Safety Selector Valve

Safety Selector ValvesAnderson Greenwood

A dual pressure relief device system that provides a safe, efficient method of switching from an active PRV to a standby, maintaining system overpressure protection

Liquid/two phase service Safety Selector Valves can be used in gas/vapor, steam, liquid or two-phase service. Figure 1 shows an Anderson Greenwood Series 400 pilot valve relieving on liquid only. Figure 2 shows the same valve transitioning to two phase flow as gas becomes entrained in the relief stream. Section I steam service As per ASME Section I Boiler and Pressure Vessel Code Case 2254, the Safety Selector Valve can be installed to provide a back-up safety valve for boilers with a maximum allowable working pressure (MAWP) of 800 psig or less. The code case requires that the switchover device must provide: positive locking, external bleed valves, certified Cv values. The SSV will provide the highest flow efficiency (Cv) of any switchover device in the same nominal pipe size, enabling it to be used with most manufacturers’ flanged Section I Boiler valves. To ensure complete compliance with the code case, please provide the model number and set pressure of the safety valves to be used.

  • Provides high Cv values, resulting in less than 3% pressure drop to the active PRV inlet, reducing destructive valve chatter.
  • One minimally sized penetration into the vessel or pipe reduces costs.
  • Reduces field installation costs and space requirements through preassembled and compact design.
  • Provides process isolation of standby PRV.
  • Allows PRV maintenance without process shutdown.
  • Bleed valve under each PRV vents entrapped process effectively and safely prior to removal for maintenance.
  • Clear, positive indication of active PRV.
  • Foolproof provisions for dual padlocking in either PRV position.
  • Tested packing design and minimal leak points reduce fugitive emissions.
  • No seat lapping required for maintenance. Minimal spare parts reduce cost of ownership.
  • Simple operation with built-in seat equalization and no special tools minimizes total valve operating time.
  • Tandem system available for dual PRV's discharging to a closed header system.

Technical Data


Change Over


Up to 6001.66 psig


-425°F - +801°F


NPS 1-10



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