Propane fill question

[12th_Man_Fan]

OK I am officially confused.

I took one of my 40lb. propane cylinders out of my new RV to have it filled. A note on the door of the propane compartment said do not fill over 80%, could cause fire,explosion etc.

I told the guy that was filing the bottle to fill to 80%, he didn't know what I was talking about and since I didn't know what I was talking about we filled it to 65 total lbs where his info showed it full at 75 lbs.

Anyhow since this is a safety issue can anyone help me out. since this is a 10 gallon tank am I only supposed to put 8 gallons in it?

I have always taken them to the guy, he puts it non a scale and fills it to the total weight on his chart. Is this 80% or is it over filled?

For those of you that want me to do a search, I did and got 503 pages and although I am retired I don't have enough time to read all of the info.

[time2roll]

First of all anyone that talks about overfilling a propane bottle to 100% of gross volume needs to explain how they are getting past the OPD valve that limits the fill to 100% of rated volume.

[wnjj]

dougrainer wrote:

RinconVTR wrote:

wnjj wrote:



The reason for not filling the garden sprayer to 100% is a functionality one. The reason for not filling the LP to 100% is a safety one. They operate on completely different principles.

No sir. They are the actually pretty similar in principle.

Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure. Liquid...it doesn't compress, remember? And LP will not remain a liquid, unless its under pressure. It requires a volume of "air"...under high pressure...for the tank to function.

SO that 20% is not just there for thermal expansion (safety), its there for pressurization as well. Just like the garden sprayer.

And that 20% is not a magic number, it can be much lower for these tanks to operate, don't get me wrong. The expansion rate of LP is very high. The US has very strict, protective rules, as we all know.

THERE IS NO AIR IN A LP TANK/CYLINDER. There is only LP vapor that is produced from the LP liquid in the tank. Soooooo, for a 100% full liquid tank, there is NO ROOM for the Liquid to vaporize. As I stated, 100% liquid will cause Liquid to flow OUT when the tank valve is opened and that will destroy the LP regulator. Doug

If you have a full container of liquid under pressure, the second you open the valve there is an increase in volume (the hose) which will drop the pressure rapidly. The first liquid to enter the hose will immediately boil off to gas. Now if the cylinder was at such a high pressure that adding the hose volume doesn't drop it below vapor pressure then liquid could flow to the regulator.

[RJsfishin]

I don't post it unless I've done it. There ain't nothing I don't know about propane, because there ain't nothing I ain't done involving propane.

When you've done it all, its not hard to tell those that don't have the foggiest idea, but insist on posting anyway,....why, so you can feel important, or end up looking stupis.

I never did call any names. I did attack, and rightfully so !

[dougrainer]

RinconVTR wrote:

wnjj wrote:



The reason for not filling the garden sprayer to 100% is a functionality one. The reason for not filling the LP to 100% is a safety one. They operate on completely different principles.

No sir. They are the actually pretty similar in principle.

Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure. Liquid...it doesn't compress, remember? And LP will not remain a liquid, unless its under pressure. It requires a volume of "air"...under high pressure...for the tank to function.

SO that 20% is not just there for thermal expansion (safety), its there for pressurization as well. Just like the garden sprayer.

And that 20% is not a magic number, it can be much lower for these tanks to operate, don't get me wrong. The expansion rate of LP is very high. The US has very strict, protective rules, as we all know.

THERE IS NO AIR IN A LP TANK/CYLINDER. There is only LP vapor that is produced from the LP liquid in the tank. Soooooo, for a 100% full liquid tank, there is NO ROOM for the Liquid to vaporize. As I stated, 100% liquid will cause Liquid to flow OUT when the tank valve is opened and that will destroy the LP regulator. Doug

[red31]

When filled to 100% the pressure rises over partial pressure since there ain't no space for vapor. Anytime there is both liquid and gas, the pressure is based on the temperature. http://www.engineeringtoolbox.com/propane-vapor-pressure-d_1020.html

We have OPDs today since 100% filling was not impossible.
Overfill when cool and then let it warm up and the cylinder is overfull (all liquid). When warmed, the pressure rises (liquid expands), the gas condenses into liquid, 100% liquid and the pressure rises sharply since there is no more gas to compress, eventually the relief valves opens (since the liquid doesn't compress much).

Using the proper liquid level gauge (not the fixed ones in cylinder valves), one can fill to 95% by volume if the liquid is 130F, this is equivalent to 80% by volume 40F.

40# is 40# at zero F, 40F or 100F. 40# @ zero F is less volume than 40# @ 100F.

[westend]

A few members on this Forum are getting a bit out of hand. I'd suggest before anyone starts trashing someone or name calling, take a second and ask yourself if that is the way you'd respond if face-to-face.

[RinconVTR]

RJsfishin wrote:

red31 wrote:

RinconVTR wrote:

Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure.

Baloney.

