Date: Mon, 9 Jan 2012 20:56:46 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: New Propane tank fill valve/fitting
In-Reply-To: <4f0b8cb8.89bde00a.664e.ffffa38c@mx.google.com>
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At 07:56 PM 1/9/2012, Edward Maglott wrote:
>I have 2 goals in mind with this modification. One is to have a more
>common fitting on the tank so that I can get it filled more
>easily. I've run out of propane on the road and had to visit more
>than one place to find one that had the adapter that fit the fitting
>on the van. I think any place that can fill a BBQ tank or an RV
>should be good to fill this 1 3/4" ACME fitting. The other is that
Erm...what you already have on there is a 1 3/4" Acme valve, unless
someone has been seriously messing with things. It's *not* the same
as what's on a 20 lb BBQ tank. That's Acme but much smaller
diameter. I initially thought that the valve you pointed to was of
this smaller size (one-inch?) which is why I responded as I did. If
you have the OEM valve still present, it has an automatic stop
facility which makes it more complicated and expensive - the tank
fitting that acts as a level gauge (by passing liquid instead of
vapor when the tank is filled to 80% of its "water capacity") is
plumbed into the side of this valve which detects the passage of
liquid and closes against the incoming fill.
The valve you're looking at doesn't have this complication and
requires the operator to observe when liquid starts coming from the
opened gauge valve and stop filling at that point. If he doesn't
stop immediately you then have to continue bleeding off the liquid
until you get back down to vapor coming from the valve.
New ASME tanks (the kind we have, stands for the American Society of
Mechanical Engineers) have a float-type shutoff similar to the ones
now required in DOT (Department of Transportation, BBQ-type)
tanks. Unlike the DOT tanks however there is no requirement to
retrofit such valves to existing ASME tanks, nor is there any
requirement for periodic testing/recertification of ASME tanks which
are constructed much more heavily than DOT tanks. If you bought a
new tank from Manchester Tank it would come with the float-type shutoff.
But regardless, all these tanks (manual shutoff, liquid-flow shutoff,
float-type shutoff) are filled from the same hose, or the same
adapter if it's an outfit that primarily fills DOT tanks.
If you *were* to put a BBQ-tank valve onto one of our tanks you would
have to remove the Overfilling Protection Device (float-type shutoff)
from the valve, and would be in at least a questionable area
regarding whether the tank would still be considered certified as an
ASME tank. In practice I think you would have difficulty finding
people willing to fill it for you, though that is a guess. And you'd
still have to install and use the manual gauge valve. If you *did*
find people willing to fill the tank I think there would be an
increased risk that the operator would fail to open the gauge valve,
since they're spring-loaded by now to expect the BBQ tanks to shut
themselves off without any operator intervention.
Purely by the way - the Acme designation no doubt comes because the
external thread used to couple the fill hose onto the valve has the
"Acme" thread form which is commonly used for leadscrews on lathes
and similar machinery and other power-transmission uses. It's a
modification - stronger and easier to machine - of the square thread form.
Yours,
David