which is the maximum discharge temp?

[almucino]

which is the maximum discharge temp on a ammonia screw compressor working with thermosyphon oil cooling?

[gregd1401]

More information needed. Compression ratio, vi, model of compressor would also help.

[gregd1401]

Also if doing booster or high stage duty.

[desA]

which is the maximum discharge temp on a ammonia screw compressor working with thermosyphon oil cooling?

What oil type are you using?
What is the long-term operational breakdown temp of that oil?
What does your compressor manufacturer recommend?

Measure the discharge line temp 150mm from the compressor discharge port under operating conditions & feed back.

[RANGER1]

Most screws are 90deg C mycom .
Howden , Stal can go up to 100 deg C
Not 100% sure on Frick , but suggest 90 deg C .
Usually a booster is 10 deg C lower ie 80 deg C .

Thermosyphon oil cooler should't make any difference as oil temp would expect 45-50 deg C .

With above oil temps oil injection is adjusted to give 75-80 deg C discharge temp (Booster 55-65 deg C approx )

[sedgy]

how many times are you going to post this thread ?

[almucino]

Thanks to all for your answer, the problem that we have, is that the oil migration from the compressor to the system ( about 100 lts/month). the operation conditions are:

DP 150 PSIG
SP 40 PSIG
OT 86 °F
ST 32°F
DT 84°F

I am thinking that the problem is that the oil temperature is to low. may be sould be higer? (+/- 113°F)?

the compressor is a 200VSD MYCOM with 250 HP motor (3500 rpm) .

[almucino]

sorry my friend i am new, but if you don't have an aswer dont´t worry

[RANGER1]

it looks like more than just low oil tempreture .


Even for this low oil temp , discharge theoretical temp should be 145 F /61 deg C with
86F / 32 deg C oil temp

Increase oil temp if possible , maybe throttle liquid into t/syphon oil cooler .

T/syphon could even be warming oil temp from your readings .

More than likely liquid refrigerant entering suction line ?

Where are you reading discharge temp exactly ?

With oil saturated with refrigerant it has a tendancy to throw more oil over into system
as you have stated .

What type of system have you got , liquid overfeed or something else ?

[lowtempman]

I agree with Ranger 1. It sounds to me very much like liquid slopover in the suction line. Virtually no other explabnation can account for lower than normal discharge temperatures. If you have a side port flow the liquid slopover can occur at that point also.

[Josip]

Hi, almucino :)


Thanks to all for your answer, the problem that we have, is that the oil migration from the compressor to the system ( about 100 lts/month). the operation conditions are:

DP 150 PSIG
SP 40 PSIG
OT 86 °F
ST 32°F
DT 84°F

I am thinking that the problem is that the oil temperature is to low. may be sould be higer? (+/- 113°F)?

the compressor is a 200VSD MYCOM with 250 HP motor (3500 rpm) .

inlet oil temp is too low ... must be 45-55C ... try to regulate oil temp at oil cooler ....

discharge temperature must be over 70C otherwise a lot of oil is carryover

check the line for oil return from oil separator to compressor suction .... there must be a small filter ... maybe clogged or regulating valve is not setup properly... that line must be warm what means oil and hot ammonia gas is coming back to compressor suction

possible problem also with coalescing filters within oil separator ..

one more possibility ... maybe you have suction gas too wet .... but. that is another story ... in that case solve the problem within plant and compressor will run OK

anyhow not enough input data ....

what about oil pressure ... steady or variable/trembling, some strange noise from compressor ...

is there another comp on that line with similar problems ....

Best regards, Josip :)

[almucino]

ok thanks,

there are another three compressors with the same problem. the system is flooded. is a Coca Cola plant with 4 lines and there is an suction accumulator to liquid carryover protection. in fact there is some superheat in the suction. the discharge temp sensor is in the oil separator exactly where the discharge of the compressor. do you think that the DT is high because that superheat in the suction? and maybe this is the problem of the oil carryover? the return line to suction is ok.

