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Re: Leaky capacitor woes.


From: 	Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent: 	Saturday, November 22, 1997 3:10 PM
To: 	Tesla List
Subject: 	Re: Leaky capacitor woes.


> From: 	Adam[SMTP:absmith-at-tiac-dot-net]
> Sent: 	Thursday, November 20, 1997 11:03 PM
> To: 	tesla list
> Subject: 	Leaky capacitor woes.
> 
> 
> I have built a flat plate cap, which at first seemed great, but now 
> demonstrates a great oil leakage problem.  The cap is made from LDPE and 
> Aluminum plates, and it is housed in a rubbermaid polypropylene storage 
> box.  I "sealed" the box by hot-gluing a plexiglass panel over the top.
> 
> This cap leaks oil something fierce.  The problem is I cannot figure out 
> exactly how the oil is getting out.  I have a clean dry cap, and then I 
> come back 4 hours later and it is sitting in a pool of oil.  The oil is 
> Exxon Univolt N61.  I have already checked for leaks, and have found that 
> the hot glue does not adhere at all with the plexiglas, allowing oil to 
> flow freely out through the junction if I tip the container so that the 
> oil is in direct contact with this seam.  However, there is normally 1" 
> of air space above the top of the oil and below the seam.  So, I have two 
> theories:
> 
> 1.  The oil is evaporating and condensing on the plexiglas (observed) and 
> must then be "rolling" along the plexiglas surface to the hot glue seam, 
> where it freely leaks out thanks to capillary action.
> 
> 2.  The oil is passing through the polypropylene container itself.
> 
> Evidence suggests theory #1, but I have not ruled out the second theory, 
> as the capacitor seems to be oily all over.
> 
> Any ideas?
> 
> -Adam
>  
> 
> --------------------------------------------------------------------------
> Adam Smith
> absmith-at-tiac-dot-net
> Epoch, Inc. Digital Music Project

Adam,
I have built several flat caps in Rubbermaid containers. 
I have the kind with a lip at the top of the container,
and a hard lid, not the soft lid that is more common. 

The way I have found to seal these is to make a rubber
gasket that goes all around the top. The rubber gasket
does not have to be all that thick, but you want to make
sure that it seals completely. The simplest way to do this
is to affix the rubber gasket using a thin layer of
rubber sealant. You can affix the gasket to either the top
cover or the main container. 

I use homemade clamps that I fashion out of sturdy scraps
of aluminum about 1/16" thick. I bend these such that they
snap on and tightly hold the top on, all the time compressing
the gasket. I usually use 8 such clamps.

For those not adept in making such clamps, you might try
placing a fair number of those LARGE heavy duty paper clamps all
around the top. It might look strange, but it would be 
effective. 

I would not recommend using screws or bolts to hold the top on,
as the holes will created many problems and possible fracture points.
If you ever DO make holes, make sure you affix a wide and thick
metal washer there so the compression force is distributed.
Otherwise the hole will create more problems than it solves.
I once used holes, but I then had a strip of fiber board 1/4"
thick running the full length of each side. This helped distribute
the compression forces more evenly. I dislike making holes, as they
tend to produce minute fractures later.

Another method is to get a tube of that clear sealant used to seal
windows and the like. I use Red Devil Clear. It contains polyacrylic
compounds and some other stuff. I have found that this stands up
well to transformer oil (I use the same one you mentioned). The surface
must be clean and dry when you put it on, of course. After laying down
a layer of this stuff, gently apply the top cover. Move the cover
around slightly to make sure the seal is complete. Apply several clamps
to hold the assembly togeteher. I would keep the clamps on once
the stuff has set, as I am not sure if the oil will otherwise
eventually work its way under the seal.

By the way, I use the Red Devil Clear caulking adhesive for all
kinds of things. I use it in my HV DC projects as an insulator.
I seal capacitors with it. I use it to hold down HV wires, and as
an all-purpous corona suppressant. I use it as a glue to hold
things together. I use it for sealing all manner of HV connections
as they enter my HV container boxes. I use it to immobilize
components that might otherwise break due to vibration. I used
in on several of my primaries to hold the copper tubing in 
place on a form that was otherwise too loose. It is an extremely
useful thing to have around.

Hope this helps.
Fr. Tom McGahee