Non-Return Valve NV400, Stainless Steel (formerly 339-ES)

Non-Return Valve NV400, Stainless Steel (formerly 339-ES)

Non-return valve, stainless steel, for the prevention of unintended gas mixtures, for flow rates up to 8100 m³/h (air), up to 16 bar for use in thermal processing plants, certified to EN746-2, G 1.1/2 – G 2

  • safety element: non-return valve [NV]
  • every non-return valve 100% tested
  • ultra-low opening pressures (approx. 3 mbar), ultra-low pressure drop
  • ideal for biogas desulphurisation systems
  • also ideal for use with corrosive gases
  • dirt filter (100 μm) on gas inlet
  • 90 X 145 mm, 2.633-2.665 g

Product of WITT



WITT non-return valves for reliable protection against dangerous reverse gas flow. Every non-return valve 100% tested.


  • a spring-loaded non-return valve prevents a reverse flow of gases which could lead to unwanted gas mixtures
  • low-pressure drops – using complex valve assembly with low opening pressures
  • no leaks – using a spring-loaded valve assembly with elastomer sealing
  • stainless steel filter (100 μm) in the gas inlet protects the non-return valve against dirt contamination, extending the service life
  • diverse applications – useful for many technical gases

Operation / Usage:

  • non-return valves are used to protect equipment and pipelines against dangerous reverse gas flow. Use is possible for applications according to EN 746-2
  • ideal for use with corrosive gases in the chemical industry, process technology or in laboratories
  • WITT non-return valves may be mounted in any position/orientation the maximum ambient/working temperature is 70 °C / 158 °F


  • annual testing of the non-return valve and body leak tightness is recommended
  • WITT is happy to supply special test equipment
  • non-return valves are only to be serviced by the manufacturer. The dirt filter may be replaced by competent staff

Company certified to ISO 9001 and PED 2014/68/EC Module H
CE-marked in accordance with PED 2014/68/EC
Cleaned for Oxygen Service according to EIGA IGC Doc 13/12/E: Oxygen Pipeline and Piping Systems

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Non-Return Valve NV400, Stainless Steel (formerly 339-ES)