Filling Propane Tanks

dougrainer wrote:
Since people do not care to research the issue, here is a simple version of what can happen with a slightly overfilled tank and THIS has happened and documented. A lot of RV'er transport 20 or 30 lb DOT tanks in there Motorhome or Towable(usually 5th wheels) storage. So, it is 70 degrees when filled and they overfill the DOT tank and you throw it in the RV and take off. You go to a climate that is 95 plus and camp out. The interior storage heats up and the LP heats up. Then its system blow out valve opens and spews LIQUID LP inside your RV. What happens when that LP reaches an Ignition source? There are lots of them inside and up in a RV. Most would blame the Norcold 1200 refer if it had one:B Same thing can happen in your enclosed Pick up bed or the trunk or interior of your car. I have seen enough REAL evidence in 40 years that I believe what Texas mandates and what we practice is the BEST way to handle LP. Doug

That is beyond silliness, it’s well into fantasy.

A 20 or 30 pound cylinder uses ,as per DOT regulations, a CG-7 spring loaded over-pressure valve. It begins to open at 360 psi, and is fully open at 480 psi, but it recloses at 240 psi, the design working pressure of those tanks.

Propane doesn’t expand much with temperature, it does however produce more vapour and therefore pressure. At 60 deg. F. propane is at 92 psi, at 130 deg. F. that has only risen to 257 psi, which is still about 100 psi BELOW the pressure relief valves opening point.

Beyond all of that, the pressure relief valve is at the TOP of the tank, thus if it opened would mean that ONLY vapour would come out, besides the fact that propane boils at -42 deg. F. and so it would in this ‘overheated’ situation be some 150++++ deg. F. hotter than that and so could not be a liquid once it’s not contained in a pressurized vessel.

Even if the cylinder were drastically over-filled, not “even slightly over-filled”, could the ‘spew liquid LP’ be remotely possible.


Rant over.