Vacuum Blower Failure

[GaTechTheron]

Have a vacuum blower just upstream of a liquid ring vacuum pump that is failing. We inject seal oil just upstream of the vacuum booster blower for the purposes of sealing/cooling. This liquid that we are using as "seal oil" is actually from the knock out pot just downstream of the liquid ring pump. Therefore when the seal oil is injected upstream of the vacuum booster pump, the liquid is vaporizing.

That's the set up. The blower has failed exhibiting thermal expansion on the lobe (contact with the casing), robbing between the lobes, and failed bearings on the non drive end. According to the PHD, the temperature on the exit never exceeded the max temperature, but we have thermal expansion failure? Is this possible?

A few questions:
1) Is it possible that vaporizing of the seal oil could have somehow damaged the vacuum blower?
2) Is is possible to have thermal expansion failure without noticing this on the downstream temperature?
3) Does the seal oil used to cool, or to seal?
4) What are the affects of too much, or too little seal oil? Could that lead to a failure?
5) Could the liquid be condensing on the downstream side of the vacuum blower, causing some sort of cavitation.

Thanks,
Theron

 

[Compositepro]

A bearing failure could have caused the other damage. Debris entering the blower (Roots type, I assume) would also cause damage. Too much liquid entering the blower would destroy it.

 

[GaTechTheron]

Yes this is a roots type vacuum blower.

What are the symptoms of too much liquid?

If the liquid changes phase from upstream to downstream of the blower what are the symptoms, and does this cause damage.

Thanks,
Theron

 

[Compositepro]

Boiling of fluid is not a problem except for limiting the vacuum. Liquid in a gas compressor will not compress in tight clearances designed to prevent gas leakage. This can generate tremendous pressures which will bend and break metal parts. The phenomenon is called hydro-lock.

 

[GaTechTheron]

It cannot be hydrolock in this case. The liquid that is fed to the blower as "seal oil" is actually from a knock out put just downstream of both vacuum pumps. Therefore, unless a very large slug somehow got into the blower, it could only (at steady state) recirculate what is being knocked out in the knock out pot. Come to think of it, the situation described is very odd, so wouldn't be surprised if this is not the best approach, and leading to some of our issues?