Safety Relief Sequence

4 valve interlock system

An initiating key, issued from a secure location (Control Room) commences the PSV changeover.

 4 VALVE PSV INTERLOCK SYSTEM

Sequence of Operation (Starting from Normal Operating Conditions):

Change-Over Sequence from PSV A Operational to PSV B Operational

  • Obtain Key ’4′ from Control.
  • Insert Key ’4′ into Valve A. Open Valve A. and lock open by removing Key ’3′.
  • Insert Key ’3′ into Valve B. Close Valve B. and lock closed by removing key ’2′.
  • Return key ’2′ to Control.
  • (Change -Over complete)

Complete Isolation of PSV A

  • Obtain Key ’4′ from Control.
  • Insert key ’4′ into Valve A. Open valve A. and lock open by removing key ’3′.
  • Insert ’3′ into Valve B. Close Valve B. and lock closed by removing key ’2′.
  • Insert Key ’2′ into Valve C. Close Valve C. and lock closed by removing key ’1′.
  • Return Key ’1′ to Control.
  • (Isolation of PSV A. complete)

Complete Isolation of PSV B

  • Obtain Key ’4′ from Control.
  • Insert key ’4′ into Valve D. Close Valve D. and lock closed by removing Key ’5′.
  • Return Key ’5′ to Control.
  • (Isolation of PSV B. complete)