Gas Report
Why and When to use Propane Gas.
Gas appliances that do not use a pressure regulator between the gas cylinder and the gas appliance,
are most often designed to operate on Propane gas.
Examples of these types of appliances are:
1. The three legged portable gas barbecue
2. Fold up camp cookers
3. Cookers that screw straight on to the gas cylinder (Primus)
You may often find a label, to this effect, on the appliance.
When using Propane you will find that the appliance will perform very satisfactorily. But Propane
gas is more difficult to locate than LPG, but it is worth looking for.
The difference between LPG and Propane is the fact that LPG, Liquid Petroleum Gas, is a mixture of both
Propane and Butane, whereas Propane gas is not a mixture.
Butane in the LPG has the effect of lowering the vapor pressure within the gas cylinder.
For example at 20oC Propane gas will provide a vapor pressure within the cylinder of approx. 120psi,
whereas LPG, which is made up of approx. 50% Propane and Butane, at the same temperature will only
provide a vapor pressure of approx. 70 psi.
Also as you use LPG on a high pressure appliance you will notice that the performance of the appliance
will deteriorate as you use the gas. The reason for this effect is that the Propane content of the LPG
is drawn from the mix first leaving increasing percentages of Butane behind which has the effect of
further lowering the available vapor pressure within the cylinder.
Because of this, it can be seen that it is important to fully empty LPG cylinders before refilling them.
If you do not, Butane enrichment will be the result, as what will be left in the cylinder before refilling
will be predominantly Butane.
When using LPG, with the high pressure type of appliance, it may be found to be burning lean or the flame
may not even burn completely around the burner circumference, it may even be difficult to light the flame.
Also the heat from the flame will only cook very slowly even when the burner control is turned right up.
It can be seen that when using Propane gas, the appliance will perform correctly, so be warned if you
use your portable high pressure BBQ the way you did with LPG, you will have 'burnt offerings' as it will
COOK, and considerably quicker than before.
To change a gas cylinder that has been used with LPG it is very important to first ensure the cylinder
is completely emptied of gas, particularly Butane. If you fail to do this, when you fill with Propane,
you will not get the full benefits of the gas as you will only be making LPG again, i.e. a mixture of
Propane and Butane!!!
The other great benefit of Propane over LPG is that it will provide usable vapor pressures in the
cylinder when the ambient temperature starts to go down, particularly during winter. Have you ever
had the problem of your gas cooker not going or producing a very orange flame on a frosty morning?
It was more than likely caused by Butane enriched LPG. This effect is very evident when using an LPG
fired gas heating systems during very cold winter months, you will find the heater won't produce heat!!!
This effect is caused by Butane not vaporizing below approx. + 4oC, whereas Propane vaporizes at approx
-40oC.
In this case it would maybe worth considering using a Diesel fired air heater in your next Motor Caravan!!
The proportions of Butane and Propane that makes up LPG, is constantly being altered by the suppliers
of LPG within New Zealand. It is worth trying to locate the highest Propane mix being supplied within
your area, as it can be seen that there are significant benefits to you for doing so.
I hope this article assist you and makes your Motor Caravanning or camping more pleasurable.
Lex Ward 12673
NZMCA LPG Advisor