LP Gas

[CHARLOTTE]

Can anyone tell me about the proper way to fill the LP gas. It's been my experience that the station fills the tank only 80%. Can anyone tell me why that is? Thanks in advance....

[whemme]

I am not an expert on LP gas tanks but I think the reason they fill the tanks to only 80 to 85% of capacity is to allow room for gas expansion under high temperature conditions. I am sure that George Boley would know more about the technical reasons for this.

And I do think it is a good policy to let the experienced experts fill this tank.

[Roger H]

Charlotte,

Let me preface my remarks by saying that like you, I'm merely a consumer of LP, not an LP professional. However, I have a couple of friends who deliver LP from our local Co-op and have learned a few things from them.

I got my education a couple of years ago when I had "vertical mounting type" aluminum LP tanks fitted with horizontal fittings with the tanks mounted horizontally in the tongue of our Airstream 34' tri-axle trailer. It was interesting to try to get those filled!

A few years ago the LP industry implemented a new valve (overflow prevention device or OPD) that shuts the supply off at 80% when filling vertical tanks. Horizontal tanks, such as ours, can't use the OPD because of the mounted orientation of the tank, but they still only fill them to 80%. Horizontally mounted tanks in motorhomes, farm equipment, and forklifts are exempt from the requirement for OPD valves. LP tanks also have an over-pressurization release valve that will vent when the pressure is too high. As you can imagine, on a motorhome it is NOT desireable for the LP to vent when your fridge has an open flame, the catalytic converter is nearby, and there are hot brakes nearby as well.

Roger

[bill crommett]

------And just imagine what would happen if raw liquid LP would come spouting out your cook top !

[Mel Wilbur]

It is my understanding that LP expands 1.5% for every 10 degrees rise in temperature. This means that if you filled the tank to 80% in Maine at 40 degrees and drove to Phoenix AZ where it was 110 degrees and did not use any LP along the way the tank would be approximately 90.5% full.

[bechlumber]

The propane tanks are only filled to 3/4. You can see this on the gauge of the tank. The propane then has room for expansion under higher temperatures. Some 27 years ago my family had a motorhome, a Ford Roll a Long, that Linda and I used for a trip to Oregon in June. It was snowing by Diamond Lake when we got the propane tank filled to the top, with no room for expanison. We went over by the coast where the temperature was over 80 and we could smell propane. The propane had expanded and was coming out of the relief pressure valve. I had to manually release propane until none came out of the valve. It was not a fun thing to do.