Reducing Welding Accidents With Flashback Arrestors
In any situation where oxygen is combined with a fuel gas for the purpose of welding or cutting, the danger of a flashback exists. Therefore, flashback arrestors are an essential safety feature for this type of equipment; whether on an individual level where a hand-operated acetylene welding torch is being used or in a large-scale industrial situation where a gas manifold system is the tool of choice.
Flashback occurs when the flame from a torch reverses course and climbs back into the equipment towards the hose and cylinders. When this occurs, it can cause the gases within the hose to combust. If the flames or highly volatile fuel-oxygen mixtures reaches the cylinder, it can result in an explosion.
Some of the circumstances that can lead to the occurrence of a flashback include:
- An imbalance of pressure between oxygen and gas within the system, which occurs most often during torch startup or shutdown.
- An obstruction in the tip of the torch.
- Leaks in the system.
- Improper velocity of oxygen or gas flow.
- Getting the flame too close to the welding or cutting surface.
Oxygen itself is not flammable. But when combined with a fuel gas such as acetylene, propane or hydrogen, the mixture becomes highly combustible. When properly harnessed and controlled, this combination makes for a very effective welding and cutting tool. However, if a fuel gas or oxygen cylinder goes empty during a welding or cutting operation, even the slightest presence of gas or oxygen will present a combustion hazard. Therefore, it is vital to maintain a proper mixture of oxygen and gas as well as to continuously check tank volumes and flow pressures.
Check valves will prevent gases from flowing back into the system. They are designed to allow gases to flow in one direction, and to block them from changing direction and heading back toward the source. Although check valves do provide a level of safety, they are not built to stop or suppress flashbacks. This is the job of the flashback arrestor.
Flashback arrestors are designed to prevent a flame or combusted gas from flowing back into the oxygen-fuel gas system. Built accordingly depending on the purpose and size of the operation, flashback arrestors are built to stop and extinguish flames. In situations where gas flow reverses direction, flashback arrestors extinguishing incoming flames using a process of heat sensors, traps and filters.
In addition to check valves and flashback arrestors, a careful inspection of an oxygen-fuel gas welding system should be performed before every use. Adherence to all safety requirements can not be overemphasized when working with the potentially deadly combination of gases and flames!