Re: water spark gaps + oil info

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net> 

Hi Sundog,

Oil will also degrade under arcing. I have seen this happen at work as both
a failure mode and a controlled test.
For the controlled test we had a spark gap apparatus that was designed
specifically for dielectric strength testing of oil. The electrodes looked
like they were spaced about 1/8" apart. They had a flat arcing surface, were
1" in diameter and were made of brass.
Normal, good clean Shell Diala AX broke down at 40 kv. This would hold true
for about 20 or so discharges, but then after further discharges, the
breakdown voltage would decrease. During an arc, a stinky gas bubble is
released and carbon particles form in the oil. No one at work could tell me
what the gas is. This certainly would produce pressure and an explosion
hazard in an enclosure. We would see failed units come off of burn in with
the rubber bladders almost ready to rupture! These bladders were designed to
compensate for the normal expansion of the oil due to component heating.

While we are on the subject of oil, another bad thing for oil is high
temperature. If it is heated above 55 degrees C, it will turn a dark Laugher
color and its performance degrades. I am not talking about heat in
combination with arcing, but just heat alone from a hotplate in another
experiment. So the high temps from an arc itself + the carbon + the gas =
trouble!

Just as a point of interest I threw some USP grade mineral oil into the
sparkgap test apparatus and it broke down at 15 Kv. That's a heck of a lot
better that air, but no where near as good as the commercial grade
dielectric oil.

Sue

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, November 29, 2000 10:12 PM
Subject: Re: water spark gaps


> Original poster: "sundog" <sundog-at-timeship-dot-net>
>
> Hi all,
>
>  I have to concur here.  This phenonemon is known as "exploding
> water", something else to do with those big 'ole pulse caps you
> have hangin' around for your cancrushers! ;)  The pressure
> generated is truly insane, and potentially dangerous.  The more
> joules, the worse it gets.  An 11kj discharge into 10cc of water
> was *quite* impressive, and blasted the aluminum tube it was in
> apart.
>
>   But as for the spark-gap worthiness of it..I dunno...I'd imagine
> the water would ionize pretty quick and become useless as an
> insulator (like air in a static gap).
>   But how about HV oil?  Might that work better?  Hmmm...Sparkgap
> under Oil...anybody tried that?
>                         Just my putterin' $.02
>                                                 Sundog
> -----Original Message-----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
> Date: Wednesday, November 29, 2000 9:17 PM
> Subject: Re: water spark gaps
>
>
> >Original poster: "$" <Steve-at-g8cyerichmond.freeserve.co.uk>
> >
> >Some years ago I experimented with discharging caps through water
> spark
> >gaps. I stopped for eone reason only, it is extremely dangerous!!.
> The short
> >puls at high energy simply converts water to high high pressure
> steam (i'm
> >talking about steam at 100s of degrees C.
> >----- Original Message -----
> >From: Tesla list <tesla-at-pupman-dot-com>
> >To: <tesla-at-pupman-dot-com>
> >Sent: Wednesday, November 29, 2000 3:01 PM
> >Subject: Re: water spark gaps
> >
> >
> >> Original poster: "Jochen Kronjaeger"
> <Kronjaeg-at-Stud-Mailer.Uni-Marburg.DE>
> >>
> >>
> >> > Has anyone ever experimented with water spark gaps?  If so,
> did you run
> >> > into any big problems?
> >>
> >> I tried this recently, though not systematically. I simply
> submerged my
> >> multiple copper tube gap in a bucket of tap water. This turned
> out to
> >> be far too conductive, i.e. shortet my OBITs without charging
> the cap.
> >>
> >> Deionized water will be better, but considering the small gap
> distances I
> >> doubt it will work well. Also, the water will propably degrade r
> apidly.
> >>
> >> I experienced another strange problem when drawing an arc
> between a copper
> >> electrode and a water surface. Sometimes, there was something
> like a small
> >> explosion, not really violent, but quite a shock. This might be
> due to
> >> electrolysis (hydrogen+oxygen production), but I somewhat doubt
> this as
> >> there was no reason for hydrogen to accumulate. Anyway, let this
> be a
> >> warning that unexpected and possibly dangerous effects might
> occur with
> >> under water gaps.
> >>
> >>   Jochen
> >>
> >>  ---------------------------------------------------------------
> ----------
> >--
> >>   Jochen Kronjaeger
> >Kronjaeg-at-stud-mailer.uni-marburg.de
> >>
> >>   The High Voltage Page
> >http://www.mathematik.uni-marburg.de/~kronjaeg/hv/
> >>     info, plans, photos of home-built HV-sources, sparks,
> HV-experiments
> >>  ---------------------------------------------------------------
> ----------
> >--
> >>
> >>
> >>
> >>
> >
> >
> >
> >
>
>
>