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zeh0085
09-09-2011, 02:43 PM
I have two of these machines sitting side by side both are thermosyphon cooling with liquid inject assist. I raised the set point of the liquid inject assist up to utilize the thermosyphon during this period of cooler weather and to get more familiar with the machine. This morning I'm looking it over and the liquid inject line going in to the side of the block is so hot it scalded my hand checked it with the IR thermometer and it read 250F. I have the liquid inject turned off right now. Is this pipe supposed to get this hot? Right after installation we had the wire that connects to the Icad valve motor literally melt because it was tied to this line from the factory. I am wondering if this is a normal occurance or a warning sign of something else this compressor is smooth as glass at full load

I recorded the stats at the moment.
Disharge pressure 139 psig
discarge temp 154 F
discharge super heat 76 F

oil pressure 137psi
oil temp 126 F
seperator temp 134

suction pressure 37 psig

outside temp 67 F
humidity 85

chillerman2006
09-09-2011, 03:12 PM
Hi Zeh

I can not see where your generating this temperature from

If your discharge temp is 154f, where is the other 100f coming from to reach 250f

I do not know this unit but if you are generating those sort of temps in liquid form, I would be inclined to say you have a blockage in that liquid line...other than that I will be very interested in seeing what others can confirm the fault to be

Make sure you have safety goggles on whilst looking at this unit, as if correct you could generate more temp/pressure and maybe even rupture the line

R's chillerman

zeh0085
09-09-2011, 03:26 PM
That is the problem I am having with this. The block is around 110- 130F depending on where you look I have frost on the top towards the front but this one pipe is way out of whack from a logical stand point I can't imagine it having any liquid in it since the liqiud inject valve is not feeding at this point. This line will get cold if I turn the liquid inject on but I would be running the expansion valve by hand till got down in temp there.

chillerman2006
09-09-2011, 03:33 PM
Do you have a refrigerant flow chart you can upload or direct me to a site where I can view this setup, then maybe can help more...I'm sure you must have a blockage

alternatively some of the lads more familar with this setup will be on after five & should be able to work out whats going wrong

Might sound a silly question but as I dont know what you there ....... could this be piped wrong ?

zeh0085
09-09-2011, 04:16 PM
It's piped right as far as I know. This was a new machine 2 yrs ago. The liquid inject works very good I had it comming on a 165F previously and it would knock the discharge temperature down 15deg like in the blink of an eye. Like I say this is a real head scratcher. Before that liquid inject was set at 120F

Grizzly
09-09-2011, 05:18 PM
Just a quick Question.
What is your liquid level in your receiver like.
It's just possible your loosing your subcooled liquid supply.
I assume the thermosyphon takes precidence over the liquid injection supply?

Or is there anyway you could of introduced any air.
Your temps seem way to high for me, but I must admit I am not used to working in Imperial nowadays!
Cheers Grizzly

chillerman2006
09-09-2011, 05:20 PM
If I am following right, this liquid injection is to control the compressors temperature & if so it will show a drop in discharge temp,

The line will remain full of liquid when not in use if it has no where to expand its mass & this is what I am thinking is the problem some how this setup does not allow for relief of pressure build up and when liquid injection valve is closed the trapped liquid is absorbing heat into the line

What is there in the liquid injection line ?

Is there anything stopping this line equalising temp/pressure with the main liquid line ?

There must be something or they would equalise ! Surely :confused::confused:

chillerman2006
09-09-2011, 05:37 PM
Just a quick Question.
What is your liquid level in your receiver like.
It's just possible your loosing your subcooled liquid supply.
I assume the thermosyphon takes precidence over the liquid injection supply?

Or is there anyway you could of introduced any air.
Your temps seem way to high for me, but I must admit I am not used to working in Imperial nowadays!
Cheers Grizzly

Evening Grizzly

The more I look at this, the more I can not see where this 100f additional temp is coming from
250f is 120c and that is off my compareter...exceeding 50 bar !

