Oil Deaeration

[HensonJM]

I am mostly just looking for some good ideas on how to remove entrained air from oil while filling a bearing assembly.

The application is downhole oilfield tools.

Currently tools are filled with three different types of oil. Their viscosities range from 46-460 cSt @ 40 degrees celsius.

During the fill procedure, oil is pumped out of a barrel into a port on one end of the housing. The oil fills the housing and flows back out of the return line and back into the barrel. The pump used is just a standard pneumatic transfer pump. Currently oil is circulated for about tenty minutes through the housing. While one end of the assmebly itself is raised and lowered. All in an attempt to remove air.

Pressure during the fill is low for most of the procedure but at one point the return line is closed and the bearing assembly is pressured to approximately 80 psi to set a floating piston that seals the bearing assembly at one end.

I have seen some inline deaeration devices for fuel oil but the pressure ratings are too low and I am not sure how the increase in viscosity would affect their function. It would be possible to bypass the dearator for the piston setting then circulate at low pressure after.

Any suggestions would be appreciated. Thanks

 

[BigInch]

The mental diagram I'm getting is a bit on the foggy side, so I may not have a realistic idea about what needs to be done, but what I think you need to do is vent that air somehow before circulating, preferably at one or more high points, rotating as necessary. A vent(s), perhaps a valve, or a hex head bull plug, or something similar, while the tool is held in a position such that oil is injected low forcing air high and out, turning at times as needed. Recirculation may be contributing to the problem. If you emulse, its too late.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[HensonJM]

That is basically the scenario right now. Imagine an annular space sealed on both ends. Oil enters near the bottom on one end and flows out at the high side of the space on the opposite end.

I am more concerned with the air that is entrained as bubbles within the oil itself.

 

[maytag]

If this is a big enough problem you could set your lube system up like a hydraulic tank-i.e. clean side for the pump with a baffle seperating a dirty (return) side-resident time in the tank helps with the air release.
also you did not mention about how your return line is routed-make sure it is terminated below the lowest fluid level. Hopefully I've understood your post and maybe this will help. If you need more details your can email me

twilson@nucor-yamato.com

Tom

 

[BigInch]

The best way to get air out is to not let it in. Or do nothing; let it sit as still as possible for as long as possible (as maytag mentioned with the resident time in one side of the tank), or moving very slowly, until its separated.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[HensonJM]

Letting it sit isn't really an option turn around on the tools is pretty quick. Using a dedicated reservoir might be an option to consider.

We have a vacuum pump that someone bought for R&D but no one used I might try that.

 

[BigInch]

I honestly didn't really figure it was a real option, but maybe something like a quick change reservoir? Is that what you mean by dedicated reservoir?

Be careful with vacuums, what's the oil temp?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[HensonJM]

The temp is ambient, about 15 - 20 degrees C. Its in a shop.

Currently the oil that is used is in a barrel. We have wheeled carts that the barrels are placed on. The transfer pump is then setup through the standard bung on top of the barrel. The return line is then setup through the other bung.

With this setup maybe a tank like Maytag suggested built into the cart might be a good idea. The volume of oil going into most of these tools isn't that large. They are sealed bearing assemblies for mud motors.

I had seen some in-line deaeration devices so I was curious about them since they aren't something I have ever seen before.

 

[hydtools]

Here is an article about a device to remove air from oil.

http://www.machinerylubrication.com/article_detail.asp?articleid=373

I don't know if it is available on the market. A short search found nothing.

Ted

 

[HensonJM]

Thanks Ted. I did a bit of searching. The company that makes the unit is from Japan they are called Opus System

http://www.opussystem.com/

Web site isn't too bad and they have a catalogue on there. It looks as though they have one that is in the size range I was looking for. Hopefully it isn't too much money.

Thanks for all your suggestions everyone.

 

[electricpete]

Out of curiosity, have you seen adverse consequences from air entrained in the oil? Or just a precaution because you suspect it might results in some problem.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

 

[HensonJM]

My main concern with the air in the oil is that the seals that we use on these bearing assemblies are Kalsi seals.

If you arent familiar with them basically they allow a certain amount of leakage of oil to maintain the seal while the tool rotates.

I think that the entrained air is helping to contribute to seal failures.

 

[hydtools]

I think your greater concern should be the shaft finish. According to Kalsi, 2-8 micro inch. This is so the seal can generate a lubricating film between the shaft and the wavy seal surface.

Ted

 

[HensonJM]

The bearing mandrels are Carbide coated. So shaft finish isnt a concern.

 

[EdDanzer]

Is the seal on the top or bottom of the assembly? Why do you use different viscosity oils? Does the assembly see a wide temperature change?

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[waross]

First, avoid entraining air. Fill low and bleed/drain high.
Second, if there are air pockets, you may be getting air entrainment during the high pressure cycle. If so, I would do the high pressure early in the fill cycle and then flush/circulate enough to remove the oil that may have picked up air during the high pressure phase.
Use one barrel to fill and another for the return. After the tool is filled, worry about removing the possible entrained air from the return barrel.
Re; vacuum. Have you considered vacuum on the tool and then breaking the vacuum with the fill oil? Possibly a coating of oil on the outside of the shaft to aid sealing and inhibit drawing air past the seals.

Bill
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"Why not the best?"
Jimmy Carter