Double block and bleed valves

The primary function of a double block and bleed valve is for isolation and the secondary function is for intervention (diverting / sampling / injection etc).

Double block and bleed valves operate on the principle that isolation can be achieved from both the upstream and downstream process flow / pressures. This is achieved by two ball, gate, globe, needle, etc. valves placed back to back, with a third “isolatable” valve in the centre cavity. Once isolation has been achieved in one or more of the main process isolation valves, the cavity that is created between these isolations can be drained. This is useful for flow diverting, sampling or injection situations, and for maintenance / integrity check situations where seat leakage can be monitored through the third “bleed” valve.


General design criteria

  • In-line Globe, Angled Globe, Butterfly, Control Ball, Eccentric Disc
  • Manual, Pneumatic, Electric or Hydraulic Actuation
  • Trim style options – parabolic plug, multi-hole cage, multiple cages, high duty labyrinth
  • Trim features – low flow, anti-cavitation, low noise, erosion resistant, high energy dissipation
  • Trim coatings – Silicon carbide (Hyc 20), Hard Chrome, Tungsten Carbide
  • Erosion resistant upgrades – Stellite weld overlay, Solid Tungsten Carbide Inserts, Solid Ceramic Inserts
  • Characteristics – Linear, Equal Percentage, Quick Opening
  • Hydrostatically body tested to ANSI B16.34
  • Seat leakage tested to ANSI FCI 70-2
  • Specialised gas, low temp and cryogenic testing options
  • Positioner options – pneumatic, electro-pneumatic, electronic digital SMART
  • Operating temperature and fluids suitability – further information available on request
  • Modification service available for all stock options

Standard pressure class ratings / end connections

  • ANSI 800, 1500 & 2500lb – Threaded, Socket Weld and Butt-Weld ends
  • ANSI 150, 300, 600, 800, 1500 & 2500lb – Flanged RF, RTJ, Butt-Weld and Hub ends
  • PN, API and other Pressure Class Valves available on request

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