Filling Butane to 80%

[Mr_D]

Originally Posted by LJowdy

Yes, the biggest thing to know is it's Propane not butane. And yes to your questions. The tank needs room to expand when it gets hot, that's why it won't fill to the maximum

https://www.reference.com/home-garde...17473470876c30

Actually, in some areas you will get butane. Problem is that it takes a higher temperature to off gas which can cause problems if you buy it where it's warm and travel to a colder area. It happened to my parents years ago.

[Petersr58]

ScottyBye
Thanks for the pictures. Most educational.

[LarryW21]

Good discussion! Thank you all for supplying this information.

[marjoa]

OP here...as I was reading these comments I happened to think about my air compressor and how it accumulates water in the tank over time and that's why you put a dryer in the air line etc. to protect your air tools AND every once in awhile I open the valve underneath and bleed out the water from the tank.

Does a propane tank accumulate water in a similar way? Do you ever have to worry about water in the tank?

[ScottyBye]

Originally Posted by marjoa

Does a propane tank accumulate water in a similar way?

No it does NOT.
When a propane tank is new there is AIR (Atmosphere in the tank) which can and will absorb moisture as temps and pressures change both inside/outside the tank.
This is why you ALWAYS purge a tank before filling with Propane for the 1st time or when excesive moisture is suspected or present.
If the purge is done properly you should have no atmosphere or moisture left in the tank.

In most cases if moisture is found in the tank, it most likely came from the LPG Supplier... and small amounts can be removed through a anhydrous methyl alcohol injection into the tank, which should be done by a reputable propane distributor/supplier

Originally Posted by marjoa

Do you ever have to worry about water in the tank?

Absolutely.... Moisture in the tank = problems.
Example - frozen regulators, insufficient/irregular burning of the fuel gas thus reducing the efficiency of any/all LP appliances, tank rusting internally, and many others...

.

[select55]

Originally Posted by MN_Traveler

It does not sound quite right to me that the 80% fill is to allow room for expansion (liquids do not expand that much). More likely (as noted in a later post) that the 80% fill is to allow headspace for vapor generation and to avoid liquid propane from getting in to the external hoses (Bad Thing). Anyone know for certain??

actually one of the main reason behind the 80% rule is for expansion
Fill a 20 lb tank right full and set in the sun I guarantee you the pressure relief valve will bleed off LPG
As soon as LPG is released from its pressure state it vaporizes instantly

[ScottyBye]

Correct on that.

As liquid propane converts to vapor through the 270:1 expansion ratio, the rapid conversion of liquid to vapor causes intense chilling that literally freezes whatever it comes in contact with. That's why smart people wear proper gloves while working with it.

It boils/vaporizes at just -44 F which for us Canucks is -42 C. A very very cold winter day here in Calgary. Hahaha...

[Bigd9]

While a propane tank doesn't generally collect water, it does collect oil. Propane is separated from crude oil during the refining process and sometimes a bit of oil tags along with the propane over time oil can accumulate in the tank. Many generators on RV's use liquid propane and convert the liquid propane to a gas in the generator itself. Sometimes when the tank has too much oil, it can be sucked up into the generator causing problems.

[select55]

Originally Posted by Bigd9

While a propane tank doesn't generally collect water, it does collect oil. Propane is separated from crude oil during the refining process and sometimes a bit of oil tags along with the propane over time oil can accumulate in the tank. Many generators on RV's use liquid propane and convert the liquid propane to a gas in the generator itself. Sometimes when the tank has too much oil, it can be sucked up into the generator causing problems.

just to be clear you don't convert liquid to gas in the generator itself
Its converted from liquid to gas via unit called a vaporizer before it ever enters the generator intake carb system.The oil can accumulate in the vaporizer and eventually cause the diaphragm to rot and leak but the small amount that may get sucked into the generator is very slight and causes no damage.
NOW if oil gets into the RV tank pressure regulator and then gets into the lines you end up with a very lazy flame and the regulator has to be replaced;; tank drained and lines blown out

[tacaem]

Originally Posted by MN_Traveler

It does not sound quite right to me that the 80% fill is to allow room for expansion (liquids do not expand that much). More likely (as noted in a later post) that the 80% fill is to allow headspace for vapor generation and to avoid liquid propane from getting in to the external hoses (Bad Thing). Anyone know for certain??

It is not for room for expansion or to avoid liquid getting into hose. The reason for the 80% is because that is a safe level to allow for building up high pressures on very hot days and popping off the relief valve.

[select55]

Originally Posted by tacaem

It is not for room for expansion or to avoid liquid getting into hose. The reason for the 80% is because that is a safe level to allow for building up high pressures on very hot days and popping off the relief valve.

yes as I just posted the same information but it is for expansion caused by temperature rises on hot days that's the whole point(room for expansion)

[ScottyBye]

Originally Posted by tacaem

It is not for room for expansion or to avoid liquid getting into hose.

Originally Posted by tacaem

The reason for the 80% is because that is a safe level to allow for building up high pressures on very hot days and popping off the relief valve.

So what you are trying to say is that 20% of the tanks is NOT for expansion. It's there for expansion... Really!

[tacaem]

Originally Posted by select55

yes as I just posted the same information but it is for expansion caused by temperature rises on hot days that's the whole point(room for expansion)

A balloon expands an LP tank does not pressure builds up inside of it. The whole point is room for pressure to build up, because you can't compress liquid gazes you can so there has to be room for pressure to build up not expand.

[twinboat]

Here are some FACTS.

The 80% fill rule is a*preventative safety measure against the fluctuations that happen inside a tank. Propane, like water, will expand when heat is added to it. Propane, however, will increase in volume nearly 17 times greater than water over the same temperature increase. To allow for this expansion,*propane containers are filled to only 80% of their capacity.

That means a tank that is 80% full on a mild March day, might register as 85-percent (or higher) at the mid-July cook out. It’s the same amount of propane, but it’s taking up more space. So the extra space in the tank is a cushion against the pressure that builds up in a tank when it’s hot.