PDA

View Full Version : Ammonia basics







TF12
27-02-2014, 12:25 AM
Hey,
Got some basic questions about ammonia and how it differs from halocarbon refrigerant systems. I'm well aware of the toxicity and trapping of liquid ammonia between valves. I've been to 2 four day training courses strictly for ammonia use, but some questions linger.
For example if you need to isolate part of an ammonia chiller for repair lets say the compressor package. Do you can you just vent the ammonia? If so what are the best practices involved? Is there recovery equipment for industrial purposes or is that a waste of money? On a basic ammonia chiller like a Vilter with a thermo syphon evaporator setup and the levels in the evap are too high... Can you drain the ammonia by gravity or is that possible? If oil from the separator gets lost out in the chiller, will it come back with run time or does if have to be drained?
I have lots of exposure to industrial chillers using R-22, 123, 507, 404a etc.
I know 717 deserves respect
Any help appreciated.

RANGER1
27-02-2014, 11:11 AM
Hey,
Got some basic questions about ammonia and how it differs from halocarbon refrigerant systems. I'm well aware of the toxicity and trapping of liquid ammonia between valves. I've been to 2 four day training courses strictly for ammonia use, but some questions linger.
For example if you need to isolate part of an ammonia chiller for repair lets say the compressor package. Do you can you just vent the ammonia? If so what are the best practices involved? Is there recovery equipment for industrial purposes or is that a waste of money? On a basic ammonia chiller like a Vilter with a thermo syphon evaporator setup and the levels in the evap are too high... Can you drain the ammonia by gravity or is that possible? If oil from the separator gets lost out in the chiller, will it come back with run time or does if have to be drained?
I have lots of exposure to industrial chillers using R-22, 123, 507, 404a etc.
I know 717 deserves respect
Any help appreciated.

Venting a compressor depends on local laws, you can vent to air, in water,or use transfer unit. Some plants may have compressors running at lower pressure or vacuum. You could connect a suitable hose to transfer to the lower pressure.
If you do a lot of it, a transfer unit is not a waste of money.

Draining a surge drum by gravity can only happen if where you are draining to is equal or lower pressure, possible but unlikely.
Usually first close liquid make up to surge drum, then limit compressor capacity & very slowly reduce pressure, also restrict compressor suction stop valve.
If you have a suction trap or slop pot you may no need to restrict suction on compressor, but definitely find out reason for it, like leaking LLSV etc.

Oil does not return, you have to drain it from all low points at regular intervals like monthly etc

PaulZ
27-02-2014, 11:18 AM
Hi TF12
Ammonia loves water and over a long period of time loses some of it's volatility and will remain as a liquid even at atmospheric pressure. This is referred to as dead ammonia and it is in all old systems to varying degrees.
Ammonia does not need to be recovered, so when you need to work on a part of a system all you need to do is pump down and then the remaining ammonia can be blown down into water. If you are in a situation where there are no people this could be blown to atmosphere as ammonia is a naturally found gas and causes no harm to the environment. If the system cannot be run there are recovery systems but to my knowledge these have been purpose built by industrial refrigeration companies, there are probably commercially available units out there.
I am not sure what you mean by draining by gravity, are you referring to dead ammonia which will sit in low points after the system is pumped down and is usually drained out of the oil drains.
If you lose oil out of the compressor or separator it will not be returned to the compressor as it does not mix with ammonia and will settle out in vessels and heat exchangers and will have to be drained, this is the reason for oil drain valves on numerous parts of the system.
You have got the first rule right, always treat ammonia with respect.
There are many ammonia guys on this forum who may add to what I have said.
Paul

josef
27-02-2014, 08:43 PM
PaulZ hat bow before you, wonderfully written, you know what you're doing, you know what's there, you're one of not many people who know what is ammonia.
I appreciate that even such a man back is a help, advice-OK

RANGER1
27-02-2014, 08:47 PM
Paul, releasing ammonia into atmosphere & water is becoming increasingly difficult for us on a lot of job sites.

Releasing into surrounds, anyone gets a wiff & WH&S come running, people claim to get sick & go to hospital thinking they are going to die.
You still have to be very careful as people don't understand.
Releasing it into water is good, but you have to dispose of water, or above happens also.
In some cases we have to try to neutralize it or send it to Orica etc if there is a lot.
You could put the contaminated water in the waste oil someone will probably complain about that as well.

We seem to have to do a lot of this type of work on weekends,so we limit effecting anyone.

Years ago you would let it go to keep sticky noses away, those days appear nearly over.

josef
27-02-2014, 09:08 PM
Ranger1, Ok, ammonia does not destroy the climate is nature, I am with ammonia and opinion Paul, ammonia added to the soil, farmers, why be averted.

Grizzly
27-02-2014, 10:32 PM
Hi Josef.
There are 2 Ammonia recovery companies in the UK.
At least 1 I know sprays the recovered Ammonia on poor quality Hay / straw as the Nitrogen in the ammonia.
Apparently improves the quality of the resultant fodder.
It is also sprayed as you say in fields as Natures own Fertiliser!!

