Synthetic Oil vs Regular (solven based refined) oils for vacuum pump 3

[tona2008]

What are the advantages of using a synthetic oil on oil sealed vacuum pump applications vs using a regular solvent-based refined oils. Does it last longer? What are the disadvantages? Is it only the price.

Please help.

 

[MikeHalloran]

In reference to evacuating a refrigeration system, since you're supposed to drain and discard the oil (and any water and contaminants) after an evacuation, I see no particular justification for synthetic oil.

If you're evacuating something that won't contaminate the oil, and I don't know what that might be, then the synthetic oil... is probably still not worth the money, because it doesn't get as hot in a vacuum pump as it would in an engine.



Mike Halloran
Pembroke Pines, FL, USA

 

[25362]

This site may be of help:

www.vpcinc.ca/Products/Leybold/leybold_vacuum_pump_oils.htm​

 

[tona2008]

MikeHalloran,

We're actually evacuating hot gas from a cvd reactor. I'm looking into reducing the amount of oil waste generated. I want to compare the rate of degradation of both oils and ultimately increase the oil change intervals in order to generate less waste. I need to determine if by using synthetic oil the oil seal is maintained longer and pump performance will remain intact longer than with regular oil. Maybe this is not the most feasible approach. May be by looking into replacing the oil sealed pumps with dry pumps will be a better choice.

 

[quark]

Your approach is not wrong. Synthetic oils have better life and miscibility with process vapors is poorer than conventional oils. Further, heat decomposition is minimised. However, I would discount the claims regarding power savings. In any case, you should have a good condenser in the suction line to avoid damage to the sealing oil. My experience with API plants is that conventional oils needed replacement every 15 days where as synthetic oils worked for 3 months.

Dry pumps are always good but expensive.

 

[kchan711]

Before going ahead and testing different oils, it's important to match the oil with the given process. I previously recall in a past situation to use Fomblin oil for a CVD process simply because of its low-reactive nature. Unfortunately in a lab environment on a budget, vacuum pumps would see many different processes.

I do think the time-study would be worthwhile to determine the cost-benefit analysis of the different oils. I also found that typical vacuum synthetic oils were changed anywhere from a month to 3 months (depending on process and cycles).

Dry pumps are expensive and so is accidentally dropping something into them during a bearing repair (another employee let his SS wool pad fall into the intake lobes of an Edwards Vacuum pump). Ugh...

Kyle Chandler

http://www.chiefengineering.net