[TowerTalk] insulating oil (also PCB issues) was Re: HN-31 Heathkit Dummy Load

[Jack - K4WSB]

The specs I read where out of the Heath manual...
They offer 2 very different key down times using what they are calling 
transformer oil and mineral oil.

At 11:17 AM 4/4/2006 -0700, Jim Lux wrote:
>At 09:22 AM 4/4/2006, jcowens at NETSCAPE.COM wrote:
> >Is anyone familiar enough with the HN-31 Heathkit Dummy Load (History
> >Lesson)to know how much power you can run to this thing in other than "key
> >down". I don't know if it has transformer oil or Mineral Oil in it. Will
> >it handle 1500W on a 50% duty cycle for a short time?? Does anyone know
> >where I can buy transformer oil, or has OSHA outlawed it by now??
> >
> >John Owens - N7SEJ
>
>Transformer oil *is* mineral oil. It's fairly low viscosity, and often has
>a small amount of an oxidation inhibitor added so it doesn't spoil.  The
>other important thing for this kind of use is that it is (very)dry and
>clean.  A very small percentage of dissolved water (well below where you'll
>see droplets) greatly reduces the HV breakdown strength. Particulate
>contaminants (cloth fibers, in particular) also cause problems with HV
>breakdown. This probably isn't an issue for cooling a dummy load.
>
>It's available in 5 gallon pails at most oil jobbers, and should run you
>about $4-5/gallon.  Shell Diala, Exxonmobil Univolt, etc.
>
>If you know anywhere local that does transformer rebuilding or servicing
>(e.g. a small electric utility), they might be able to sell/give you a
>gallon (they buy it in 55 gallon drums).
>
>If you can't get real insulating oil in small quantities, you can go to a
>feed store and get regular old USP white mineral oil (used as a laxative
>for horses/cows/etc.) by the gallon.  It's not guaranteed dry or clean, so
>I wouldn't use it for HV insulating.  You also want to get the lowest
>viscosity grade (so that thermal forces can make the oil circulate in the 
>can).
>
>Certain kinds of hydraulic fluid will also work (NOT brake fluid. You want
>the stuff used for cylinders on tractors, etc.).  You want something that's
>low viscosity, and with minimal additives.
>
>Tesla coil hobbyists also use straight weight non-detergent motor oil. You
>want the cheapest of cheap, with minimal additives.. all those additives
>help with lubrication, but cause problems with insulation.
>
>
>Now, to the OSHA thing...A LONG digression
>
>Some decades back, a class of miraculous HV insulating liquids (askarels)
>were developed that was a) nonflammable, b)a good insulator, c)immiscible
>with water, d)didn't chemically decompose or oxidize.   They were a
>wonderful material for the HV industry: oil fires are a BIG problem
>(particularly in an urban environment) and were a big motivator to going to
>Gas Insulated Switchgear using SF6, but that raises its own set of
>problems. Imagine the effect of a large fault in a piece of oil filled
>switchgear. The extreme heating of the arc causes the oil to decompose, and
>the evolved gas causes the oil to be sprayed out in a large cloud of
>droplets which is ignited by the spark.  Kind of a king-size molotov
>cocktail.  So, Askarels were a god-send.  But....
>
>
>These were all in the generic class of PolyChlorinatedBiphenyls (PCBs), and
>for the most part are non-toxic and pretty inert, EXCEPT, that there are
>inevitable small amounts (ppm,ppb) contaminants of certain other compounds
>(dioxins) which ARE toxic.  And, sadly, because they're so darn inert, they
>never decompose, so they accumulate and never go away. By the way, toxic
>effects occur just because the molecule is there, and it doesn't get
>consumed in the process of doing its evil work, so that contaminant can do
>its stuff for a long, long time.
>
>So.. big process of getting rid of PCBs (which are contaminated with
>dioxins), leading to superfund sites, etc.  Note that if the PCB is sealed
>into a metal can (as in a fluorescent light ballast), there's little
>likelihood of it ever being released, and even if it did, it's a small
>quantity.  The problem comes in with truckload lots of used insulating
>fluid being used, for instance, as road oil on dirt roads to keep the dust
>down, or with manufacturing facilities draining their (supposedly) inert
>stuff into a big pit.  That's when those ppbs and ppms start to add up
>(especially because the stuff never degrades and tends to sit down in the
>mud in the bottom of the pond/river).
>
>The PCB problem as applied to hams and electrical hobbyists is that that
>there's an enormous amount of really old electrical gear around, some
>filled with oil, some filled with PCBs, some re-filled with oil after
>having had the PCBs drained.  Think of all those pole transformers
>scattered around the country, many having been sitting up there since the
>1940s and the REA.  Think of all the non-existent records of just what's in
>that piece of electrical gear in the salvage yard.  You have no idea
>whether that "oilfilled" widget might have PCBs in it.
>
>Then there is superfund, which creates cradle to grave liability for those
>materials. Cradle to grave liability comes from the practice back in the
>bad, old days, of hazmat disposal by hiring a guy with a tanker to drive
>down the road with the valve "accidentally on purpose" cracked. The waste
>generator says: "We transferred it to our (now-out-of-business with no
>assets) hazmat hauler" {No surprise that this kind of thing was a big money
>maker for organized crime, eh?}
>
>NOBODY who deals with this stuff on any large scale wants the prospect of
>being the "bad guy" in the next Erin Brockovich style movie.  So, they tend
>to take a VERY conservative view of handling.  You want to store a piece of
>electrical equipment with "oil" in it?  Either you have ironclad
>documentation showing it was made recently OR you have concrete pads with
>berms, absorbtion blankets, hazmat spill procedures, etc., etc., etc.  This
>tends to foster a sort of "PCBs are the devil incarnate" sort of
>paranoia.  The actual hazard is quite low, the potential legal and
>publicity exposure is HUGE (particularly if you have assets, and the fickle
>finger of fate points at you).
>
>
>The upshot is:
>Get your oil from somewhere "known good", preferably in brand new
>containers.  Keep the records.(put them in a plastic bag and tape it to the
>dummy load)  Somewhere down the road, someone might want to dispose of your
>dummy load, and life is much easier if you can prove it's nice safe oil.
>
>
>By the way, there are a couple quick and dirty tests: oil floats on water,
>askarel sinks. A piece of paper soaked in oil burns (real well), a piece of
>paper soaked in askarel doesn't burn very well, if at all.
>
>These tests won't tell you, though, whether you've got one of those
>horrible PCB contaminated equipment refilled with oil situations.
>
>
>Jim, W6RMK.. (who's bought and spilled a lot of Diala AX over the years)

Jack Hartley
K4WSB
ARRL - QCWA - OOTC
DXCC Honor Roll