Re: Cleansing Transformer Oil (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 18 Dec 2003 07:24:22 -0700
From: Gomez <gomez@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Cleansing Transformer Oil (fwd)

On Dec 17, 2003, at 10:07 PM, High Voltage list wrote:

> ---------- Forwarded message ----------
> Date: Tue, 16 Dec 2003 16:45:39 -0500
> From: G <bog@xxxxxxxxxxxx>
> To: hvlist@xxxxxxxxxx
> Subject: Cleansing Transformer Oil
>
> Hi All,
>
> I have some transformer oil that I'd like to put to use. The problem
> is that it has been stored outside in questinable containers. I am
> planning to heat the oil above 212 degrees Fahrenheit with some
> water-heater elements to drive off any absorbed moisture. How might I
> test the oil to see when it is finished drying? Thanks for the input.
> Oh- this is for a 75 kv project.

  I believe the simplest method is to test the dielectric strength
rather than
trying to measure the moisture content directly, since dielectric
strength
goes down as moisture content goes up.  I don't have the document
handy, but
try googling around for "ASTM" and either D877 or D1816, which are the
ASTM
dielectric test methods for insulating oil.  Essentially, it consists of
putting two electrodes of specific dimension and shape into the test
sample,
impressing a DC (I think) voltage across them, and measuring the leakage
current.

  Beware of heating the oil too hot, as you will break down its chemical
structure above a certain point.  You should probably be able to heat
it to
300 degrees F without damage - use a thermostatically controlled heat
source,
an oven or candy thermometer, and heat it up slowly.  Keep the heat
applied
for as many hours as you have time to monitor it in person.  Do this
outdoors,
not indoors, and make sure you keep an eye on it and have an ABC fire
extinguisher handy, just in case.  Don't leave it alone until it has
cooled.

  It's also a very good idea to run it through a stack of fine cotton
cloth or
other fine filter medium to make sure there are no particulates of any
sort
in the oil, such as flakes of rust or other gunk.

  - Gomez

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