This will be a long one, I hope a lot of people chime in and add good info, and I will give it my very best effort because IT IS a safety issue.

Propane is a Petroleum product - and in theory LPG actually stands for Liquid Petroleum Gas, as opposed to Liquid PROPANE Gas. Technical, but true...

It is also a compressed gas, so tank recertification is an issue with it. We have to know the tanks can hold whatever pressure we can expect in them.

I guarantee you this thread will become more technical than you thought...

TANKS TODAY (APRIL, 2007):
BY LAW, all portable US tanks must be equipped with an Overfill Protection Device. What it does is close the filler when the tank is 80% filled with liquid LPG. This allows for adequate overpressure protection if the tank warms up. There is also a pressure release built into the tanks. You will notice if you had a tank filled during the winter that there may be some "Outgassing" as the weather warms up. It doesn't mean the tank is leaking due to a bad valve. It means it's doing what it was designed to do....

As the LPG expands, the excess pressure is bled off. This is normal. It also means you can fill a tank with more LPG in the winter than you can in the summer. I thought you should know that in case you heard a hiss from one on a warm day and flat freaked out over it....

Portable tanks are the ones you use for a grill, or that can be mounted on a travel trailer, etc...

There is another kind, it is called a DOT tank, and these are chassis mounted kind of like the big tanks we see next to old country houses. Those (odd as it may seem) do not require recertification. And no - I don't know why not. My best guess is that the vehicle is expected to be scrapped before the tank goes bad. (Pessimistic, but there it is)

My focus here is mainly on the portable tanks. They have to be certified, and they can be recertified after the original certification runs out. Initial certification is good for twelve years. The date is stamped on the carry-handle or collar skirt on the top of the bottle. It will be a four digit mark with something like a letter "A" shape in the middle. The first two digits are the month, last two are the year. 07A99 would be july of 1999...

After twelve years, the tanks can be recertified, but recertification is only good for FIVE years, so why would you? It's better to trade in the tank...

DENTS and DINGS in tanks: You should get rid of any tank with a dent in it deeper than one tenth of the width of the dent. That's the standard, right straight out of the RVIA (Recreational Vehicle Industry Association) manual. This in turn is based on a higher authority - OSHA.

There is another point that comes up because of a safety device included long enough ago that it applies to all fifty states now, Tennessee being the last to include it in their legislature.

This is an "Overfill Prevention Device Valve" (OPD Valve) and you can tell if your tank has one because the valve to turn it on on top of it will be shaped like a triangle. What it is - it's a float inside the tank that prevents the tank from being filled beyond a pre-set point with liquid gas by shutting off the inflow. Kind of like a gas tank level sensor. These can also cause problems when filling tanks if the person filling the tank leaves the tank valve open when turning on the supply hose - it will SLAM the OPD Valve, and lock the filler channel shut. These tanks have to have the "on" valve closed before filling, and then the gas valve is opened slowly. The bottom line here though, is that if you don't have a triangular valve handle on your tank - NOBODY will refill it. The fines for being stupid are memorable...

LPG is NOT the same as Natural Gas, and the two should never be mixed. You can't add an adapter and run a trailer off of "HOUSE" gas, because the system is not designed for it. In fact NG will destroy an LPG gas system if it is used in it. Just think of NG (natural gas) as "NO GOOD" for simplicities sake.

I think this is a pretty big bite to chew on for now, I'll add more to this later on.

~Wolf

 

Great stuff Wolf, keep it coming! I own a fifth wheel and am always trying to learn more about the propane system on it.
Thanks

 

Good points. Natural gas appliances have different sized burner orifices - definitely incompatible. This isn't just for campers - a gas range for your home must be converted (oven and burner parts changed or adjusted) if you're moving from where you had one fuel source to the other.

 

Greywolf, one correction to your post, portable "cylinders" such as the ones used on BBQ grills and TTs, are DOT cylinders, the permanently mounted "tanks" on MHs and what you see in the yard are ASME "tanks".
I just finished the LP or Propane course in the RV tech training I am working on and this is one of the things that was on the final exam.
Keep up the good work, a lot of people need the info that you provide on these RV subjects. Hopefully I can join you in relating some of my own someday.

 

Excellent info! Thanks for the lesson Greywolf.