Both pressure & temp is well above design spec .... me really :confused::confused:

R's chillerman

Grizzly
09-09-2011, 06:01 PM
We are talking about liquid injection oil cooling.
Rather than woffling on.
Read the attached chillerman.
It's pretty basic stuff really only his temps are not.
Hence my question about air or where has the liquid gone?

chillerman2006
09-09-2011, 06:09 PM
We are talking about liquid injection oil cooling.
Rather than woffling on.
Read the attached chillerman.
It's pretty basic stuff really only his temps are not.
Hence my question about air or where has the liquid gone?

Nice One, cheers mate

will have a read,

R's chillerman

zeh0085
09-09-2011, 06:20 PM
Okay reading your thoughts since the last post the Receiver level is normal for operation. My problem is not present when the liquid inject is utilized it only showed it's ugly little head when I stopped using it. If there is liquid present in that tube at a high pressure I don't know how it would get there unless my liquid inject is flowing the opposite direction.

Grizzly
09-09-2011, 06:21 PM
Of Course!

We are taking the measured temps as gospel!
Since when has anyone trusted a IR Thermometer. Most the ones I have used are OK for reference.

But may I suggest Zeh that you check again with a surface probe and hand held thermometer.

Only to this Luddite Brit it will eliminate all uncertainty.
Grizzly

chillerman2006
09-09-2011, 06:25 PM
Looking through tha attached by 'Grizzly' am wondering is this a complete skid purchased or has this been put together on site and the tubework/reciever has not been correctly sized ?
or
the only other thing I can see there, is the isolation valve
Is this fully open ?

zeh0085
09-09-2011, 06:57 PM
It was a complete skid. I believe the temp reading cause it fried my hand on contact with it. Let me ask this how does the liquid inject feed from the port on the side of the block to the actual injector/injection point.

I guaruntee I could go and enable liquid inject right now and the tube would cool off immediatly which would tell you that there is a lower pressure than discharge pressure in the liquid inject tube.

zeh0085
09-09-2011, 07:00 PM
And really IR guns are pretty good given the application but still anything over 180f is gonna make me a little more than concerned that is way to close to shut down temp

chillerman2006
09-09-2011, 08:04 PM
It was a complete skid. I believe the temp reading cause it fried my hand on contact with it. Let me ask this how does the liquid inject feed from the port on the side of the block to the actual injector/injection point.

I guaruntee I could go and enable liquid inject right now and the tube would cool off immediatly which would tell you that there is a lower pressure than discharge pressure in the liquid inject tube.

Zeh

your ok I have seen your other posts your No Rookie at this & agree with both of you on IR thermometers, they are inacurrate but this is a long way off normal temp

We are just trying to help get to the bottom of this

Logic still tells me there is trapped liquid between the block & injector...as its the only viable answer to such an increase in temp

If this was vapour there would need to be 100f of temp transfered to the line
If its liquid a slight increase in temp will increase pressure alot which in turn increases temp

Can we agree or dissagree on that ?

If agreed, then each end of the line must be isolated from the rest of the system when liquid injection is not energised

It's really baffling me, will take another look through the attachments Grizzly has supplied & see if I can spot something we missed so far

chillerman2006
09-09-2011, 09:05 PM
Right had another look, we have a reciever feeding the liquid injection line (either bottom fed or dip tube) there is an isolation valve at the reciever end, the other end is the injector into the oil cooler

Is there anything else in the line or at either end ???

Grizzly asked about liquid level...You confirmed this as ok ...plus confirmed liquid injection works when energised

If this is dip tube fed(not bottom feed) ....... is it possible the the dip tubes are piped wrong and priority is to evap instead of oil cooler ???

zeh0085
09-09-2011, 10:11 PM
My only problem liquid present in the line arguement is, if it were that pressure it would be well in excess of 700psig and the whole line should be near that temperature from one end to the other. The fact remains that the line gets cooler the further you get away from the block. The second fact is as soon as the liquid inject solenoid is actuated the line drops to a cold temperature rather quickly going towards the compressor since my HPL supply is 135psig nominally if I were charged with liquor in that line 200+ deg F the thing would flow the other way.

