Oil seperator trouble

[Comms1]

Can anyone help?
I have got a AC&R seperator with servicable float on a Pack running on R22 5 x Bitzer Machines.
Recently the float was constantly passing hot discharge gas into the Oil resevoir, the float was changed and was o.k for a couple of days but after that the fault returned.
Any idea's?

[Brian_UK]

Contaminated oil blocking the float and or the float chamber; check the oil quality.

[chillin out]

Hi Comms1,

It will be the oil regulators on the comps.

Put your hand on each one, and whichever one is hot, that will be the knacked one.

Chillin

[Gary]

What kind of oil is in the system?

[wambat]

Sometimes a high-performance oil filter can remove the tiniest of particles (i.e., two microns) so they do not collect and affect system components.

[bernard]

Hi Comms1,

It will be the oil regulators on the comps.

Put your hand on each one, and whichever one is hot, that will be the knacked one.

Chillin

Hi chilling out, Can you please explain in more detail the above as I,m interested

Cheers Bernard

[chillin out]

Hi Bernard,

Hi chilling out, Can you please explain in more detail the above as I,m interested

Comms1 has a pack of 5 comps which has a oil sep on discharge which will feed a oil reservoir which in turn will feed the comps.

but it will pass through a S/V and a regulator bolted to the side of the comp, which has a float inside that controls the oil level,
http://www.outokumpucopper.com/pages/Page____18531.aspx



If the float inside sticks which it usually does, the oil and all else behind it will flood into the comp.

Chillin

[Mark]

I believe the fault explained is associated with the oil separator float assembly.

[bernard]

Hi chillin out

Thanks for that, I have a couple of oil problems on the Moducel ht packs.

1.Problem with intermittant oil return,when sep is dropped its full of froth,I think the froth is holding the float up therefore closing it.

2.The 2nd problem is with a different pack where the oil comes and goes.Sep has been dropped and is clean.

Any advise would be grateful

Regards Bernard

[chillin out]

Hi Bernard,

1.Problem with intermittant oil return,when sep is dropped its full of froth,I think the froth is holding the float up therefore closing it.

How do you know the froth was there before you opened it?

What I mean to say is, if the oil sep has oil in it and you reclaim the gas from the sep, the oil will throw out the gas causing it to froth.

Even if the froth was holding the float up this would allow the oil to flow to the res.
So I would say problem is down stream of the sep. Maybe the oil filter? Maybe over-condensing dropping discharge pressure too much? heater on oil sep not working? lots of other things, would need to see a picture of pack in question.

2.The 2nd problem is with a different pack where the oil comes and goes.Sep has been dropped and is clean.

Funny how everyone thinks the sep is at fault when there is an oil problem.
If all controls are working for oil return then it is probebly a system fault, comps going into a vac or very low suction pressures.
Again a picture would help.
Is the Moducel ht packs for air con?

Chillin

[bernard]

Hi thanks

Its a Sainsbury Ht fridge pack with 4 recip comp on R22 and shell SD oil.As you advice I will check further down stream.

Regards Bernard.

[Gary]

I am not familiar with Shell SD oil, but if this is not an approved refrigeration oil, it could be the source of your problems. Non-refrigeration oils contain high percentages of wax.

[chillin out]

Its a Sainsbury Ht fridge pack with 4 recip comp on R22 and shell SD oil.

I think there are differant kinds of this oil, (there is a number to go along with shell SD) and one of them does froth up when used in the wrong application.

but I cant remember which one!!

Chillin

[parry]

UR PROBLEM MAYBE A FAULTY OIL REGULATOR ON ONE OF THE COMPRESSORS OR TO HIGH DISCHARGE I AM 99per cent sure it aint ur seperator in fact u could have cleaned the original and it would have worked again there r also other reasons why ur seperator maybe stickin

[dill]

hi parry, sorry I am a bit late with this advice but I have had tunnel flu and so have been laid up for a couple of weeks. I had 15 years experience of sainsburys packs so I think I can point you in the correct direction. Hot oil into the oil regulator is a classic sign of a problem with the oil seperator. AC&R seperators were notorieous for sticking open allowing hot distcharge gas into the compressor, the float inside would stick open, I have even had them drop off. The only answer is to replace the float which involves a bit of brazing. moducell did not include a sight glass in the line off the top of the seperator for some reason but I fitted them to the packs on all my stores. This gave a perfect indication of the performance of the seperator. expect to see a nice stream of bubbles in the oil and not a mad rush of oil and gas wich would indicate that the float is stuck open. No movement in the glass usually means the orrifice is blocked. anytime dill.