[RANGER1]

From reading you gave discharge temp is way to low .
Are you sure you have thermosyphon oil cooler , not liquid injection cooling ?

From everyones previous posts we all think oil temp is to low as well as discharge temp way to low from what you describe .

Would expect that if you could not put your hand on discharge line or oil seperator due to being to hot .

Is there any other lines entering compressor from say an economizer ?

[almucino]

From reading you gave discharge temp is way to low .
Are you sure you have thermosyphon oil cooler , not liquid injection cooling ? yes the oil cooling is thermosyphon, the heat exchanger I think is of more capacity and that´s why the low oil temp.

From everyones previous posts we all think oil temp is to low as well as discharge temp way to low from what you describe . yes the oil temp is to low , but we can increse it by closig some the ammonia inlet valve. it is a flow regulating valve. Do you think that can help to avoid the oil carryover?

Would expect that if you could not put your hand on discharge line or oil seperator due to being to hot .

Is there any other lines entering compressor from say an economizer ?. no any else. only the suction and the oil injection.

[RANGER1]

I agree , shut t/syphon liquid regulator in to increaseoil temp to at least 110 f ( 45 deg C )
Are the oil injection regulating valves restricted or fully open ?
This can then be adjusted if necassary to control discharge temp to approx 150 f (70-80 deg C ) .

Let us know how it works out .

[almucino]

I agree , shut t/syphon liquid regulator in to increaseoil temp to at least 110 f ( 45 deg C )
Are the oil injection regulating valves restricted or fully open ?
This can then be adjusted if necassary to control discharge temp to approx 150 f (70-80 deg C ) .

Let us know how it works out .
Sure, thanks ranger1

[That's too cold]

Hi
I have the same setup. I think my is at 200F. Probably 220F max. The main concern here is to keep the oil from burning and carbonizing.

[That's too cold]

Hi
I have the same setup. I think my is at 200F. Probably 220F max. The main concern here is to keep the oil from burning and carbonizing. Your head pressure is very important. Do not go over 200psi (pop relief valves). Cycle the head pressure around 160 to 180 psi for TXV coils. To save energy, I am operating at 120 to 130 psi. head pressure.

[almucino]

Hi
I have the same setup. I think my is at 200F. Probably 220F max. The main concern here is to keep the oil from burning and carbonizing. Your head pressure is very important. Do not go over 200psi (pop relief valves). Cycle the head pressure around 160 to 180 psi for TXV coils. To save energy, I am operating at 120 to 130 psi. head pressure.

ok thanks, do you think that, if the oil temp is higher than 176°F could be oil carryover because oil propoerties degradation.

we have in operation a mycom 200 svd screw compressor (TSOC) , the DT is 176°F and the OT is 86°F and the oil in there is carryover. We are thinking that problem is because the DT is to high.

what do you think?

which are the operation limits of a coalescent filter .?

[alan wolf]

hello
i think we would need to know a lot more about your system and what cooling you are doing, system ambient condensing temps, lp pressures and temps and other parameters. 86 def oil temp sounds cool, is it getting liquid back? does it have oil cooling?
ammonia runs hotter than r22 so 200 deg f can be normal in hot areas depending on condensers etc.

AWW

[la461]

We like 165-175F for high stages and 145-165F for boosters. If discharge temps are running high the oil temp should trend up with it and it could just be the 3-way mixing valve on the oil cooler. There are many other reasons, could just be the oil injection valve closed too much.

[la461]

You may want to check the liquid feed to the Carbo Coolers or whatever style you have. If the liquid feed is closed and not opening you could be leaking through the solenoid or if it never closes it usually is oil in the float column.

[almucino]

hi the system is a thermosyphon oil cooling and the discharge pressure is about 180 Psig , the suction pressure is 45 Psig. the oil temperature we just calibrate is to 110°F by closing the ammonia feeding to the oil cooler. but seems that the oil still is going to the system. I am thinking that the coalescent elements are no working well. what do you think?