Safety Selector Valve (switch over device)
Sizes: 1" to 10" Pressure Class: ANSI Class 150 to 2500 Maximum Temperature: 800°F [426°C] Recommended Specifications Changeover device inlet connection is to be the same size and rating as the pressure relief valve inlets.
Pressure drop through the changeover device’s active side cannot exceed 3% with pressure relief valve fully open.
Changeover device is to have external indicator, showing which side is active.
Provisions for double padlocking in either position are required.
A valve bleed port must be located under each pressure relief valve connection for pressure venting under the inactive pressure relief valve.
The Safety Selector Valve is designed specifically to function as an effective “switchover” device.
Features & Benefits:
- Designed to provide a safe, efficient method of switching from an active pressure relief device to a standby, maintaining system overpressure protection regardless of Safety Selector Valve position.
- Provides high Cv values, resulting in less than 3% pressure drop to the active PRV inlet, when used with the largest API orifice available in a given valve size, in accordance with the recommendations of API RP520 Part II and ASME Section VIII, Division 1, Appendix M, helping reduce the possibility of destructive chatter of the PRV.
- Requires only one minimally sized penetration into the vessel or pipe, reducing costs.
- Reduces field installation costs and space requirements through preassembled and compact design.
- Provides process isolation of standby pressure relief device.
- Allows pressure relief device maintenance without process shutdown.
- A bleed valve is provided under each safety relief device as an effective and safe means of venting entrapped process under an isolated pressure relief valve prior to removal for maintenance.
- Bright red indicator for positive indication of active pressure relief device.
- Meets all mandatory requirements of ASME Section VIII, Division 1, UG-135 (b).
- Foolproof provisions for dual padlocking in either pressure relief valve position, in accordance with the recommendations of ASME Section VIII.
- Packing design has been tested to ASTM E427, Method A halogen leak test, reducing probability of fugitive emissions.
- No seat lapping required for maintenance. Only recommended spare parts are soft goods, which reduces cost of ownership.
- Meets standard temperature applications from cryogenic to +800°F [427°C].
- Offers materials of construction compatible with pressure relief devices. Duplex and 6MO material available.
- Helps deliver a reduced number of leak points to atmosphere, reducing probability of fugitive emissions.
- Isolates a standby pressure relief valve in accordance with joint recommendation of API Subcommittee on Pressure Relieving Systems and Subcommittee on Refinery Inspection.