Dirty oil

[nanuuk]

Was wondering if someone can help me out? Have a Mycom compound recip compressor which has its own intercooler and oil separator. Our medium is anhydrous ammonia. So the problem we are having is soon after an oil change the oil turns black to a point that we can't see the oil level through the site glass of the crankcase which of coarse makes it hard to see the oil level. We have done a couple of oil changes with the same result shortly after..........shortly after being a week of run time. There is no inline filter off the oil pump just thought i would throw that in not that i think it would make to much of a difference.

[mbc]

Hi
What is the pressure of the suction and discharge
Is your system is clean?
Check the circulation of water on the compressor
and on the top of head cylinders

[Grizzly]

An Interesting problem!
Just a few simple questions to start.
Have you changed the Oil you use recently?
Historically with the Old style Mineral Oils, you would get a carbonisation of the Oil over time.

Or if the running Oil temps were being elevated!
But for the oil to turn in a week is unusual as you say.
Another is the flushing of the Old Carbon Deposits around the system by the Fresh Oil.
We used to see this when the Synthetic Oils first came in, but over a week is definitely fast.

Do you have another running Machine you can compare Cylinder Head Temps with?
Only like mbc, I am wondering if High discharge temps are cooking the Oil. Especially between the LP and HP heads.

I suspect you are an Old School Engineer so please accept my basic questions as coming from someone who is looking at your problem blindly from afar!

There could be a Discharge Valve Plate Issue (we have all accidentally at some point.Nipped a Valve plate etc when rebuilding the Heads.) That's assuming someone has done a Top End Rebuild at some point along with the Oil Change.

Have you tried a drop test to confirm Valve tightness.
Last few questions for now, does this system have a Oil Reclaim System and are its control Valve/s operating correctly
Lastly what is the Oil level like in the separator, has this inadvertently been drained at some Point. ?

Hope this Helps Grizzly

[RANGER1]

Nanuuk, Just to add to above posts.

maximum oil temperature for Mycom 50 degC
maximum discharge temp 140 degC

what type of oil, s it clean from drum
was sump cleaned thoroughly when cleaning sight glass?
have water jackets & oil cooler been cleaned with good water flow?
is oil return very hot, what type, float or other?
is intercooler working correctly (second stage suction cold or ice build up)?

Does liquid receiver have a good level for liquid seal? otherwise if air in system can oxidise oil quickly.

Also close off oil return to see if oil stays clean, only add new oil to test if oil separator contaminating oil.

Have installed a inline filter in oil line in the past, cannot hurt as long as suitable for ammonia & has internal bypass if it blocks up as well as pressure gauges to monitor pressure drop across it.
May not necessarily clean the oil, more for good quality oil feeding bearings.
Probably a 10 micron oil filter, oil flow about 24 litres a minute.

[passandscore]

I like what RANGER1 recommended.
"Also close off oil return to see if oil stays clean, only add new oil to test if oil separator contaminating oil."

How clean was the original oil prior to changing the oil for the first time? Did you flush the primary oil circuit (Oil cooler, bearings, etc) by connecting an oil pump to clean oil and flushing it through? If not, the dirty oil will simply blend with the clean oil and give you a dirty sight glass before you know it. So, how thorough was the oil change?

I have also heard of other experiencing this issue and they have told me it had to do with the cleaning agent they used. In their case it was due to a particular type of solvent.

Please share your finding as I am sure all of us here would like to know the cause.

[Glenn Moore]

Had a number of customers with dirty oil and also control valves failing due to wear or friction. Danfoss for a while produced a solid core filter drier for Ammonia. the drier core was made from pure molecular sieve. THe maintenance engineer at a nearby ice cream factory called me to discus his problem of dirty oil and sticking valves on an ammonia system. He strangely enough was an Aussie engineer who was keen to try anything new as was I. So I got some cores and a large drier shell and gave it to him to install. He then monitored the system and although the system clean up was very slow it did work and cured the problem . I then supplied similar kits for several other problem plants fitting drier shells to both the high and low sides of the system. These also worked and got a major manufacturer out of trouble.
Danfoss then stopped doing the NH3 drier cores shells as there was limited sales.
But as our experimental site had resolved the problem my Aussie mate continued using the Molecular Sieve cores as he was more than happy with his results ,even though the solution was no longer supported
Due to the difficulty in finding out what actually fitting the drier was actually doing to the system ,whether it was simply cleaning the system and refrigerant and/or removing the moisture content to a normal level .
I can’t for certain say fitting a core drier is the answer as no tabulated results were made of the results but from our own little experiment the results although slow were extremely encouraging in cleaning up a dirty NH3 system
During operation the shell became extremely warm to the touch , which evidently is caused by some sort of chemical reaction ,but is not a problem.
You learn nothing if you don’t experiment