Grizzly

TF12
28-02-2014, 05:34 AM
Paul,
Thanks for the reply. I'm 27 and just getting into the industrial side of the industry. What I meant by gravity drain is in my scenario I have a VILTER VSM single screw serving a chiller in an air separation plant. As previously stated I'm a halo carbon veteran and in our systems the oil is miscible and returns with run time at a proper head. In low temp applications -25 C we have " oil distillers " and the oil eventually comes back. So to clarify gravity drain... I had a situation where the chiller got too cold and shut off for an extended time and the ammonia left the receiver and migrated to the evaporator. In the process the oil in separator seemed to leave as well. I disabled the high level float and unloaded the screw and closed the hand ex. Valve. I brought the ammonia back to level but the oil isn't coming back. So in regard to this issue I need to find the low sections of the system and drain the oil and add precisely what I recover back to the separator? And this is normal? Where can I go to get more training and exposure? My goal is industrial refrigeration but I'm stuck in the HVAC world. Any advise appreciated! Thanks again
P.s hope all that made sense..,

kiwi
28-02-2014, 07:13 AM
Hi TF12
over a long period of time loses some of it's volatility and will remain as a liquid even at atmospheric pressure. This is referred to as dead ammonia and it is in all old systems to varying degrees.

Please explain? I have yet to encounter such a thing. This is a degradation process?


the remaining ammonia can be blown down into water This adds a new problem as you now have a hazardous material to dispose of. Convenient yes, just ecotoxic if disposed of incorrectly.

Ammonia should never be considered thermodynamically any differently than any other refrigeration fluid. It is a heat transfer medium as are all refrigerants.

RANGER1
28-02-2014, 09:50 AM
Please explain? I have yet to encounter such a thing. This is a degradation process?

This adds a new problem as you now have a hazardous material to dispose of. Convenient yes, just ecotoxic if disposed of incorrectly.

Ammonia should never be considered thermodynamically any differently than any other refrigeration fluid. It is a heat transfer medium as are all refrigerants.

Kiwi, agree with you 100% of course mostly difficult to do the right thing.
Concentration of water/ammonia to high & it kills or burns everything for awhile.

Dead ammonia is found in systems that over the years draw in air & moisure. We purge air but not moisture
over time. Can end up in oil pots & drain out with the oil.
Or someone makes a mistake & adds water to system while purging into water.
Maybe you are referring to Paul's comment in a different way?

RANGER1
28-02-2014, 10:06 AM
Paul,
Thanks for the reply. I'm 27 and just getting into the industrial side of the industry. What I meant by gravity drain is in my scenario I have a VILTER VSM single screw serving a chiller in an air separation plant. As previously stated I'm a halo carbon veteran and in our systems the oil is miscible and returns with run time at a proper head. In low temp applications -25 C we have " oil distillers " and the oil eventually comes back. So to clarify gravity drain... I had a situation where the chiller got too cold and shut off for an extended time and the ammonia left the receiver and migrated to the evaporator. In the process the oil in separator seemed to leave as well. I disabled the high level float and unloaded the screw and closed the hand ex. Valve. I brought the ammonia back to level but the oil isn't coming back. So in regard to this issue I need to find the low sections of the system and drain the oil and add precisely what I recover back to the separator? And this is normal? Where can I go to get more training and exposure? My goal is industrial refrigeration but I'm stuck in the HVAC world. Any advise appreciated! Thanks again
P.s hope all that made sense..,

TF12 some systems do have an oil recovery system with ammonia.
Oil collects in oil drain pot or distiller's, then transferred back into compressor suction by either a small pump or hot gas pressure.
Believe all the oil will end up in evaporator surge vessel or whatever you have, & you will have to keep draining it
until you recover it all.
There is a special miscible oil for ammonia, but only works on DX systems I think. It's like brake fluid & takes paint off, or a least the one I've seen.

kiwi
28-02-2014, 08:30 PM
Kiwi, agree with you 100% of course mostly difficult to do the right thing.
Concentration of water/ammonia to high & it kills or burns everything for awhile.

Dead ammonia is found in systems that over the years draw in air & moisure. We purge air but not moisture
over time. Can end up in oil pots & drain out with the oil.
Or someone makes a mistake & adds water to system while purging into water.
Maybe you are referring to Paul's comment in a different way?
Now I follow. Not really "dead" ammonia, more its contaminants.
Water can be a funny thing in large plants trapping in some very confined sections, typically the coldest points but not always. Oil rectifiers can remove a fair amount of water if used correctly and are inhibited from boiling the water out (regulated heater). I had seen some modest water removal with the Hansen APP dual water/purger and I have seen good results with the older Stal/JCI WDO systems.

PaulZ
03-03-2014, 01:01 AM
Ranger
I agree that letting it go where people can smell it is a problem but I did say if there were no people around it could be blown to atmosphere and this would be a very small amount as the relevant part of the system would have been pumped down probably to less then 50 kpa. I don't disagree with any of what you have said and have experienced the going to hospital bit even when there is less then 50 ppm in the area. There are times when what I have said can be done without any problems but in a built up area those practices would lead to trouble.
Kiwi
Ranger has answered your question regarding "Dead Ammonia" for me.
I agree that the water with ammonia dissolved would be classed as a hazardous substance but it can be disposed of safely as any other hazardous substance can be.
TF12
If the oil is to be recovered make sure it is clean. Oil that is taken out of the system could be dirty because as it moves through the system it collect scale, dirt, carbon from burnt oil etc.
Unless you are going to put it through a filter I wouldn't put it back into the compressor.
You say the ammonia left the receiver, does the liquid line feeding the accumulator have a solenoid, if so it could be leaking. With the loss of oil out of the separator it sounds like there could be liquid coming back to the compressor or the coalescer elements are damaged if this is a constant problem.
Paul

passandscore
03-03-2014, 03:01 AM
Disposing of saturated ammonia water has become somewhat of a nuisance these days. Our company policy states:

Ammonia should not be discharged into occupied areas, or areas containing product
affected by ammonia. In the case of ammonia, discharge any vapour left into a container
of cold water, making sure that the discharge hose remains submerged at all times. Water
may have to be changed to absorb all the ammonia; about one gallon of fresh water is
needed for one pound of ammonia.

