Product information

This product supersedes product no: 619262

Maritime authorities, such as the Norwegian Maritime Directorate, require the installation of flashback arrestors for acetylene and oxygen, as incorrect maintenance or use of gas welding equipment may cause flashbacks of various types.

Normally these will stop in a well designed torch, and are only noticed as a popping sound in the torch. However, faulty handling, maintenance or gas pressure setting may lead to a penetrating flashback. This means that the gas flame passes back through the hose(s). In some cases it may also pass the regulator and ultimately reach the cylinder.

The flashback arrestors supplied by Unitor are designed for use both with gas cylinders and gas outlet stations and incorporate several safety functions:

  • Non-return valve preventing reverse flow of gases, thereby preventing a gas mixture from reaching pipelines or cylinders
  • Flame filter to quench the flame front of a flashback or a burnback
  • Temperature activated cut-off to prevent further gas supply in case of fire (activated if the temperature rises to approximately 100° C)
  • Pressure activated cut-off to prevent further gas supply after a flashback (activated by the pressure shock in front of the flashback)
  • Indicator ring showing that the pressure activated cut-off has been activated; the ring is also used for resetting the flashback arrestor
  • The flashback arrestors are build Conform to: EN 730/ISO 5175 and with BAM Certification no.: ZBF/009/12


For safety reasons we strongly recommend annual testing of the Flash back arrestors, and to change flashback arrestors every 5 years, calculated from the date you start using the equipment.


  • Pressure activated cut-off valve
  • Temperature activated cut-off valve
  • Flame arrestor
  • Non-return valve


  • Stops the pressure front
  • Prevents fire from being supported by gas
  • Stops the flame front
  • Stops gas from back feeding into the system



Product name Product number Diameter [mm] Length [mm] Product catalog URL Capacity Operating pressure [bar]
FLASHBACK ARRESTOR S55 AC 708537 (supersedes 619254) 27.5 119 https://www.wilhelmsen.com/product-catalogue/products/gases-refrigerants-and-cylinders/gas-distribution-system/outlet-station/flashback-arrestor-s55-ac/?epieditmode=true 8,5 m3/h 1.5
FLASHBACK ARRESTOR S55 OX 708545 (supersedes 619262) 27.5 119 https://www.wilhelmsen.com/product-catalogue/products/gases-refrigerants-and-cylinders/gas-distribution-system/outlet-station/flashback-arrestor-s55-ox/?epieditmode=true 50 m3/h 10
FLASHBACK ARRESTOR W-66S ACETYLENE 183970 https://www.wilhelmsen.com/product-catalogue/products/welding/gas-welding-brazing--cutting/gas-cylinder-regulators-and-flashback-arrestors/flashback-arrestor-w-66s-acetylene/?epieditmode=true 19 m3/h 1.5
FLASHBACK ARRESTOR W-66S OXYGEN 302976 https://www.wilhelmsen.com/product-catalogue/products/welding/gas-welding-brazing--cutting/gas-cylinder-regulators-and-flashback-arrestors/flashback-arrestor-w-66s-oxygen/?epieditmode=true 105 m3/h 10