Re: stopping leakage of mineral oil from wire feedthroughs? (fwd)

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---------- Forwarded message ----------
Date: Thu, 11 Nov 2004 08:47:29 +0200
From: Kristian Ukkonen <kristian.ukkonen@xxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: stopping leakage of mineral oil from wire feedthroughs? (fwd)

High Voltage list wrote:
> From: Jack Vandam <snotoir7674g@xxxxxxxxxxxxxx>
> I have been working on a project that requires a small, high frequency
> transformer, not too much unlike a flyback, in mineral oil.  I am using a
> small plastic container to hold the transformer and have the input/ output
> wires passing through the plastic container at several points.  However,
> just after completing my first immersion of the transformer, I discovered
> that oil was leaking through one of the feedthroughs.  Originally before
> adding the oil, I thought I had sufficiently sealed around the feedthrough
> holes with plastic weld epoxy.  However, apparently not.  What a mess I had
> today draining out the oil and starting over again.  Getting rid of the oil
> residue required both mineral spirits and finally acetone.  Now I have to
> reapply a sealant around the wires/ feedthroughs.  What is recommended so I
> don't have this happen again?  I'm thinking of trying to dispense a generous
> amount of silicone around the areas, but would this be better or should I
> stick with the epoxy?

Use mechanical feed-throughs, with o-ring seal to the
wall of the oil tank, and the feed-through body used as
the electrical conductor. Simplest model would be a
bolt, with a o-ring groove machined to the base of the
bolt. Your local marine or pipe store might have something
like this - perhaps hull feed-through for pipe with
compression fitting - just use rod instead of pipe..

If you have to use a wire, you might make some mechanical
teflon packings, like those used in stems of valves, and
again a o-ring seal to the wall of the oil tank from the
packing body. Propably difficult to find as ready-made.

If you must use epoxy, make yourself a favour, and use
a metallic oil tank.. Epoxy will have no problem with the
metal to make oil-tight seal.. The metallic tank is much
better from RFI point of view as well.

   Kristian Ukkonen.