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semoo112
21-07-2014, 04:06 AM
hello all .

i would like to have you kind assistance in this problem .
i have 1 MYCOM compressor unit .
and suddenly the oil temperature became too high ( 65C)

i have charged the ammonia properly(more than 50%) in the surge drum but still too high.
the oil cooler is working normally without problem .
i have changed the oil and charged the oil separator with new oil . (mobil Gargoyle Arctic SHC 226 E) and i have changed the oil filters as well with new oil filters .

the compressor model is : 250VLD .

what should i do ??

thank you

RANGER1
21-07-2014, 04:37 AM
Semoo, assume you have thermosyphon oil cooling from your brief description.
Firstly verify that oil temperature is really 65deg C before anything else, then the following.
pump out refrigerant from refrigerant side of oil cooler.
Then carefully drain to see if any oil in it. Any oil is to much
Also purge air from thermosyphon vessel & main high pressure liquid receiver.
Also would like to know

discharge temperature
discharge pressure
oil pressure above discharge pressure
liquid & return line temperature of oil cooler refrigerant side

Magoo
21-07-2014, 06:14 AM
HI Semoo.
interesting problem with high oil temp at +65'C, that would normally create high discharge temperature faults, or in range of faulting. Is the oil cooling thermo syphon or water cooled or other
As per Ranger1 suggestions what are pressure and temperatures. possibly a sensor or transducer problem.

semoo112
21-07-2014, 08:16 AM
Dear Ranger 1 , Magoo
thank you for the reply .
yes its a thermosyphon oil cooling system
i will confirm with you about what you asked for but what do you man by
(oil pressure above discharge pressure )??

thank you in advance

semoo112
21-07-2014, 10:26 AM
hello again Ranger

when i work on 40% capacity of the compressor :
OT : 61.4
OP= 14.1 bar
DT = 83.1 c
DP = 11.1 bar
when i work on 40% capacity of the compressor :

OT 64.5
OP= 15 bar
DT = 87.2 c
DP = 12.2 bar


hope that we can find a solution for this issue ...

by the way , my auto purger is broken .

thank you

semoo112
21-07-2014, 10:28 AM
sorry mistake
when i work on 80% capacity of the compressor :

OT 64.5
OP= 15 bar
DT = 87.2 c
DP = 12.2 bar

RANGER1
21-07-2014, 10:39 AM
Dear Ranger 1 , Magoo
thank you for the reply .
yes its a thermosyphon oil cooling system
i will confirm with you about what you asked for but what do you man by
(oil pressure above discharge pressure )??

thank you in advance

Semoo,
Possibly ignore that reading for the time being.

Normally most Mycoms have oil pressure which is above discharge pressure.
Not sure what you have as some also have what is called differential oil pressure feed, which only use a small oil pump for loading & unloading.

Usually on control panel oil pressure is worked out already in programme, which subtracts discharge pressure from oil pressure.

Compressor with full lube oil pump lubricating machine, oil pressure should be 2-3 bar above discharge pressure.

Low Oil pressure trip point minimum 1 bar
High discharge pressure trip point is 90 deg
High oil temperature trip 60deg C

Let us know what you can as previously asked & we will go from there.

RANGER1
21-07-2014, 10:50 AM
hello again Ranger

when i work on 40% capacity of the compressor :
OT : 61.4
OP= 14.1 bar
DT = 83.1 c
DP = 11.1 bar
when i work on 40% capacity of the compressor :

OT 64.5
OP= 15 bar
DT = 87.2 c
DP = 12.2 bar


hope that we can find a solution for this issue ...

by the way , my auto purger is broken .

thank you

semoo, if auto purger is broken then could be air in system if system runs in vacuum or you have recently opened to atmosphere for service.
The current discharge pressures seem good but suggest drain oil from oil cooler & purge air to see what you find.
IF auto purger broken, purge air from top of. Thermosyphon surge drum & liquid receiver. Connect a hose from top of each vessel. & crack open valve into a bucket of water, if a lot of bubbles rise to top of water, it's probably air.
Purge until no more bubbles, change water every so often.

semoo112
21-07-2014, 02:16 PM
ranger , thanks again for your concern
actually am doing as you suggested( pumping out refrigerant from refrigerant side of oil cooler.
Then carefully drain to see if any oil in it. Any oil is to much).

i'm doing this operation now but i seems to take too much time. (evacuating the ammonia from the oil cooler )

any ways , will inform you with the results once i finish , but could you explain to me how to purge the air in more simple steps and details .

thank you and very sorry for bothering you .

