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LAN_403

Tonic

Tue Feb 19 2008, 09:22PM

Registered Member #528 Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166

I have one question - if something will arc inside oil, what consenquences might be? Toxic fumes, or something? The reason why I'm asking is that I'm wondering if I can seal oil hermetically inside pipe.

Proud Mary

Tue Feb 19 2008, 10:04PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

There could indeed be toxic fumes generated by arcing, especially if you use mineral oil rather than vegetable dielectric fluid.

If you seal your unit, be sure to leave some air/gas space at the top, which can be compressed as the liquid expands as it warms, or some kind of over-pressure vent, or your apparatus will leak or burst!

GimpyJoe

Wed Feb 20 2008, 01:50PM

Registered Member #316 Joined: Mon Mar 13 2006, 01:30PM
Location: Marietta, GA
Posts: 212

I have never had a problem with mineral oil. The only oil I've ever had a problem with is motor oil, which didn't seem to suppress corona very well.

Mates

Wed Feb 20 2008, 03:33PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Avalanche wrote ...

Which leads me onto another idea - couldn't automatic transmission fluid be used? I used this in my forks when I needed some good quality low viscousity(?) oilage.

Once I bought a brake fluid which had great dielectric properties (it was in Czech rep. few years ago). Recently I bought another one DOT3 in Denmark and this one is quite conductive. Unfortunately I have no idea what liquid was the first one, but viscosity of that fluid (which is actually for me the best argument why not to use the cheap cooking oil) was just perfect... Maybe Jan can give the try, he lives in Czech rep.

Dr. Dark Current

Thu Feb 21 2008, 09:42AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Mates wrote ...

Once I bought a brake fluid which had great dielectric properties (it was in Czech rep. few years ago). Recently I bought another one DOT3 in Denmark and this one is quite conductive. Unfortunately I have no idea what liquid was the first one, but viscosity of that fluid (which is actually for me the best argument why not to use the cheap cooking oil) was just perfect... Maybe Jan can give the try, he lives in Czech rep.

thanks, I'll give the brake fluid a try :)

I had another idea, what about pouring hot melted parrafin wax into the transformer? I know it has good dielectric properties and it is very viscous when heated enough... Maybe it would be a bit difficult to disassemble but it should be possible by baking it in an oven for a while then pouring the hot wax out

Mates

Thu Feb 21 2008, 10:10AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

jmartis wrote ...

I had another idea, what about pouring hot melted parrafin wax into the transformer? I know it has good dielectric properties and it is very viscous when heated enough... Maybe it would be a bit difficult to disassemble but it should be possible by baking it in an oven for a while then pouring the hot wax out

I tried the paraffin once (the normal white candle) to isolate my ignition coil and it did not work. Oil is much better according to my experience. But, I was working with 50KV at 6KHz which is kinda special situation

Mates

Sun Mar 09 2008, 10:21AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

I've just discovered a liquid of great dielectric and viscosity properties. It is the lamp oil (the stuff for burning in the home lamps). Works perfectly and it has one more big advantage. It evaporates after some time, so when you work with it nothing stays oily (great for gluing etc...)

br]

Kizmo

Sun Mar 09 2008, 10:59AM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

I wouldn't use that.

One of transformer oil most important feature is that it is highly non-flammable and when heated does not generate flammable fumes. I once burned my facial hair with lamp oil fumes from stove.

Mates

Sun Mar 09 2008, 11:31AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

Kizmo wrote ...

I wouldn't use that.

One of transformer oil most important feature is that it is highly non-flammable and when heated does not generate flammable fumes. I once burned my facial hair with lamp oil fumes from stove.

It is not so easy to ignite this oil. But the fumes are a good argument. It would have to be sealed without any air inside and only for mild temperatures (below 100C) emitting devices. But sparking inside the oil is harmless I tested it. (you need oxygen in the oil to start a fire). However you 100% right, this could be a pretty dangerous design...

Proud Mary

Sun Mar 09 2008, 01:33PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

The flashpoint of generic lamp oils is generally between 60Â° C and 120Â° C, depending on the proportion of aromatics.

If an oil filled transformer case is to be hermetically sealed, then it is essential to make provision for the expansion of the oil as it heats, or the case will leak or even burst, as the oil is all but incompressible. Allowing an air - or gas - space at the top of the transformer is a common solution.

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