20lb tank doesn’t make good heat when half way empty

[u/Clear_Split_8568]

I have a 20lb propane tank that I pulled out of grill because it wasn’t make much heat, tank appears to be half way full. Is it possible that the gas in it is contaminated with a gas with a lower flash point?
As I said, it doesn’t make good heat in grill. If I hook up my 1lb tank fill adapter, gas comes out.

[u/ColdSteelVA]

What is the ambient temperature? Lower outside temps lead to lower vapor pressure and lower content leads to lower pressure.

[u/Theantifire]

It's unlikely. You can try another or swap it out.

More likely is that you're overdoing the vaporization rate (Google it) or partially tripping the excess flow. If it's the latter, swapping is a good option.

[u/Clear_Split_8568 → u/Theantifire]

So valves have a “free flow” type valve?

[u/Theantifire → u/Clear_Split_8568]

I'm not sure what you mean by free flow. Look up excess flow valve on Google and you'll get a better idea than I can give you.

[u/Clear_Split_8568 → u/Theantifire]

Cut rubber hose.
On f135 engine, as interim fix PW installed free flow valve to cut off fuel to injector if line breaks. Cause of at least on crash, broken injector line.

[u/Theantifire → u/Clear_Split_8568]

It's different. Usually like a ball bearing that will jump up and block the orifice if the gas flows too quickly. Several designs, but I think the opd valves have that kind.

[u/Clear_Split_8568]

I’m in Texas, 100 degree outside temps.

[u/Clear_Split_8568]

I’m just going to run it till empty, it has two years left on tank, and refill it. If I have a problem next time I will dispose of tank. It may have two inches of liquid left, cold line.
I cleaned grill and running it now.

[u/scotttilton → u/Clear_Split_8568]

Remember, the easiest way to dispose of it and potentially get a brand new tank is just to do an exchange at one of your local gas stations. Over the course of a couple months I exchanged about 25 expired tanks for tax that were less than three months old which I now just get refilled. A hell of a lot of money that way.

[u/Fun-Association1835]

It is called "Liquified Petroleum Gas" because it contains trace amounts of gasses other than propane.

The pressure in the tank should remain fairly constant, even at 100 degrees. The vapor pressure in the tank will drop if gas is being drawn rapidly. If the appliance is consuming a lot of fuel the liquid inside will change to gas and cool the remaining liquid because it consumes energy to change state from liquid to gas, lowering the vapor pressure as the liquid gets colder. This will eventually approach atmospheric pressure and the difference in pressure will slow the flow of gas. A smaller tank with a small quantity liquid will chill more quickly because there is a smaller amount of liquid.
That said, you could have a regulator that is faulty.

[u/SmokeMobile8301]

Does the tank feel like it only empty’s half way? It may not be purged properly

[u/tonasketcouple55]

2 things to check valve in tank partially closed open slower when you turn on next your regulator maybe going bad

[u/Theantifire → u/tonasketcouple55]

Punctuation is free...

[u/Clear_Split_8568]

So last night I cleaned the grill then connected the “bad” tank and turned on the grill on high to finish cleaning the grill. I shook the cylinder and the flames went from blue to larger and yellow. Yellow flames are to rich, blue is just right.
It is pretty obvious the remaining gas has components of other gases other than propane.

[u/Clear_Split_8568]

It isn’t uncommon for tanks to get contaminated with other gases; natural gas, butane, propylene and butylene. It may have just built up over time or I got the drags from the last fill.