Although working with fuel gases is a safe process in the hands of trained personnel, it can lead to a dangerous situation if the equipment is used incorrectly. Fuel gases should not be used unless proper safety procedures have been understood and applied. Special safety devices as flashback and flame arrestors prevent dangerous backfire and flashback.
WITT flashback arrestors or flame arrestors are used to protect single cylinders, outlet points or pipelines and can be used for almost all technical gases such as acetylene, propane, propylene, ethylene, methane, hydrogen or oxygen.
Through the combination of established safety elements, flashback arrestors provide protection against flashbacks and backfire. Flashback arrestors or flame arrestors also prevent the formation of dangerous gas mixtures within the pipeline.
The main reasons for flashbacks and backfire
Very often the main reasons for flashbacks and backfire: faulty torch assemblies and incorrect gas pressures being used. Approximately 80% of all incidents are due to human error. In a backfire the flame burns back into the torch with a cracking sound. Either the flame is extinguished, or it is reignited at the nozzle opening. In a sustained backfire the flame continues back into the torch, often reaching the mixing point for oxygen and fuel gas. An initial crack is followed by a whistling sound.
A gas mixture in one of the hoses in combination with a backfire when igniting a burner can cause a flashback. The gas mixture in the hose results from reverse flow, i.e. when gas at a high pressure flows into a hose with a lower pressure. In a flashback, the flame recedes through the torch back into one of the supply hoses. At twice the speed of sound the flame races through the hose. Quick action is therefore impossible. Should an application result in a flashback –the consequences are highly dangerous. For example, gas hoses bursting, flame located at the pressure regulators or -in the worst-case scenario -the explosion of the pressurized gas cylinder.
Flashback and flame arresters prevent reverse flow and flashback
High quality WITT flashback arresters or flame arresters have been well-established safety products to avoid the risk of flashbacks. These small, compact devices have revolutionized safety in welding. Today each flashback arrestor features at least three safety elements: the non-return valve, the flame arrestor and the thermal cut-off valve. A possible reverse gas flow is stopped by the action of a spring-loaded non-return valve, thus preventing the two gases mixing. The formation of a highly explosive gas mixture is therefore impossible. A filter protects the fine mechanism against dirt. At the centre of the flashback arrestor is a hollow cylindrical filter made of sintered stainless steel. It's essential for effectively stopping a flashback. The mechanism is based on the highly porous structure of the cylindrical filter. The flames flow through the filter, losing their energy, which brings about a cool down. In this way, every single flashback is extinguished in fractions of a second. The temperature-activated cut-off valve is the third important safety element Before the device reaches dangerous temperature levels, an integrated plastic seal component melts and instantly activates a springloadedvalve -automatically cutting off the gas supply. The critical ignition temperature can no longer be reached upstream the flashback arrester anymore. The dangerous backburnis quenched and no harm is done.
WITT flashback arrestors or flame arrestors meet all relevant standards
WITT flashback arrestors or flame arrestors meet all relevant standards DIN EN ISO 5175, with the according tests from licensing offices such as the BAM (Federal Institute for Materials Research and Testing). A 100% product control assures highest quality.
The flashback or flame arrestors are mountable in any orientation and are available with all connections and in brass or stainless steel. High-quality materials and filters in the gas inlet provide long service life of WITT flashback or flame arrestors. Flashback and flame arrestors can either be torch-mounted, hose-mounted or regulator-mounted. Maximum safety is achieved by having arrestors on both regulator and torch. It is important to apply this protection not only to the fuel gas but also to the oxygen side.