Semoo

semoo112
21-07-2014, 02:57 PM
sorry again , but i dont understand this ( Connect a hose from top of each vessel. & crack open valve into a bucket of water)
what do you mean by crack open valve ??

sorry for asking too much.

semoo

RANGER1
21-07-2014, 09:03 PM
Crack open valve means open a small amount (less than 1 turn open).

sgull
21-07-2014, 09:16 PM
hi Semoo
Some of the procedures mentioned above are quite dangerous. Draining oil from a thermosyphon oil cooler can be risky, sometimes dirt can block the valve and you can get a sudden surge of HP liquid. Dirt can also stop the valve from re-seating again. All of the suggestions above are excellent but should only be carried out if you are 100% confident in what you are doing. If you are unsure of anything I would suggest getting some outside help with this. The discharge temperature is also a little high, can you check if there is a separate filter on the line feeding oil to the rotors. How old is the compressor?. Wear will also cause high oil temperatures. Can you measure the oil temperature between the inlet and outlet of the oil cooler.
Regards
Denis

sgull
21-07-2014, 09:21 PM
Semoo
If your compressor has a start bypass you should also check if this is not passing with the compressor running. check the suction pressure and temperature. if the superheat is high this may indicate another problem.

RANGER1
21-07-2014, 09:45 PM
ranger , thanks again for your concern
actually am doing as you suggested( pumping out refrigerant from refrigerant side of oil cooler.
Then carefully drain to see if any oil in it. Any oil is to much).

i'm doing this operation now but i seems to take too much time. (evacuating the ammonia from the oil cooler )


any ways , will inform you with the results once i finish , but could you explain to me how to purge the air in more simple steps and details .

thank you and very sorry for bothering you .

Semoo

Semoo thermosyphon should empty in minutes as when empty oil temperature increases.

In your case oil temperature is already operating above its maximum recommended.

semoo112
21-07-2014, 11:02 PM
Semoo thermosyphon should empty in minutes as when empty oil temperature increases.

In your case oil temperature is already operating above its maximum recommended.



i'm confused guys ..dont know what to do

semoo112
21-07-2014, 11:21 PM
sorry but can you confirm with me what is the Thermosyphon surge drum?? is it the ammonia surge drum ??

semoo112
21-07-2014, 11:27 PM
hi Semoo
Some of the procedures mentioned above are quite dangerous. Draining oil from a thermosyphon oil cooler can be risky, sometimes dirt can block the valve and you can get a sudden surge of HP liquid. Dirt can also stop the valve from re-seating again. All of the suggestions above are excellent but should only be carried out if you are 100% confident in what you are doing. If you are unsure of anything I would suggest getting some outside help with this. The discharge temperature is also a little high, can you check if there is a separate filter on the line feeding oil to the rotors. How old is the compressor?. Wear will also cause high oil temperatures. Can you measure the oil temperature between the inlet and outlet of the oil cooler.
Regards
Denis
dear sgull ...thanks for your reply.

i bought this compressors on 2008.
there is no separate filter on the line feeding oil to the rotors

RANGER1
22-07-2014, 09:08 AM
Semoo,
Have you checked for oil in refrigerant side of oil cooler,
also air in surge drum?
How do you know level in surge drum, is there a sight glass or electronic probe?
Are you 100% sure level in surge drum supplying liquid ammonia to oil cooler is correct.
In your first post you mention 50%, is that correct, as you have to have a level for correct oil cooler operation.
What level have you seen in the past when oil cooler working ok?

semoo112
22-07-2014, 09:17 AM
Semoo,
Have you checked for oil in refrigerant side of oil cooler,
also air in surge drum?
How do you know level in surge drum, is there a sight glass or electronic probe?
Are you 100% sure level in surge drum supplying liquid ammonia to oil cooler is correct.
In your first post you mention 50%, is that correct, as you have to have a level for correct oil cooler operation.
What level have you seen in the past when oil cooler working ok?


