Venting Propane tank

[Padlin]

Had a strong gas odor out by the 2 30G gas tanks yesterday. Pulled off the cover and sprayed down all the connections with soapy water looking for a leak. When I did so the pressure vent at the back of one of the valves started to discharge for maybe 10 seconds. I weighed the tank that discharged and it still shows full, the selector is pointing to the non discharging bottle. Other then that no leaks.

This morning I can not detect any odor.

Yesterday was sunny and close to 90, this am it's cloudy and 50.

Could it just be an issue of a full tank heating up and going over pressure?

I'm not using the trailer for a couple weeks so I can keep an eye one it, I'd be pretty nervous if we were in it.

[Old-Biscuit]

naturist wrote:
There are portable propane tanks like the 20 pounders people use for gas grills that come in 5, 10, 15, 20, 30, 40, 60, and 100 lb sizes. THOSE should NEVER be stored inside for the very reason this thread exists. There are also permanently mounted (usually horizontal) propane tanks on some of the bigger RVs as well as on some trucks. The permanent-mount jobs have a vent that discharges outside the rig, even though the tank itself is mounted inside.

IF they are 'portable' they are 'cylinders' (not tanks) and under DOT
If they are permanently mounted they are 'tanks' ASME

[SCVJeff]

mlts22 wrote:
Are we meaning propane tanks that are permanently mounted under a vehicle (which can/do vent), or propane cylinders (which are vented, but are portable)?

The propane cylinders I see in fifth wheels and motor homes almost always have venting, especially on the bottom (as propane is heavier than air.)

I had a neighbor next to me in the storage facility who's just filled tank vented and the spring shattered, venting the entire (at least) 40G tank out FAST. Conditions couldn't be worse... warm day and dead air. And there is nothing you can do to stop it.

[brholt]

Clay L wrote:
The vent pressure of most LP tanks is 250 psi.
I found a chart that shows that propane at 80 F will have a pressure of 140 psi. Using the ideal gas law I found that the temp would have to go to 500 F before the tank pressure reached 250 psi. That seemed high and even though the calculation is simple I used a couple of on-line calculators and got the same answer.

The chart is HERE and one of the calculators I used is HERE

It doesn't appear that an enclosed compartment, truck or car interior is going to get hot enough to cause venting.

The temperature is actually about 125 F to reach 250 psi. You need to calculate the vapor pressure of propane.

[Larryect]

It happened to me once before the new type tank valves we have now. Had them filled near home, went on a trip. Higher elevation, hot day, sun hitting the tanks. Tanks vented. I figured all of the above plus possible overfill by the guy filling them - overfilling is less likely now.

Flip the regulator so it uses some of the propane from the tank that vented.

[Clay_L]

The vent pressure of most LP tanks is 250 psi.
I found a chart that shows that propane at 80 F will have a pressure of 140 psi. Using the ideal gas law I found that the temp would have to go to 500 F before the tank pressure reached 250 psi. That seemed high and even though the calculation is simple I used a couple of on-line calculators and got the same answer.

The chart is HERE and one of the calculators I used is HERE

It doesn't appear that an enclosed compartment, truck or car interior is going to get hot enough to cause venting.

[naturist]

There are portable propane tanks like the 20 pounders people use for gas grills that come in 5, 10, 15, 20, 30, 40, 60, and 100 lb sizes. THOSE should NEVER be stored inside for the very reason this thread exists. There are also permanently mounted (usually horizontal) propane tanks on some of the bigger RVs as well as on some trucks. The permanent-mount jobs have a vent that discharges outside the rig, even though the tank itself is mounted inside.

[mlts22]

Are we meaning propane tanks that are permanently mounted under a vehicle (which can/do vent), or propane cylinders (which are vented, but are portable)?

The propane cylinders I see in fifth wheels and motor homes almost always have venting, especially on the bottom (as propane is heavier than air.)

[dave_from_mesa]

bid_time wrote:

TenOC wrote:
That is why you should NEVER store a propane tank indoors.

So all those fifth wheels and motor homes running around with propane tanks are doomed?

Both our mh's had the tank in an area that had a door but no floor. While closed not really indoors.

[bid_time]

TenOC wrote:
That is why you should NEVER store a propane tank indoors.

So all those fifth wheels and motor homes running around with propane tanks are doomed?

[SkiingSixPack]

Had pretty much the exact same thing happen .... Got our tank filled when it was cool, then it got hot and the relief valve started to leak. I just turned on the furnace and all the burners. This allowed enough of the propane to release and stop the relief valve from spewing.

Great lesson on why to never store propane tanks inside, as TenOC pointed out.

[Padlin]

Thanks

[TenOC]

That is why you should NEVER store a propane tank indoors.

[ken56]

yep. the relief valve worked correctly. it did what it was supposed to do.