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Posted by spaco on November 2, 2007, 1:31 pm
Please log in for more thread options Answering "how do you figure that?" A friend of mine brought a failed
acetylene regulator to a meeting a couple of years ago. He told about
how quickly the regulator caught on fire and how hard it was to get to
the valve that was in the middle of the fire. Acetylene is one of
the most dangerous flammable gases I know about. And you certainly
don't want a regulator to tell you that you've got 15 psi when it's
really 40!
Pete Stanaitis
-----------------------------
Neon John wrote:
>
>
>>You didn't get any other replies, probably because most folks would be
>>afraid to give advice on this one. This situation is potentially so
>>dangerous that they probably don't want to get involved.
>
>
> How do you figure that? An MC tank is barely larger than a propane torch tank
and
> only holds 10cf in the standard fill. Hard to imagine much of anything so
dangerous
> that one would be afraid to give advice. (Lack of a round tuit is the reason
for my
> delay) Hard to imagine much danger, period.
>
>
>>I know I
>>wouldn't unless I say this: Either throw the regulator away immediately
>>or take it and the tank to your welding supplier for advice.
>
>
> I used to own a compressed gas distributorship. Does that count?
>
>
>> I assume that you must have been using the tank on its side to need
>>to ask this question.
>
>
> Bad assumption. Especially on MC and E tanks, too rapid a withdrawal will
cause
> acetone carryover. In any event, I've never had any problems operating an MC
tank on
> its side and firing either a Prest-o-lite or a mini oxyacetyelene torch, both
low
> demand applications. Too little acetone too tightly bound to matter much.
>
>
>>>If acetone got into an acetylene regulator, could it cause
>>>sputtering? How about leaks? My regulator has the gauge needle going
>>>up and down when I try to run it.
>
>
> You didn't say how much the pressure is varying. Aged regulator needle valve
seats
> (neoprene or equiv) will get soft. This results in the needle sticking,
increasing
> the force needed to unseat the needle. The result can be pressure pulsations
instead
> of smooth linear regulation. The seat has to be resistant to acetone because
the
> acetylene is saturated in acetone vapor when it exits the tank.
>
> I've seen otherwise OK regulators that would pulse when the tank was almost
empty. If
> that's the case here then your regulator might be OK.
>
>
>>I did a leak check and gas was
>>
>>>leaking at the connection between the tank and the regulator. Could
>>>it be bad tank threads? An undertightened regulator? This is for a
>>>little MC tank. I find it really hard to try to tighten the nut
>>>without the bottle turning.
>
>
> NO, bad threads are not involved. No CGA gas fitting relies on the threads for
> sealing. The seal is a metal-to-metal joint and the threaded nut simply
provides the
> force necessary to hold the two mating parts together. Only a snug fit is
needed. If
> you're having trouble holding the tank then you're tightening WAY too tight.
>
> The tank fitting has a concave spherical mating surface and the spud (the part
> screwed into the regulator, also called the nipple) has a mating convex
surface. Both
> must be clean, smooth and symmetrical to achieve a seal. Inspect both for
burrs,
> dirt, digs and warpage. If you tighten the nut finger-tight and then spin the
> regulator back and forth a little, you should see a continuous shiny band of
bright
> brass on both the tank and spud. If you don't see these shiny rings then one
or both
> mating surfaces probably have been damaged, either from dropping or
overtightening.
>
> Given how cheap MC regulators are, I'd not spend much time on this. Do just
enough
> to verify that the tank valve's mating surface is OK, then toss the regulator
and get
> another one.
>
> John
> --
> John De Armond
> See my website for my current email address
> http://www.neon-john.com
> http://www.johndearmond.com <-- best little blog on the net!
> Tellico Plains, Occupied TN
> Save a tree, kill a beaver
>
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