Right - NEVER turn a cylinder upside down. This allows liquid propane to go to
the pressure regulator, which can't maintain the required burner pressure
properly on liquid. In tests the results are very unpredictable - the system
may seem to work fine, then suddenly produce high pressure and / or vent gas
from the regulator relief valve.

Propane is stored as a liquid under high pressure (~150 psig but varies
greatly with temperature) and vaporizes as propane vapor (gas) is drawn off
through the valve/regulator. The regulator reduces the pressure to about 11
in-wc (less than 1/2  psig). When the liquid vaporizes it absorbs a lot of
heat - so the tanks will often "sweat" or frost around the liquid area from
moisture in the air condensing on the colder tank.

If liquid reaches the regulator it flashes to vapor as it passes through,
expanding and cooling greatly. A "gas" regulator is not designed to handle
this, and the outlet pressure will surge around. The pressure may go high
enough to open the regulator's pressure relief valve (which they are required
to have), thus venting propane through the regulator vent. (This venting is a
designed safety feature, since by code the regulator is supposed to be outside
where it's safer to vent gas than allow high pressure into the piping.)  The
vaporizing liquid will also COOL the regulator - possibly to -40 and it may
frost up and freeze the mechanism, thus losing pressure control. It's also
possible with continued use for the piping from the regulator to the burner to
cool enough that liquid propane at low pressure can flow all the way to the
burner, where the heat will vaporize it fast and then the pressure may......

The possibility of liquid sloshing to a regulator on RVs is one reason the
codes changed to require 2-stage regulators on them instead of single-stage
"grill" regulators - the 2-stage has higher tolerance for momentary liquid.
Keep this in mind if replacing a Winne regulator.

Propane, like gasoline, represents a LOT of stored energy in a small space
(that's what makes it useful) - and mis-using it can release that energy in
very destructive ways.

Sorry for the lecture - I spent years on the National Propane (then LP-GAS)
Association Safety Committee, and saw too many results of mis-using the
equipment and fuel.

Tom
Austin, TX

----------
From:   Vanagon mailing list on behalf of Eric Zeno
Sent:   Tuesday, October 21, 1997 7:03 AM
To:     Vanagon@GERRY.SDSC.EDU
Subject:        Propane Problems! Proxy heater warning!

   This happened last year.

   A friend a mine heats his garage with a 20 lb. propane tank and
   a construction sight, style heater. (looks like a karosone).
   Some other people who rent one of the adjacent garages, liked
   this heater and bought one. As we were talking over the holiday,
   the tank was running low on propane, so my friend walked over
   to it, and turned it upside down. He said he did this to ensure
   the tank would completely empty. I didn't like the idea, but if
   it was almost empty, not much could happen. Well the people with
   the adjacent garage saw this, and inverted there brand new full tank
   of propane. After sometime THE GARAGE BURST INTO FLAMES! For
   some reason, up at the tank end, something failed, the regulator
   or maybe the hose burst. This sent propane across there garage
   and flamed up, instantly, as it got near the heater.

   3 Fire companies were called to put out the fire. Later It was
   found that the hose had burst. I don't no if this was a resault
   of inverting the tank or not. The hole thing was brand new, so the
   problem wasn't wear. Anyone have any ideas on this? I'm thinking
   that inverting the tank forced liquid out of the hose, maybe causing
   an over pressure. If this is true could driving with a proxy heater
   turned on cause the same problem?

            Eric                   86-VW4x4
            vw4x4@fyi.net          72-240z
            Pittsburgh, PA USA     1936-Chrysler