Refrigeration Oils - yet again....

[Brian G]

Hi All -

The 'Search' function returns so many 'near-misses' on this that I'm thorougly confused.... I apologize if this has been asked and answered previously. I'm a marine engineer, not a refrigeration tech. and you guys have been good enough to help me out in the past. Here's hoping you can do it once again.

I've recently been posted to a ship with Bitzer 4T.2 reciprocating compressors for the provisions freezer and cold room. The system had the R22 replaced with R422 not long ago; however, I can find no reference to the oil type having been changed - if indeed it needs to be. We're using a synthetic - Mobil Gargoyle Arctic SHC 226E - but are losing oil to the (water-cooled) condenser to the point where both units will shut down on low oil pressure.

Any comments - including suggestions as to how to get the oil back to the compressor - would be greatly appreciated.

Thanks,
Brian

[Goober]

R422 is a "Drop in" replacement for R22, Also known as Isceon MO79. And appears to be able to run on either Mineral or Polyol esther oil (I think). Are you sure oil is logging in Condenser and not Evaporator? Unusual to log in condenser. Would suspect its logging in Evap. Try pumping down system sevral times. The sudden in rush of refrigerant to evap after pumpdown can force oil back to compressors. You can also heat up the evaps when pumped down(if electric defrost available) this will cause the refigerant to boil off more violently when you open liqiud line receiver valve, thus flushing out the oil from evap and back to compressor.

[Brian G]

Hey, Goober - (sounds like a '60's sit-com :-)

I'm not positive that the oil is in the condenser - but looking through the sight glass the liquid appears to be more viscous than refrigerant. There also seems to be (the glasses are not very clean) an interface line a centimeter or so below the liquid surface.

I'll certainly try pumping the system down a few times and try jumping the defroster elements as you suggest. Thanks.

[Goober]

Those sight glasses you're lookin through...where are they on the system? Sounds to me like they are on the receiver?

[monkey spanners]

I have seen similar sightglasses with R413A and 3GS mineral oil. After reading this link i suspect though your oil is synthetic it is not compatable with HFC's you need a Polyolester oil such as Emkarate for HFC's which will make up most of your R422D.

http://www.atlanta.ro/fise-tehnice/G...226E%20pds.pdf

Jon

[cricri]

Hi brian,
you are right the oil is floating above the Mo79 in the condenser. as to much oil is carried over by the compressors you are getting phase séparation in the condenser.
the oil will be drained back to the crankcase by the R600 (less than 4%) added to the Mo 79. if there is to much oil getting away it won't come back.
best solution: add oil separators at the discharge of your compressors
other way: use ester oil (beware, some O rings to not apreciate ester oil and could leak)
as I think it's impossible for you to do those solutions the other way for you is to pump out some réfrigérant, when the level will be low enough, the oil will be drained to the liquid line and then to the compressors.

[Brian G]

Hi -
The sight glasses are on the condensers/receivers and we actually do have oil separators between the compressors and condenser inlet. Why they are not separating is a bit of a mystery to me.

Jon -
We have some Shell Clavus T32 on order which is a POE oil and will hopefully help with the problem. This would be an 'ester oil' as mentioned by Cri-cri, right? Any special precautions I need to take when changing oil types?

Cricri - am I understanding you correctly when you say I can add a small amount of R600 to the system to aid oil return?

Thanks everyone!

[monkey spanners]

Yeah, POE/Polyolester/ester all the same stuff. POE as i'm sure you know is hygroscopic so will easily absorb moisture from the air, once it has done this you can't remove it by vacuum so its important to not have the lid off the drum too long etc.
It can also make some o rings leak such as in solenoids and comp sight glasses. It will depend on how old and the type of materials used in your system. May be worth keeping an eye on it once oil has been changed.

The R600a is already in the R422 refrigerant from the factory, its part of the blend which is made up of R125/R134a/R600a. No need to add any more.

This link may is worth a read,

http://www.tecumseh.com/en/united-states/library/~/media/Files/Guidelines%20and%20Manuals/Refrigerant%20Documentation_North%20America/Tecumseh%20Service%20Guidelines%20HCFC%20R22%20to%20HFC%20Blends.ashx

Jon

[Brian G]

Hi Jon -

Well, that link seems to have the definitive answer:

3. Do NOT use MO or SA oil with HFC blends in
systems using a receiver tank. MO or SA will
suspend on top of the refrigerant and collect in
the receiver. In such systems the MO or SA oil

must be replaced with POE oil.

I appreciate the help,
Brian

[Windy Allah]

I am currently changing a similar Bitzer compressor for a watercooled Unit. As far as I am aware these compressors come precharged with Polyol ester (and also checked with Bitzer). The compressor that I'm changing now was installed by other Tech in an R22 system. The 4Gs oil that was currently in the Unit mixed with the Polyol ester and the result was Compressor failure within 3 months.
POE and Mineral Oil mixed even at small amounts causes blockage (hence LP tripping)to the TX Valve and spider etc. Mixture also turns acidic and wears out the internal winding insulation withnh the compressor which eventually shorted them to earth.
Best way to deal with it, reclaim,flush,triple vac and freshly charge with R22 or whatever Drop ins you have, but never mix your poly with mineral.

