High oil temperature

[mfmsheri]

Hi,

I have a proplem and that's "High oil temperature" in a sabroe screw compressor

What is the causes?
and How i can solve it?

[Sandro Baptista]

How is done the oil cooling?

I guess the oil is not been cooled properly...


Give me data.

[Sandro Baptista]

Mfmsheri, Welcome to REF Forum.

[mfmsheri]

we're using NH3 to cooling the oil

and thanks

[mfmsheri]

Mfmsheri, Welcome to REF Forum.

Thanks sir i'm very happy to find this.
and i need alot of helping.

[passandscore]

Mfmsheri,

I order for specifics you needs to provide specifics yourself. More the better! What model of compressor, Discharge Psi, temp, suction psi, temp, oil psi. What is the Oil temp inlet and outlet across the oil cooler. What is the superheat set at? Are you utilizing an economizer side port?

If the oil is not being cooled enough then start by checked the cooling medium. What is your current oil temperature at the compressor?

[Josip]

Hi, mfmsheri :)


Hi,

I have a proplem and that's "High oil temperature" in a sabroe screw compressor

What is the causes?
and How i can solve it?

welcome to RE forums ...

1. check what is the set point of inlet oil temperature within your UNISAB II or III ... I assume you have it ...

2. check the level of ammonia within your system ... maybe you need to add some

of course to help you we need as much as possible data about your system evaporating/condensing temperature/pressure i.e. one stage or two stage system ... compressor type, oil cooler type, condenser ...

Best regards, Josip :)

[RANGER1]

As above, also carefully check for oil on refrigerant side of oil cooler. Should be a drain valve on bottom of oil cooler. Drain carefully & slowly.

[Sandro Baptista]

Mfmsheri,

Touch on the inlet and outlet of NH3 pipe that feed the oil cooling. If they are hot...or if the outlet one is at higher temperature than the inlet then you may have a problem. If you capture NH3 liquid at condensing temperature then the inlet and outlet pipes at the connections shall have aprox. the same temperature.

[Sandro Baptista]

If the NH3 temperatures are fine then you may have oil on the NH3 side.

[mfmsheri]

Thanks alot guys,this is the oil cooler i have.


http://im36.gulfup.com/gOGro.jpg (http://www.gulfup.com/?XL36Sh)

[mfmsheri]

As above, also carefully check for oil on refrigerant side of oil cooler. Should be a drain valve on bottom of oil cooler. Drain carefully & slowly.

thanks ,but why slowly?

When i drained with inlet close the draining was NH3,
When i drained with inlet open the draining was oil ?

[passandscore]

Check the temperatures across the Danfoss (3way) mixing valve.

Here's the manual. http://www.quadrotek.ru/uploads/data/production/03/15.pdf

I come across this problem quite frequently. Assuming that this valve is the problem and the thermostat needs replacing you may read temperatures as follows. This is what I usually come across. The port on the bottom will be oil temp from the bottom of the compressor (say 180f), the port on the left is from the oil cooler ( say 120f), making the return oil temperature roughly 165 - 170f. Once I removed the 4 bolts and replaced the thermostat the supply oil was 140f because the machine was off. The oil from the cooler was 90f and the return oil temp back to the compressor was 125f. Those are rough temps. I am running on memory.

Even if you determine this to be the problem I recommend that you confirm that all the oil is out of the refrigerant side of your oil cooler as mentioned by others. How much oil have you already drained?

[Sandro Baptista]

mfmsheri,

Have you checked the temperatures on the refrigerant pipes? Where do you capture from the liquid R717 to feed the VATHERUS oil cooler?

[mfmsheri]

.

Even if you determine this to be the problem I recommend that you confirm that all the oil is out of the refrigerant side of your oil cooler as mentioned by others. How much oil have you already drained?

sir,i drained more than 10 liters.
and why when closed the inlet,the draining was NH3.
and when opened the inlet,the draining was oil.