There has to be some kind of logic to this. Thanks so far. I think what ever is going on is in the block like maybe I'm getting hot oil or superhot gas back up in there. While typing that last two words it made me wonder if there ifs a check valve in the block that could be letting something hot flow back into that line.

Grizzly
09-09-2011, 10:16 PM
Interesting comment about the 100f temp as that is the figure used to calibrate the quantum ezecool
(Liquid injection control).


Zeh.
Have you seen the attached before?

If this not of any help?
I am going to wait and see if our colleagues from your side of the pond.
Can shed more light on the issue.
Please accept my apologies but this is beyond me at the moment.

Good Luck Grizzly

RANGER1
09-09-2011, 10:52 PM
zeh0085,
You mentioned that you had 2 packages the same, are they behaving the same regarding liquid injection high temps?

I have seen this before, usually with compressors that we have converted from liquid injection to water or t/syphon oil cooling.
Having left the liquid injection connected for emergencies we sometimes see it.

To me its recirculated superheated gas only, as the gas pocket in liquid injection line does not flow, so same gas keeps getting compressed over & over in this short piece of pipe.
(laymans terms superduper superheated gas):D

Maybe others will agree?

I find it interesting that someone would instal thermosyphon & liquid injection!
Its either a back up or maybe something to do with your winter weather conditions.

If t/syphon is installed correctly its the most reliable efficient cooling there is.

chillerman2006
09-09-2011, 11:00 PM
To me its recirculated superheated gas only, as the gas pocket in liquid injection line does not flow, so same gas keeps getting compressed over & over in this short piece of pipe.
(laymans terms superduper superheated gas):D

Maybe others will agree?


Morning Ranger

Your experience makes good sense to me

If this is the case is this breaking down the refigerants properties ???

R's chillerman

zeh0085
09-09-2011, 11:28 PM
The Liquid inject was a added option to both compressors because previous engineering had shown that the thermosyphon was not capable of supporting so many machines at the same time. Reallity being head pressure was so high due to lack of purging that failure was emminent. Anyways we'll not go down that road.

The other or sister compressor cannot be ran on the thermosyphon only at this moment. I found this out when the thermostat valve after the oil cooler appeared to not be functioning correctly. Replacement parts on the way.

RANGER1
10-09-2011, 01:25 AM
Morning Ranger

Your experience makes good sense to me

If this is the case is this breaking down the refigerants properties ???

R's chillerman

Chillerman,

Well I would assume Ammonia is being used in this application so doubt whether any break down of refrigerant is happening. i would have thought oil breakdown in this area could cause contamination locally.

Have also seen hot oil return lines from oil seperator to in some cases, where economizer port connection( which is not being used for anything else ) is being used for oil return instead of suction line of compressor.
The oil return pipe is very hot for about 300-500mm for same reason as stated on liquid injection scenario.

chillerman2006
10-09-2011, 04:21 AM
Thanks Ranger

much appreciate the info/explanation

R's chillerman

desA
10-09-2011, 06:08 AM
...This morning I'm looking it over and the liquid inject line going in to the side of the block is so hot it scalded my hand checked it with the IR thermometer and it read 250F. ...

Can you re-check with a contact temp probe? Could be the IR is giving a dud reading due to surface emmissivity.

If this is all good - electrical short on this line?

Grizzly
10-09-2011, 09:25 AM
Ranger.
Thanks for the sound advise makes sense to me.
Sounds like Zeh has walked into a plant that needs some TLC. A new Amot valve is a good start.
I agree with thermosyphon oil cooling being the "muts nuts".
Simple usually is!

I had a situation recently where a Grasso screw pack on thermo cooling. Would randomly have it's oil cooling Fail and trip on high oil temp.
This had a shared liquid line from the receiver feeding both the S/T oil cooler and the Surge drum liquid feed.
Liquid feed would always take precedence due obviously to it's lower operating pressures.
Problem solved by fitting a preferential pot with the bottom port to the oil cooler.

Once again thanks for the (I assume) Logical answer, it will be interesting to see what zeh finds?

Des we discussed that idea earlier in the post but you and I think similarly!