 

I stand corrected - DOT tanks are indeed the small ones.
-Stands for Department of Transportation obviously...

ASME stands for American Society of Mechanical Engineers, oddly enough. You would think it'd be something more specific to pressurised gas or petroleum but it isn't.

Another point, and maybe Mechmagcn can help out some here (since my notes are all at work) the reason LPG is more common in the lower 48 is because it can and does freeze at a certain point - which would absolutely suck if you were trying not to get frozen your ownself! In Canada I'm not sure what is used, although I doubt you will see a big propane tank in anyones side yard there.

Kerosene is likely one alternative, but I would not expect to see it in an RV. Just file that under "LPG Properties" and we'll go on.

Under some conditions it is very possible for LPG to freeze in a tank valve or connection, and the fix is to warm it up somehow. HOT water I recommend. A HEAT GUN I definitely don't! If you suspect you have a frozen LPG blockage in a tank valve, get some hot water from somewhere, wrap the valve in a rag or towel, and pour on the hot water. Don't let it freeze on there if you can help it, just keep the hot water coming. This can sometimes get you up and running again.

It usually happens when switching the valve from an empty to a fresh tank.

Another point: You remember the vent I mentioned? The one that releases excess pressure? On the bottom of your regulator is about a half to three quarter inch wide hole with a screen in it. THAT is the vent. The regulator must always be mounted so that the vent is pointing DOWNWARD. If not, it can get water in it, water freezes, and guess what happens next? It don't work no more...

All modern regulators also have to be two-stage regulators. In the old days they were single stage. If you have a single stage regulator, there is no backup if the regulator fails. You can tell if an older type regulator goes bad because the cooktop burners have flames that reach the cieling... (he says, drily)

Here comes an energy budgetting tip:

ONE gallon of LPG contains roughly 90,000 BTU's of energy. Most RV furnaces average (when continuously running) around 30,000 BTU's per hour.

What this means is that if your furnace is on full-blast (running all the time) you can go through a gallon of LPG in about three hours. Most travel trailers and fifth wheels are equipped with two seven gallon tanks. The math is simple - crank the thermostat up to ninety in very cold weather, go in and out the door a lot, and both tanks can be used up in about 42 hours...

In practice, a tank will last a lot longer if it is kept down to a reasonable level. Since the roof A/C is not being used, you have an extra 15 amps you can use to run an electric heater. I strongly advise it!

ALSO, the interior of the trailer will absorb latent heat over time so it won't take as much heat to maintain an already warmed up unit.

A friend of mine told me he sets his thermo to 55, and turns on a space heater when he gets in at night. Once he gets under the covers he turns the electric heater off. He said a tank will last him more than three weeks...

 

Greywolf. Propane really doesn't freeze, it just exceeds the rate of vaporization during cold weather. This means that the liquid propane won't vaporize fast enough to keep up with the demands of a large demand appliance.
Actually all of the LP that we buy contains some butane along with the propane, usually more so in the south and even more in summer, because butane will stop vaporizing at 15 degrees, while propane will continue to vaporize down to -44 degrees, but at a slower rate relative to how full the container is.
A 20lb cylinder will have 36,000 BTU available at +20degrees at 60% capacity, but will have only 4250 BTU available at -15 degrees at 60% capacity. This is quoted from the 2005 RVIA textbook from the LP training course.
I really had no idea of these facts until I took this course, which ended yesterday!

 

Yeah, the vaporization can go way down in the cold. For a v8 generator where I work, we had to bury the tank in the ground to be sure it would have enough flow if needed in a New England winter.

 

Debatable - everything freezes at some point - but the evaporation point is a big consideration.

Here's a goody for YA! ETHYL MERCAPTAN... (NO, she don't live down the block...)

This is the substance added to LPG that makes it STINK! One part in ten thousand, I think it is. So it doesn't take much.

BUT! (and here is the thing) In older systems there was an oil based, ummmm... "STINKER" that was added. It was re-engineered for a very simple reason -
It caused a thick tarry sludge in the LPG lines over time.

Bits of it could get into gas orifices and plug or partially plug them. Once cleaned out or replaced, ANOTHER wad of the stuff could do the same thing. A good point to beware of in an older RV. I'm trying to think what year they made the change, and 1987 seems to ring a small bell at the back of my mind.