper sight glass!

We had many of the original style j comps running for years with zero trouble and then they try and upgrade it


Al

[Grizzly]

Hi Grizzly

have seen this on the old j models, (2nd generation onwards), they fitted a pump which wore down the drive shaft, this led to intermittant failures on oil pressure!

also even after retrofitting the new style pump the oil levels had to be dramatically incresed, beyond top of the upper sight glass!

We had many of the original style j comps running for years with zero trouble and then they try and upgrade it


Al

Thanks for the input Al.
I also have had to fit the newer style pump retrospectively.
But I have never experienced these almost instantaneous fluctuations up and down before?
And I have never had any yet as bad as you describe, but in fairness we are allowed to overhaul ours at the required intervals.
In fact this one was "Top ended" with an oil and L.l. filter change by me last August.
All the same I will let you know how it goes later in the week.
Once again thanks for the input,
I was beginning to think that I had offended people somehow?
Grizzly

[GHAZ]

Hello Grizzly york j body compressor has a o ring in the hydrulic unloading piston ,which becomes worn and needs replacing,the compressor will still load and unload but as the oil gets hot it will lose pressure,on 8 cyclinder theres 6 hydrulic pistons, to check run the compressor with solnoid coils energised,if having problems with finding o rings send me a pm with your email . good luck

[Grizzly]

Hello Grizzly york j body compressor has a o ring in the hydrulic unloading piston ,which becomes worn and needs replacing,the compressor will still load and unload but as the oil gets hot it will lose pressure,on 8 cyclinder theres 6 hydrulic pistons, to check run the compressor with solnoid coils energised,if having problems with finding o rings send me a pm with your email . good luck

Thanks Ghaz.
For your help and knowledgeable answer.
sadly though however.
I did check for loading issues.
With exactly what you describe in mind hence my comment on checking capacity load.
Basically the fluctuations don't correspond to any particular load situations.
But appear to be totally random.
Hence my questions so far.
I worked on the premise that if there was a gradual reduction of pressure then what you describe could
be the cause. Or even.
A blocked strainer - partially, high oil temp. fluctuating pressures ECT I have checked.
And drawn a blank.
Al may have something with the worn drive?
But the confusing thing is the fluctuations are more like pulses of pressure differential of sufficient length
to potentially trip the Compressor out on low oil pressure.
But not sustained or proportional enough to narrow down the cause and effect!
It is most strange!
Thanks again Grizzly

[1torr]

Hi Steve, what about a leaking 1/4" oil (loading)line in crank case?

[Grizzly]

Hi Steve, what about a leaking 1/4" oil (loading)line in crank case?

Hi Kev.
May be!
I just hope we can find something conclusive.
It's definitely something unusual anyway.
Thanks for the input.
Steve. AKA Grizzly.

[baskaran]

During deforsting time our howden screw compressor more hunting

[1torr]

Got to the bottom of it yet?

[Gary]

Possibly a weak/sticking high oil pressure relief device?

[Grizzly]

Got to the bottom of it yet?

Yep!
Not that I am enjoying admitting it!
It would appear that I made some fundamental errors in my diagnosis.
From the discussions with my friend and colleague who revisited site on Tuesday.
It would appear that several factors contributed.
The Glycol Tank working level was low giving a 4c split across the evap at 50% load
In my defence this site dump the Glycol when carrying out CIP on the PHE's.
Secondly the system was overcharged by 30 kg's.
Which apparently only caused an issue because the
EEV power element or orifice is playing up!
So in summary the system by Tuesday was short cycling on lack of load / poor flow.
So whilst overshooting on suction pressure / temp.
Or having Liquid carry over. The oil pressure was dipping below it's cut out value.
I though I had covered liquid carry over,
but it would appear that i did not look hard enough.
None of us can remember when this particular system was last charged, probably 2 yrs or more ago!
(It has a large remote air cooled condenser).

All very embarrassing for me cause I was looking in a totally different area.
In my defence, in the past I have caught the site Engineers removing the LWT probe because it was above it's threshold limit of +70c.
Yes that is true, it has been known for production to leave the primary chilled water pump circuit open.
Whilst sterilising the plate packs at 90c Steam.
So between visits anything can and does go on.
So I guess we will be sending the oil pump back to York Parts.