Did you notice that it does not talk about the disposal of the saturated water? Our company will not put that part in writing! They don't want to be liable if something goes wrong. So what do you do? I have found when dealing with only a couple of pails of saturated ammonia water that disposing of it inside the condenser water tank works well. Of course you must make sure that your tank has enough water to dilute the ammonia. Most tanks do! This technique allows you to dispose of the ammonia quite nicely. I have never had a problem. If I will be dealing with a lot of saturated water I will bring a large tank from the shop, do my thing and have a vac truck come to site and empty it. I see no alternative. It is costly but still cheaper than being fined for carelessness.

RANGER1
03-03-2014, 06:50 AM
Ranger
I agree that letting it go where people can smell it is a problem but I did say if there were no people around it could be blown to atmosphere and this would be a very small amount as the relevant part of the system would have been pumped down probably to less then 50 kpa. I don't disagree with any of what you have said and have experienced the going to hospital bit even when there is less then 50 ppm in the area. There are times when what I have said can be done without any problems but in a built up area those practices would lead to trouble.
Kiwi
Ranger has answered your question regarding "Dead Ammonia" for me.
I agree that the water with ammonia dissolved would be classed as a hazardous substance but it can be disposed of safely as any other hazardous substance can be.
TF12
If the oil is to be recovered make sure it is clean. Oil that is taken out of the system could be dirty because as it moves through the system it collect scale, dirt, carbon from burnt oil etc.
Unless you are going to put it through a filter I wouldn't put it back into the compressor.
You say the ammonia left the receiver, does the liquid line feeding the accumulator have a solenoid, if so it could be leaking. With the loss of oil out of the separator it sounds like there could be liquid coming back to the compressor or the coalescer elements are damaged if this is a constant problem.
Paul

Paul,
No worries it's getting a bit harder, as everyone wants to cover themselves these days, as P&S states with his management.
You probably have to be seen doing the right thing in a lot of cases with WMS JSA procedures etc.

PaulZ
03-03-2014, 09:24 PM
Ranger
Agree completely but there are ways to do things without anyone knowing if you are careful and don't rush things. Normally you can pump down most parts of a plant, the hardest is the condenser if only one.
A 20 litre bucket of water will absorb a lot of gas, as P&S said the condenser is another place but care has to be taken not to damage the galvanizing on the tubes. Another way is to put the hose in the air inlet of the condenser, what doesn't get absorbed by the water will get exhausted out but once again don't be in a rush.
Paul

passandscore
03-03-2014, 10:42 PM
Ranger
Agree completely but there are ways to do things without anyone knowing if you are careful and don't rush things. Normally you can pump down most parts of a plant, the hardest is the condenser if only one.
A 20 litre bucket of water will absorb a lot of gas, as P&S said the condenser is another place but care has to be taken not to damage the galvanizing on the tubes. Another way is to put the hose in the air inlet of the condenser, what doesn't get absorbed by the water will get exhausted out but once again don't be in a rush.
Paul

I agree completely

TF12
04-03-2014, 11:55 PM
The liquid line out of the receiver goes directly ( uphill) to the hand expansion valve. The chiller normally never shuts off but the plant was having issues at the time causing the chiller to get too cold and shut off. The NH3 migrated uphill to the chiller barrel. And caused a high level fault.
The superheated refrigerant vapor at the suction stop is 20-25 degrees above saturation so I don't think liquid is coming back or carry over is occurring.
The system does have an oil return system... Unless I'm confused so ill describe it. At the base of the chiller barrel ( not to be confused with the liquid inlet )
There is a drain leg much like a drip leg on gas piping. Out of the chiller barrel, into a hand expansion valve, stopped by an electromagnetic solenoid. When energized NH3 vapor expanded with oil goes directly into a Tee from the condenser and pushed into the suction line just before the stop valve. So therefore oil recovery. Anyone familiar or am I speaking nonsense.
Bottom line I have a separator that lost oil out to the chiller
I told the plant engineer with time and proper head psig the oil will return.

PaulZ
05-03-2014, 02:19 AM
Hi TF12
The best thing is to do a drawing or take a few photos that way there is no misunderstanding.
Paul

kiwi
05-03-2014, 06:43 AM
The liquid line out of the receiver goes directly ( uphill) to the hand expansion valve. The chiller normally never shuts off but the plant was having issues at the time causing the chiller to get too cold and shut off. The NH3 migrated uphill to the chiller barrel. And caused a high level fault.
The superheated refrigerant vapor at the suction stop is 20-25 degrees above saturation so I don't think liquid is coming back or carry over is occurring.
The system does have an oil return system... Unless I'm confused so ill describe it. At the base of the chiller barrel ( not to be confused with the liquid inlet )
There is a drain leg much like a drip leg on gas piping. Out of the chiller barrel, into a hand expansion valve, stopped by an electromagnetic solenoid. When energized NH3 vapor expanded with oil goes directly into a Tee from the condenser and pushed into the suction line just before the stop valve. So therefore oil recovery. Anyone familiar or am I speaking nonsense.
Bottom line I have a separator that lost oil out to the chiller
I told the plant engineer with time and proper head psig the oil will return.
What you describe sounds very much like a venturi oil return system.

