Filling Butane to 80%

[ModestMonk]

Originally Posted by Gary RVRoamer

There is nothing "fraudulent" about that. You are buying LP (Liquified Petroleum) gas, not "propane" or "butane". In warmer climastes, the LP blend typically contains a higher percentage of butane because that performs better at higher ambient temperatures. Butane-rich LP, however, may not work well if you move to a cold climate because it doesn't vaporize as well at low temps. The bottom line is that the LP blend is a regional difference, not malfeasance on the part of the retailer.

Originally Posted by ModestMonk

Worthy of mention certain dealers fraudulently substitute butane for propane. Something I had never heard of until reading it here on iRV2.

*snip*

The whole quote says propane not LP. Taking it out of context is serving the wrong side of the issue. Substituting butane while selling "propane" is an issue.

Selling soy milk as cows milk is an issue. I don't mind your qualifier if you had noted if it's advertised as LP.

[select55]

Originally Posted by firedoc

Does surface area of the exposed fuel come into play?

no and that's my point all u need is the same volume area to accept the same expansion

[select55]

Originally Posted by twinboat

I think MOST is a pretty broad statement.

There are hundreds of post in RV forums claiming that their tank gauges read 3/4 when the tank is full.

" SOME LPG tank makers " would be a better statement.

in the 25 years I did conversions and tank installs and fillings I stand by most
the gauge is there for you to know usable liquid volume not tank volume

[ModestMonk]

Originally Posted by select55

no and that's my point all u need is the same volume area to accept the same expansion

however, the larger surface area allows a quicker replenishment of the vapor.

[select55]

Originally Posted by ModestMonk

however, the larger surface area allows a quicker replenishment of the vapor.

not at all ;; as LPG is released from the tank pressure(high) to the regulator(low) it vaporizes instantly

[ModestMonk]

Originally Posted by select55

not at all ;; as LPG is released from the tank pressure(high) to the regulator(low) it vaporizes instantly

Are you telling me that the propane company sold me on this huge freaking tank because I need more surface area to supply all my devices because of the the demand. And all I needed was just the line to replenish it I'm really confused

[select55]

Originally Posted by ModestMonk

Are you telling me that the propane company sold me on this huge freaking tank because I need more surface area to supply all my devices because of the the demand. And all I needed was just the line to replenish it I'm really confused

not sure what u are saying or asking?
you suggested that a large surface area is needed to supply vapour to run your stove and fridge and furnace in your motorhome
this is not true
look at a travel trailer and its upright 20 and 30 lb bottles
one of those at a time will run fridge,stove and furnace all at the same time
they have very small surface areas

[ModestMonk]

Originally Posted by select55

not sure what u are saying or asking?
you suggested that a large surface area is needed to supply vapour to run your stove and fridge and furnace in your motorhome
this is not true
look at a travel trailer and its upright 20 and 30 lb bottles
one of those at a time will run fridge,stove and furnace all at the same time
they have very small surface areas

No I'm speaking of the two 250 gallon bottles I had and being told I needed to convert to a 500 or thousand gallon horizontal tanks to get more surface area during cold weather months. (In the S&B's)

You're suggesting that there's no truth in their request?

[select55]

Originally Posted by ModestMonk

No I'm speaking of the two 250 pound bottles I had and being told I needed to convert to a 500 or thousand pound horizontal tanks to get more surface area during cold weather months. (In the S&B's)

You're suggesting that there's no truth in their request?

I say theres no truth in the RV system ;;now no doubt one needs some surface volume in a RV LPG tank because unlike a Automotive tank system where there is a unit called a converter where the gas is converted from liquid to gas before entering the engine intake system

we are talking RV here not about houses I seriously doubt its even true for a house though but a huge 100000 BTU house furnace may have a large enough vapour demand that this may come into play

[ModestMonk]

Originally Posted by select55

I say theres no truth in the RV system ;;now no doubt one needs some surface volume in a RV LPG tank because unlike a Automotive tank system where there is a unit called a converter where the gas is converted from liquid to gas before entering the engine intake system

we are talking RV here not about houses I seriously doubt its even true for a house though but a huge 100000 BTU house furnace may have a large enough vapour demand that this may come into play

So my 16 K generator a couple of propane heating devices stove etc. in the house that was their answer and that logic does not apply to the RV industry. Just goes to show you how a little mis information goes along way. I defer to your experience and expertise. But I would think I will ask them why they specifically told me the number of square inches of surface area allows the recovery rate to be faster. It was the deciding factor in spending all that $.

