Oil level on Maneurop MTZ80?

[Swedal]

Fixed a leak on a MTZ80 that had a crack in the discharge line just after compressor and it lost some of it's oil. I added some (maybe 700cc of 1800cc total capacity) but I think it is still pretty low on the sight glass. There is another unit running side by side and it too seems to be low on oil. What is normal level on these when running and when they're off? I can just barely see the level at the bottom of the glass and when it's running it kind of splashes around that low level. Should I add more? Any good tips on how to add oil without evac the compressor and pump it through the oilplug?

[chemi-cool]

You need an oil pump to fill it up again. Maneuropu compressors are sensitive to low oil level.

[Glenn Moore]

The oil charge for Maneurop reciprocating compressors is 1 litre per cylinder i.e. The single cylinder machines need 1 litre ,the 2 cylinder 2 Litres and the 4 cylinder 4 litres. The oil level when running should be around the 1/2 to 3/4 sightglass level. The level will change slightly from running to standstill due to the vortex effect inside the shell when the compressor is running. When the oil level drops to the bottom of the glass or just slightly lower then you are in danger that the oil level is lower than the crankshaft oil pick up point which will quickly cause the machine to run without lubrication and the connecting rods will seize onto the crankshaft and the powerful motor will then break the rods and the compressor will destroy itself. So it is very urgent that the oil levels are topped up to just over the half glass. Also never overfill a compressor with oil as if there is too much oil the crankcase starts to fill up were the connecting rods and crankshaft and piston are spinning at 3000 revolutions per minute and hydraulic damage can take place to this motion work.
Each time the compressor starts oil leaves the compressor housing and enters the system ,the system run time and pipe work design should allow for this oil to return back to the compressor. In the U.K the MTZ 80 compressor is mostly used on close control computer rooms etc where the compressor short cycle this leads to low oil levels and also discharge pipe fractures and I've even seen situations where the short cycling has broken off the compressor mount feet. These feet are now reinforced welded to prevent that happening .
So firstly top up the compressor oil levels and then check the running cycles to make sure they are not being damaged from short cycle abuse.
I used to carry out the warranty inspections on Maneurop and every MT 80 compressor returned under warranty was low on oil and smashed to pieces . It's an expensive error to make
There are some Why Compressors Fail articles on Google or the Danfoss web site explaining these situations which I wrote to help prevent these failures or you can pm me and I'll mail the set to you.

[Grizzly]

Virtual rep points again I am afraid Glenn.
Good sound advise all the same!
Grizzly

[Swedal]

Thank you Glenn for expert advice! Ok I have to adress this problem as soon as possible then! Last time when I added 0,7 liters I used a bottle with a pointy tip through the oil plug. Will I be able to get more oil in that way or will it come out that same port? Do I need some teflon tape to seal that oil plug? Didn't use anything last time and it did not leak.

[Glenn Moore]

Hi Swedal
Emkarate oil is ok to use for top up, the additives in the compressors original oil Will have done its job .
To fill the compressor with oil you can use an oil pump directly in to the 1/4" flare Schroeder fitting. This can be a tiresome job, or an easier way is to fit a system analyser onto the suction valve ,run the compressor into a slight vacuum and dip the charging hose into the oil can. Close the suction valve and the suction inside the shell will suck the oil into the compressor.close the analyser valve once sufficient oil has been added to the compressor, back seat the suction valve and carefully remove the analyser from the compressor. Open the suction valve fully and check the oil level.send me you email on a pm and I'll attach the why comps fail articles for you

[Grizzly]

OK.
Showing my Old Age here!
What's a System Analyser Glenn?
Grizzly

[chemi-cool]

Grizzly my friend.
Here is a pic of analyzer for you
14967

[RANGER1]

System analyser used to be called refrigeration technician or engineer!

[Glenn Moore]

Hi Grizz
Chemi got it right,
Correct term for a set of gauges = System Analyser
That what us tech boys call them .
Ain't this site great we learn something new everyday and for free ,magic ha ha

[Grizzly]

I will be retired before we engineers see anything like that!
Thanks for the update all the same.
Grizzly

[Swedal]

Just to make this oil refill clear. I can use both the compressor housings "spare" Schrader valve or the suction valve service port to add oil? I won't damage the compressor by flooding it with oil when it runs? My idea was to isolate compressor and evacuate it. Using vacuum to suck oil into the spare Schrader valve. But if I can do this without evac using the compressor itself that would be great.

[chemi-cool]

Swedal. Are you a qualified refrigerarion engineer?
There are a few things in your post that should be clear to every fridgy.
I an only asking as I'm afraid you might suck air into the compressor and you never heard of hand held oil pump.

[cadwaladr]

I will be retired before we engineers see anything like that!
Thanks for the update all the same.
Grizzly
Dont retire just go fishing more often!

[Swedal]

Swedal. Are you a qualified refrigerarion engineer?
There are a few things in your post that should be clear to every fridgy.
I an only asking as I'm afraid you might suck air into the compressor and you never heard of hand held oil pump.

Yes I am certified. I usually work on heat pumps and car ac. And yes I know that air does not belong in a refrigeration system. And I have heard of oil pumps but I don't have one because I usually don't need one. I can't find anything contributing in your post though.

[Glenn Moore]

Hej Swedal
I have used this method several times, as well as the method you were going to do using a vac pump. The vac pump method is simpler but if you haven't a vac pump you use your ingenuity by using the compressor as the vac pump. Ps never do it with a Scroll as you will wreck it.
Ps The articles will be with you shortly
Glenn

[malik55]

I would like to add and recommend to have a handy oil pump always in tools kit, It does not cost much and will cover its prices quickly if working on these type of units. Also if a system is working let it pump down to bring back all oil from the system before to charge additional quantity.
Observed oil problems mostly on the split unit, due to field piping (Long runs, Over sizes, No oil traps or traps at not where it should be) which is not designed and implemented as per recommendations of the manufacturer or industrial codes. Less failures for Package unit as those are perfectly designed and have short piping.
Compressor should not to use for self vacuum, it is not good for motor winding and may damage it.

[Swedal]

Yes I will get myself that oil pump. For this time I used the vacuum method and it worked great. Even got too much oil in it so had to drain some out. Ended up adding 0,6 liters and that seems to work fine. It actually ran just fine without that extra oil for 2 weeks but it should be more safe now.

[malik55]

Mark it the level and keep eye on sight glass, observe it on daily bases if possible for some time, Remove extra oil if sight glass shows above 3/4.
Let be happy your compressor with proper lubrication.