Optical window assemblies

[BrainEater]

I am working on a project where I need to 'pop' a mylar burst disk inside a pressure tank.

One of the methods I came up with to do this, is to use a laser.

However, to do this, I need an optical window assembly I can screw into a tank : basically, a stainless steel fitting with say a 1/4" NPT thread on one side and a pressure sealed optical window on the other.

It needs to be rated for 150 Psi @ 100 C, Helium service.

I can find the 'windows' no problem, what I can't find is a premade assembly/fitting.

I'm curious if anyone here has seen what I'm after.

 

[BrainEater]

I know you are asking why.

I need to burst/trigger "diaphragm 1".

 

[Anthony P]

Just spit-balling. For something professional, I would look into Conflat fittings or similar. For home made, I have had good luck on pressure and vacuum projects using brass plumbing compression fittings... replace the copper ferrule with o-rings to sandwich the lens.

 

[BrainEater]

Nice !

We are on the same page, I was thinking a modified 'swagelok' fitting with a plastic ferrule....
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As much as I'd like the 'cool factor' of the laser trigger, I have gone with a simple co-axial helium line and a $50 'air actuator' with a pin.

I should have it next week, I'll get a picture up.



I may pursue this later....

 

[farbe2]

You could also use some cantal wire as a heating element.
I would make something that holds the foil and the heater.
This would allow for a simple electrical trigger and just current pass toughs would be needed.

 

[BrainEater]

Yep !

The world record holder, to my knowledge, was just using a thin wire and a neon sign transformer to 'arc-melt' the mylar.
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Here's the cannon :



The 'popper' needs to be inside that stainless helium tank, or isolated with a window or something.
The mylar burst disk is held by the flange assembly.
My air cylinder should be here tomorrow.

Make no mistake, what I want is a premade sapphire window and a 4 watt cyan laser, but I'm sure I can't afford that right now.

hehe

 

[kecked]

Why not put a laser diode inside the tank. No window. Just two wires coming out. I vote hot wire. Also using a laser would seem to slow you down as it only makes a slight hole that then has to expand while a hot wire could be set to blow the whole outside off at once. Not sure if that makes a difference or not.

 

[BrainEater]

That would totally work, I considered it.
You lose the cool factor of the laser trigger though.
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Ultimately, it boiled down to price.
I got it done for $52 with pneumatics.
I got my cylinder today, I'll put another pic up an an hour or so.
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There is no delay !!
One slight defect in the burst disk it goes bang !
Hehe
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I have gotten a lead or two on 5mm windows, might order one to play with. I do have a good contact at SwageLok so...

 

[BrainEater]

Here's the popper.



The 3/8" tube assembly with the cylinder goes inside the tank via the 'tee' assembly at the back, it's coaxial.....
Tank fill is through the side port with the valve. The trigger is done with the straight through tube...Trigger is tank pressure+50Psi.
The pointy bit is a TIG tungsten.