Science/Engineering/Technical forums

I got a hold of a scrapped Varian V70 and have been trying to 'nurse' it back into health.

It had a significant quantity of some oil within it when I got it. I drained it all out over a long time, but it still doesn't run right. I can get it to spool up and it sucks good, but after a few moments the controller seems to give up on trying to drive it and shuts down. My conclusion is that there is oil in the bearings, which is slowing it down.

Any thoughts if that sounds about right? And if so, is there a fix? Could throwing some suitable solvent in help? (A spider to catch a fly?)

Looking at the catalog on this series pumps the bearing have some sort of dry lubrication.

So, two options as I see it. Wash out the pump with something like IPA, hopefully it wont wash out the dry lube, whatever it is. Worse case is you may have to replace the bearings.

Second is replace the bearings.

Chris
At this point I think a good wash with degreaser is in order and then a strip down. I haven't done one of these so maybe its your turn to document for others.
BOCA bearings sell high speed lubricant that will probably be ok for a lub afterwards.
I use a pencil to mark all the stator plates as they come out so they can go back in the same order. Also mark the shaft to rotor position before taking the rotor off the shaft.
If you are up to it a disassemble first and a clean of all bits you maybe lucky that the bearings haven't got oil in them.

A third possibility is simply a leak on one side or the other of the test rig -- it wouldn't have to be large. All my turbos will shut down in a little while in that situation as the controller kind of integrates input power and shuts down to avoid overheating the pump windings. In fact, an open needle valve on either end on my systems will prevent the turbo from ever reaching full speed, and it will shut down in a little while in that case, after giving it a good try, sort of. Do you have a gage on this?

It pulls down steadily to an indicated 1e-4 torr, after a minute or two, then shuts off. It certainly doesn't sound like it is running to full speed. Bear in mind the V70 is a turbo-drag.

Sounds like oil, then. Most of those bearings are fairly well sealed, so I'd bet that if you find something that's a good solvent for that oil (pray it's not silicone) you could just wash it out and go.
It's probably getting slung off the vanes and getting into the drag part....real close clearances there. I'd try that first and listen close for bearing issues, and if that seems fine, done!

When I first started it up, and for several more spoolups, I could hear what sounded like droplets getting flicked off, a bit like a slow crackling sound. It has gotten less and less as I run it for a few moments each time. Hence my term; 'nursing' it back!!...

I reckon someone's just done a big awful suck-back from the backing pump, and it was then dumped as it wouldn't stay spooled up. A bit of perseverance may pay off here!?

Add solvent to persistence, and yes, most likely. But I'd not let it fling oil in there, at those speeds it might bend things!

Kluber also makes some very good, and expensive greases.

That crackling sound might be 'cavitation', for lack of a better word, caused by the 'oil/solvent' that's in there rapidly vaporizing and then re condensing. Can you get it completely dry?