I know! I know! LP tanks are boring!!! Well... they may be BUT since you'll find them on all sorts of rv's including motor homes, fold down campers, truck campers, travel trailers, and 5th wheels it only stands to reason that since we're using them we should also under- stand them. REMEMBER, liquid propane is a gas, it is stored under pressure, it is flammable, and IT CAN BE DANGEROUS. There are not only rules, which must be followed in their use, but also laws have been enacted to help insure the safe use of liquid propane. All of this is especially pertinent for older units and many purchasers of these units who thought they "got a steal" on that old trailer get a surprise when they learn the LP cylinders are "out of date" and subsequently "illegal".



OK, let us review some basics.

First, there are two types of tanks or cylinders.

DOT (Dept. of Transportation)

Dept. of Transportation container is the one most of us are familiar with. They are

Vertical in style and are referred to as DOT cylinders.

- used primarily on fold down campers, truck campers, travel trailers,

and 5th wheels.

- can be removed from the recreational vehicle

- usually used in the vertical position, BUT not always. Some may be used

in the horizontal position but each cylinder MUST be used in the manner for

which it was designed. (they are usually marked for the position in which they should be used)

Pre l998 cylinders without OPD devices could be used both ways both this does not apply

today as OPD, devices are required on ALL cylinders.ASME (American Society of Mechanical Engineers)

-manufactured to the code of the American Society of Mechanical Engineers

-most commonly referred to as "tanks"

-usually found in motor homes

-are mounted permanently

ASME SERVICE VALVE

-marked "vapor withdrawal"

-used only for vapor withdrawal

(ASME tanks have a separate fill valve - one with the yellow cap)

TYPES OF SERVICE VALVES

Three types have been available for RV's in recent history

1) Most common was the POL CG 510 (Presto Lite)

-identified by its 5 or 6 prong twist handle and its

metal left-handed hose connect

2) OPD service valve with "quick disconnect" which is primarily used

by the BBQ industry and is NOT permitted for use on rv's

Quick Disconnect fittings can be used downline on rv's on such

things as gas grills but are not permitted at the LP cylinder

3) Type I OPD service valve which is now mandatory (May l, 2002) and

has a 1 5/16" ACME thread and is easily distinguished with its black

or green connector for the high-pressure hose connection.

The open/closing twist handle will also only have three prongs which

distinguishes it as the new style.

"NOTE"

There is an exception however. You can run into the "POL style" with

the left handed brass hose connectors with OPD devices. It is easily

distinguishable as the open/closing twist handle will NOT have the old

style 5 or 6 prongs but will have the new style 3 prong handle which

will be clearly labeled OPD. You can rest assured you are not only

up to date but also legal.

OPD DEVICE (Overfill prevention device)

OK, so what is the big deal about the OPD device we have been referring to? OPD devices

are now required on all recreational vehicles cylinder and tanks are a safety device to

insure that cylinders and tanks are not filled above the 80 full range.

While they are not foolproof, for the most part they accomplish their intended purpose. Obviously

the float devices differ between the horizontal and vertical containers so cylinders and tanks with

OPD devices MUST be used in the position (horizontal or vertical) for which they were designed.

FIXED MAXIMUM LIQUID LEVEL GAUGE

The fixed maximum liquid level gauge is another device, which all rv'ers should be familiar with

and understand its purpose. The following will help distinguish it from other devices.

-used to determine the 80 level -on ASME tanks it is physically located at the 80 level.

How it is used

-should always be OPEN (turned out) when container is being filled

-during the filling process vapor will be emitted until liquid reaches the

80% level when a "white mist" (liquid propane) will be emitted signifying

the container is FULL.

If the container is filled past this level, the excess propane should be

"bled off" until only vapor is emitted to insure container is not overfilled

in addition, to avert any possible future problems with the container.

For instance, an overfilled container could become dangerous if left in a vehicle

or in the sun as temperature increases the pressure inside the tank.

Now you have a basic understanding of what you are looking at when you see a LP tank or cylinder and you will know if it is up to date. One more thing to note is the condition of the tank. Tanks that are either rusted or missing paint should be closely inspected for any other possible damage. If you question anything on the tank or cylinder, have it inspected by a professional.