Gas Bottle Refill – How is Gas Bottle Refilling Done?
Gas bottle refilling is done in two ways: refill gas bottle by weight using digital scales or gas bottle refill by decanting using the bleed screw. Fill gas bottle or bulk LPG tanks can also be done by a tanker via a hose and meter, in addition to LPG gas bottle refill.
We’ll look at the details and the pros & cons of both methods of how gas bottle refilling is done …
Fill Gas Bottle – Gas Bottle Refilling – LPG Gas Refill
Gas bottle refilling goes through the main valve. You fill gas bottle in two ways – gas bottle refill by weight or LPG gas bottle refill by decanting until it starts to vent gas.
LPG gas bottle refilling 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 refill gas bottle is referred to as ‘decanting’, which is how LPG gas bottle refill is typically done at service stations.
When doing LPG gas bottle refill by weight, the filling hose is controlled by the scale, which shuts it off when the appropriate weight is achieved.
When gas bottle refilling 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 refill and close both the vent screw and main valve.
How to Fill Gas Bottle – Video
Disclaimer: This video on How to Refill 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 to Refill Gas Bottle
No matter which of the LPG gas bottle refill methods are used, gas bottle refilling must be done with a current inspection date. It is the responsibility of the gas bottle refill technician to check the inspection date stamped into the neck ring of the gas bottle before gas bottle refilling takes place.
Out-of-date gas bottles cannot be refilled until they are re-inspected and stamped with a new inspection date.
How to Refill Gas Bottle Using Digital Scales
Using digital scales helps ensure proper and safe gas bottle refill, based on weight. When the total weight equals the empty weight plus the appropriate LPG gas bottle refill weight, the gas bottle refill is complete.
The scales are set for each individual gas bottle to refill, based on its empty (tare) weight, as well as the desired LPG gas bottle refill 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 a gas bottle (fill propane tank) the technician connects it to the LPG supply.
The refill LPG gas cylinder is automatically stopped by the digital scale, after reaching the target weight.
This ensures a very accurate gas bottle refill and avoids dangerous overfilling or lost value through under filling.
The LPG gas bottle refill accuracy achieved is why the use of digital scales is the preferred method to fill a gas bottle.
Not surpisingly, this is how major suppliers, like SWAP’n’GO®, fill a gas bottle (fill propane tank).
Faster Way to Fill Gas Bottle with Carousels
A side benefit of using scales to refill gas bottle (fill propane tank) 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 refill process, resulting in dangerous overfilling.
Digital scales and pump driven LPG also allow for the use of high speed carousels to fill gas bottles (fill propane tank) , like the SWAP’n’GO carousel in the accompanying image.
In fully automated plants, with gas bottle refill 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
To transfer LPG gas from one cylinder to another you use the decanting method.
Decanting is the process seen if you have ever watched a service station refill LPG gas cylinder.
After connecting the gas bottle to a larger LPG storage tank, the trained operator begins to fill a gas bottle (fill propane tank) until some gas starts leaking out of the loosened bleed screw.
The operator is supposed to stop refill LPG gas cylinder 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 refill LPG gas cylinder, is avoided with the digital scale method.
Decanting can also result in either over filling or under refill LPG gas cylinder, as well as correct refill LPG gas cylinder, depending on the gas bottle and the operator filling it.
For example, if the operator is slow to stop the gas bottle refill when the liquid LPG starts to bleed out, the gas bottle could easily become overfilled.
As previously mentioned, over filling 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 to filling gas bottles, at petrol stations, 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 refill, there can be inconsistencies in the dip tube lengths.
Dip tubes can even be missing or have fallen out of the bottom of the valve.
The accompanying picture shows some examples.
Dip tubes lengths are important because they are connected to the bleed screws.
The refill LPG gas cylinder 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 LPG gas cylinder.
Short or missing dip tubes will cause over refill LPG gas cylinder.
A missing dip tube is the worst case scenario, as 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 will expand.
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
Only trained technicians should attempt to fill a gas bottle (fill propane tank) by either method.
LPG gas bottle refill is not a do-it-yourself handyman procedure and should never be attempted by untrained personnel.
The trained operators know all about the appropriate procedures, what personal protective equipment (PPE) to wear, the importance of the proper type of clothing (including material), 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 to dangerous overfilling of a gas bottle.
The simple message for people who are thinking about trying to refill their own gas bottles…