Chillerman we learned a lot on this one did we not?

Grizzly

RANGER1
10-09-2011, 10:14 AM
Grizzly,I'm pretty confidant but would be good for some other feedback.

If the screw is only 2 years old you would have to say its pretty fresh, so can't imagine there would be anything wrong with it.

You would have to agree that it is unusual for both liquid injection & thermosyphon to be hooked up together!

RANGER1
10-09-2011, 10:17 AM
The Liquid inject was a added option to both compressors because previous engineering had shown that the thermosyphon was not capable of supporting so many machines at the same time. Reallity being head pressure was so high due to lack of purging that failure was emminent. Anyways we'll not go down that road.

The other or sister compressor cannot be ran on the thermosyphon only at this moment. I found this out when the thermostat valve after the oil cooler appeared to not be functioning correctly. Replacement parts on the way.


zeh0085,
Can you please advise if 2nd machine is the same once AMOT valve is repaired.

Ranger1

Grizzly
10-09-2011, 10:46 AM
Grizzly,I'm pretty confidant but would be good for some other feedback.

If the screw is only 2 years old you would have to say its pretty fresh, so can't imagine there would be anything wrong with it.

You would have to agree that it is unusual for both liquid injection & thermosyphon to be hooked up together!


Spot on, I cannot imagine it's normal, hence my original question of our American colleagues.

Grizzly

Grizzly
10-09-2011, 10:57 AM
Hi Guys.
Zeh.
Is the liquid injection fed from a independent dip tube from the receiver?
Because if so it is just possible?
If you have a float type level control on your receiver?
That the low level setting may be to low and starving the supply of refrigerant needed to provide your cooling?
Please keep us all informed as it's all very interesting and a good learning curve.
Grizzly

chillerman2006
10-09-2011, 03:29 PM
Chillerman we learned a lot on this one did we not?

Grizzly

Oh ! Yes, these are always the best threads, the ones that just dont sound right, get you thinking, chasing your **s, until along comes a man (Ranger) that has before & penny drops

The clue to a good thread, is when its posted by an experienced engineer (Zeh), within his own specialality

Amot valves only lasting a couple of years ( something to note ! )

How is this piped ? We still do not know if its bottom fed or dip tube & if they are in fact the right way round ? Do these recievers have sight glasses lik LPR's ? So this can be confirmed, as from the doc you kindly uploaded it should not just be lower tube but have a minimum liquid feed fail safe level of 5 minutes !

R's chillerman

NH3LVR
11-09-2011, 04:06 PM
I do not claim great expertise with Frick, nor have I ever worked on a combination Thermosyphon/Liquid injection machine.
But lets try this. In order to get hotter than discharge temperature you need to have something leaking back up the line. That can only be hot gas. Is it possible that the hot gas is leaking back up the line? Again as I say I am not an expert on Frick, but if the machine is over compressing (A function of VI) you may have a higher pressure at that point than the discharge. The ideal VI for your conditions is three. Is this a variable VI machine? If so perhaps a adjustment might solve the problem.

zeh0085
14-09-2011, 11:46 PM
Sorry about the dead thread for a minute I was on my rotation days off. I am still working on the how part I was talking to a couple former engine room guys one that retired from here and one that moved over to plant maint. the old guy is saying it's heat of compression.

The liquid feed is a dipper style tube the receiver has the long type sight glasses liquid supply is never the problem so that is not the part of the problem. My IR gun is a muchly used tool and is giving acurate readings.

We are waiting for a opprotunity to get to it currently we had a thought about inductance from the motor possibly throwing us a curve but running production heavy is not the time to experiment with this thing.

