Re: Oil leak at pig Horn cable clamp

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Jim,

I assume that you're referring to one of the high voltage input
ceramic bushings that protrude from the top cover of the the
transformer tank? The top tank cover can be easily removed
by loosening the "barrel clamp" ring around the top of the tank
and lid junction. There will be some clamping hardware on the
underside of the tank lid and the HV bushing(s) feedthrough
hole that secures the bushing to the underside of the tank lid.
You will, of course, have to remove the lid to gain access to
the bushing clamping hardware underneath. There are several
different types of clamping mechanisms that are used in pole
pigs for this purpose. It's kind of hard to explain the clamping
mechanisms in writing, but once you take off the lid and see
it for yourself, torque adjustment is pretty self explanatory.

I have heard others speak of a "wicking" action that can
cause leaks around the bushing, but I have personally ne-
ver witnessed this myself. That's certainly not to say that
it dosen't happen, just that "I" never have experienced it.
There is a cloth-like insulation material that's wrapped around
the inner conductor inside the porcelain barrel tube that
could act as a wick, I suppose. Someone else will have to
share their experience on this issue.

As mentioned above, I would take off the lid and try to
tighten the "bushing-to-lid" clamping hardware first and see
it this fixes the problem. If that dosen't do the trick, you may
need to replace the gasket material. BTW, is the leak at the
bushing/tank lid junction or is it around the HV bronze hook
up clamp at the top of the bushing? If it's the latter, then there
may very well be some wicking action going on here. As a
side note, I have experienced leaking around the low voltage
input bushing insulators on the side of the tank before. I ended
up taking off the tank lid and draining down the oil low enough
to take out the LV bushings without the oil running out of the blank
LV bushing holes in the side of the tank. I simply reseated and
retightened them, refilled with the removed oil, put the tank back
together and the leak was fixed :^)

If all else fails, you may have to go to a transformer rebuilder
or manufacturer and see if you can purchase another HV bushing.
You will probably have to bring the tank lid with you to make
sure that you get the right type of bushing, as there are numerous
different types and manufacturers of these bushings. This should be
a last resort though as these ceramic bushings are rather pricey.
(I paid $41 a piece for 14.4 kV HV bushings for my 10 kVA pig).

Hope this helped you out.

David Rieben

PS: Be careful when removing the top lid of the tank as there usually
isn't much slack in the HV leads from the underside "barrels"
of the bushings to the internal transformer. If you yank it up
with any force, you may break the insulator saddle of the internal
transformer. Ask me how I know this ;^)

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, July 01, 2005 12:18 AM
Subject: Oil leak at pig Horn cable clamp


> Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>
>
> Hello,
>
> I have had a leak problem on one of my pole pig cable clamp gaskets. It 
> really squirts if I apply any angular force on it. In this case I have a 
> couple of rods attached to do power control testing with a Jacobs Ladder. 
> It appears slightly off center. Maybe it took a hit in transport.
>
>    * How does one tighten these without busting the horn or inner 
> connections?
>    * What dynamics bring the transformer oil into the horns? Is there a 
> wick or is it simply a reservoir?
>
> It came from T&R a couple years ago on a pallet.
>
> Thanks,
> Jim Mora
> Ojai, Ca.