Valve Interlock for Actuated Valves
The most common requirement for key interlocking of poweractuated valves occurs in Pig Launcher/ Receiver systems, Scraper Traps and Sand Filter systems etc. where poweractuated valves need to be interlocked with manually-operated valves and the vessel closure.
Because of the ultra-critical nature of such valves, special considerations arise which the design of a key interlock system must address:
Where such valves are part of an ESD system, the key interlock system must not compromise the valve’s fail-safe function. Where such valves are part of an ESD system, the key interlock system must not compromise the valve’s fail-safe function.
Where pigging operations occur, the key interlock system must verify the valve’s absolute position (Open and/or Closed) independent of any on-board instrument indication.
On electrical actuators where the key interlock system de-energises the valve, any anti-condensation heating circuitry etc. must remain uninterrupted.