Safety Group 645/FN40

Parallel bundle of 2 or 4 decomposition arrestors FN4, to protect against dangerous decomposition of acetylene in low-pressure pipelines, for high flow rates

  • highest quality from the world market leader
  • safety elements: flame arrestor [FA],  temperature-sensitive cut-off valve [TV]
  • stops the explosive decomposition of acetylene via pressure-controlled quick-acting piston valve
  • every device is tested before delivery
  • 470 X 260 mm, 46 kg
  • Q= ca. 560 m³/h (free flow-off)

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Parallel connection from 2 and 4 Flashback Arrestors model FN40.
WITT Safety groups for reliable protection against decomposition of acetylene. For applications with high flow rates. Every safety group 100% tested.


  • a large surface area flame arrestor FA of stainless steel construction:

     - stops dangerous decomposition of acetylene independent from flow direction
     - extinguishes any dangerous flashback entering the device in any direction

  • a temperature sensitive cut-off valve TV extinguishes sustained flashbacks long before the internal temperature of the arrestors reaches a dangerous level

Operation / Usage

  • as a Decomposition Arrestor for acetylene in medium pressure pipe-lines for protection from cylinder equipment and bundles according to DIN EN ISO 14114
  • as a Decomposition Arrestor to protect pipelines in supply systems
  • WITT safety groups may be mounted in any position / orientation
  • the maximum ambient / working temperature is 60 °C / 140 °F


  • it is recommended that an annual body leakage test is performed
  • safety groups are only to be serviced by the manufacturer


  • flange end connections (nominal diameter 32 - 65)
  • connection: two-sided female thread (G-; NPT-thread; Rc-thread)

Company certified according to ISO 9001and PED 2014/68/EU Module H
CE-marked according to PED 2014/68/EU


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