[select55]

Originally Posted by ModestMonk

So my 16 K generator a couple of propane heating devices stove etc. in the house that was their answer and that logic does not apply to the RV industry. Just goes to show you how a little mis information goes along way. I defer to your experience and expertise. But I would think I will ask them why they specifically told me the number of square inches of surface area allows the recovery rate to be faster. It was the deciding factor in spending all that $.

not debating recovery rate; BUT your talking about a house and its much larger demands. its not apples to apples at all
the 16K generator would have had its own converter system and made its own vapor or at least when I was converting cars and gen sets that's how it was done that may have changed nowadays
I was discussing RV usage;; never house high demand usage

[ModestMonk]

Originally Posted by select55

not debating recovery rate; BUT your talking about a house and its much larger demands. its not apples to apples at all
the 16K generator would have had its own converter system and made its own vapor or at least when I was converting cars and gen sets that's how it was done that may have changed nowadays
I was discussing RV usage;; never house high demand usage

Well thank you ,for purposes of discussion on this forum I believe it would be best sticking to the description that you have given... thank you. I do understand that having the 20% volume is all important in the RV world. That on a much larger scale and demand square inches may have to figure into it with how many BTUs we're burning through. Gotcha!

[slickest1]

I used to deliver bulk propane years back. I would fill each tank(many different sizes) the same. I would open the bleeder valve and fill until i was getting a flow of vapor out.

On occasion I would fill a tank and then the weather would turn very hot and the relief valve would blow off excess pressure. This happened very rarely and in my estimation the bleeder valve may have been compromised or they are not all that accurate.
The gauges on these tanks are not very accurate and I would never take them for exact measure. The tanks I would fill to 80 % would read anywhere from 70 to 90%.

On the size of tank needed for any application usually is based on the demand. The bigger the tank the bigger the regulator. To me that means a steadier supply of gas that will vaporize at a rate to avoid problems in different weather. Have you ever seen a regulator freeze up?
Bigger tank size also can be needed for longer times between fills in more remote locations, or just plain convenience of not needing a delivery every month
On the 20 lb. cylinders there is a date on them to be re certified. I am not sure but wonder about the bigger tanks in RV's

[MN_Traveler]

Originally Posted by ModestMonk

Are you telling me that the propane company sold me on this huge freaking tank because I need more surface area to supply all my devices because of the the demand. And all I needed was just the line to replenish it I'm really confused

ModestMonk - I suspect (emphasize "suspect") your propane company had good reason to recommend the larger tank. What I believe is missing from this conversation (and several of the posts below this one quoted) are the issues of "heat transfer."

We all know that propane tanks get cold when propane is drawn out of them. this is because it takes energy (heat) to convert the liquid propane into the gas form. That heat comes from the remaining "liquid" molecules immediately around the ones that vaporize. So the surface of the liquid gets cold and then that cold liquid would sink (with warmer liquid from below rising to replace it). That warmer liquid rising is necessary to supply heat for more (i.e. additional) molecules to go into the vapor phase.

Do the "thought experiment" of a "tank" that is really a very very tall, but very very small diameter cylinder (oriented in the vertical dimension). As molecules evaporate at the surface, the remaining liquid at the surface gets cold. Two things: with very small cross sectional area for the "cold" liquid to sink, the exchange of cold for hot is slowed. Second, even if that exchange does happen ... all you get is a slightly thicker layer of cold liquid ... and the system needs to "reach" further down the tube to find the heat to evaporate more molecules from the surface. If this goes on long enough, you will have warm liquid **way** down low in the tube, and really, really cold liquid at the surface ... and not enough time for the warm liquid down low to be transported to the surface to supply heat for more evaporation .... and so the rate of evaporation slows down (or virtually stops in an extreme case).

That "thought experiment" is an extreme case ... but hopefully leads one to conclude that a "short-wide" tank allows for faster evaporation than does a tall-thin tank. I would think that the tolerance for just how "tall and thin" depends on the expected rate of draw of vapor.

The OTHER thing regarding "area" is the total surface area of the tank. When that remaining liquid in the tank gets cold .... more heat needs to come from somewhere to allow evaporation to continue. That heat comes from the world outside the tank ... and needs to pass through the surface of the tank material to get to the liquid inside. In general, bigger tank = more surface area of the outside of the tank = faster replenishment of the heat in the tank lost to evaporation (for a given total rate of vapor generation that is).

I am skipping over some fine points ... but hopefully that generally makes sense?????