Just when you thought you had seen everything

[RANGER1]

Called to site as compressors out on overload & high level fault on NH3 coolstore.

Addressed high level problem, no liquid in compressors as sumps warm.

Both booster compressors (8 cylinder) unable to start & could only turn over with considerable force.

Basically checked sump etc & found nothing unusual , so removed heads etc.

In a nutshell all pistons seized in liners, not with mechanical damage but chewing gum type varnish/sludge.
Had to heat liners & pistons up to 80 deg C to remove pistons from liners.
All other parts of machine in good condition, only cylinder/pistons gummed up

Oil is Suniso 4SA & oil analysis says OK but viscosity a bit high.
High side compessors OK


Anyone ever seen or heard of such a thing?

[josef]

Hi Ranger, I was 20 years ago, maybe two similar cases.
1. The new cool for about 5 years, never a problem with fluid in the compressor.
One of the problem and the wet steam to the compressor. I removed the compressor and, like you, 80 ° C water and separating from the piston cylinder. Going compressor and wait for what will work and I lived to see the next day, wet steam and stop the compressor again. The remaining compressors OK and not suck the liquid. Think and find manure floated on the surface of the liquid. Evaporated and recruited up liquid, defecate manure and not a problem.Make an analysis of manure, but not a lot of smart-origin idea. Perhaps the pipe-gatherers do not know.
2. In my country we have a lot of smart engineer, and the mitt a great idea to add the product to the compressor for a car to defend wear.

Those are my experiences.

[Grizzly]

Hi Ranger,
I don't know what temps your booster are supposed to be operating at, but would the fact that 4SA has a pour point of -40c and a floc point of -30c.
I am thinking of the oil breaking down or rather waxing of your oil at temps below -30c.
Is this relevant?
Could you be getting liquid carry over into your comp sumps?
I know that there was none when you arrived but was anyone present when these comps failed?
Cheers Grizzly

[Josip]

Hi, RANGER1

Called to site as compressors out on overload & high level fault on NH3 coolstore.

Addressed high level problem, no liquid in compressors as sumps warm.

Both booster compressors (8 cylinder) unable to start & could only turn over with considerable force.

Basically checked sump etc & found nothing unusual , so removed heads etc.

In a nutshell all pistons seized in liners, not with mechanical damage but chewing gum type varnish/sludge.
Had to heat liners & pistons up to 80 deg C to remove pistons from liners.
All other parts of machine in good condition, only cylinder/pistons gummed up

Oil is Suniso 4SA & oil analysis says OK but viscosity a bit high.
High side compessors OK


Anyone ever seen or heard of such a thing?

Sounds like a flooded compressor - possible liquid refrigerant must come first in oil sump and mix with oil (compressors probably are without low oil temperature protection), then oil (mixed with refrigerant) pumped via oil pump to hot pistons&cylinders where refrigerant rapturously evaporate, causing freezing of lube oil on the surfaces, then piston ring passes over, but cannot remove stick residues only increase temperature due to high friction and small/thin film of oil became fried and remain on hot surfaces of pistons and liners in a form of chewing gum ....

... after long standstill all refrigerant from oil sump evaporate due to high temperatures and when you arrived "killer" of your compressor already disappear-evaporate .... I can be wrong but this can be a scenario...

this is my theory

... anyhow, I believe you'll come back with new facts when you discover them ...


Best regards, Josip

[RANGER1]

Thanks for everyone's input.

Currently still don't know anything , but to answer a few question.

-30 C SST -10 C SDT

Definately no additives on this plant

Had another high level but sumps still warm & next to no carryover on restart (oil foam until pressures settled down)

System did have ammonia added fron another plant a few years ago so can only
put it down to that at this stage.
There are another 8 compressors in this plant with no problems, but they were not subject to a high level.

I have seen some grubby poorly maintained plants with no problems, so this one is a surprize.

[Grizzly]

You yourself seem to be leaning to-wards Liquid carry over / oil waxing.
This oil foaming issue may be relevant?
Out of interest, what is the oil operating level?
Is it the same as the others?
What is the state of your discharge non return valve.
Your SST does appear close to the oils floc point but I am assuming the other systems are the same?
Maybe someone added old incompatible oil when they added the Ammonia?
As you say strange this one!
Please keep us all posted.
Cheers Grizzly

[RANGER1]

Have overhauled both compressors & flushed oil seperators,oil return floats.
Can only run & see.
Will be changing oil in sump after a few weeks with oil sample.
After that its the wait & see.

Grizzly we use 4SA down to minus 40 with no real problems, as its a pretty common
oil used in Industrial fridge plants.
Of course though, there are better oils.

[Grizzly]

No Problem Ranger.
As I don't use that oil, I looked at it's Properties and noticed the floc point.
As it was near the operating temps you stated I thought it worthy of questioning.
If you are happy that that is not an issue, then so am I.
Grizzly

[RANGER1]

No worries Grizzly, thanks

[TXiceman]

I had a case like this several years ago. The system "had" mineral based oil in it and they had a gummed up mess in all of the compressors. We had to have an oil chemical analysis done and they found that a synthetic oil had been added at a couple of service intervals. Seems that some of the additives between the two oils did not get along and formed a polymer sludge. The system was a mess to clean up.

Ken