Gas Bottle Refilling – How to Fill Gas Bottle

Gas bottle refilling is done in two ways: you can fill gas bottle by weight using digital scales or gas bottle refilling by decanting using the bleed screw.  To refill gas bottle or bulk LPG tanks can also be done by a metered tanker.

We’ll look at the details and the pros & cons of both methods of how to fill gas bottle is done …

Fill Gas Bottle – Gas Bottle Refills

Gas bottle refilling goes through the main valve.

You fill gas bottle in two ways – fill up gas bottle by weight or gas bottle refilling by decanting until it starts to vent gas.

LPG gas bottle filling by weight involves inputting the tare weight (empty weight) and the desired amount of gas to be filled into a digital scale.

The other method to fill up gas bottle is referred to as ‘decanting’, which is how LPG gas bottle refilling is typically done at service stations.

When doing LPG gas bottle filling by weight, the filling hose is controlled by the scale, which shuts it off when the appropriate weight is achieved.

To fill up gas bottle by decanting, a small vent screw is opened which allows gas to vent when the gas inside the bottle reaches the full refill level.

The venting gas is the operator’s cue to stop the gas bottle refilling and close both the vent screw and main valve.

How to Fill Gas Bottle – Video

Disclaimer: This video on How to Fill Gas Bottle is only a supplement and refresher for those who have completed the Elgas decant training course. It is not the complete training course and other training materials apply. LPG decanting must not be attempted by untrained individuals.

Current Inspection Date Required for Gas Bottle Filling

No matter which of the LPG gas bottle filling methods are used, gas bottle refilling must be done with a current inspection date.  It is the responsibility of the gas bottle filling technician to check the inspection date stamped into the neck ring of the gas bottle before gas bottle filling takes place.

You cannot fill up gas bottle when out-of-date until they are re-inspected and stamped with a new inspection date.

Gas Bottle Refilling Using Digital Scales

Using digital scales helps ensure proper and safe gas bottle refilling, based on weight.

When the total weight equals the empty weight plus the appropriate LPG gas bottle refilling weight, the gas bottle filling is complete.

The scales are set for each individual gas bottle fill up, based on its empty (tare) weight, as well as the desired LPG gas bottle refilling content weight, when full.  (see the image to the right)

How the Scales Work

The tare weight (empty weight) is stamped into the neck ring by the bottle manufacturer.

The operator inputs the tare weight of the gas bottle into the scale’s keypad.

After inputting the weight, to fill gas bottle the technician connects it to the LPG supply.

The gas bottle filling is automatically stopped by the digital scale, after reaching the target weight.

This ensures very accurate gas bottle refilling and avoids dangerous overfilling or lost value through under filling.

The LPG gas bottle filling accuracy achieved is why the use of digital scales is the preferred method to fill gas bottle.

Not surprisingly, this is how major suppliers, like SWAP’n’GO^®, fill up gas bottle (fill propane tank).

Faster Way to Fill Gas Bottle with Carousels

A side benefit of using scales to fill gas bottle is speed.

The LPG supply line can be pump driven for faster gas bottle refilling.

This is not possible with decanting, as the operator might be too slow to stop the gas bottle filling process. This could result in dangerous overfilling.

Digital scales and pump driven LPG also allow for the use of high speed carousels to fill gas bottles, like the SWAP’n’GO carousel in the accompanying image.

In fully automated plants, with gas bottle filling carousels, even the keypad step can be automated.

The carousel digitally reads an RFID chip on the cylinder that contains the tare weight, as well as the rest of the manufacturing specifications of the gas bottle.

LPG Decanting Procedure to Fill Gas Bottle

Decanting is the process seen if you have ever watched a service station fill gas bottle.

To transfer LPG gas from one cylinder to another, you use the decanting method.

After connecting the gas bottle to a larger LPG storage tank, the trained operator begins to gas bottle filling process until some gas starts leaking out of the loosened bleed screw.

The operator is supposed to stop fill gas bottle as soon as liquid LPG starts coming out of the bleeder opening.

The liquid LPG escaping is unmistakable, as it looks like a white cloud.

This intentional venting of gas into the atmosphere, during the gas cylinder refills, is avoided with the digital scale method.

Decanting can also result in either overfilling or underfilling the gas cylinder, as well as correct gas cylinder fill, depending on the gas bottle and the operator filling it.

For example, if the operator is slow to stop the process when the liquid LPG starts to bleed out, the gas bottle could easily become overfilled.

As previously mentioned, overfilling a gas bottle is a significant safety hazard.

Gas Bottles Refilling at Petrol Stations

Gas bottle refilling at petrol stations is done using the decanting method.

After connecting the gas bottle to a larger LPG storage tank, the trained operator begins gas bottle filling.

They continue until some gas starts leaking out of the loosened bleed screw.

Dip Tube Variation Effect on Gas Bottle Refill

In addition to operator performance variances in gas bottle filling, there are inconsistencies in the dip tube lengths.

Dip tubes can fall out and be missing. The accompanying picture shows some examples.

Dip tubes lengths are important because they are connected to the bleed screws.

The refill operator opens the bleed screw to fill a gas bottle until the level of LPG reaches the bottom of the dip tube, at which point liquid LPG will start to bleed out.

This is his signal that the cylinder is full.

Long dip tubes can result in under refill.

Short or missing dip tubes will cause overfill of the gas cylinder.

A missing dip tube is the worst case scenario because the entire ullage space would be filled, allowing no room for expansion.

This is one of the reasons that swap is a much safer alternative, as dip tube variances have no effect when filling a gas bottle by weight.

20% Oversized for Expansion

LPG vapour pressure rises with temperature.

If a gas bottle is exposed to higher temperatures the gas expands, increasing the pressure.

LPG bottles are designed to be full while allowing 20% of the space, called “ullage”, for the natural expansion of the LPG, as shown in the accompanying picture.

Properly filled gas bottles, with the required 20% ullage, should never have a problem.

Overfilling is Unsafe

One of the big advantages of gas bottle refilling by weight is the avoidance of dangerous overfilling.

When over filled, a gas bottle has less than 20% ullage, creating the possibility of the unwanted release of gas to the atmosphere, through the pressure relief valve.

The pressure relief valve is incorporated into the main gas valve on the bottle.

It’s actually a valve within a valve that prevents dangerous overpressure situations.

So, overfilling combined with heat can result in gas venting from the pressure relief valve, which creates a significant safety hazard.

This is especially true in the warm Australian climate.

Gas Bottle Refilling is NOT a DIY Procedure

LPG gas bottle refilling is not a do-it-yourself handyman procedure and should never be attempted by untrained personnel.

Only trained technicians should attempt to fill gas bottle by either method.

The trained operators know all about the appropriate procedures. This includes personal protective equipment (PPE) to wear, static -free clothing, proper cylinder grounding, static electricity hazards, ignition sources, fire protection and more.

In-depth safety training is mandatory for these technicians.

Doing it incorrectly could result in cold burns (liquid LPG is -42°C), fire or even an explosion. In addition dangerous overfilling can occur.

The simple message for people who are thinking about trying to refill their own gas bottles…

Just DON’T do it!