DC-704 Oil Failure?

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
Post Reply
User avatar
Jason C Wells
Posts: 113
Joined: Sun Oct 20, 2013 11:11 pm
Real name: Jason C Wells

DC-704 Oil Failure?

Post by Jason C Wells » Wed Sep 02, 2015 10:43 pm

Can DC-704 have an "almost" failure?

The oil I have installed now sat in a partial container for a few months before use. I did allow air into my pump by accident for a brief few seconds in recent testing.

I've read about oil failure where the oil becomes sludge. I've inspected my pump by shining a light down into the boiler and there is no sludge. It's hard to see well at the bottom of the pump though. The oil that was clinging to the removed jet assembly was perfectly clear.

I can pump down to only .003 Torr currently. The system holds fairly tight with no pumps running. I'm at a loss to figure out why I can't get <10E-4 Torr any more. I had a big problem a few weeks ago and have had every joint apart and put back together since then. I've got all the same quality of gear I had before plus I upgraded to stainless swageloks. I'm pulling my hair out. Maybe some comments from you guys will inspire me.

Thanks,
Jason C. Wells

Jerry Biehler
Posts: 902
Joined: Tue Nov 24, 2009 8:08 am
Real name:
Location: Beaverton, OR

Re: DC-704 Oil Failure?

Post by Jerry Biehler » Wed Sep 02, 2015 11:14 pm

704 is a silicone and it does not react to air like the the old mineral oils. What my have happened is you blew a bunch of oil out the foreline into the mechanical pump and there is no longer enough in the diff pump. Open it and check the level if it does not have a dip stick.

John Futter
Posts: 1625
Joined: Thu Apr 22, 2004 2:29 am
Real name: John Futter
Contact:

Re: DC-704 Oil Failure?

Post by John Futter » Thu Sep 03, 2015 7:31 pm

Jason
When you removed the jet assembly did you notice the outlet hole position near the base of the jet assembly. This has to face the backing outlet.
Also a diff pump that has been up at air for a long time can take a couple of hours to self degas before it pumps.
The last point is the heater in good contact with the bottom of the pump -rust -buckling- correct tension are all important here

User avatar
Jason C Wells
Posts: 113
Joined: Sun Oct 20, 2013 11:11 pm
Real name: Jason C Wells

Re: DC-704 Oil Failure?

Post by Jason C Wells » Thu Sep 03, 2015 11:43 pm

Thanks you guys. I will check all of these things.

Regards,
Jason

Gleedaniel Martin
Posts: 12
Joined: Thu Mar 05, 2015 10:03 am
Real name: Gleedaniel Martin
Contact:

Re: DC-704 Oil Failure?

Post by Gleedaniel Martin » Wed Sep 09, 2015 1:02 pm

Jason
When you removed the jet assembly did you notice the outlet hole position near the base of the jet assembly. This has to face the backing outlet.
Also a diff pump that has been up at air for a long time can take a couple of hours to self degas before it pumps.
The last point is the heater in good contact with the bottom of the pump -rust -buckling- correct tension are all important here
I did not know it also and I am very thankful for this good information.:)

User avatar
Jason C Wells
Posts: 113
Joined: Sun Oct 20, 2013 11:11 pm
Real name: Jason C Wells

Re: DC-704 Oil Failure?

Post by Jason C Wells » Sun Sep 13, 2015 12:44 am

This follow up is a little bit late. It may also be out of sequence with the advice given.

I did take the diff pump apart. It was too full. I sucked some rough pump oil up into the diff pump and also up into the gauge lines to the manometer that I had connected to the rough side. I do not believe that I ever left the isolation valve on my rough pump open with the rough pump stopped. That was one of the very first mistakes I made in this endeavor a couple years ago. Maybe the oil leaked past the rough pump isolation valve (part of the pump itself).

So I still don't know what my original problem was, but I do know what this recent problem was. Now I am on a different path since I have brandy new DC-704 installed in my diff pump.

Regards,
Jason C. Wells

Post Reply