Cathodic protection

When two metals are coupled the metal with the least resistance will corrode, thereby protecting the other metal. Rail tracks are the best known example of this. The tracks are coupled with a block of zinc at regular intervals. To provide additional protection against corrosion, a propane tank is coupled with less resistant magnesium.

Dielectric strength

A basic requirement imposed by the government is that the dielectric strength of the coating must be at least10kV/cm2. If a voltage of 10,000 volts is appliedto the tank and the outside of the tank is tested (sparked) with a copper brush, no sparks must flash over between the tank and the brush. Sparks can only flash over in those places where the coating of the tank is imperfect. This test should be carried out both after construction and before placement of the tank under the supervision of an authorised inspection body. Any defects should be repaired immediately and the test repeated.

Epoxy Coating

The basic protection of the single-walled underground propane tank comprises a two-component coating. These two components, once combined, form a very solid and very hard protective layer on the tank. This layer meets the criterion for dielectric strength. This very hard layer is, in a certain sense, also very fragile. It's like glass. That is why our tanks are finished off with another protective layer, which protects this undercoat while the tank is being buried. This ensures that a stone accidentally falling on the tank will not immediately have adverse consequences.

Isolation valve

An isolation valve is placed after the pressure-relief valve. The object is that the cathodic protection will protect only the steel tank and not the copper pipes that connect the tank to the domestic appliances. This valve therefore has a very high resistance, which limits the effect of the cathodic protection to the tank.

Pressure regulator

Depending on the outside temperature, the pressure in a propane tank is between 4 and 10 kg/cm². This pressure must be reduced to
1 à 1.5 kg/cm^2. This first regulation occurs right at the outlet of the tank by means of a pressure regulator. This pressure regulator is usually fitted with a pressure gauge, which allows you to read the pressure after regulation. Note that this pressure is still much too high for consumer appliances. A second low-pressure regulator must be installed for each appliance.

Density of the liquid compared to water

These values indicate that propane and butane are appreciably lighter than water.
On the other hand, it is also possible to deduce from these values that 1 kg of liquid propane or butane is approximately equal to 2 litres of liquid gas.

Density of the vapour (the gas) compared to air

These values indicate that propane and butane are appreciably heavier than air. That is why escaping gas will always travel along the ground.
Leaking gas can therefore accumulate in low spots (e.g. basement) and remain there if there are no draughts or ventilation.

Boiling temperature

The values indicated are the boiling temperatures at atmospheric pressure.
Note that liquid butane in the cylinder only becomes a gas when the ambient temperature is at least 0°C. Propane, on the other hand, vaporises (i.e. boils) at -42°C. Propane can therefore be used even in extremely cold conditions.

Solidification temperature

This is the temperature at which a liquid becomes a solid. Just as water becomes ice at 0°C, propane and butane can also be transformed into a solid.
This change in physical state occurs at very low temperatures.

Auto-ignition temperature

Before a mixture of propane and air can ignite, the ratio of gas to air must be within certain limits and there should also be a source of ignition.

If, however, the temperature of this mixture is sufficiently high, this will produce a reaction without the need for an initiator, i.e. a spark.

Calorific value

The calorific value indicates how much energy a unit mass contains. The higher the calorific value, the more heat can be produced per kg or per m³ or per litre.

Expressed in MJ/kg kWh/kg or kcal/kg

Latent heat of vaporisation

So that a liquid will continue to vaporise, in other words change into a gas, heat is required. When water boils, the boiling process will last as long as heat is applied to the liquid. Furthermore, the temperature of the water remains constant for as long as it boils. The same principle applies to butane and propane. Since propane boils at -42°C it will first of all use the heat present in the liquid itself to turn into a gas. If the gas consumption is too high, however, the liquid will cool down to its boiling temperature and will extract heat from the surroundings to enable it to vaporise. This explains why ice can sometimes form on the tank or the cylinders with high-consumption appliances.

The lower the latent heat of vaporisation, the less heat the liquid needs to turn into vapour.

Vapour pressure

This is the pressure exerted by a gas on the inside walls of a receptacle, tank, pipe, cylinder, etc. The vapour pressure is the force with which the gas presses on the inside walls of the container in which it is enclosed.
This pressure depends only on the temperature of the liquid. This pressure is affected only by external factors.
The higher the temperature of the liquid, the higher the pressure in the container.

Note also that the liquid expands as its temperature increases.

This pressure can be expressed in kg/cm², bar or Pa (pascal).

Maximum temperature in air

If you burn these gases on your stove or in your heater, the object is to guarantee a certain amount of heat. At these combustion temperatures you do not have to worry on that account.

Maximum temperature in oxygen

When mainly propane is mixed with pure oxygen and then ignited, substantially higher temperatures are obtained. This application is used to cut or melt metals, with propane being a cheaper alternative to acetylene.

Gas/Liquid ratio

When a liquid becomes a gas, the quantity of gas formed takes up more space than the liquid. For instance, when 1 litre or 0.001m³ (approximately 0.5 kg) of liquid propane vaporises, it occupies a volume of 270 litres or 0.270 m³.

Perfect combustion

Ideal combustion means that after combustion the flue gases comprise only CO₂ and H₂O (water). Hence no CO. Efficiency is then 100% and combustion is complete. For this to happen there must be sufficient air.

In practice, this is usually achieved by regulating the injection pressure of the gas and adjusting the diameter of the injection nozzle.

Lower explosion limit LEL

LEL or "lower explosion limit" refers to the minimum quantity of gas that must be present in a space before a spark can cause ignition.

Theoretically, you should be able to smell gas when a space is filled with just 0.6 vol% of gas. (25% of LEL).

Note that gas is heavier than air and will therefore accumulate at ground level. This ideal ratio of gas to air will usually be found at a certain height. Coincidentally, right where sparks can occur. For example, a switch, the compressor of a fridge, etc.

Upper explosion limit UEL

UEL or " upper explosion limit" refers to the value above which the gas/air mixture can no longer be ignited by a spark.

Maximum filling level

Since a liquid takes up more space when its temperature rises, a receptacle containing liquid gas must NEVER be filled completely.
This is because as the temperature rises, the pressure on the walls of the receptacle also increases.
These figures indicate the maximum number of kilograms a given volume may contain.
For example, a gas cylinder with a water content of 26 litres may contain a maximum of 13 kg of butane.