Novice question about damaged Conflat flanges

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Chris Giles
Posts: 61
Joined: Mon May 14, 2018 6:46 pm
Real name: Chris Giles

Novice question about damaged Conflat flanges

Post by Chris Giles »

Friends,

I have a quick novice question about reconditioning a conflat flange. I just received a nice Varian 4.5" cross but it had been damaged in transit and bashed the outer edge of one of the fixed flanges. It is a used item at a good price so I would rather fix it than return it. The other 3 flanges are in perfect condition.

The knife-edge is perfectly smooth. I guess that given it is on the outer edge of the flange, this is fairly easily recoverable. I can tell it is pushed in by about 0.5-1.0mm by placing a steel rule across it. The length of the dent is about 10mm. I'm thinking i can just sand the local area of the dent by hand (with 600 grade paper?) until it appears to be flat by checking with the still rule. I don't have any machining equipment. I also don't yet have other DN63 parts to mate it with.

I have read some other posts about damage to the knife edges but I just wanted to check in case I damage it further trying to fix it. Am i correct in thinking that so long as i get this area fairly flat it should be OK given the high pressure from the bolts?

Best regards
Chris
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Robert Dwyer
Posts: 89
Joined: Sun Sep 04, 2016 5:34 pm
Real name: Robert Dwyer

Re: Novice question about damaged Conflat flanges

Post by Robert Dwyer »

From the looks of that picture, that flange should hold a perfectly fine seal how it is. The actual vacuum seal is made from the knife edge 'biting' into the copper gasket to form the seal. If you are using a rubber o-ring the compression still is on the interior of the flange right behind the knife edge. In either method of sealing, nothing that far out from the center should effect the vacuum seal. Personally I wouldn't try taking sandpaper to the dent as you may accidentally scuff up the knife edge which would create a vacuum problem.
ian_krase
Posts: 636
Joined: Mon Nov 28, 2016 2:48 am
Real name: Ian Krase

Re: Novice question about damaged Conflat flanges

Post by ian_krase »

I would fix that by filing with a file, at an angle so that you aren't coming anywhere near the knife edge (basically chamfer off the dented area).
Chris Giles
Posts: 61
Joined: Mon May 14, 2018 6:46 pm
Real name: Chris Giles

Re: Novice question about damaged Conflat flanges

Post by Chris Giles »

Thanks very much Robert & Ian. I will carefully file it down...
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