Flashback Arrestor
What specific mechanisms allow a flashback arrestor to extinguish a flame in an oxy-fuel line?
The core mechanism is rapid heat removal and flame speed reduction. The flame barrier element (sintered metal, mesh, or foam) has many small channels with large surface area. Hot combustion gases enter the element and are cooled below the minimum flame velocity for the gas/mixture, so the flame cannot propagate further and is extinguished.
How does ISO 5175-1:2017 relate to WorkSafeBC requirements for flashback arrestors?
WorkSafeBC OHSR 12.120 is performance-based, requiring suitable safety devices. ISO 5175-1:2017 provides specific design, performance, and test criteria for such devices, including endurance against flames, non-return valve performance, and thermal shut-off behavior. In Canadian practice, arrestors meeting ISO 5175-1 are typically considered suitable for compliance.
Why does WorkSafeBC require flashback prevention devices on each hose between torch and regulator, instead of only at the cylinder?
Installing devices on each hose provides localized protection at the most likely flashback origin (torch/nozzle area), redundancy even if a torch-mounted device fails, and improved protection for portable systems where hoses are frequently moved. Arrestors only at the cylinder leave multiple metres of hose and regulator internals unprotected.
A flashback arrestor is a safety device installed in oxy-fuel gas systems that stops a flame (flashback) and prevents reverse gas flow from traveling back into hoses, regulators, manifolds or cylinders. It typically incorporates a flame barrier, non-return valve, and often a thermal cut-off, ensuring fire, explosion, and equipment damage are prevented. WorkSafeBC requires these devices on each hose between torch and regulator.
On a shop floor, flashback arrestors are installed on each oxy-fuel hose between the torch and regulator for both oxygen and fuel gas lines, per WorkSafeBC requirements. They function by using a sintered metal filter to cool and extinguish flame fronts, while internal check valves prevent reverse gas flow that could create explosive mixtures. Workers must perform pre-use checks for correct gas-specific arrestors, proper flow direction, and physical damage. After any flashback, operators must close cylinder valves, allow cooling, and inspect arrestors before reuse. Annual inspections and functional tests are recommended to ensure continued protection.
Missing or incorrectly located flashback arrestors, such as only one on fuel gas line or installed only at cylinder, violating WorkSafeBC 12.120 and leaving hoses unprotected.
Confusing check valves with flashback arrestors, as check valves only prevent reverse flow but do not stop flame fronts, leading to unprotected systems.
Using incompatible, damaged, or unmaintained arrestors, such as wrong gas rating, reversed flow direction, or continued use after flashback, reducing protection.