TF12
06-03-2014, 12:46 AM
Kiwi
It is definitely a oil return system. So the oil should be coming back. I was looking at the startup info and the chiller was originally charged with 40 gallons of oil and at least 5 gallons has been removed during service, ie changing oil filters. So the oil level is below the lower sight glass and it has them stressing. If the oil in ammonia systems is heavier than NH3 than it will be at the lowest points of the system. So can you drain the oil/refrigerant into water as you mentioned above or if it is just oil drain until it isbe apparent when ammonia starts to vent?
Also important to mention when I found this chiller they had the modulating valve set to maintain 215 psig! Being ammonia an ideal head should be 150 for approx 85 saturation. The were operating with a condensing saturation around 105 with 100 condenser water temperature.
I suggested they adjust the set point of their modulating valve to maintain 150. I know that there is no chiller on earth that requires 110 degree operation to bring oil back...
Thoughts?
BTW dropped their amperage from 127 amps to 84

RANGER1
06-03-2014, 03:23 AM
I would say 95F or 35deg C is normal SCT.
Oil will go to low points & liquid start to come out when oil is finished.
Drain slowly taking all precautions, quick closing valve PPE etc.
Venturi using hot gas is type of oil recovery system.

kiwi
06-03-2014, 08:52 AM
Kiwi
It is definitely a oil return system. So the oil should be coming back. I was looking at the startup info and the chiller was originally charged with 40 gallons of oil and at least 5 gallons has been removed during service, ie changing oil filters. So the oil level is below the lower sight glass and it has them stressing. If the oil in ammonia systems is heavier than NH3 than it will be at the lowest points of the system. So can you drain the oil/refrigerant into water as you mentioned above or if it is just oil drain until it isbe apparent when ammonia starts to vent?
Also important to mention when I found this chiller they had the modulating valve set to maintain 215 psig! Being ammonia an ideal head should be 150 for approx 85 saturation. The were operating with a condensing saturation around 105 with 100 condenser water temperature.
I suggested they adjust the set point of their modulating valve to maintain 150. I know that there is no chiller on earth that requires 110 degree operation to bring oil back...
Thoughts?
BTW dropped their amperage from 127 amps to 84
You have me a bit lost there but I think I get what you're saying. The SCT was artificially high. Only thing is your cooling water is 100degF? How have you bought that down to achieve the 85degF SCT? I am useless with PSI and degF so could be reading it all wrong.
The oil return I would hope has a sight glass? This should help you diagnose if the oil is returning. The hot gas from the condenser and the oil return from the evaporator drop leg solenoid valves both need to be opened to create the venturi effect and recover oil. Often these want to be on a timer to terminate the oil recovery process. Once it has performed its function it is just a energy cost from there on. BTW what is the function of the system? Also be aware if you reduce your SCT you can have knock on effects with reduced pressure differentials across valves like you liquid make up etc.
Congrats on a 33% power consumption reduction too. This is what differentiates good service from the rest.

TF12
06-03-2014, 11:23 AM
It is an ammonia chiller. It is used in an air separation plant... Nitrogen, argon, oxygen, etc. what I meant by head pressure control is the machine is water cooled condenser and water cooled oil cooler. On chillers we use a modulating valve on the outlet side of the condenser to control water flow therefore control head pressure.
The cooling water was 100 degrees but after some convincing that this wasn't a halocarbon high pressure system they heeded my advise and changed the set point on the modulating water flow control.
Any way the chiller doesn't actually chill water, it has a barrel just like a chiller but is actually chilling air from the air compressors inside, from 70 degrees to about 35 ( 20C-0C approx?)
It pulls all the H20 out of the air
Pretty fascinating plant actually.
I did adjust the hand operated valve because the reduced head changes everything.
Please explain the differentials across liquid make up valves and what purpose they serve
The valve on this machine is ICK20-B (027H1262)
Oh yeah and should I add oil to the separator and then proceed to drain?
Can all this be done to a RUNNING system?

kiwi
06-03-2014, 08:56 PM
Its a great big air drier :D
I've seen a few similar just smaller for methane drying on refuse recovery systems.

Please explain the differentials across liquid make up valves and what purpose they serveThe differential pressure is the driver on every valve. The bigger the differential the greater the mass flow will be for a fixed port/orifice. Kv (or in your case Cv) values will determine valve selection based on differential pressure. With the reduction in discharge pressure the make up valve will now run on average a greater % open to maintain the same mas flow rate.

Oh yeah and should I add oil to the separator and then proceed to drain? Why are you adding oil? No point adding oil if your going to lose it again. Allow the oil return to recover what it can first and try to work out why it is getting there in the first place if it is carrying over in large quantities. There will always be some carry over hence the installation of the oil return. The oil separator may be at fault. Does it use coalescers?

Can all this be done to a RUNNING system? Yes. On a screw you can normally pump modest amounts into the compressor suction. I have very little experience with Vilters (mono or twin screw?) so somemone else may be able to pipe up.

TF12
07-03-2014, 03:40 AM
Kiwi,
Thanks for the continued interest.
We are adding oil on account of the fact that oil was lost during a plant malfunction. The air compressors supplying air (load) to this chiller repeatedly shut down during the plant startup. The result was an instant and drastic drop in suction pressure ( lowest I saw was 20 psig) and refrigerant migration to the evaporator. I think that when the suction dropped severely as it did it pushed oil out of the separator much like any screw does when you close the suction stop.
What I mean by that...
I have two 600 HP Frick compressors that have a tendency to shut down during low load conditions at another plant. At times the slide valve will not go back to below 30 %. So the only way I can get the compressor to start is to close the suction stop almost completely and slowly load the compressor by manually opening the suction stop. Anyway during these experiences I have noticed almost always the oil level in the separator drops. This is an R-22 unit with an automatic distiller and the oil always comes back.... With time
In regard to this ammonia VILTER machine (single screw) I think that the repeated starts and stops during the plant shut down and the associated low pressure condition caused the oil to be spat out the discharge line into the condenser, draining to the HPR and THAT is where I believe we will find the oil tomorrow.
Also the oil filters have been changed multiple times resulting in loss of oil but no make up has ever been added.
Furthermore the maintenance tech there says the level has always been in the lower sight glass about half way. The level should be much higher in the second glass half way or so.
Yes it has coalescers.
We intend to drain as much oil as possible from all the low points in the machine
Calculate what we recover
Recharge the separator based on these results.
Thoughts?

