Type 646/641

> Safety valves with Stainless Steel body
> Enclosed discharge valve with threaded connections

Product Description

Type 646/641

Enclosed Discharge Safety Relief Valve for Compressed Air & Gases, available with 10, 13, 18, 20 or 25mm nominal bore.


Available for Same-Day Despatch


Example Applications:
  • Air/gas compressors
  • Pressure vessels
  • Pneumatic systems
  • Medical gases
  • Technical gases



View or Download Datasheet


Technical Information

Technical Information for Type 646 / 641

  • Min. Pressure
    6.6 bar (95.7 psi)
  • Max. Pressure
    55.20 bar (800.40 psi)
  • Temperature Range
    -30 °C to 200 °C (subject to seal material)
  • Inlet Connection(s)
    3/8" to 2" BSP, BSPT orNPT
  • Outlet Connection(s)
    3/4" to 2" BSP or NPT
  • Flow Rate
    Refer to Flow Tables on the datasheet
  • Materials
    St. Steel
  • Seal Materials
    Viton® / Nitrile / Neoprene Ethylene / Propylene
  • Test Certification
    Included - supplied Free of charge
Flow Rates

See Datasheet


  • Maximum permissible built up back pressure is 10% of set pressure
  • Stable operation on flows down to 50% of valve rated capacity
  • Relieving pressure is set pressure +10%
  • Reseating pressure is set pressure -10% (0.3 bar minimum)
  • Below 1.55 bar, PED certified only


  • Designed in accordance with BS EN ISO-4126-1 & -7
  • PED 2014/68/EU (CE)
  • PE(S)R UK SI 2016 No. 1105 (UKCA)
  • CRN
  • EAC


Adaptable Solutions

Available in a range of sizes, materials, and pressure ratings, these valves handle diverse fluids and conditions, from delicate instruments to high-pressure steam boilers.


View or Download the Type 646 / 641 Datasheet

Full Technical Information - Including Flow Rates

View or Download the Type 646 / 641 Datasheet

Seetru offers a wide range of downloadable datasheets for our products, including safety relief valves, liquid-level gauges, and sight glasses.  These datasheets provide detailed information on the technical specifications, features, and applications of Seetru products.  They are an essential resource for engineers, designers, and other professionals who need to select the right Seetru products for their specific needs.


Find your PDF Download for the 646 Air/Gas  Range below…
Visit our downloads page for other Seetru product brochures and catalogues
Visit our Downloads Page View the Type 646 / 641 Datasheet