Tall tales of High Pressure dept:

A friend of mine worked on a nuclear sub in the navy.  He said the method
they used to find a high pressure steam leak, in a mechanical room full of
fog, was to wave a broom around near the pipe.  If the broom head gets cut
off, there's your leak.

I personnally would not mess with DIY pressure vessel design, any sooner
than I'd smoke a rubber cigar loaded with a stick of dynamite.


--lawrence


----- Original Message -----
From: "Peter L. Peres" <plp@ACTCOM.CO.IL>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, March 05, 2002 1:31 PM
Subject: [OT]:A Physics problem


> >Any physics people lurking? This is PIC related, because solving the
> >problem will give me what I need to attach a PIC to for my latest hobby
> >project. I am working on an addition to my home-made SCUBA gear. I want
> >to make a sensor that I can screw in to a hig pressure port on my 1st
> >stage regulator
>
> Uhh. Pistons leak, especially at 3000psi and if they don't leak they don't
> move (tight fittings). You can bend a suitable steel tube in a half circle
> and weld it shut. You will have to temper and anneal it probably (you can
> do that, right ?). This would be a Bourdon gauge, the end will move maybe
> 2-3mm at your pressure (for a cord length of 2 inches). The required pipe
> wall diameter can be deduced from tables. You can't just say 'Aluminium'
> or 'Steel', you need a specific alloy and thermal process combination,
> from a specific manufacturer. So your best bet is to use a manometer rated
> for that pressure, remove the gears and add something electronic that
> measures the displacement of the Bourdon tube inside it. Have a machinist
> qualified for SCUBA gear (!) do the fitting. I haven't worked with SCUBA
> gear, but:
>
> Safety notice: High pressure gas (air) and liquids are extremely dangerous
> to people. You can inject yourself directly under the skin with air, gas,
> oil, or whatever you are using, by simply passing your hand/foot/eye etc
> in front of a 'small' leak. The resulting bubble can travel into your
> brain or heart and then you will not be able to post to the piclist. There
> is a demonstration that involves hydraulic fluid from a pinhole leak in a
> rubber hose on a tractor that will cut a rolled newspaper neatly in two.
> Four strong people cannot tear that newspaper. The pressure was lower than
> 3000 psi.
>
> Also 3000 psi is roughly 200 kgf/cm^2 which is a very serious mechanical
> load. Be very careful, you could literally shoot yourself in the foot with
> something even if you do not inject yourself with air.
>
> Peter
>
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>

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