Jumpin' flashback: Air Liquide Canada Inc. develops safer equipment and gas delivery solutions.

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Acetylene is an unstable hydrocarbon that must be handled with care. For over 100 years, it has been the number one choice, worldwide, for welding, cutting, brazing, and heating. The oxyacetylene process is still one of the best techniques available for many applications. Thus, it is very important to respect all safety measures and applicable regulations when using, transporting, or storing this gas.

Respecting the correct rules-of-use and the safety measures that exist in each country and province, and using the equipment safely, depends on the worker's knowledge, ability, and professional training. The apparatus is now easier to use and safer than ever thanks to major innovations introduced by gas equipment manufacturers, and the oxyacetylene flame (oxygen and acetylene combined) remains one of the most convenient methods for welding and cutting steel. Advantages include low cost and portability compared to other techniques, particularly electrical processes.

Beware of backfire and flashback

The use of oxygen and acetylene gases presents a number of potential hazards including high pressure, flammability, asphyxiation, and oxygen enrichment. Among possible occurrences, the flame can momentarily burn back into the torch tip and make a loud popping sound. This is called a "backfire." Occasionally, the flame relights by itself and the worker can continue working, but at other times the flame does not relight and torch valves should be shut off immediately. A backfire is normally caused by using the wrong tip pressures, by overheating the torch, or by touching the tip to the workpiece.

A persistent high-pitched squealing sound with sparks issuing from the tip indicates a more serious backfire that can create an explosive situation. The flame has entered the tip and continues to bum inside the torch at the gas mixing point. It is extremely important to shut the oxygen valve off first, as quickly as possible, then to shut the fuel gas valve to prevent damage to the torch. Before attempting to relight, make sure the torch has cooled and verify the complete set-up. An improper working pressure or defective equipment can be the cause of sustained backfire.

A "flashback" can occur when lighting the torch if a mixture of oxygen and fuel gas is present in the system. In this case, the flame burns so fast that the user has no time to shut the torch valves before it passes through the torch and into the hose. The most feared consequences of a flashback are either the bursting of hoses or that the burning progresses back to the regulators and cylinders. To avoid flashbacks, it is mandatory to purge the hose lines, one at a time, to make sure there is no mixed gas in the hoses before lighting the flame.

To protect yourself, check valves and flashback arrestors should be installed on your equipment. A check valve will help prevent the formation of an explosive gas mixture and a flashback arrestor will stop the flame if a flashback does occur. They are a great way to prevent accidents. Different provinces in Canada have different regulations specifying where these safety devices shall be located. Some require installation at the regulator outlet, while others require them at the torch inlet. Be sure to check your local requirements.

A new type of cylinder

Dedicated to safety, Air Liquide has developed Altop and Minitop. These unique products are, arguably, some of the most significant innovation and technical advancement in cylinders designed for the welding industry in the past 75 years. They are simply the safest oxygen and acetylene cylinders on the market.

Traditionally, regulators have been separate devices that are installed onto the cylinder valve outlet. They are often found in bad conditions that can lead to accidents. Air Liquide has developed a new type of regulator that is integrated with the cylinder valve, Designated Altop for large size cylinders and Minitop for small cylinders, these regulator/valve combinations come with the cylinder, forming a complete package. Each time an Altop or Minitop cylinder is returned for refill, it is verified at the filling plant. Users no longer need to provide and maintain their own regulators. Of course, all the important safety rules and instructions still apply when it comes to operating torches, tips, and accessory devices with Altop and Minitop cylinders.

Altop and Minitop cylinders make transportation between jobs much safer and more convenient. Their designs incorporate built-in protective caps that remain permanently in place. Valve protective caps are mandatory when transporting cylinders to prevent any damage to the valve. A major leak from a damaged valve could turn a compressed gas cylinder into a rocket. Just try to imagine an oxygen cylinder with an inside pressure of over 2,200 pounds per square inch! With standard cylinders, this means you must remove your regulators from the cylinders to install the safety caps before you move them. This takes time and, in the long run, increases the risk of contaminating or damaging the regulator while it is not installed on the cylinder.

Other unique features of Altop and Minitop make them safer and easier to use. Both have a built-in gauge to tell you how much gas remains in the cylinder. This can be very reassuring when on a remote jobsite. Altop also has a built-in delivery pressure gauge, while Minitop has a calibrated delivery pressure-adjusting knob. To control the flow of gas there is an ON/OFF lever that makes it easy to shut your torch down for a few minutes without losing your pressure settings. Simply flip the lever back to ON and the flow starts up again. Altop also incorporates a reverse-flow check valve in its outlet hose connection fitting and has an ergonomically designed knob on the top of its protective cap to facilitate rolling the cylinder. Minitop can easily be picked up and moved by its built-in carrying handle. With Altop and Minitop, all you have to do is hook up your hoses and torch and you're ready to go!

The Air Liquide R&D team has been addressing the needs of welders for over 100 years in order to create safer equipment and gas delivery solutions. The use of new cylinders such as these will contribute to safer working conditions and a reduced number of accidents in the welding industry.

Tom Dixon is program development manager of flame and cutting processes at Air Liquide Canada Inc.