TF12
07-03-2014, 03:46 AM
Oh yeah could the high pressure this system was subjected to have damaged the coalescers?

kiwi
07-03-2014, 04:57 AM
Oh yeah could the high pressure this system was subjected to have damaged the coalescers?
No I doubt it. Check they have not come loose though.

PaulZ
08-03-2014, 09:43 AM
Hi TF12

[QUOTE]The air compressors supplying air (load) to this chiller repeatedly shut down during the plant startup. The result was an instant and drastic drop in suction pressure ( lowest I saw was 20 psig) and refrigerant migration to the evaporator. I think that when the suction dropped severely as it did it pushed oil out of the separator much like any screw does when you close the suction stop.

Does this system a have a discharge bypass valve or a false load valve that keeps the suction up when the load drops off. Most air driers have these valves fitted between the suction and discharge. If there is something like this it may no be opening or controlling properly and could be causing some of your problems.

Paul

TF12
10-03-2014, 09:52 AM
Paul,
It does have a hot gas bypass valve. It is working but what was happening was abnormal. Kinda like shutting off a blower across an evaporator, or turning off a chilled water pump while the chiller is running etc.
Just to let you guys know.
I went up there last Thursday and worked on it on Friday. The oil level was just barely below the second sight glass. We drained oil from all the lowest points in the chiller and came up with maybe 2 gallons of oil total. Most of it was in the sight glass column for the evaporator! I suppose this was giving us a false read on where the evap level was and perhaps duping the level control.
Anyway I adjusted the HXV to match the load we put about 6 gallons R717 oil in and it's running nice. In the future I'll be checking for oil in the low places. But the system does have an oil recovery system.
HEY! THANKS FOR ALL THE INPUT AND ADVICE,

MazlanZ
27-03-2014, 06:48 AM
Agree,,,,,,

Depend on capacity of NH3 capacity/volume, we also operate & maintained the ammonia refrigeration system which having about 5,000 Kg in the system.

If the volume is small, usually we dilute with air by tube /pipe it to the air suction of the condensor fans. If the volume is big, we will transfer those liquid to the skid tank or any vessels within the systems.


we are not rich enough to have the portable pump for pumping the ammonia,,,,,, we will use gravity flow tranfer or differential pressure tranfer.


mz


Venting a compressor depends on local laws, you can vent to air, in water,or use transfer unit. Some plants may have compressors running at lower pressure or vacuum. You could connect a suitable hose to transfer to the lower pressure.
If you do a lot of it, a transfer unit is not a waste of money.

Draining a surge drum by gravity can only happen if where you are draining to is equal or lower pressure, possible but unlikely.
Usually first close liquid make up to surge drum, then limit compressor capacity & very slowly reduce pressure, also restrict compressor suction stop valve.
If you have a suction trap or slop pot you may no need to restrict suction on compressor, but definitely find out reason for it, like leaking LLSV etc.

Oil does not return, you have to drain it from all low points at regular intervals like monthly etc

RANGER1
27-03-2014, 07:39 AM
Agree,,,,,,

Depend on capacity of NH3 capacity/volume, we also operate & maintained the ammonia refrigeration system which having about 5,000 Kg in the system.

If the volume is small, usually we dilute with air by tube /pipe it to the air suction of the condensor fans. If the volume is big, we will transfer those liquid to the skid tank or any vessels within the systems.


we are not rich enough to have the portable pump for pumping the ammonia,,,,,, we will use gravity flow tranfer or differential pressure tranfer.


mz

I don't think you have to be rich for one of these.
I would suggest less than US$1000 excluding labour.
Compressor $300, motor $200, HP switch $100, belt, pulley, guard & base $200.

RANGER1
27-03-2014, 07:46 AM
Interesting to me how a number people post that screw oil separators throw over oil under certain loads.
Can't say I have experienced it!
Not with coalescer type separators anyway.
Usually related to mass flow rate if anything, so unless tightly engineered why would they throw
over oil unless undersized or no margin for slightly varying system pressure fluctuations.

Grizzly
27-03-2014, 05:30 PM
Interesting to me how a number people post that screw oil separators throw over oil under certain loads.
Can't say I have experienced it!
Not with coalescer type separators anyway.
Usually related to mass flow rate if anything, so unless tightly engineered why would they throw
over oil unless undersized or no margin for slightly varying system pressure fluctuations.

Hi ranger.
They throw over oil when the load goes through the roof, not when operating normally.
For instance, I have a chilled water system with a remote plantroom.
Which when there is say a power failure or blip and the ops staff / engineers don't notice quickly enough.
The return water instead of being around 6c can be in the 20's.
So upon start-up, unless manually trimmed the load of the compressor can ramp up so fast.
That the gas flows are higher than the coalescer can cope and huge amounts of oil is blown through the system.
One system with a large vsd driven screw we added an external coalescer and changed the oil to a fully synthetic type rather than part synthetic.
Which made a big difference.
Grizzly

manishtambat
27-03-2014, 05:40 PM
I want to know that , What is the H.P. of motor required to run the Kirloskar KCX-2 compressor with Ammonia Gas, to run between 6 to 35 degree celsious temperature range.

