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marthe1994
16-02-2015, 05:19 PM
I have an ammonia plant, with 5 screws and 2 pistons. I have 4 recievertanks, one priority tank, 5 freezingtunnels, and one big freezingroom. I now and then fill oil on compressors. And now and then I take the oil out of the plant. But I fill more oil then I take off. Where can it be? I take oil from under the prioritytank, and I have an oilboiler also. But still I fill up more then I take off. Suggestions?

Tycho
16-02-2015, 06:17 PM
I don't know how old your system is or how long you have been operating it (no offense, just my observation)

Depending on the layout of your system, and how it is run (defrosts and freezing cycles), there will always be X amount of oil trapped somewhere out in your system.

Let's say that it's a new system that has been running for 1 year.

the service technician that commissioned the plant filled up all compressors to the correct amount of oil.
after 2 months of running, the piston compressors were getting low oil level so you recharge the amount needed to bring them back up to the "max" mark on the sight glass.

and that amount was 20 liters, however when you drain oil from all the drain points you only end up with 10 liters in your bucket, and you start wondering where did the rest go?

the rest of the oil is clinging to the inside of the pipes, tanks and evaporators, or it is trapped in dips or oiltraps in the piping, and because of the flow of ammonia through the pipes, a certain amount of oil needs to be trapped in those places before the refrigerant flow is restricted enough for it to start pulling excess oil back to the drain points on the LP side of the system (I'm assuming liquid overfeed/pump circulation).

Depending on the construction and size of the pilot tank, a small amount will get trapped here, usually the oil collection point on these are not very big. I have seen pilot tanks that have a capacity of 3000 liters and the oil sump has a capacity of maybe 10-20 liters.

Depending on what the priority tank supplies, if it is for LRI discharge gas and oil cooling on the screw compressors, the oil lost from the piston compressors might get returned to the screws, and you may notice that some compressors have a higher oil consumption than others. I don't know the brand of the piston and screw compressors, but I would expect the piston compressors to have a higher oil consumption than the screw compressors :)

Also, if it's a york system with thermosyphon oil cooling (self circulating), there is bound to be oil collecting in the refrigerant side of the oil cooler (on one system I drained over 200 liters of oil from one of these... multiple times... )


I try to instill in machinists to keep a ledger of how much oil they put in and how much oil they take out, but I get the feeling that you have been doing this and have noticed that you put in more than you take out (which is good, not your oil problem, but that you actually noticed it :))


I just read your other posts, and I'm going to say Tranvaag, if that is correct, then I was the one who did the oil and filter change on your Howden compressor a short while back :)


If the above is correct, then I have a tip for you and everyone else running a Howden WRV 255 with a vertical oil separator from SES.
I have learned, painfully, over many trials, and with the good help of onsite engineers, that these oil separators are very sensitive to the amount of oil filled, and that as long as you don't have any oil level alarm you should not fill any oil.

We have one system where we have maybe 1-2 cm of oil level in the sight glass before the oil pump starts, and the on site engineer told me, that if he had a higher level than that, the machine would chuck all the oil into the system in a few minutes of running.
I didn't believe him, and he was gracious to let me try it out, so I filled another 20 liter into the system (another 1 cm on the sight glass) and 15 minutes after the start we got an low oil level warning.

RANGER1
16-02-2015, 08:26 PM
I have an ammonia plant, with 5 screws and 2 pistons. I have 4 recievertanks, one priority tank, 5 freezingtunnels, and one big freezingroom. I now and then fill oil on compressors. And now and then I take the oil out of the plant. But I fill more oil then I take off. Where can it be? I take oil from under the prioritytank, and I have an oilboiler also. But still I fill up more then I take off. Suggestions?

You say now & then you drain oil, maybe more regular draining as oil might be a bit slow to flow & you don't get it all out.
Also drain slowly, as if to fast can also cause less amount drained.

Grizzly
16-02-2015, 09:34 PM
Hi Marthe1994.
Yours is a very open ended question.
Meaning without knowing or seeing your system it's just guesswork.
However the basics are the oil will migrate around a system and will collect where the oil is the coldest and thickest.
That normally means the evaporators. plate packs or Bordello Towers. Which inevitably means that unless you have a production shutdown of long enough duration. A lot of oil is going to stay suspended within the plant or trapped in the low temp side.
If the Oil amounts added to the system continue to grow and the amounts removed are less. Then you need to plan a system shutdown. Where you can either using your defrost system cook the evaps or allow the low side to warm up.

Once the natural trapping points have been warmed, you then need to drain the oil!
Again system design will dictate how you achieve this?
The type of oil is also highly relevant.

Yours is a Basic question and proper oil level logging as Tyco suggests is fundamental. If not addressed to much Oil has a huge effect upon system efficiency. Not to mention loosing correct control of the refrigerant levels within the system.

It sounds like you need Tyco or at least someone like him. (Or a Ranger, Might be a bit too cold for him though?)
Good Luck and please keep us posted.
Grizzly

Tycho
16-02-2015, 10:38 PM
Marthe1994, hvis du har et spørsmål, uansett hvor lite eller rart det virker, så kan du slå på tråden på mobil: ni elleve trettitre to nittito, så skal jeg gi deg et svar så godt jeg kan eller vi kan avtale at noen kommer innom dersom du ønsker det :) :)

marthe1994
17-02-2015, 08:17 AM
Tranvåg er korrekt :)

Grizzly
17-02-2015, 05:52 PM
Marthe1994, hvis du har et spørsmål, uansett hvor lite eller rart det virker, så kan du slå på tråden på mobil: ni elleve trettitre to nittito, så skal jeg gi deg et svar så godt jeg kan eller vi kan avtale at noen kommer innom dersom du ønsker det :) :)

Tranvåg er korrekt :)

Care to enlighten Guys?
Grizzly

Magoo
18-02-2015, 04:13 AM
Good point Grizzly.
Tycho is this your first training exercise ?, care to enlighten the rest of the world please.

RANGER1
18-02-2015, 07:14 AM
[QUOTE = Tycho; 304892] Marthe1994, if you have a question, no matter how small or odd it seems, so you can turn on the thread on mobile: nine eleven thirty two ninety-two, and I'll give you an answer as best I can or we can agree that some come back if you want it [/ QUOTE]:) :)


This may be the translation, we will see if Tyco agrees.

RANGER1
18-02-2015, 07:16 AM
[QUOTE = marthe1994; 304905] Tranvåg is correct :)[/ QUOTE]

mikeref
18-02-2015, 07:30 AM
I had the same rough translation. Ranger 1. Tycho should have chosen to PM his fellow Norwegian.

marthe1994
18-02-2015, 10:16 AM
Sorry about the norwegian writing between me and Tycho. Won`t happen again.

Grizzly
18-02-2015, 04:15 PM
Sorry about the norwegian writing between me and Tycho. Won`t happen again.

Marthe.
Nothing to say sorry about.
It's just that I not speaking Norwegian wondered if I had missed something important to do with your post!

Still keen to hear how you get on though!
Grizzly

Tycho
18-02-2015, 04:17 PM
Yeah, sorry about the Norwegian, He didn't have enough posts to be allowed to receive PM's :)
and I figured out that we have crossed paths before and told him that I'm available for phone support if he has small or large questions :)

I saw you called yesterday and I tried to call back but it's a land line and I guess you don't spend your time in the office :D

I'll be driving to misund tomorrow, so I'll be available 8-10 :)