[AMPS] Xfmr Oil

[John T. M. Lyles]

We use many gallons per year of Shell Diala X Transformer Oil. It is 
widely available from Shell jobbers, and comes in 55 gallon drums. 
There are much more expensive silicone based oils called Envirotemp 
or something like that, but they aren't recommended except in extreme 
cases. As W5NA said, to get the full dielectric strength of this oil, 
as it would be required for a 4160:13,800 V transformer, it must be 
processed, heated, filled with vacuum on top, then a nitrogen blanket 
added at the end to prevent oxidation products from forming and 
eleminate most moisture ingress. We use Diala up to 90 kVDC in some 
modulators for klystrons.

For 1 kW Dummy Loads, it would be fine to use without all the 
precautions. It is made esp for electrical gear and can handle 
occasional arcs, although this is detremental to oils in general (and 
equipment). S D Meyers Company (headquartered in Ohio, but having 
district offices all over the US) does a lot of powerline transfomer 
rebuilding and oil processing, and may sell you small quantities if 
you call them. We have a contract where a semi-truck mounted hot oil 
processing system comes every year. They recirculate our transformer 
oils through Fullers Earth (a clay) and other filtration. Also 
checking the chemistry for various gases which indicate overheating 
and arcing. In this way, we have extended the lifetime of some 2 MVA 
transformers beyond 30 years without failure.

73
John
K5PRO
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