Dear Ranger , thank you for the reply .
yes there is a sight glass to know the level of the surge drum.
and yes i'm Are 100% sure that the level in surge drum supplying liquid ammonia to oil cooler is correct.
What level have you seen in the past when oil cooler working ok ?? normal level . more than 50%.

so what do you think ??

best regards
semoo

RANGER1
22-07-2014, 10:53 AM
[QUOTE=semoo112;298535]Dear Ranger , thank you for the reply .
yes there is a sight glass to know the level of the surge drum.
and yes i'm Are 100% sure that the level in surge drum supplying liquid ammonia to oil cooler is correct.
What level have you seen in the past when oil cooler working ok ?? normal level . more than 50%.

so what do you think ??

best regards
semoo[/QUOTE

semoo,
Can you measure with thermometer or by hand, any temperature difference of liquid ammonia lines going in & out of oil cooler?
Can you hold hand on oil line going into compressor, or is it way to hot?

semoo112
22-07-2014, 11:00 AM
dear ranger ,
will measure it and inform u with the results .

by the way , i did all what you suggested but the problem still exist.

dont know what to do again ???

semoo112
22-07-2014, 11:39 AM
[QUOTE=semoo112;298535]Dear Ranger , thank you for the reply .
yes there is a sight glass to know the level of the surge drum.
and yes i'm Are 100% sure that the level in surge drum supplying liquid ammonia to oil cooler is correct.
What level have you seen in the past when oil cooler working ok ?? normal level . more than 50%.

so what do you think ??

best regards
semoo[/QUOTE

semoo,
Can you measure with thermometer or by hand, any temperature difference of liquid ammonia lines going in & out of oil cooler?
Can you hold hand on oil line going into compressor, or is it way to hot?




ranger , her you are the temperature of liquid ammonia line going in & out of oil cooler

in = 31c out = 33 c ( as you can see , there is no temperature difference between the in and out temperature - just 2 degrees )

and i can not hold the oil line going into the compressor because is hot ( 57c)

please advise what to do.

sgull
22-07-2014, 12:31 PM
Hi Semoo
Since it is a thermosyphon oil cooler there should be very little difference between the ammonia liquid in and out as most heat transfer is by latent heat. A better measurement to take is the oil in and out of the oil cooler. Also if you can get the suction temperature and pressure we can see what kind of superheat you have. The oil line to the compressor of 57 C is not exceptionally hot.
Regards
Denis

semoo112
22-07-2014, 02:40 PM
Hi Semoo
Since it is a thermosyphon oil cooler there should be very little difference between the ammonia liquid in and out as most heat transfer is by latent heat. A better measurement to take is the oil in and out of the oil cooler. Also if you can get the suction temperature and pressure we can see what kind of superheat you have. The oil line to the compressor of 57 C is not exceptionally hot.
Regards
Denis

the suction temperature : -18.8c
the suction pressure :0.13bar
dp 12.5 bar


by the way , the economizer set point is
55 c - 90% / 65c 85%

that means , when the capacity become 90% the economizer will work .
and the cut out temperature will be 55c

we changed it to be 85% and the cut out temperature is 65c

is that related to the problem ??

please help

RANGER1
22-07-2014, 09:20 PM
the suction temperature : -18.8c
the suction pressure :0.13bar
dp 12.5 bar


by the way , the economizer set point is
55 c - 90% / 65c 85%

that means , when the capacity become 90% the economizer will work .
and the cut out temperature will be 55c

we changed it to be 85% and the cut out temperature is 65c

is that related to the problem ??

