Safely transporting propane

[HenryJ]

Want a horror story of propane transported in an SUV?

Our department responded to a car fire. Todd attacked it from the rescue. Within seconds the explosion launched him backward about 50 feet.
The driver received 2nd degree burns.
He had just filled a 10 gal. tank and it was on its side in the back of his Bronco II. The vent valve was not closed fully and leaked liquid petroleum. This pooled in the back and when he hit his brake lights the fire was sparked. He jumped out when he saw the flames. By the time we arrived the flame impingement on the tank was enough for a BLEVE . The pressure relief system was unable to function properly since it was on its side and under the liquid level.
Half a city block away a screwdriver was found lodged in the tree. The whole tool box in the back was shot everywhere.
No one was seriously hurt.
It was a big bang to say the least.

Most propane tanks to not have resettable pressure relief devices. Most have frangible disks that release and do not close. Large tanks do have auto resetting pressure relief valves, but are required to be located in areas where its function would not offer a dangerous atmosphere.
Mount the tank on the exterior. Do not hide it, please.
If your vehicle is on fire and I respond to put it out, I want to see the danger of a propane tank and have the ability to keep it cool if at all possible.
Hiding one inside is not only a danger to you, it is one to me.

 

[MountainBiker]

Does anybody know if the 16oz green cylinders are also designed to vent off excess pressure? Most of us have driven around with them many times with no problems.

Those cylinders are non venting before you first use them. After the first use, they are technically not designed to vent, but the valve can leak.

Keep in mind that propane is heavier than air, so it settles into the low spots. On a boat, this is the bilge, and can easily build up without being noticed!

 

[gearguywb]

A couple of thoughts....

Propane is indeed heavier than air and expands from liquid to vapor at a ratio of 270-1. That is the reason that tanks must be transported in the "upright" position. If the relief valve opens and it is in the liquid space of the cylinder then the escaping liquid will immediately turn to vapor at the expansion rate. Means a small escape turns into a big one.

It is not physically possible for propane to "pool" in it's liquid form. The boiling point to transform from liquid to vapor is -44 degree farenheit.

The National Fire Prevention Act limits the amount of propane to be carried in a passenger vehicle, without a seperat compartment, at 90 lbs. This includes the weight of the cylinder and gas.

The main issue that I have come across that leads to opening of the relief valve is the improper filling of the cylinder. Typically when you are having a cylinder filled at the local hardware or grocery store the person doing the filling has received little or no training.

 

[slomatt]

HenryJ,

I completely understand your concerns about making sure tanks of flammable gas are visible in or on the vehicle. One of my roommates is a contractor and usually has a tank or two of acetylene in the back of his truck. Two months ago there was a car fire in our neighborhood, and his truck happened to be parked next to the burning vehicle. We called 911 to make sure the first responders knew about the tanks (and had to explain to the operator what acetylene is), and still had to run out the door warning the police office who arrived first when he went right up to the back of the truck.


mk4,

The odor will help you notice the leak if you are in the car, but I would be more worried about parking the car on a hot day and having the tank vent while I was not around. At that point it would just take a single spark to cause an explosion.


- Matt

 

[ntsqd]

snip......
Does anybody know if the 16oz green cylinders are also designed to vent off excess pressure? Most of us have driven around with them many times with no problems.

- Matt

There is a second valve on these tanks. Looks like a Schrader-type core, but since it is outside of the threaded port perhaps it is some sort of over-pressure vent?

 

[HenryJ]

A couple of thoughts....It is not physically possible for propane to "pool" in it's liquid form. The boiling point to transform from liquid to vapor is -44 degree farenheit.

True. The liquid turns to vapor and pools in the low areas.
Thank you for making that clearer than I was able to. Sometimes you just assume that everyone knows propane is in a gaseous state under normal atmospheric pressure and temperatures as well as it being heavier than air and that it lays or pools in low lying areas. My reference to the liquid leak was to relay that a small leak was multiplied over 250 times by the fact it was below the liquid level of the full tank. Again, perhaps I should have been clearer.

I am not a propane expert. I am a Hazmat Tech and firefighter. We know a little bit about a lot of things. As far as I know the smaller cylinders are not built with a resettable vent valve. This means that the valve designed to open when internal pressure maximum has been exceeded opens and will not close. This will vent the entire contents of the package.
That being said the propane bottles are pretty well over built. I have seen the small green cylinders go through some very harsh conditions and remain sealed. It is going to take more than sitting in the back of a hot car to get them to fail. The little ones are not too scary when they blow. Nothing like an oxygen bottle, or 150 lb acetylene tank. Those make you pucker pretty good.

 

[TeriAnn]

It's sounding like there is no good option for propane storage in an SUV. Since the tank has to be mounted vertically it would be very difficult to fit it under the truck

I beg to differ because there is a class of horizontally mounted propane tanks. The normally come with a welded on cradle, the cylinder horizontal in the cradle and the valve mounted at the top (side) of the cylinder above the cradle.

Horizontal mount propane tank built into my Land Rover.
It is mounted to the front frame outrigger of my rear leaf spring.

A different brand horizontal tank

Horizontal tanks are designed to be permanently mounted in place.

If you are looking for a used one a Westfala VW camper van usually has a horizontal mount tank.
​

 

[njtaco]

FWIW...

IMHO, LP tanks are safe when properly filled, properly installed, and not inside a vehicle or on fire.

That is a pretty brash statement, so here is why I say it.

I have seen a 100lb LP tank vent, when overfilled, then let to sit in direct sunlight. It did "reset" without emptying all contents. Worked as designed.

I have replaced tanks that had parted company with the travel trailer, been dragged down the road by their supply hoses and sucked under the trailer. One tank became lodged forward of the axle before coming to a stop. No leaks, no fire.

Another tank, like the one TerriAnn pictured, fell out of a class A motorhome at 60 mph. It contained about 64 lbs (80 lb tank at 80% full) of propane. They had to jack up the vehicle to remove the tank from underneath. Again, no leaks, no fire.

The tanks can take a beating!

I'll temper that with a sad story. One that may have involved human error.

This took place at a campground where I used to work. A (possibly) overfilled 100# LP tank vented in the sun, as the one described above. A local volunteer firefighter decided to try to shut off the "main" valve, not knowing it could not stop the vent from operating. He probably figured the rubber supply line had failed. The propane water heater fired as he was trying to shut down the tank, and ignited the whole mess. He died in the fire. Others were injured nearby. Material damages were costly. If the tank had been less full, venting may not have happened. If the tank were positioned further from the heater, there would have been less risk of ignition. A firefighter's nightmare come true.

We have lost many homes, especially condos, to grill fires due to the tank venting while grilling. The mandated OPD fill valves have drastically cut down on these fires.

My point? As usual, the product works when used as intended. Use common sense. Follow the rules. Safety first.

I like the OP's idea of a 1 gal (4.5lb) tank, or even a 2 gal (10LB) tank, mounted on the roof or rear bumper mounted. Keep it out of the cabin.

Oh, don't lock it to the truck. The faster it can be removed from a fire nearby, the better.

My rambling 2C.

 

[grahamfitter]

Somewhere I saw an interesting setup with squatish roundish 10 poundish propane tank attached mostly inside a rear mounted spare tire on a Land Rover. It looked like a good use of space and was outside the vehicle.

Cheers,
Graham