Personally, the use of quench oils used in heat treating also works well. It
is typically a high grade paraffinic mineral oil, with oxidation additives
added for this severe duty. These can be obtained from either supply houses
like Brownells (a gunsmithing supply company), Quench oil manufacturers (like
Houghton International - my employer), or small oil supply distributers
(usually found locally). The oils can also be obtained either new or used
(which would work fine) from a local commercial heat treater.
Does any one have the viscosity specifications of the transformer oil used (cSt
or SUS)?
Thanks
Scott
-------------- Original message --------------
From: Jack - K4WSB <K4WSB@arrl.net>
> 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@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
>
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