Thanks for the input everyone.
much appreciated!
Grizzly

[Grizzly]

Hi Guys!
Further to my last post where I basically ate humble pie.
Well it turned out that some of the pie tasted a little better!
Meaning, that after my colleagues visit and subsequent diagnosis.
About a week later I was called back to site, because of problems with the other system (no1).
Which was exhibiting signs of refrigerant shortage.
Anyway I had gone to site with some large cylinders of R22 as backup.
Having identified that this no1 system was short of gas.
I started to top it up with refrigerant.
Basically with the chiller running and sufficient load for both systems.
Then it started to get strange!
Despite adding the R22 straight into the liquid line before the expansion valve.
I could not add the refrigerant fast enough to prevent that system tripping out on L.P.
At the same time System 2 started to exhibit high discharge pressures.
On checking the condenser fan operation I discovered various phase / fuse issues.
Even after repairing these the system pressures continued as before.
Some of the more astute will probably already know where this one is going.
At this point I advised the maintenance team that we are contracted to on site.
That I was very concerned with what I thought was happening and that possibly the evaporator was damaged!
I then phoned a couple of my colleagues to try and confirm my suspicions.
Basically my colleague who had earlier taken the 30kg's of 22 out the week before. Suggested that the refrigerant circuits may be passing between each other.
Given that each circuit was randomly exhibiting low and high pressure issues.
It was deemed not a bad idea!
Back to the errant chiller where I attached a 1/4 hose line between the 2 liquid line filter service ports.
Upon start-up I watched in amazement as the pressure in system 1 grew and the pressure in sys 2 dropped.
Mystery over:- The severe pressures that the chiller had been subjected to,
due to the boiling of the glycol had (or appeared to of) blown the gasket dividing the 2 refrigerant circuit, tube bundles.
Back to the on-site facilities guys and the Customer.
Who were not about to enjoy my diagnosis that their main production
line would have to be shut down.
2.5 weeks before Christmas.
A week later with a huge hire chiller in place we were able to remove the refrigerant (230kgs per system).
Strip the evaporator end plates and renew the rubber gaskets.
These were then leak tested with Nitrogen prior to the recharging and re-reinstatement of both systems.

Prior to the hire chiller being installed then systems were kept running.
By my colleague returning to site periodically and transferring the refrigerant across from 1 system to the other, as described above.
This at least enabled the production line to keep running.
The supply of Devon's favourite custard and associated products was maintained.

I must admit prior to identifying the actual problem we were all mystified as to whom had over charged system 2 by 30kg's.
Anyway I hope this update has been of interest as the operating conditions that i described were certainly a new phenomenon to me!
Grizzly

[monkey spanners]

I had something similar recently with a DX milk tank with four evaporators run in pairs, with two prestcold units, which also ran another DX milk tank with two evaporators via solenoids etc, i had reset the hp switch to about 360psi (R22) from about 460psi as set by the previous company.
Was then called back and found the overloads tripped on that unit. Run the system and found all ok for about ten minutes then head pressure started to climb until it cycled on the hp switch.

Found that when it was installed they had piped evaporator inlets A + B and outlets A + C on one unit and inlets C + D and outlets B + D on the other unit! Had been like it from new! About four years, with only the high hp setting keeping it running.

The units run fine when serving the other tank.

Kept it running with a 1/4" line between the recievers till i could get some fittings and a day when the tank was empty so i had time to re pipe it

Jon

[US Iceman]

Sorry Grizzly. I must have missed this post somehow. I had a similar issue on two DX split air conditioning systems one time. Another contractor had installed them about year before he asked me to investigate. After the same head scratching (which I'm sure you underwent also) I finally found the liquid and suction lines crossed between the units. The suction lines were OK, but the liquid lines were crossed up. Same result you described.

When I told the owner of the firm what the problem was I thought he has going to have a stroke right there!

[Grizzly]

Jon and Iceman.
Many thanks for the reply.
It is always interesting to hear of slightly different issues regarding fridge work.
And all the more comforting to know that it is not "just me"!
Cheers Grizzly
I look forward to more words of wisdom from you both in the new year.

[US Iceman]

It is the weird ones like these that will keep you up at night, that's for sure...

[Sturt]

Hi Guys

A great set of events Grizzly thanks for the final conclusion.

In my early years this sort of fault would have had me in a panic especially with the added pressure from production demands etc.
You showed a calculated knowlagable approach for sure and got the result in the end.

I remeber working on a low temperature R22 chiller at a pharmaceutical site on the south coast which had always shown very low suction superheat on part load.
I had stressed myself for ages trying to explain and correct this but ended up too close to the problem you know.

The shell and tube evaporator was split in two although it was a common system and was fed by four solenoid and expansion valves with two suction lines out.
It wasnt until the evaporator end caps were off finding a leak on the tube ends that the problem was answered. It was noted the expansion valve phials were not corresponding to the evaporator halves so on part load the two expansion valves were wide open reading the second halve suction temperature.

It was a factory build error as the second chiller was the same on inspection.

Sturt.

[Greengrocer]

Sooner or later everyone gets a problem like that Grizzley. It's how you get out of it and keep a customer happy that makes the difference.
We had similar problem to Iceman recently. 4 off Misti City VRF systems 2 per 1st & 2nd floor of a 3 storey building. 2 outdoor units on one floor had 1 pipe crossed from BC controller & the control wiring was crossed on the other 2 outdoor units serving the other floor.
Just to even up the score the sparkies hadn't done a brilliant job either - 1st floor outdoor units were fed from 2nd floor distribution board & 2nd floor units fed from the ground floor distribution board. All this on systems that were supposedly commissioned over a year ago!!!