Grasso expert needed

[geoffg]

Hi

I was on a site last week where a grasso RC11 had somehow got oil in all its cylinders and hydraulic locked throwing the belts off. Anyone know how this much oil has managed to get itself up there. We took the heads off, checked all the valves, replaced the loading piston seals etc. i've heard it's thrown its belts off again within one day.

cheers
Geoff

[Grizzly]

Hi Geof.
You obviously know what you are doing as you replaced the loading piston seals.
Which is the first place to look what state were the pistons and their cylinders is?
Although thats doubtfully the problem if this is a sudden phenomena.

Another area which can cause major oil carry over is where the oil level in the crank is high.
where the con rods and big ends of the crank cause what used to be known as a "splash bath".
The violent slashing of the oil is carried up between the piston and liner.
This is exasperated if the piston rings are worn.
A high oil level can be caused by someone overfilling the crank with oil.

Or as is more likely in your case the oil level float controller is malfunctioning.
Where it can stick open and as the compressor loads up more and more oil is returned to the crankcase eventually overfilling it!
This is more pronounced if you have several compressors on a common oil return.

Sorry about the long explanation but it is where I would look next, but in fairness this is a strange one and maybe someone else has another idea?
Cheers Grizzly

If the compressor has been carrying oil over for a long time (site records of oil added should confirm this).
Then there will be a large amount of oil in the system to be returned.
Which obviously will compound the problem.

[albionharley]

Hi - if it was me i'd try to determine where the oil is coming from ie via the suction line or from the crankcase. What kind of oil level is in the c/case when you get to site? And as Grizzly has said ,is there a history of oil being added to the system?

[Andy]

Hi Albianharley

Usually a compressor will fill up with oil if theirs damage internally.
Or if pumping liquid.
Or possibly when pulling a vacum with no gas flow (blocked suction).

But in all these cases the oil is removed from the sump, so you know where it is comming from.

I did see one case where the oil from one compressor ended up in the sump of the other. The fault was traced to a discharge check valve. It only happened when one compressor was off for a period of time.

Kind Regards Andy:)

[albionharley]

Hi Andy - sorry i think maybe you have miss understood where i was coming from-As Grizzly pointed out if there is a large amount of oil in the system it will return to the compressor via the suction line. I was just suggesting that it may be an idea to try and see if this is the case and not just assume the oil is being pumped out due to a damaged compressor.
Cheers, Phill

[RANGER1]

How do you know its oil that hydraulics cilinders ie did you pull heads off and it?
Does it happen when its running or on start up ? Maybe leaking discharge valves or dicharge check leaking , condensing liquid in heads/cylinders.
Its hard to believe that much oil could enter cylinders but anything is possible.
Are belts plus pulleys in ok condition?
Is plant ammonia or *****?

[chillin out]

It sounds like the oil is coming back on the suction line.
With the rise in ambient temp the cond pressure may have risen and sent any oil collected in it through to the evap and back up the suction line.

Is there an oil separator on the system?
If so, check the gas valve on it, in case the oil is flying through it into the suction header.

Chillin:):)

[geoffg]

Hi we took all the heads off and found the cylinders full of oil. Its an ammonia plant. A theory that we are going to look into is a passing discharge check valve from the oil sep, allowing oil to be pushed back from the sep that we believe may be overfilled. The on site engineer said they have to keep adding oil to it.
I'll just need to wait until i get back on site to have a look.

cheers
Geoff

[albionharley]

Thanks for the update :)

[Andy]

Hi Andy - sorry i think maybe you have miss understood where i was coming from-As Grizzly pointed out if there is a large amount of oil in the system it will return to the compressor via the suction line. I was just suggesting that it may be an idea to try and see if this is the case and not just assume the oil is being pumped out due to a damaged compressor.
Cheers, Phill

Sorry Albionharley:)

I ment geoffg


Kind Regards Andy:)

[Grizzly]

Hi we took all the heads off and found the cylinders full of oil. Its an ammonia plant. A theory that we are going to look into is a passing discharge check valve from the oil sep, allowing oil to be pushed back from the sep that we believe may be overfilled. The on site engineer said they have to keep adding oil to it.
I'll just need to wait until i get back on site to have a look.

cheers
Geoff

Ditto Albionharley.

Geoff just a thought please also check that your H.T. and H.P. Switches are set correctly and are operational!
I would of thought one of them would of tripped before enough oil could return.
I suspect you may be correct in that the non return valve could be faulty.
The std Danfoss ones dont last forever and are prone to sticking ect. once worn.
But you normally get high H.T. or H.P. (ALSO AS A RESULT OF AIR IN THE SYTEM.) try bleeding from the top of the condensor. Well before the oil would return to hydrolically lock the compressor.
The more you tell us the more I am begining to suspect the oil is as a concequence and not the initial cause.
If you understand what I am trying to say.
I could be wrong but am keen to hear more when you no more!
Once again thanks for keeping us posted.
Grizzly:D

Had time to think further. Have site stopped adding oil and has anyone done a oil drain recently.
Is the oil regulated from the seperator via a solenoid valve or float valve?...Possible area's for concern.
Because as Andy suggests, if a non-return valve has failed somewhere else then the oil return lines can be pressurised.
But for the oil to flow into a compressor sump it's "regulation valve" has to fo failed surely??
cheers.

[ammonia101]

Geoff, Oil mangement problem from discharge or the lube in overflowing from suction due to lack of oil mangement from plant operators> last but not least piston rings....
Hope this helps let us know your findings

Ammonia 101