Only once in a lifetime

[Ken Taylor]

Only once in a lifetime you can possibly experience half
a foot of 1mm^2 evaporate. With just an hour left to do
a final spectrum measurement, we threw a bunch of cables,
filters, coupling capacitors, connectors and screw
blocks, stepdown transformer into a shoebox and plugged
the 100Amp connector into the isolated system with a
generator then delivering 3x460V @ 2000A just a few
meters away. My makeshift wiring must have had a
fault, it took a noticeable delay after flipping
the switch until the wire evaporated with a thunder.
Strange enough, the plastic insulation stayed there,
perforated, just the copper was missing but the
surrounding cables and cases were copper covered.

No question was asked why they had to put a main
breaker back in ... oops.

Rene

Back in my training days we were working on an old ship's gunnery radar. It
was running of 3-phase (415V), and had an OFF/Standby/On (from memory) main
power switch. Off was, well, off, standby was still off but had the 3-phase
input to the power supply shorted out and on was exactly that. This switch
remotely operated the contactors in the power distribution room. One day I
was working with a colleague and we decide we were finished so switched
off - we got to 'standby' and thought "Hang on, one more measurement...." so
switched back on. Nothing powered up. Hmmmm. Went inside the main building
to check the breakers to see another training group standing stunned outside
the power room.

When we switched rapidly On/Standby/On the contactor made-before-break and
vaporized a large part of the switchboard, which was deposited as a film
around that room which was thankfully vacant at the time (but caused various
people outside it to soil themselves!). There had been two problems - a
break-before-make contactor was changed, and the replacement was mounted
vertically instead of horizontally as specified.

Ken

 

[Noone]

Only once in a lifetime you can possibly experience half
a foot of 1mm^2 evaporate. With just an hour left to do
a final spectrum measurement, we threw a bunch of cables,
filters, coupling capacitors, connectors and screw
blocks, stepdown transformer into a shoebox and plugged
the 100Amp connector into the isolated system with a
generator then delivering 3x460V @ 2000A just a few
meters away. My makeshift wiring must have had a
fault, it took a noticeable delay after flipping
the switch until the wire evaporated with a thunder.
Strange enough, the plastic insulation stayed there,
perforated, just the copper was missing but the
surrounding cables and cases were copper covered.

No question was asked why they had to put a main
breaker back in ... oops.

Rene

Back in my college days I worked in an University R&D shop. We were
asked to design a device known as an Exlpoding Wire detonator.
Essentially, you charged a big capacitor up to 20 KV and then triggered
a spark gap to dump the charge across a wire "fuse". The wire would
convert to a plasma in a few microseconds. The detonator was used to
ignite an oxygen/actelyne gas mixture. Since only an exploded wire
would ignite the mixture, the tanks were resonable safe to handle. It
was always an impressive display.

Blakely

 

[Winfield Hill]

Noone (Blakely) wrote...

Back in my college days I worked in an University R&D shop. We
were asked to design a device known as an Exlpoding Wire detonator.
Essentially, you charged a big capacitor up to 20 KV and then
triggered a spark gap to dump the charge across a wire "fuse".
The wire would convert to a plasma in a few microseconds. The
detonator was used to ignite an oxygen/actelyne gas mixture.
Since only an exploded wire would ignite the mixture, the tanks
were resonable safe to handle. It was always an impressive display.

What was the purpose of igniting the oxygen/actelyne gas mixture?

 

[Paul Hovnanian P.E.]

This made me think of an old joke. If you were a softwre developer,
you'd plug it in to see if it would do it again.

;-)

 

[Ken Taylor]

This made me think of an old joke. If you were a softwre developer,
you'd plug it in to see if it would do it again.

;-)

Once the smoke gets out though it's only half as much fun.

Ken

 

[Rene Tschaggelar]

Only once in a lifetime you can possibly experience half
a foot of 1mm^2 evaporate. With just an hour left to do
a final spectrum measurement, we threw a bunch of cables,
filters, coupling capacitors, connectors and screw
blocks, stepdown transformer into a shoebox and plugged
the 100Amp connector into the isolated system with a
generator then delivering 3x460V @ 2000A just a few
meters away. My makeshift wiring must have had a
fault, it took a noticeable delay after flipping
the switch until the wire evaporated with a thunder.
Strange enough, the plastic insulation stayed there,
perforated, just the copper was missing but the
surrounding cables and cases were copper covered.

No question was asked why they had to put a main
breaker back in ... oops.

Rene

 

[Robert Latest]

On 12 Oct 2005 18:55:58 -0700,

What was the purpose of igniting the oxygen/actelyne gas mixture?

fun?

robert

 

[Noone]

Noone (Blakely) wrote...

What was the purpose of igniting the oxygen/actelyne gas mixture?

Win;

This was part of a middle 70's Bureau of Mines research project on
creating more cost effective explosives for removing material. The lead
researcher was Dr. Thomas Blythe. The gas mixture was contained in a
reusable cylinder. At one end was a shear plate and at the other the
exploding fire fuse. The idea was that the fuse would ignite the gas
mixture and when the internal pressure reached 100,000 psi, the end plate
would shear off and send a huge shock wave throughout the surrounding
area.

When you see the classic mining explosion, there is always some skyward
component. Debris being blasted into the air, while impressive, is a
waste of energy. What the project was attempting to create was the ideal
mining explosive - one which was cheap, could be safely planted, safely
detonated, and one which would simply crack the surrounding rock without
blowing it skyward. Thus the idea for the CERB - Controlled Electronic
Rock Blaster was born. You could carry the gas mixture without threat of
accidental electrical detonation.

My job was to develop and build a safe and reliable detonator as well as a
multiple input high speed ion conductivity gauge which was used to
characterize the combustion wave.

Blakely