Thanks to all for your thoughts

CHIEF DELPAC
15-09-2011, 11:53 PM
Hi I have been following the thread with great interest. I have two , Mycom 250 lud in NH3 service. Today Itried an experiment. I shut off the medium temperature port on one of the comps. The port is used for the nh3 liquid sub cooler suction. After running the comp. at 100% capacity the comp. discharge temp was 160 F. At the shut off valve the temp. was 240 F. The shut off valve is about 3 feet from the comp. port. So I have simular results as zeh has found. So where is the extra heat coming from? C.D.

zeh0085
16-09-2011, 11:16 PM
Maybe it is a heat of compression situation who knows we'll figure it out next week. Now I shall go have brewski and try to reflect on it. NOT

Magoo
17-09-2011, 03:20 AM
Hi CD,
the Mycom requires cooling from vapour through compressor, with side port load added, the oil circulation regulation through injection is reduced, stop the side load vapour and the compressor has less cooling, hence high discharge temps. the heat comes from heat of compression, motor imput, if you increased the injection rate the discharge temp would come down. Not a good idea to play with things like that, you will end up with high discharge faults and oil carbonizing .

CHIEF DELPAC
17-09-2011, 06:42 PM
Hi Magoo The Mycom comp. does not have liquid injection. The oil is cooled by a thermosyphon system using a shell and tube heat exchanger. The side ports are for the suction line from the sub cooler which cools the liquid NH3 which is feeding the low pressure receiver. The feed to the low presure is on off controlled by a column with mercoid switches. The liq. feed is intermitant so the cold vapour is not a constant load. I checked the discharge temp 160 F. on the compresor. It is the same whether the suction line valve is open or closed. When the suction valve is open the line temp is around 28 F. When I closed the valve the temp. at the valve reached 240F. I am not sure why the temp goes that high and not stay at the comp. discharge temp. The temp of the comp body around the port is close to the discharge temp. 0f 160 F. C.D. [Still Confused about the temps. but then its raining today first rain in along time.]

Magoo
20-09-2011, 02:21 AM
Hi Cheif
you should maintain an average discharge temp at 75 'C / 167'F exiting compressor, regulate the oil injection vav to control that, the side port cooling effect is a bonus unless totally saturated, sounds like you have an open flash economizer [ I hate them with a passion ] and should have a suction pressure regulator with pilot sensing main suction pressure so as to be proportional to compressor loading. Oil temp at compressor should average + 45'C / 113 'F after the oil cooler.
Best advise is get the Mycom compressor select prg and load all you conditions, things will become alot clearer.
Send me a PM and I can possibly help further.
magoo

RANGER1
20-09-2011, 09:35 AM
CHIEF DELPAC,
It appears to be a characteristic of Mycom & possibly other brand screw compressors from my experience.
The female rotor which passes over this port which basically has no flow into compressor, slightly expands & recompresses this already superheated gas.
The pocket of gas reaches an equilibrium, which is much higher temps compared to normal discharge temp.

The economizer Magoo describes can achieve massive subcooling if correct lenth liqud line cooling coil is used &
so economizer port is 100% utilized at compressor full load.

Grizzly
20-09-2011, 09:52 AM
Hi Ranger and Magoo.
Thanks for your knowledgeable input.
All screws with a side load port suffer in some way,
As the pulsing of these gases particularly against a closed valve can cause a resonance (Vibration).
Which if the solenoid valve or control valve is not positioned correctly can cause pipe fractures.
Slightly off topic I know but still relevant to the discussion.
Grizzly

zeh0085
22-09-2011, 11:35 PM
Okay update time finally got the thermosyphon cooling working on the sister unit both thermostats on the oil cooler had failed and were not letting oil from the heat exchanger mix therefore no cooling effect. I ran the compressor for a period of 24 hrs with no liquidinject assist cooling all seamed good today until just about an hour ago got a wif of a melting plastic smell looked the machine over and the same problem exists on this unit that does on the other only th hot spot is in a different place and the liquid inject feed pipe was well over 400deg. The pattern and the way this is heating up is pointing towards a inductance or eletrical problem I can't see how anything on this compressor mechanically or refrigeration wise can make these ungodly high temps. Bottom line if you have one with liquid inject and thermosypon use them both.

Segei
26-09-2011, 07:56 PM
I see only one explanation. Screw compressor compress gas in the cavities. Injection port will let gas to be bypassed from high pressure cavity to low pressure cavity. This bypass can create very high temperature.