Where does the propane go?

[D_E_Bishop]

Ol biscuit and I disagreed on whether or not is was possible for there to be air in a propane system basically with the tank valve shut and all the appliances turned off(valves shut). He said impossible but I say there is a gas(inert) in the system that won’t burn but will blow a match out.
As he said, it is a closed system and I agree, however, there is that gas flowing through the pipes that won’t burn. How is this possible? My system is all hard piping, no rubber hoses. I have never had an alarm that I didn’t want, i.e., testing of the alarm. Each appliance has at least three valves between the tank and the igniter and burner.
It makes no never mind, it is just that an inquiring mind wants to know. If I shut off the appliance, turn off the solenoid and shut the valve on the tank, where does the gas go? I’m sure there is a good answer, I just don’t think it is logical.
Any ideas from you experts?

[darsben]

If air was not able to enter then the guy filling the tank would not have to open the bleed valve until gas is expelled. A lot of refillers do not but most LP gas companies do. It is always done b the refiller on my motorhome

[donn0128]

He may be a retired something but gas specialist he aint. Leave my gas off for a couple of weeks turn it on and it takes several minutes for gas to refill the lined enough to light a burner. Been that way on every RV I have used or owned way back to 1977. Same RVS have been tested with no gas leaks! Where it goes? No clue. I'm not small enough to crawl thru the lines to watch my gas excape. I just know it is so.
BTW rubber hoses can and do leak. Even brand new.

[nomad297]

352 wrote:
Light a match and you will figure it out real quick.

It will only be effective (light) if the match is held far enough away from the outlet to allow the appropriate amount of oxygen to mix with the LP. If you hold the match right against the outlet, it will be blown out before the flow of LP is small enough to have the correct amount of oxygen to combust.

The LP remains in the pipe and is not displaced with air or turned into some magical inert gas.

Bruce

[rhagfo]

Chris Bryant wrote:
The solenoid valves are not perfect. Also, LP is extremely temperature sensitive, so after the pressure reaches equilibrium, negative pressure will be created when the temp drops, drawing air back in to the system.

Air should not be drawn into the system through a closed valve. Propane is capable of blowing out a match, and not ignite.

Personally I keep the system pressurized all the time. I believe far better for the valves, I have had several homes with gas never shout off the gas there either.

[Dakota98]

In the propane tank. :S :B

[newman_fulltime]

Dude I hate to be the one to bust your bubble but old- biscuit is a RETIRED RV TECH

So the gas in my gas line on my truck won't burn if the ignition is off?

[352]

Light a match and you will figure it out real quick.

[Chris_Bryant]

The solenoid valves are not perfect. Also, LP is extremely temperature sensitive, so after the pressure reaches equilibrium, negative pressure will be created when the temp drops, drawing air back in to the system.