Do 20 lb propane cylinders use back seating valves?

[bigb]

I always assumed the small 20 lb BBQ and RV cylinders used back seating valves and I can find some confirmation and opinions either way but nothing from an official source.

[smithdoor]

The propane type valves typically is all on so seat does not leak. But could have changed over the years to a better valve.
You need to see if your valve want to be fully on.

Dave

I always assumed the small 20 lb BBQ and RV cylinders used back seating valves and I can find some confirmation and opinions either way but nothing from an official source.

[smithdoor]

FYI I use the 20lb exchange tanks and have filled at the gas station.
Exchange when the tank is out of date or the valves leak.

Dave

I always assumed the small 20 lb BBQ and RV cylinders used back seating valves and I can find some confirmation and opinions either way but nothing from an official source.

[Sberry]

I am not sure how much the ones I saw today at the exchange really were, the sign says 15# and the 20$ price sign was well scratched over. The supply hose finally sprung a leak after 25 years or so and I had nice chunk of copper line on hand to replace it.

[whtbaron]

I always assumed the small 20 lb BBQ and RV cylinders used back seating valves and I can find some confirmation and opinions either way but nothing from an official source.

Interesting... my search turns up the same variety of answers. I wonder if it varies between manufacturers or geographical location/local codes?

[Oldiron2]

I always assumed the small 20 lb BBQ and RV cylinders used back seating valves and I can find some confirmation and opinions either way but nothing from an official source.

I have removed and disassembled quite a few propane valves, particularly the older versions no longer legal but even a few newer ones with the fluid level shut-off. My memory isn't the greatest wrt details like this that don't (then) catch my interest but I don't recall seeing any valves that did have back-seating. For two/three days I've been looking for some scrap ones to photograph, but none were readily found, so no pictures today.

I do recall some valves w/ a diaphragm separating the control from the fluid side, but don't think they were for propane; probably for an industrial Freon.

[whtbaron]

This guy is probably more of a lesson in what not to do, but it doesn't appear to have back seating....

[bigb]

I watched that video of the guy taking the valve apart and there are two orings so I wonder if one oring seals the stem in each direction?

[whtbaron]

Not sure... I was wondering the same thing.

[danielplace]

I watched that video of the guy taking the valve apart and there are two orings so I wonder if one oring seals the stem in each direction?

They aren't. Too close together. They just travel up and down the smooth bore above the seat. They seal the same open or closed or any position in between. It doesn't even have seats at all for the stem in either direction. Only at the tip for closing off the valve and two orings.

Just two orings running up/down in the bore. Nothing else above this sealing anything.

[shortfuse]

Why not call a place that provides propane to residential and industrial customers and ask them?? Or better yet, a company that makes the 20# tanks???

[danielplace]

Why not call a place that provides propane to residential and industrial customers and ask them?? Or better yet, a company that makes the 20# tanks???

Likely to get mixed responses there as well depending on just how intelligent the individual that answers your question is.

That probably would not be ok for a gas valve to be leaking just because someone didn't open it all the way.


Think about that question for 1/2 second. Nope they DO NOT have to be back-seated. Lol.

"Darn it, seems the wife only opened the barbecue tank valve 1/2 way and lit it 20 minutes later and blew the back of the house out".

Fuel gases would have different rules than for inert gases.


The video posted shows one being dissected. It doesn't have any seats above the one at the tip that closes off the flow.

Those orings would have been dead centered in a taper if they were seating into/against a taper. There is no other brass on the stem sealing just the threads and maybe a top seal but nothing valve operated at each end of the threads travel. They would be the stops if they were there but they don't exist.

[bigb]

Think about that question for 1/2 second. Nope they DO NOT have to be back-seated. Lol.

"Darn it, seems the wife only opened the barbecue tank valve 1/2 way and lit it 20 minutes later and blew the back of the house out".
.

That is the likeliest reason they don't need to be back seated as how could you make that a requirement for the general public who is not even smart enough to know you don't get in and out of your vehicle when fueling? I was only wondering if perhaps one did leak a bit at the stem if back seating it would stop it. I have one now that leaks when opening but seems to stop when fully open, at least I get a big whiff when opening it that goes away once opened. It's very old and expired and is just about empty, will give it to Blue Rhino for a fresh one soon.

[William McCormick]

That is the likeliest reason they don't need to be back seated as how could you make that a requirement for the general public who is not even smart enough to know you don't get in and out of your vehicle when fueling? I was only wondering if perhaps one did leak a bit at the stem if back seating it would stop it. I have one now that leaks when opening but seems to stop when fully open, at least I get a big whiff when opening it that goes away once opened. It's very old and expired and is just about empty, will give it to Blue Rhino for a fresh one soon.

It could just be the wear is right at the spot where it opens, and then hits fresh meat as you back it out. I think they seal because I had a few forklift tanks that leaked and if you backed them out all the way they would stop too.

That is one of the things I was wondering about Oscars three acetylene tanks all connected together.

I am assuming he has high pressure check valves on each tank, but even so if one of the check valves went bad and you hit an empty tank with a couple hundred pounds from a new tank what kind of heat would you generate?


Sincerely,

William McCormick