[Richard1000]

i agree with chillin out. do you have a good oil level in the Reservoir? If you have a good level, then yes more than likely a problem with either oil sep or further down stream. If you cant keep a level in reservoir then maybe not discharge gas passing and you are just cycling oil straight through sep, and through faulty oil reg.

[Comms1]

Thanks dill

Sounds like you have hit the nail on the head, the seperator i'm working on is an AC&R.
Did'nt know there was an issue with the floats sticking....now i do Cheers.

[chillin out]

If the oil sep was stuck open this would not cause the oil regs to get hot.

I bet that if the oil res is empty and the oil is flashing like mad then it must be a faulty reg.

If the sep was stuck open then you would hear the pressure relief to suction rattling but the res would still be full of oil and the regs would not be hot.

Why would the reg get hot when there is a res full of oil which is cooling?

The main givaway is the pressure relief rattling, meaning the oil res if getting full and it has to vent to the suction.

Dont mean to at 15 years exp but it is just my thoughts and exp.

Chillin

[chiller563]

Comms, if you have an oil level in the main resovoir check the pressure balance line or lines. I had this problem and the pressure rated check valve was bleeding hot gas into the suction line. You may also want to make sure it is actually "hot gas" you are feeling in the oil return line. If a compressor has a worn cylinder(s) it will pump excessive amounts of oil, especially if your running at low suction pressures which will also cause it to heat up. It may feel like 100% hot gas when it is not. It could be taking on so much oil that the separator is continuosly "feeding" oil to the resovoir and back to the compressor with the bad cylinders.

Chill

[willie]

if you have same rack systems we use ,you would have a high side float from oil sepreator which then feeds up to you oil reservoir which then feeds down to your ac/r floats on each comp .which also has a 15psi check vavle back to suct header .so you should be able to deduce from which point is feeding back hot discharge gas

[dill]

hi chillin, I respect you questioning my thinking because thats how I learned. I worked directly for sainsburys in the early years and then was swallowed up when sainsburys had their cull at coventry. I was involved in troubleshooting their packs and when a new design or peice of kit came out I used to field test it and report to the area engineering manager with any problems I came across. Moducell and carters were building two compressor packs using bitzer 6g 25 compressors and ac&r oil regs and seps at that time. They used, at first 10psi ac&R check valves wich proved to be prone to blocking. As they were brazed in, they were a pain to test and replace so we retrofitted them using 3/8 gill valves. After a time we started getting a lot of compressors tripping on oil pressure. Different causes were found the most common being the oil filter under the oil pump blocking. But one recuring fault was a lack of oil in the compressor. I spent many hours observing the operation of the packs and noting what was failing. At first we found the oil regs had an alarming failure rate. After sainsburys contacted ac&r about the problem they supplied us with adjustable regulators incorperating small fine filters in the oil supply line. the failure rate improved. At no time did a faulty regulators ever cause the compressor to injest hot oil. Having changed single components to entire oil systems on these packs over many years the only thing that would cause hot supply oil was a faulty oil seperator. If you have ever opened an ac&r oil seperator you can see how small the orrifice is, so tails of " rattling suctions" is wide of the mark. The gas flashes off with the oil and heats the oil line up to near discharge temps but the suction pressure on the compressor dos'nt alter. Again after numerous failures the packs were redesigned to incorperate only one oil seperator per pack instead of per compressor. The oil seperator was redesigned to have a bottom operating float instead of a top float witch made changing them a lot better. This also had the trick of making them more reliable. It's seven years since I left sainsburys so I am not up to speed on latest kit but they seemed to be making their packs a lot simpler and more reliable.

[bernard]

Hi

Looked at a pack today with a history of taking out the same compressor every 6 months.Noticed the oil regulator sight glass full and very hot.Found the float rolling around.

Would you agree that this was the reason for compressor failure.

Also I was not involved in previous comp changes.

Regards Bernard

[chillin out]

Hi

Looked at a pack today with a history of taking out the same compressor every 6 months.Noticed the oil regulator sight glass full and very hot.Found the float rolling around.

Would you agree that this was the reason for compressor failure.

Also I was not involved in previous comp changes.

Regards Bernard

It certainly wouldn`t help!

If you have the same comp failing quite regularly i would look at all aspects of control (contactor, lp/hp switch, oil switch, wiring)

Chillin