RANGER1
27-03-2014, 07:49 PM
Hi ranger.
They throw over oil when the load goes through the roof, not when operating normally.
For instance, I have a chilled water system with a remote plantroom.
Which when there is say a power failure or blip and the ops staff / engineers don't notice quickly enough.
The return water instead of being around 6c can be in the 20's.
So upon start-up, unless manually trimmed the load of the compressor can ramp up so fast.
That the gas flows are higher than the coalescer can cope and huge amounts of oil is blown through the system.
One system with a large vsd driven screw we added an external coalescer and changed the oil to a fully synthetic type rather than part synthetic.
Which made a big difference.
Grizzly

Thanks Grizzly, still an uncommon scenario to me even under those conditions.
We must be doing something different with our design, or sizing of oil separators.
We use vertical separators 99% of the time which are a lot better to work on no matter
what anyone says.
The only situation that comes to hand is a dual duty machine that predominantly works
on high side operation & has a separator sized for that duty.
If you run as booster, expect a bit of oil carry over due to increased flow rate.
Booster duty oil separator is approx 40% bigger.

We installed a system with 4 Howden WRV3212.2 screws on water chiller duty & each oil separator
has over 20 coalescers 9" diameter x 42" in each one, maybe that tells a story in itself, by keeping velocity down through filters (high spec job).

Maybe I'm dreaming?

Grizzly
27-03-2014, 09:00 PM
Thanks Grizzly, still an uncommon scenario to me even under those conditions.
We must be doing something different with our design, or sizing of oil separators.
We use vertical separators 99% of the time which are a lot better to work on no matter
what anyone says.
The only situation that comes to hand is a dual duty machine that predominantly works
on high side operation & has a separator sized for that duty.
If you run as booster, expect a bit of oil carry over due to increased flow rate.
Booster duty oil separator is approx 40% bigger.

We installed a system with 4 Howden WRV3212.2 screws on water chiller duty & each oil separator
has over 20 coalescers 9" diameter x 42" in each one, maybe that tells a story in itself, by keeping velocity down through filters (high spec job).

Maybe I'm dreaming?

Not dreaming. Just know what you are doing and allowed to show it!
The one I was referring to was sized for 1 megawatt of cooling 24/7 and 3.3 total.
Not for the end result which was a third of design a third of the time.

As you say sized and designed correctly there is no drama!
Sadly not always the case1
Grizzly

sandybapat
11-06-2014, 07:34 AM
"On capacity reduction oil carryover from screw compressor unit is more" - problem stated by TF12. I was just thinking why it should happen, since the discharge gas flow rate will reduce and oil separation efficiency of Coalescing filter will improve and oil carry over will be less. However on systems with out oil pump where the oil is circulated by differential pressure, when suction pressure lowers the oil flow to compressor may increase and the discharge gas will be having higher oil content which coalescing filter may not be able to cope up. Especially when the suction pressure drops suddenly. Am I thinking correctly? expect comments from experts.

Superfridge
14-06-2014, 10:55 PM
Interesting to me how a number people post that screw oil separators throw over oil under certain loads.
Can't say I have experienced it!
Not with coalescer type separators anyway.
Usually related to mass flow rate if anything, so unless tightly engineered why would they throw
over oil unless undersized or no margin for slightly varying system pressure fluctuations.

I have delt with oil chuckers all my industrial life.
Maybe the design engineers need to go back to school or the market is too small and to get jobs they down size equipment. Oil problems have kept us busy over the years.........maybe that the whole idea?

RANGER1
14-06-2014, 11:22 PM
I have delt with oil chuckers all my industrial life.
Maybe the design engineers need to go back to school or the market is too small and to get jobs they down size equipment. Oil problems have kept us busy over the years.........maybe that the whole idea?

If it can get past warranty period I guess good luck.
A lot of major suppliers talk 10-15ppm which is bugger all. You would forget to check oil levels like modern cars.

You would only have to have 1 incident under warranty & proper design might be paid for.
Cost of oil to top up & more than likely synthetic oil, labour to possibly check coalescers to see if OK, drain excess oil from plant & hopefully it didn't upset the system as well.
If your real lucky plant is in town, not in a remote location.

Old type with no coalescers, yes throw over lots of oil.

Like you say keeps us in a job

Magoo
15-06-2014, 01:29 AM
I have delt with oil chuckers all my industrial life.
Maybe the design engineers need to go back to school or the market is too small and to get jobs they down size equipment. Oil problems have kept us busy over the years.........maybe that the whole idea?
If design engineers designed the perfect plant to cover all possibilities they would go broke. So design to a specific load profile that generally is lost with time . Load rates etc.,

RANGER1
15-06-2014, 04:06 AM
If design engineers designed the perfect plant to cover all possibilities they would go broke. So design to a specific load profile that generally is lost with time . Load rates etc.,

So that's why we were broke for awhile!
I think being competitive with oppositions can cut things to the bone if you want the job.
A lot of the time people put in what they know works as well, so you aren't re-inventing the wheel on each job.

RANGER1
15-06-2014, 07:57 AM
Magoo, we had a Kiwi consultant on a job years ago, he wanted 3 independent control systems on each screw compressor.
He was a hobby pilot who decided to bring the plant up to aeronautical standards.
If one system failed 1 of the other 2 were switched on.
Nightmare to commission apparently.
I heard he is not around anymore (passed away).
When he opened up his jacket to my amazement was full of tools, all sorts of pockets with
everything you could think of.

