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From: highflyer <>
Newsgroups: rec.aviation.homebuilt
Subject: Re: Paint Gun Danger
Date: Tue, 22 Sep 1998 10:25:40 -0500

Craig C. wrote:

> a bunched snipped....
> There is no reason to be using more than about 40 psi with any air
> powered spray gun. More than that pressure and all you do is maximize
> waste and overspray. My touch-up gun is rarely ever used above 25 psi
> and the big gun usually sees only 35-40 psi.
> 100 psi air from a very small orfice can cause air/fluid/particle
> injection though...
> Craig

This is a real problem with the airless rigs.  They eject the paint
at very high pressures, similiar to the output jet from a pressure
washer.  Blocking the orifice with a finger to "clean" it can easily
inject you.

High pressure hydraulics is serious.  I remember one time in upstate
New York.  We were inspecting a hydraulic system.  There was a small
smear of oil on an elbow.  One of the fellows casually wiped it off
with his thumb.  His thumb instantly swelled up like a golf ball.
There was a pinhole through the cast fitting.  When he wiped his
thumb across it, it filled his thumb with hydraulic oil.

When I was first learning about high pressure superheated steam
systems they had a demonstration that made a believer out of me.
They had a steam line well overhead with a series of pinholes in
it.  They pressureized it with superheated steam.  You could hear
it leaking.  YOu could see a cloud of condensation forming about
six feet away from the pipe.  You couldn't see a darn thing near
the pipe.  The instructor took a two by four and swung it over his
head past the leaking steam pipe.  It cut off the two by four!

I am very careful when I look for leaks in high pressure systems! :-)

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