please help

semoo, As sgull mentions there should be no temperature difference between in & out of refrigerant side of oil cooler.
Are the stop valves in this area fully open?
We can already tell what the oil in & out temperatures are, but you now mention oil temperature is 57 deg C, previously it was 65 deg C in earlier posts?
Can you please tell us again what oil & discharge temperatures are.
THe economiser cut out temperature was 55 now 65 deg C, what temperature is that referring to to cut out its operation, is it oil temperature or something.
NOrmally economiser runs all the time when & can be turned off only when compressor unloads like you say.
What type of economiser is it, or can you explain how it is piped up & works, as we have no real idea of how your system works or what it is doing.
The economiser may slightly cool compressor if working properly.
Also why did you change set points of economiser operation, was it causing some issues somewhere.

IS there anything else that has changed recently, as you mentioned in first post about adding ammonia.

Magoo
23-07-2014, 12:02 AM
Hi semoo.
do you have sufficient liquid head in liquid receiver vessel to fully flood oil cooler vessel?. The liquid in and out temperatures are in line with 12 bar discharge pressure. A low level in receiver will give high oil temperatures out of thermo syphon cooler.

semoo112
23-07-2014, 01:28 AM
Hi semoo.
do you have sufficient liquid head in liquid receiver vessel to fully flood oil cooler vessel?. The liquid in and out temperatures are in line with 12 bar discharge pressure. A low level in receiver will give high oil temperatures out of thermo syphon cooler.

Dear Magoo , Dear Ranger 1

when i measured the temperature of oil line going into the compressor ( 57c) but on the screen of the CP it was 65c ...

therefore , do you think that the problem is related to the sensor or the transducer as you said before ??? and what should i do about this problem ?? should i change the transducer or the sensor and how do i confirm that the problem is really related to those devices ??

is there any other way that i can confirm that ???

thank you
semoo

Magoo
23-07-2014, 03:16 AM
Hi Semoo.
I do not know your control system, you may be able to rescale the temp sensor with an off set correction factor now you know that actual oil temperature entering the compressor. If you cannot rescale definitely replace it, because it is a false indication and creating an alarm condition.
I cannot recall the actual discharge temperature from compressor, should be in mid + 70' s, you may have to regulate the oil injection regulator, that will control discharge temp and oil temperature follows along. Have you adjusted that valve during shut down period.

PaulZ
23-07-2014, 07:48 AM
Hi semoo
You did not answer Magoo's question regarding the liquid level in the receiver.
Is the receiver being used to supply liquid to the oil cooler or does it have a preferential feed vessel above the oil cooler.
If there is not enough liquid in the receiver or preferential feed vessel the oil cooler will not work properly, if the oil cooling side is short of liquid the oil will not be cooled properly.
Regards
Paul

RANGER1
23-07-2014, 10:29 AM
Dear Magoo , Dear Ranger 1

when i measured the temperature of oil line going into the compressor ( 57c) but on the screen of the CP it was 65c ...

therefore , do you think that the problem is related to the sensor or the transducer as you said before ??? and what should i do about this problem ?? should i change the transducer or the sensor and how do i confirm that the problem is really related to those devices ??

is there any other way that i can confirm that ???

thank you
semoo

I'm not convinced oil temperature sensor is faulty, not yet anyway.
Depends where you read oil temperature on oil pipe or if there is tube to measure it in the oil flow (thinner or smaller diameter pipe).
Temperature sensors are usually in a pocket, in the oil flow so if measuring externally add 3 to 5 deg C to your reading.
Hopefully your thermometer is accurate as well.
To test sensor it could be places in boiling water or an ice slurry for example or to something that is a known temperature.
Removing any temperature sensor make sure it is in a pocket.
If any doubt only remove sensor after isolating & bleeding off all pressure to 0 pressure for safety in compressor package.
If ordering or changing sensor it has to have the same temperature range to work properly & accurately.

Can you also explain economizer operation as from my previous post.

