Blackning Of The Interior Of Refrigeration Pipe Work.

[Rickyjb64]

Hello all. I have a colleague who has been sending me reports of work carried out on some vacuum driers and has come across an anomaly. Please read and submit your ideas.
Below is a paragraph from an email I received after asking about compressor over heating and burnouts.

"Well that's the strange thing, that systems never had a burnout we've changed the compressor because it was noisy and the report came back saying that the oil was too thin causing excessive wear on all components. So we changed the comp, oil Sep, filter drier and fitted a burnout drier. It lost its gas when a pipe broke off due to vibration a month ago, carried out repair and changed the liquid drier, it was completely black inside all the pipes and sight glass."



Many thanks in advance.

Rick

[monkey spanners]

Sounds like its been running with excessively high discharge temperatures and burnt the oil, possibly the compressor has bad valves. This can lead to noise as it makes the gudgeon pin wear as the piston is never unloaded.

[Glenn Moore]

Hi Ricky
I used to do the warranty on Maneurop compressors, and often I would see compressors come back under warranty that when cut open were totally black with a black lacquer looking fluid over the entire machine. The motor was still in perfect working condition but the small end of the con rods were completely elongated along with the piston gudgeon pin hole causing the con rod to move up & down but the piston hardly moving and the machines capacity was reduced to zero. All other parts were covered with this black shiny fluid.
I actuallyvisited several sites from where these machies had been returned from to carry out some site investigations to try to find the cause of the problem.
One of the prime issues that was found was that the additives in the polyester oil in the compressor were no longer present in the oil. It was found that the driers used had adsorbed these additives leaving the oil without their enhancing additives .
Danfoss produce a drier called a DML drier which is pure molecular sieve which is made for systems which use polyolester lubricants. These do not touch the oil additives which are left to do their job in the system. These additives over time permeate into the metallic structure of the moving metallic parts and prevent wear due to the higher bearing loads associated with the newer gases.
On several of these sites it was found that not one but several compressors had failed on these systems all with the same problem.
One site in Canary Wharf in London had had 5 failures , one in Chester had experienced 3 on the same unit.
So I helped the customer to change the compressors on these sites and fitted the DML driers in place of the old silica gel/ activated oxides types that had originally been fitted. These systems were evacuated and charged and test ran for a few days and then the driers both in the liquid line and suction lines were replaced after a further week of operation the liquid line drier was further replaced and the suction one completely removed. No further problems from these and several other sites were reported.
This seemed to cure the problem but there are several other factors which can cause this issue as a combination of any of the following can cause this to happen
1) Fitting a poor quality drier, 2) Poor evacuation,3) running with high suction superheat /low suction pressure,4) running with high discharge pressure, poor condenser fan control set up.
We called it Black Oil Syndrome
ON A NEW SYSTEM ALWAYS FIT A PURE MOLECULAR SIEVE DRIER, WHICH HAVE A HIGH MOISTURE ABSORBTION RATE . A NEW SYSTEM HAS NO ACID IN IT SO WHY WASTE THE CAPACITY OF THE DRIER WITH ACTIVATED OXIDES WHICH ONLY ABSORB ACIDS.
USE THE COMBINATION TYPE DRIERS WITH MS/SILICA GEL/ACTIVATED OXIDES FOR SERVICE WORK AS OVER TIME MOISTURE AND WEAK ACIDS WILL APPEAR AND NEED TO BE REMOCED BY THE DRIER BUT BY THIS TIME THE OIL ADDITIVES WILL HAVE DONE THEIR WORK

[monkey spanners]

Not to hijack the thread but here is a series of vids i took on a failed Maneurop compressor,

https://www.youtube.com/watch?v=EpOZXEfByfE

https://www.youtube.com/watch?v=cZdH0sF5XVw

https://www.youtube.com/watch?v=Fu0f5vdLCSE

[Rickyjb64]

Thanks for your attention to this guys. It is all very interesting. I shall forward the info to my friend and see what he comes back with.
Rick.

[Rob White]

Hi Ricky
I used to do the warranty on Maneurop compressors, and often I would see compressors come back under warranty that when cut open

Snippy snip

What an excellent post and extremely informative.
If I could I'd add to your rep but I have to spread my luuuuve around.

Glenn did you ever do a talk at Grimsby college, mid 2000's, about 2005/6?

I obtained a set of slides from Danfoss/Maneurop about comp failures and
it demonstrated the fault you described with photos.

Rob

.

[Grizzly]

Wise words Rob.
I have the same problem where Glenn is concerned.
I cannot give him a rep point either!
Hey Ho! another day maybe?
Grizzly

[al]

Found this on Bitzer comps on freeze driers, units are running on the edge of what they can do, oil was sometimes like water.

[mikeref]

Yes. Glenn's post was well written and informative.
It's a shame a certain Company in my area completed a refit to a popular public bar with 3 liquid solenoids. They obviously didn't run it under the various combinations 3 individually controlled compartments can do to a Maneurop compressor. They lost 4 Pots before calling it quits.

[frank]

Me too mus5 spread the love...
Great post Glenn

[Glenn Moore]

Hi Lads
Thanks for the positive comments its appreciated.

Hi Rob
Yes I did a few lectures at Grimsby but I also gave copies of that presentation to Jane Gartshore and Geoff Yarborough. Since then I have written a series of training presentations called WHY COMPRESSORS FAIL which can be downloaded from Google or from the Danfoss website . There are 9 or 10 parts to it . I wrote them to try to prevent compressors being returned under warranty , and to help the wholesalers to explain to their customers exactly why the compressors failed to help them prevent further failures. I know many people have downloaded them as I used to be mailed on a regular basis from all over the world for parts that were missing on the web for different reasons. have a look and let me know what you think Kind regards Glenn

[Rickyjb64]

The vacuum driers are all running Bitzer compressors coincidentally Al.

[Glenn Moore]

Hi Ricky
It not a compressor problem its a system build problem

[Rob White]

Hi Lads
Thanks for the positive comments its appreciated.

Hi Rob
Yes I did a few lectures at Grimsby but

Snippy snip

have a look and let me know what you think Kind regards Glenn

Small world, I did not know it was you?

Excellent presentation Glen.
I've been using your work for the last ten years, to show
anyone I can and I use the black oil syndrome description
you explained at the time.

Rob

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