-----------------------------------------------------------------
Bull is right !
If ya don't have the foggiest idea what yur talking about, its much better to just stay out of it all, and not look so stupid.

EDIT. Post modified. Nothing wrong with the original, but its not worth continuing here. People don't post anything to back their stance, they just attack.

LP does "boil" and expand in a sense when you open the valve, so my thinking may indeed be wrong. Not entirely, but its hard to prove over the internet otherwise.

But if you are going to call someone out this way, at least state some sort of reasoning and not just call names.

[time2roll]

RJsfishin wrote:

red31 wrote:

RinconVTR wrote:
Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure.

Baloney.

-----------------------------------------------------------------
Bull is right !
If ya don't have the foggiest idea what yur talking about, its much better to just stay out of it all, and not look so stupid.

Easy there guys. Everyone knows that is why you need a dual tank system and crossover regulator. The second bottle is to keep the first bottle pressurized. 😉

[RJsfishin]

red31 wrote:

RinconVTR wrote:

Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure.

Baloney.

-----------------------------------------------------------------
Bull is right !
If ya don't have the foggiest idea what yur talking about, its much better to just stay out of it all, and not look so stupid.

[hotpepperkid]

If it as 40 lb tank put it on a scale and put 40 lbs of propane in it, wheather that is 80% 90% or 100% it doesn't matter

[hotpepperkid]

If it as 40 lb tank put it on a scale and put 40 lbs of propane in it, wheather that is 80% 90% or 100% it doesn't matter

[red31]

RinconVTR wrote:

Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure.

Baloney.

[RinconVTR]

wnjj wrote:



The reason for not filling the garden sprayer to 100% is a functionality one. The reason for not filling the LP to 100% is a safety one. They operate on completely different principles.

No sir. They are the actually pretty similar in principle.

Go ahead and fill an LP tank 100%, it will not be functional for long due to lack of pressure. Liquid...it doesn't compress, remember? And LP will not remain a liquid, unless its under pressure. It requires a volume of "air"...under high pressure...for the tank to function.

SO that 20% is not just there for thermal expansion (safety), its there for pressurization as well. Just like the garden sprayer.

And that 20% is not a magic number, it can be much lower for these tanks to operate, don't get me wrong. The expansion rate of LP is very high. The US has very strict, protective rules, as we all know.

[wnjj]

RinconVTR wrote:

wnjj wrote:

RinconVTR wrote:

sato4000 wrote:
My RV dealer said he will fill up the propane 100 percent if you want.

Impossible.

For perspective...take a pressurized garden sprayer. Fill it to the brim, 100% filled. Then try to add air pressure and spray. You might get a drip of water, if your lucky.

Same principle here with LP tanks, but there are yet more reasons as to why 80% max fill is standard, and already mentioned.

The garden sprayer works nothing like your LP tank. With the garden sprayer, you need air that is compressible to store the pressure needed to push water out the hose.

LP boils at -44F so it wants to convert to gas and flow out of the hose, all by itself. There's no pressurized air helping to move the LP along.

The 80% is for thermal expansion.

I was hoping that when I started my post with "For perspective...", using the reference as only a crude example to help others understand 80% fill issue...would not be taken as a claim that pressurized water tanks are the very same as LP tank.

I didn't take it as a claim that the two are the same, only the claim that they worked the same. You used the words "same principle". That means the same theory of operation. I simply pointed out that a garden sprayer operates NOTHING LIKE an LP system. There's no more point is suggesting that overfilling a garden sprayer is "perspective" for an LP cylinder than overfilling a wheelbarrow is. The only thing they share is that both are some kind of liquid in some kind of container.

The reason for not filling the garden sprayer to 100% is a functionality one. The reason for not filling the LP to 100% is a safety one. They operate on completely different principles.

[dougrainer]

red31 wrote:
An overfilling prevention device must not be the primary means to determine when a cylinder is filled to the
maximum allowable filling limit.
NFPA 58, §7.4.4.1

Overfilling Prevention Device [“OPD,” “stop valve”]. A safety device that is designed to automatically prevent a
container from being filled beyond its maximum permitted filling limit.
NFPA 58, §3.3.49

Fixed Maximum Liquid Level Gauge [“outage gauge,” “spitter valve,” “spew gauge”]. A fixed liquid level gauge that
indicates when the liquid level in a container has reached its maximum permitted filling limit.
NFPA 58, §3.3.29.2

The formula for filling LP-gas containers by weight is as follows:
(1) Determine the propane capacity in pounds by multiplying the total water capacity in pounds by 0.42.
(2) Add the tare weight of the cylinder to the liquid weight of the product plus the weight of the hose and
nozzle. The total weight of these three is the proper scale setting.
LP-Gas Safety Rules, §9.136(a) (TEXAS)

This is correct, but Texas is one of the few states that has a comprehensive system and laws/rules for LP. A LOT of states is fly by the seat of your pants. ANY IDIOT is allowed to fill and service LP systems and containers, which is too bad. Doug