We then on the other hand have clients who would bypass safeties to get it going, or remove a filter that kept blocking up, remove high level float switch & forget to put it back on.

Grizzly
15-06-2014, 02:17 PM
Hi Ranger

we had a Kiwi consultant on a job years ago, he wanted 3 independent control systems on each screw compressor.
The above describes a Unisab II or III in auto, or working together they are in remote!
I would think Other controllers are similar?
Sorry my friend I just reread your post correctly this time.
Ignore the above.
Grizzly

Magoo
15-06-2014, 10:46 PM
Magoo, we had a Kiwi consultant on a job years ago, he wanted 3 independent control systems on each screw compressor.
He was a hobby pilot who decided to bring the plant up to aeronautical standards.
If one system failed 1 of the other 2 were switched on.
Nightmare to commission apparently.
I heard he is not around anymore (passed away).
When he opened up his jacket to my amazement was full of tools, all sorts of pockets with
everything you could think of.

We then on the other hand have clients who would bypass safeties to get it going, or remove a filter that kept blocking up, remove high level float switch & forget to put it back on.

Hi Ranger1, yes I knew the chap well, a definite character, brilliant guy though. Sadly died from a heart condition.

Superfridge
16-06-2014, 05:24 AM
If design engineers designed the perfect plant to cover all possibilities they would go broke. So design to a specific load profile that generally is lost with time . Load rates etc.,
Agreed but also installing problematic plant is also a good way to go broke. The saving grace is that the only one's who know the issues are us. Shhhhhhhhhhh mum's the word.

I didn't get to meet A.M but I have see a few of his projects and they did not chuck oil!!!!!

Segei
18-06-2014, 04:51 PM
Coalescent filters designed to work well in certain rage of the gas velocity. If for some reason, velocity is not in designed range, oil carry over will occur. Sometimes it can be mistake of the designer. Sometimes manufacturer to save money put undersized oil separator. Recently, talked to fried of mine. He mentioned that customer doesn't want to pay additional 5% to get over sized oil separator to operate plant at 100 psig head pressure. Probably, several years later this customer will start thinking about energy savings and he should invest in new over sized oil separator to reduce condensing pressure. Sometimes operators try to save energy increase suction pressure and reduce cond. pressure. Yes, it saves energy but at certain point oil carry over can occur.

RANGER1
18-06-2014, 08:44 PM
Coalescent filters designed to work well in certain rage of the gas velocity. If for some reason, velocity is not in designed range, oil carry over will occur. Sometimes it can be mistake of the designer. Sometimes manufacturer to save money put undersized oil separator. Recently, talked to fried of mine. He mentioned that customer doesn't want to pay additional 5% to get over sized oil separator to operate plant at 100 psig head pressure. Probably, several years later this customer will start thinking about energy savings and he should invest in new over sized oil separator to reduce condensing pressure. Sometimes operators try to save energy increase suction pressure and reduce cond. pressure. Yes, it saves energy but at certain point oil carry over can occur.

Compressor electric motors can also be undersized by many.
We usually size for slightly extreme circumstances (summer hottest day), as well as a bit of pull down if rooms turned on etc & pressures up/down a bit. Same scenario with oil separators, possible varying loads catered for.
When controls improved say 30years ago marginal motors installed, as could unload on amps, also cheaper motor.
Unfortunately the days you need these motors they are backing off on amps reducing plants capacity.

Tycho
29-08-2014, 11:06 PM
oy vey, oy vey :) so many things to grab onto

Gonna start somewhere in the middle here :)

TF12 said (before you guys started arguing in between yourself), that oil was lost into the system when the compressor shut down on an alarm.

I know many/all of you hate having a PM valve on the discharge on a compressor because it reduces capacity slightly. however, imagine having a screw compressor running on 100% load suction pressure is at -0,3 bar, discharge pressure is at 10 bar, pressure in the oil seperator is 10 bar, condensing pressure is at 6 bar... the compressor shuts down on an alarm and stops, there is no PM valve or anything to keep the pressure in the oil separator. the pressure drops like crazy and causes the oil to boil/foam up like crazy and it goes the shortest way which is out the discharge valve and into the condenser, poooof, it's like shaking a bottle of coke and unscrew the cap as fast as you can.

another reason for loosing oil could be a faulty suction non return valve, again in an "alarm stop" condition, the compressor is directly connected to the oil reservoir, so if the non return valve on the suction fails to close, you will loose A LOT of oil.

I spent three days on a system with a frequency drive trying to figure out why the oil left the system, the coalescer filters were new, I barely had any return in the coalescer-suction return, but every time the system stopped I lost a bucket of oil...

I was so focused on the fact that the compressor didn't spin the wrong way when stopping that I didn't even consider the oil to be leaving through the suction.

Thing is, this compressor was on a frequency drive, and at 20hz or so, a twin screw looses it's compression... the non return valve on the suction was broken and stayed open.
the second thing was that the frequency drive powered the motor all the way down to 5 hz before it released it to free coast so I never saw and "spinning the wrong way" because the motor was powering down and at 5 hz there wasn't enough pressure difference to spool the compressor the wrong way.

Oil return on ammonia systems... I know a few companies that do it, and they have had to incorporate a few extra filters, a mesh filter and an extra oil filter on the return line that need to be changed every time the solenoid for the oil return has been opened, timers, temperature sensors on the oil pots out on the system, hotgas and yadda yadda yadda. if you have a properly functioning system with a coalescer section on the oil separator that is dimensioned properly there will be so little oil carryover that it is cost efficient to drain the dirty oil and replace it with new oil. I personally just don't see it being feasible to have an oil return on a ammonia system, there are just to many contaminants, especially moisture, since most freezing systems run on vacuum.

