Foamy oil in sight glass

[NH3ISFORME]

I have been a ammonia tech for 1 year now and the guy I work with is a boring trainer. We have a 58,000 lb ammonia high temp perishable facility of 700,000 square feet with 7 Frick TDSH screws. Of the 7 screws you can only see oil in three of the sight glasses one of which is foamy. I mentioned this to my mentor and he said no worry if they run out of oil it will just cut out. I am CARO certified so I have been studying my RETA manuals and remember reading about foamy oil in the sight glass as a possiblity of liquid in the oil seperator. He doesn't think so. What does everyone else think?

[RANGER1]

Tell us more ..

Is it top sight glass ?
Have the other screws got same oil level ?
Does it have liquid injection oil cooling ? What type
What is discharge and oil temps ?
Are the compressors all on same system high/low temp ?

Sometimes foam on top of oil is nothing to worry about as its just the refigerant boiling out of the oil as its hotter than the saturated discharge temp .

[Josip]

Hi, Ranger1

Tell us more ..

Is it top sight glass ?
Have the other screws got same oil level ?
Does it have liquid injection oil cooling ? What type
What is discharge and oil temps ?
Are the compressors all on same system high/low temp ?

Sometimes foam on top of oil is nothing to worry about as its just the refigerant boiling out of the oil as its hotter than the saturated discharge temp .

Good questions..

one more maybe... Is the oil pressure ok and constant?

Some of those units are equipped with low oil level float and oil could be invisible within oil sight glass...but unit is capable to work fine ... after stop oil level is visible...

... in case of lack of oil this float will stop the unit ... also due to low oil level there is no permission signal from float for start...

Best regards, Josip

[mrfreezeit]

1. Foam in the oil of an ammonia compressor can also be a sign of water in the system. Buy an oil sample kit and send it in for a report.

Another check is to use a cold flo sampler on the lowest temp liquid to determine water level. A cheaper method would be to don PPE and remove some ammonia into a coffee can and place it outside to boil off. If there is anymore than a 1/4 tablespoon of liquid left at the bottom, their is too much water in the system.

Water comes from maintenance activities, vacuum leaks, and bad ammonia charges. Water will begin to corrode your pipe from the inside out and eat away at impellers, valve buttons, and control valve pistons.

2. If running liquid injection, the TXV could be overfeeding liquid. If running Thermosyphon oil cooling, you could have a hole in the shell and tube allowing liquid to enter the oil side during shutdown periods, but worse during operations, the oil will migrate to the system.

If it is in one compressor, than I would assume it is the first one on the way to the vessel from which you are pulling.

[Magoo]

Could be something as simple as oil turbulance, quite often if over charged with oil.
magoo

[NH3ISFORME]

Thermosyphon oil cooling, Oil is at 128 F and 132 PSIG, suction 35 PSIG discharge 125 PSIG high temp, small foam layer is a t top of oil level half way on bottom sight glass. We have done oil analysis no water was found in the sample.

Is it a good practice to allow other compressors run without being able to see any oil in either sight glass. I know there are safeties for low oil but, isn't there a reason for sight glasses? The guy I work with believes that there is no reason to add oil.

[RANGER1]

You and i might add oil to keep us in our comfort zone , where other people don't worry .

He's not wrong but at what point would he add oil ? After it cuts out on oil failure or low oil float level ?

I have seen no level in some sight glasses and it is still running ok .

Its a matter of knowing the limitations sometimes if you need to use them .

[Frank Day]

It is a normal and good practice to have the top sight glass showing a level of 50%.

If of the 7 compressor sets only 3 are showing a level, one must ask where is the oil going and at what rate?

Are you draining oil out of the surge drum oil pot and how much?

When was the last time the oil separator coalescing elements changed?

[Josip]

Hi, NH3ISFORME

Thermosyphon oil cooling, Oil is at 128 F and 132 PSIG, suction 35 PSIG discharge 125 PSIG high temp, small foam layer is a t top of oil level half way on bottom sight glass. We have done oil analysis no water was found in the sample.

Is it a good practice to allow other compressors run without being able to see any oil in either sight glass. I know there are safeties for low oil but, isn't there a reason for sight glasses? The guy I work with believes that there is no reason to add oil.

Oil pressure is only 7 psig (0,5 bar) over discharge pressure oil pump runs continuous or only during start up .... what is the exact type of the unit TDSH....


Maybe you can stop one by one machine, wait for some time and then check the oil level...within sight glass...

Sometimes oil level is not visible when compressor is running, but when you stop the unit after 5-10 min both glasses are full..


Best regards, Josip

[Frickman]

What type of oil is it? What size package?