Thanks

semoo112
23-07-2014, 03:24 PM
i will tell you some info it might be useful to you

first of all , i have charged the liquid into the high receiver and its ok now .

but you have to know that my system is .. 2 grasso compressor , 1 mycom compressor .

when i work with the mycom compressor only , the compressor is working fine and the oil temperature is low but when i work with all together , the of the oil temperature is very high as i explained before ...


what do you think ??

semoo112
23-07-2014, 03:44 PM
i will tell you some info it might be useful to you

first of all , i have charged the liquid into the high receiver and its ok now .
and its level is ok now .

but you have to know that my system is .. 2 grasso compressor (1 high stage - 1 low stage ), 1 mycom compressor . 2 condenser (1 condenser = 600KW , 1 condenser = 200KW)

when the mycom compressor is working with the high stage compressor , the oil temperature is fine (62C ) and the compressor keeps running without cut out.

however , when the mycom compressor is working with the low stage compressor , the oil temperature became high (65c) and the compressor cut out ( stops running) .

and also as i mentioned before , the set point of the economizer was 55C / 90%
and another company came and checked it and i complained to them that the oil temperature is high and it cut out when the oil temperature became 55c so they changed it to 65c /85%

so as you can see , the 55c and the 65c of the set point of the economizer is referring to the oil temperature .

thats what i know about my system.



what do you think ??



the Quote is the correct explanation.

RANGER1
23-07-2014, 09:08 PM
the Quote is the correct explanation.

Semoo, the service company complained oil temperature was to high so they raise the cut out.
So they did not investigate why?
HAs it been a new problem, or has it worked before?

THe economiser & oil temperature cut out is confusing, it must be terminology, as it makes no sense to me.IF oil temperature to high does not matter what % load compressor is.

Sounds like a lot of little things not quite right, but can only suggest with the information given, is to restrict liquid into Grasso oil coolers a bit so Mycom is not starved of refrigerant.
Close Grasso inlet stop valves to refrigerant side of oil cooler, then open 1 turn, see what happens, maybe they need to be opened or closed depending on if their oil temperatures goes up.
Basically experiment by restricting flow to Grasso's to see if Mycom oil temperature improves.

PaulZ
24-07-2014, 05:40 AM
Hi semoo
You said oil temp is ok when only Mycom is running but high when other compressors come on. Have you had the size of the lines going to the oil coolers checked, if they are too small it could cause the high oil temp problem.
Regards
Paul

haris
16-08-2014, 03:32 PM
I am a bit late but this surely seems like a priority vessel / line size problem - more like starving the oil cooler. I may be wrong but most likely. What was the actual problem?

Josip
16-08-2014, 08:17 PM
Hi, semoo112 :)


hello all .

i would like to have you kind assistance in this problem .
i have 1 MYCOM compressor unit .
and suddenly the oil temperature became too high ( 65C)

i have charged the ammonia properly(more than 50%) in the surge drum but still too high.
the oil cooler is working normally without problem .
i have changed the oil and charged the oil separator with new oil . (mobil Gargoyle Arctic SHC 226 E) and i have changed the oil filters as well with new oil filters .

the compressor model is : 250VLD .

what should i do ??

thank you

This thread has 36 posts ... quite much and still without good outcome for you ... why!?! ... maybe you miss to describe your problem in whole ...

(it should be similar to full explanation of your problems when you visit your doctor ... otherwise ... doctor can give you a wrong medicament what will hurt you)

...sorry, maybe I sound rude ;), but unfortunately in this way it is not easy to help you in a proper manner ...

the very best is to explain all problems you have/had with all activities and actions you did ... like charging of refrigerant, oil, checking your instruments i.e. probes ... what happen when you run one, two or three compressors in parallel ... all this is very important for us, otherwise, we are lost in asking more and more question then to give you some answer/s ...

the best will be if you can upload schematic diagram of your plant ... there we can see almost all and ask good question/s and hopefully you'll get your answer the soonest ...


Best regards, Josip :)