From: John De Armond
Subject: Re: Replacing a propane tank's valve with a new OPD (Overfill 
	Protection  Device) valve.
Date: Thu, 06 Jan 2000 01:28:51 EST
Newsgroups: rec.outdoors.rv-travel

pjrich wrote:
> 
> In a couple of years, federal law will require that all propane tanks
> be fitted with an OPD valve.  Must a RVer take his older propane tanks
> to a service center to have the existing valves changed to OPD valves,
> or is it possible to DIY?  If you can DIY, are there other changes that
> must be made as well--such as to your propane hoses that screw into the
> OPD valve?  And, if you can DIY, where can you purchase the OPD valves
> at a decent price (and how much are they?)

OPD valves are available with both POL and Type I threads so you
won't have to convert your hoses if you don't want to.

Changing a valve is a DIY job if you're handy.  Here's an overview.

Safety points:

Make sure the tank is completely empty and depressurized.  Open the
valve and allow it to vent to atmospheric pressure.

Be aware that as you admit air to the tank interior, an explosive
mix can result.  Avoid heat sources and sparks while working on the
tank.

The procedure:

Most valves are set in the tank with a thread sealant that hardens
over time.  That, coupled with the fact that most valves seemed to
have been installed by a gorilla with a 10 foot cheater wrench means
that the valve is hard to remove.  You will need a means to turn the
valve and a means to hold the tank.  At my shop, I had a clamping
fixture to hold the tank that consisted of a welded steel "V" and a
couple of nylon ratchet straps.  The assembly was bolted to the wall
and held the tank very tightly.  I used a large crow's foot wrench
and a 3/4" drive to turn the valve.  A basin wrench of the type that
has a 90 deg head can often be used, though it will break on really
tough valves.

The first step is to heat the valve and tank top to soften the
thread sealant.  A heat gun works well for this.  I have used a
propane torch but I did so with tremendous care.  The valve must be
SHUT during the heating process to make sure the interior cannot be
ignited.

Grip the tank and turn the valve with the wrench of choice.  A heavy
rope wrapped several times around the tank can serve as an
improvised tank holder. If the tank is not too old, the valve
shouldn't be that hard to remove once warm.

While the valve is out, use a flashlight and inspect the inside of
the tank.  If there is any rust present, the tank should be taken to
a refurbishment depot  for refurbishment or else discarded.  Make
sure no thread compound falls into the tank.  Make sure there is no
other loose residue in the tank.

Pour a couple of ounces of anhydrous methyl alcohol (methanol) in
the tank.  This traps and removes moisture that enters the tank. 
This can be bought at Ace, home depot, etc, in the paint department.

Coat the threads of the new valve with gas rated (yellow) teflon
tape (preferred) or gas rated (blue or green) thread sealant and
screw it in place.  Tighten until secure and continue to turn until
the outlet lines up where it is supposed to be.

When you take the tank to be filled, tell the operator that the tank
needs to be air purged and leak tested.  It should be pressurized
with gas only and the valve and threads checked for leaks with a
soap solution or leak checker.  This gas is vented which carries out
most of the air.  Another pressurizaton and vent will remove enough
air to proceed.

The tank is then filled normally.

All that said, here are a couple of things to think about.

Check around.  You might find that you can get the valve changed out
for little more than you'll pay for the valve.  That's the case
around here.

If your tank's hydro date is about to expire, it will be cheaper to
allow the hydro tester replace the valve during the test.  The valve
has to come out anyway so the only additional cost will be for the
valve itself.

Especially for 20 lb tanks, it may be as cheap to simply replace the
tanks.  I've seen tanks for about $20 on occasion at Wal-Mart,
usually in the off-season.  Not only do you get the OPD valve but
you also get a new hydro date.

John