Welding Safety | The Dangers of Welding Flashback
Welding is a practice used on a lot of job sites across the country everyday. Oxy-acetylene torches are great for welding, cutting, brazing, and heating materials and make a lot of jobs easier than they normally would be without them. However, there are still too many injuries related to welding each year due to simple mistakes or just sheer ignorance. Workers should make it a habit to inspect the equipment they will be using and know the proper welding safety best practices before ever performing any welding work. We will run through some of the things workers should have in mind every time they perform a welding job so they can better prevent fires and explosions.
One of the biggest causes of welding incidents is an unsafe amount of gas pressure. If there is more than 15 pounds of acetylene pressure being used, the gas becomes unstable and will explosively decompose. Due to this, other fuels such as MAPP, propane, natural gas, and propylene are used since they can operate safely at higher temperatures. Workers need to know the correct amount of pressure relative to the gas they will be using.
Another cause of welding incidents is burn back. Burn back is when the oxygen in your cylinder gets low or empty and the gases start to reverse their flow. Since the fuel gas is at a higher pressure, it can travel up the oxygen line and mix with the gas inside the hose, cylinder, and regulator. Workers need to make sure to purge the lines or they could cause an explosion inside the hose, cylinder, and regulator. A closely related problem to this is backfire. Backfire occurs whenever there is high oxygen pressure but low fuel pressure. This is usually caused when workers hold the cutting torch to close to the work they are doing. This causes the gas to become starved and the flame will be sucked into the head of the torch. When this happens there will usually be a popping or whistling sound.
Workers also need to be aware of flashback. Flashback is when backfire occurs inside the mixing chamber. If workers don’t shut off the oxygen valve when this happens the flame burning in the head of the torch could ignite the gases in the hoses and cause flashback. When flashback happens, an explosion progresses through the torch, hoses, regulators, and into the cylinders. This could be a small problem, with just a hose bursting, or it could be devastating, with a violent explosion of the cylinders and regulator.
To prevent all of the things we just mentioned, keep in mind the following.
- Keep the pressure below 15 pounds whenever using acetylene. If you are using a different gas, know the correct pressure to keep it at.
- ALWAYS purge the hoses before ever lighting the torch.
- NEVER light the torch with a mixture of oxygen and fuel. Light the torch with ONLY the fuel gas valve open. This should all be done AFTER purging the hoses.
- Inspect the equipment beforehand to make sure that check valves are installed on both of the torch inlets and that they are operating correctly. Keep in mind that check valves can stop gas from reversing flow, but it will NOT prevent flashbacks.
- Flashbacks can only be prevented by installing flashback arrestors on both regulator outlets and torch inlets.
Always be sure to check the torch. Workers need to have the knowledge to know if the torch they are using has a flashback arrestor and check valves. When looking at the torch closely, there should be a small cylindrical valve on each inlet with the hoses screwed onto the valve. The hoses should NOT be hooked directly onto the torch. The entire point of the valves is to prevent flashbacks from happening. These valves will say what they are on the valve body, such as whether it’s a combination flashback or check valve.
Be sure to know your welding safety and what you can do to help prevent welding flashbacks, burn backs, backfires, and incorrect gas pressure!