Oil Seperator

[jwasir]

What kind of oil seperator is recomended for ultra low temp application?

Is coalescent better than centrifugal?

[icecube51]

how low will you go??

Ice

[jwasir]

Suction will go down to -90F and discharge +95F!

[icecube51]

i can be wrong ,but in my opinion at those themperatures is better to have centrifugal, law of viscosity....

Ice

[Grizzly]

i can be wrong ,but in my opinion at those themperatures is better to have centrifugal, law of viscosity....

Ice

Ice.
Please be gentle with me as I am only a Thick Engineer.
But how does a centrifugal oil separator work on a fridge system.
As I have never seen one and am intrigued as to what sort of kit would have one?
Cheers Grizzly

[Sturt]

Hi Jwasir

I think the helical type is best over impingement for low temperature application.

Selection is crucial to ensure the best gas velocity ensuring the oil seperates by centrifugal force to the out side of the seperator wall and drains down.

Some form of discharge gas temperature regulation is beneficial otherwise the oil will become excessively thin and may carbonise.

Sturt.

[icecube51]

sorry grizzly, only had it from hearing. a technician that works in a factory were they use NH³ in very low temperatures,told me they had problems whit the old oil separator and they now switch to centrifugal and they have much better results. i asks him if i could have a look,but they don't allow strangers. security reasons. so don't shoot me if the info is not correct. it seems logic to me.
there are so many possibility's, we can not now them all.

Ice

[US Iceman]

I think it would be difficult to compare or make judgments on these two types of separators. Most of the industrial applications I have seen all use coalescing filters. These are designed for very small oil particles (micron sized).

I think these would work much better than a centrifugal separator where you are trying to remove the larger quantity of oil.

After you remove the large droplets you still have to remove the fine mist aerosols. A suitably designed oil separator using coalescing filters should do just that.

[Grizzly]

Icecube..
No Problem.. we are all here to learn or help, or both!
Iceman.
Thanks for the informative and logical as usual.
Sturt.
I assume "helical" refers to a conventional oil sep?
these surely are the most common?
Grizzly

[Sturt]

Morning gents

Grizzly - Yes I would say the helical type is most commonly used. On recips anyway. The cost and size of coalescing filters and the relatively small volumes of oil from a recip would not make fitting them viable.

Coalescing filters from my understanding are purely for screw compressors because of the large volume of oil in the discharge line that needs to be removed. The oil is used for sealing, lubrication and cooling of the compressor and this is mostly rejected.

Traditional "helcal" type of seperation by centrifugal force is more than adequate for recips.

This is why I enjoy the forum/industry there is never a completely simple answer because of the many variables in plant and application.

Sorry to mention points that you all probaly know but i tend to waffle when i get going.

Sturt.

[US Iceman]

Coalescing filters from my understanding are purely for screw compressors because of the large volume of oil in the discharge line that needs to be removed.


The majority of the oil is removed/separated from the gas stream in the primary section of the separator. Let's call this the liquid part.

Even though a majority of the liquid oil is removed, the gas stream still contains a larger percentage of mist/aerosols. That is what the coalescing filters remove.

You do not want the coalescing filters to be subjected to larger volumes of liquid oil because they will flood out. What this means is; the elements become saturated with liquid oil which is then sheared off and re-entrained back into the gas stream. Not good...

[keepitcool]

I use coalescing filter on recips quite often. A recip can throw a lot of oil out to the plant. If they are taken care on the filters will last for quite a while.