[Brian G]

Ohh..Kaaay. Now it's getting good...

The following from Dupont Technical Information Document ART-46 (Retrofit Guidelines for Isceon M029 Refrigerants:

Field experience has shown that ISCEON ® MO29 will work successfully with the existing mineral (or alkylbenzene) oil in most DX systems.



In systems where oil return is a potential concern, such as systems where the suction line accumulator acts as a low pressure receiver, replacement of all, or part (~30%) of the compressor oil charge with an OEM approved polyol ester oil is recommended.

(Italics mine)

My plan was to add a small amount of PEO and see if things improved but it now sounds like that would be a BAD idea?

Brian

[Quality]

I would not advise mixing mineral and polyester oil.
As the article suggests to replace all the oil with polyester would be the proper action to take

[Fri3Oil System]

Hi there,

an Adding of POE would probably create a phases separation between the oils mix (old and new) and the POE+refrigerant, harming the lubricity index.

Regards,

Nando.

[monkey spanners]

I would replace all the oil in the compressor that you can get out.
You will then need to watch the system as the ester oil will mix with the old oil and bring it back to the compressor, if the level has been topped up before you could then have too much oil in the compressor.
After a day or so i would change the oil again, then maybe a week and then another week. When we used to do a lot of R12 to R134a conversions we found it took four oil changes to get the residual mineral oil level to below 3%.

POE is a very effective cleaning agent and will shift any cr@p in the system, much more so than the old oil, it depends on how well the system has been installed and maintained.

I have heard of different makes of oil not mixing well (going frothy) etc, different manufactures have different aditives in there oil so who knows what brand 'x' and 'y' will do for sure, but i haven't seen any blockages or acid problems as WindyAllah has, i have seen wax problems in txv's but i believe this from the motor windings (used as lube during manufacture) and not a reaction between the two oil types.

If you have any concerns, have a word with Bitzer technical and the oil companies too.

[Fri3Oil System]

Jon, why not changing all the oil in one operation directly to less than 1%?

Regards,

Nando

[monkey spanners]

Jon, why not changing all the oil in one operation directly to less than 1%?

Regards,

Nando

Hi Nando,

You can only get out what is in the compressor sump with this method, so what is around the system will graduallly be diluted with the successive oil changes.

We used to do it on planned maintenace visits so it didn't really cost much to do other than 15/20 minutes and a couple of litres of oil.

No doubt your Fri3oil machine would have flushed it all out in one go!

Jon

[Fri3Oil System]

Dear Jon,

We used to do it on planned maintenace visits so it didn't really cost much to do other than 15/20 minutes and a couple of litres of oil.

During this period, you can have the risk of:

Adding of POE would probably create a phases separation between the oils mix (old and new) and the POE+refrigerant, harming the lubricity index.

That's why it might be better to solve it in one operation,wouldn't it?

Regards,

Nando.

[Brian G]

I would replace all the oil in the compressor that you can get out.

Thanks Guys!

The vessel's Chief Engineer, who has been keeping one eye on this thread, agrees that as we are currently offshore Angola and the ship is not likely to go back to civilization in the near future, the progressive oil-change method is what we should do.

Best Regards,
Brian

[DCoker]

Stop! No! And Don't if you are running anything other than a POE oil in it now than don't switch to a POE. POE doesn't mesh well with others exspecially if it is an older system. POE oil works as a solvent and will strip every bit of trash and grim in your system and bring it back to your compressors! This will cause major oil problems in the system you will be changing oil and cleaning screens for months. I know I had someone put in a new compressor on a refrigeration rack that had POE in it and the rack ran on C-3 mineral oil. We lost three other compressors in a row due to this ACCIDENT! Not to mention I was cleaning screens on TXV's every other day for months literally. Hope this got to u before you made the change best of luck.

[DCoker]

An oil separator should fix your problem. To me it sounds like you may have a compressor pumping oil excessively. Busted piston rings or more than likely bad discharge valves. Is the oil really dark almost brown? That would point to bad valves....

[Brian G]

No, we haven't done anything yet. We have no POE oil on board (it's on order). The current (synthetic) oil does not appear to be discoloured. The level in the compressor crankcase does fluctuate wildly - from very low to above the glass to back to low in 12 hours or so. We're also waiting for parts for a compressor overhaul. Oil separators are installed but as the problem started on both compressors simultaneously, I'm doubtful that it's a separator problem.

Some say yes; some say no - I guess you pays your money and you takes your chances! Hopefully the Chief Engineer makes the right decision.

Thanks.

[DCoker]

Just curious what kind of compressors are they?

[Brian G]

They're Bitzer 4T.2 reciprocating each with their own water-cooled condenser. The current oil is Mobil Gargoyle Arctic SHC 226E synthetic and the system is charged with R422D refrigerant. The 2 compressors run either/or into a common freezer/coolroom circuit.

Hth,
Brian