[mfmsheri]

mfmsheri,

Have you checked the temperatures on the refrigerant pipes? Where do you capture from the liquid R717 to feed the VATHERUS oil cooler?

yes,i checked it , i had a difference between the inlet and outlet temperature, the inlet was less than the outlet.

[passandscore]

sir,i drained more than 10 liters.
and why when closed the inlet,the draining was NH3.
and when opened the inlet,the draining was oil.

If you drained 10 Liters of oil from the refrigerant side of your oil cooler I would then start the machine and check you temperatures. That is alot of oil! Problem should be resolved.

With the valve closed, liquid is contained in that supply line, temporarily displacing the oil so when you open the drain valve it is that liquid you see. If you were to wait a while the oil should fall back to the bottom and you could begin draining. If you were to open the valve the liquid is in motion and the oil will naturally settle on the bottom and then you can begin draining. I have done it both ways.

[Sandro Baptista]

yes,i checked it , i had a difference between the inlet and outlet temperature, the inlet was less than the outlet.

If you have a huge difference then it means lack of NH3 flow. The difference should be aprox 0ºC because the NH3 liquid will just change part of them from liquid to vapor.

Where are you getting from the liquid? Whats the level height of NH3?
Maybe you are feed the oil cooler with pockets of NH3 vapor, which is very bad.

[cricri]

Hi Sandro,
about the piping, dont you think that the oil connections are wrong?
connected to the oil inlet on both side of the Vathérus.
regards

[Grizzly]

Hi mfmsheri.

The ORV valve that regulates the cooling of the oil has a history of faults.
Dependant upon their age.
Try reading this link.
http://www.refrigeration-engineer.com/forums/showthread.php?36450-Danfoss-ORV-(Oil-Regulating-Valves-similar-to-the-old-Amot-valves!)&highlight=Danfoss+ORV

As the other guys are suggesting an indication of what temps are where, would be helpful in the diagnosis of your fault.
Grizzly

[Sandro Baptista]

Hi Sandro,
about the piping, dont you think that the oil connections are wrong?
connected to the oil inlet on both side of the Vathérus.
regards

I don't think so. The units already came like this from factory.

[josef]

Hi all, looking at the picture I see that Sabroe and Frick compressor and auto Vi, calibration can also be a problem?
Just thinking out loud.
Josef.

[RANGER1]

yes,i checked it , i had a difference between the inlet and outlet temperature, the inlet was less than the outlet.

mfmsheri, what the latest on this problem after draining oil from refrigerant side of oil cooler? I guess you would expect a 50 deg C oil temperature under all conditions. Is this the only compressor with high oil temperature? What is discharge temperature & is suction & discharge pressures "normal" for this plant?

[mfmsheri]

Thanks alot guys.you have agood and a big bachground .

[mfmsheri]

mfmsheri, what the latest on this problem after draining oil from refrigerant side of oil cooler? I guess you would expect a 50 deg C oil temperature under all conditions. Is this the only compressor with high oil temperature? What is discharge temperature & is suction & discharge pressures "normal" for this plant?

1- The latest is as you are talking, 50c but not always some time the tempreature is high again.
2-The discharge pressure is 12.5 and shutdown at 14.5
The suctoin pressure is 3.2 is good.
but i have in discharge tempreature ,it's 76.9 is too high.

[Grizzly]

1- The latest is as you are talking, 50c but not always some time the tempreature is high again.
2-The discharge pressure is 12.5 and shutdown at 14.5
The suctoin pressure is 3.2 is good.
but i have in discharge tempreature ,it's 76.9 is too high.

Just out of interest, what is the High Oil Alarm set-point within the Unisab set to?
I have some sites where at some times within the chill / freeze cycle the oil will get quite hot.

Especially on start-up from a trip where the condenser has variable speed fans.
We are all worrying about a high oil temp scenario but have yet to determine what the trip point is set to!


Worth asking anyway.
Grizzly

[mfmsheri]

Just out of interest, what is the High Oil Alarm set-point within the Unisab set to?
I have some sites where at some times within the chill / freeze cycle the oil will get quite hot.