Dead ammonia, I like that term because it's so fitting...
Dead Ammonia is a problem in all systems that run on vacuum, the air purger removes non condensables that enter the system through leaking shaft seals or other places on the system which are at negative pressure.
The moisture that comes along with those non condensable gasses however are left in there and will over time turn the ammonia into a very corrosive liquid and also remove most of it's refrigerating properties, or turn your ammonia charge into a household cleaning liquid :)
There are however remedies, because you can re-purify your ammonia charge and remove the water, oil and moisture and turn your ammonia charge from a detergent and back into a refrigerant :)

It's called an ammonia purifier, it's a tank with a heating coil, and you feed it from the LP side, a level switch feeds the ammonia side with LP ammonia until a temperature sensor on the heating side says that the in-out difference is too small and that we need to drain the crap :)
My company tested our prototype on a system at a local fish factory, we made a deal with them that if we could test our equipment on their site we would give them a service contract for a year (we would go on site once a week and log the condition of the system and make sure everything was OK for further operation)
So we connected our gear to the system and after 1 week of trial operation we drained 7 liters of water from our contraption (1.8 gallons) and some oil.
Needless to say, 3 years later we still have them as a once a week client to check the condition of their plant.
we have sold 2 units to Russia, and we have 3 units in operation on Norwegian vessels, and one unit in Peru that is used to decontaminate a system that suffered damage during some earthquake, with great success

Releasing ammonia into the "wild"
In Norway the law states that we can freely release gaseous ammonia as long as it does not cause any discomfort to anyone, too me, this means "check the wind direction" before releasing any ammonia :)
However, we all know that ammonia is hard to boil off so releasing it in gas form may take you 12 hours holding the end of a hose on top of a roof, minding the wind direction while you have some poor guy with propane torch or electric heater pointed at the pipe downstairs.
I always choose to purge in liquid form if I can, I have a ball valve attached to the end of my hose, and a 2 meter pipe (6feet) attached after the ball valve, so I can purge liquid and see which way the white gas cloud moves :)
Also, I am also mindful of my surroundings before purging ammonia, my co workers tell me I am paranoid, but I have no intention of shutting down production or causing a ruckus, and in 19 years I still haven't, so there, jokes on them :))

10 years ago, it was perfectly normal to drop the hose overboard, or over the edge of the quay, because the ammonia would be absorbed by water.... YOU SHOULD HOWEVER ALWAYS HAVE A NON RETURN VALVE at the end of your hose before you drop it into water. You may have worked on refrigeration systems for 200 years, but you never know at which pressure ammonia decides to reverse flow and suck the system full of water.

12 year ago, when we had to purge an ammonia system, we would hook a 0.1 bar non return valve on our hose, chuck it overboard into the sea and purge liquid as if there was no tomorrow, the collapsing ammonia would resound throughout the ship *BOM BOM BOM* like depth charges. the first time I heard it I thought something was breaking. The water around the ship would turn milky white and nobody cared.

Then a service technician from a world known company that has a name that ends with eknotherm, purged a piston compressor into a bucket of water, when he was done with the job on the piston compressor he poured that bucket of water into a drain... **** luck, that drain lead straight into a river, turned out it was a salmon river that the rich people used to fish in... Lot's of fish died and floated down to the rich people who ended up catching dead fish (not like the fish could have survived much longer if they had been caught alive) jokes aside :)
Some agency located the source as that place, and later did a Sherlock Holmes and found that when this guy poured out the ammonia contaminated water into the drain he almost killed off some fish

in the end, the service technician was fined X amount and the company xcnotherm was fined 500.000 nok.
After that, releasing ammonia into water became a no go for us.
I must admit that it was all much easier when you could just drop the hose over the side of the ship, make sure it was about 3 feet under the surface, then open the valve and go to town. (less than 3 feet and in might blow back to the surface and go crazy hose :))

Tycho
29-08-2014, 11:21 PM
Coalescent filters designed to work well in certain rage of the gas velocity. If for some reason, velocity is not in designed range, oil carry over will occur. Sometimes it can be mistake of the designer. Sometimes manufacturer to save money put undersized oil separator. Recently, talked to fried of mine. He mentioned that customer doesn't want to pay additional 5% to get over sized oil separator to operate plant at 100 psig head pressure. Probably, several years later this customer will start thinking about energy savings and he should invest in new over sized oil separator to reduce condensing pressure. Sometimes operators try to save energy increase suction pressure and reduce cond. pressure. Yes, it saves energy but at certain point oil carry over can occur.

We use SES (from holland) as our compressor package manufacturers, and they use the same size oil separator for a howden XRV 127 as they do for a howden XRV 204 for ease of manufacturing, the only difference is the amount of coalescer filters, on a XRV 127 unit there are 4 filters and on a XRV 204 there are 7 filters.

on our RSW systems on various compressors we have found that oil carryover is little to none existent.
both units are charged with 110 liters of oil, manual says 120 liter, at 110 liter it is middle of the higher glass, any more than that is just a waste.
so... the primary charge is 110 liters of oil, the machinist asks me when he should fill oil. I tell them "keep a log of how much you drain, and refill as much as you drain, however, if you drain oil and the level is still above the bottom sight glass, don't fill. once the level drops below the top of the bottom sightglass, fill oil to the bottom of the top sightglass.