
A flashback arrestor is a gas safety device most commonly used in oxy-fuel cutting equipment to stop a backfire or reverse flow of gas back up into the torch equipment.
This safety device is crucial for preventing a fire/explosion while using your torch. It is often overlooked and taken for granted. A torch check valve prevents gases from mixing and responds to pressure changes. This article will explain the application of these devices.
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Torch popping, backfires, and flashbacks are reactions that occur when using your torch. It is important to recognize these situations and make sure your torch has properly installed and functioning safety devices to prevent injuries.
The flash arrestor responds to backfires/ flashbacks and extinguishes them using a stainless-steel screen/sintered element as a block. It protects the user and equipment from damage or explosions. Required by the Occupational Health and Safety Administration (OSHA), they can be installed on the inlet of the torch handle or on the output of the torch regulator. If regulator-mounted arrestors are used, flashbacks can still occur in the torch handle and hoses with a high potential for injury.
Regulator arrestors are typically larger and have a higher flow capacity than torch modelsbecause the blocking element has more surface area, allowing for more flow. These will protect regulators and cylinders from the effects of flashback but not the torch handle and hose, whereas the torch-handle-mounted type will stop the backfire before it gets to the hose, regulator, and tanks. The size of the torch-mount arrestor is smaller so as not to make the torch too cumbersome to handle.
There is a restrictive property (friction loss) to flashback arrestors and check valves, so the regulator pressures may need to be adjusted to compensate for this. Refer to the manufacturer for the proper amount of adjustment. If the flashback arrestor is torch-mounted, there is potential for foreign material to enter the system and plug the device. This will further restrict gas flow and starve the tip. Like check valves, flashback arrestors need to be checked periodically. There is no field test for a flash arrestor—either replace it or send it to the manufacturer for testing.
The average lifespan of a typical flashback arrestor is 18 months, depending on average use, by the Compressed Gas Association (CGA) and OSHA requirements for industrial applications. Most flashback arrestors are also check valves—check to confirm. You can install them in both places. Refer to the manufacturer’s recommendation.
TORCH CHECK VALVE
A torch check valve is different from an arrestor. This device prevents gases from mixing and responds to pressure changes. Many torch manufacturers combine both of these devices into one appliance. A check valve will not stop a backfire.
Check manufacturers’ information regarding placement and pressure requirements for the installation/replacement of arrestors/ check valves. These safety devices, if not properly sized/installed, can cause an excessive pressure drop, resulting in a malfunctioning torch. Use Underwriters Laboratories-approved and OSHA-compliant replacement devices.
COMBINATION ARRESTOR/CHECK VALVES
Safety devices such as these should be test- ed/replaced periodically. A check valve contains a rubber diaphragm that will stop the reverse flow of gas and operates at 2 to 5 pounds per square inch (psi). If a flashback occurs, the check valve will be damaged but will show no evidence of this. To check, remove the check valve and reinstallwith the flow direction arrow point toward the regulator. Turn on the tank valve and adjust the regulator output to 3 to 5 psi. If gas blows through the backward (submerge in a glass of water, look for bubbles) arrestor/valve, then it needs to be replaced. The manufacturer will also test them.
An oxy-fuel cutting torch is a powerful tool that can increase your rescue capability. Get good training and keep training; read the manuals; and maintain your equipment to make safe, confident rescues.
RESOURCES
- harrisproductsgroup.com/en/Resources/ Knowledge-Center/Articles/A-Commentary-On-Backfires-Flashbacks-and-Flashback-Arrestors.
- fireapparatusmagazine.com/magazine/identifying-metals-and-torch-troubleshooting/#gref.
- oxyfuelsafety.com/flashback-arrestors-vs-check-valves-do-you-really-know-the-difference.
STEVE SHUPERT is a lieutenant (ret.) from Miami Valley Fire District, Montgomery County, Ohio. He is rescue team manager and training officer for Ohio Task Force #1 US&R. He is a veteran of 11 federal deployments including WTC and Hurricane Katrina, a member of DHS/FEMA Rescue Sub Group, a certified rescue specialist, a structural collapse specialist instructor, and a heavy equipment rigging specialist instructor. Shupert is director of training for Crash Course Village, a 501C3 nonprofit organization.