Especially on start-up from a trip where the condenser has variable speed fans.
We are all worrying about a high oil temp scenario but have yet to determine what the trip point is set to!


Worth asking anyway.
Grizzly

Grizzly,
1- THe good range is between (48-65)c
The warning alarm is between(66-73)c
The alarm shutdown is 75c
2-What the connection between the oil temperature and the condenser?

[Josip]

Hi, mfmsheri :)


i drained more than 10 liters.
and why when closed the inlet,the draining was NH3.
and when opened the inlet,the draining was oil.


1- The latest is as you are talking, 50c but not always some time the tempreature is high again.
2-The discharge pressure is 12.5 and shutdown at 14.5
The suctoin pressure is 3.2 is good.
but i have in discharge tempreature ,it's 76.9 is too high.


Maybe I will sound rough, but when you visit the doctor you tell him all the symptoms you have to be able to help you, right? So it will be nice to tell us the most about your plant ... but no data ... :confused:

anyhow ...

When you open ammonia inlet valve and then you drain the oil seems your inlet pipe is full of oil ... you need to drain oil from that pipe completely .... also from intermediate receiver if you have one and from condenser too ...

Looking at your photo .... your outlet pipe from oil cooler is installed wrong ... outlet pipe from oil cooler should always go straight or with vertical inclination all the way back to condenser or to intermediate receiver ... but newer with sections of horizontally installed pipes ...

Data from UNISAB manual for screw compressors:

Discharge temperature
High alarm Min 50oC Max 120oC Factory 90oC
High shutdown 60oC Max 130oC Factory 100oC

your discharge temp is a little bit too high ...

why, because at condensing pressure of 12,5 bar corresponding temperature is 35oC + 40oC of max discharge superheat give us 75oC discharge temp .... you need to check your suction superheat ... if it is too high then you should have discharge temp also high ...

Your evaporating pressure is 3,2 bar what is about -0,6oC ... i.e. set point of evaporating temperature is 0oC ....

Oil temperature
High alarm Min 30oC Max 70oC Factory 60oC
High shutdown Min 40oC Max 80oC Factory 65oC

Sabroe recommendation for inlet oil temperature is 50oC, but can be slightly higher ... up to 55oC ... depending on the type of 3-way mixing valve for oil temperature and refrigerant...

If you use mineral oil then you set up high alarm at 60oC and high shutdown at 65oC

If you use synthetic oil you can set up high alarm at 70oC and high shutdown at 75oC ...

Hope thi is of some help to you

Best regards, Josip :)

[mfmsheri]

you are very good Josib,you have my symptoms more than me :D


Hi, mfmsheri :)


Looking at your photo .... your outlet pipe from oil cooler is installed wrong ... outlet pipe from oil cooler should always go straight or with vertical inclination all the way back to condenser or to intermediate receiver ... but newer with sections of horizontally installed pipes ...



Best regards, Josip :)

this is the best .

[RANGER1]

1- The latest is as you are talking, 50c but not always some time the tempreature is high again.
2-The discharge pressure is 12.5 and shutdown at 14.5
The suctoin pressure is 3.2 is good.
but i have in discharge tempreature ,it's 76.9 is too high.

mfmsheri, You should check again for oil in refrigerant side of oil cooler & maybe air in system effecting discharge pressure/temperature which has to be purged out. Your pipework may not be perfect but assume it has worked in the past. Not sure do you also have a good working level in liquid receiver, is condenser working to its fullest potential, fans & sprays etc.

[RANGER1]

thanks ,but why slowly?

When i drained with inlet close the draining was NH3,
When i drained with inlet open the draining was oil ?

mfmsheri, recommend to drain slowly for a few reasons high pressure liquid ammonia comes out of this connection so is dangerous, as well as you want to get all oil out. If you open valve to far refrigerant may pass oil because it is like water & not as thick as oil.