Actuated Valves Operating Sequence

A typical operating sequence is shown below. The interlock system functions ‘passively’ and relies on the as-built actuator mechanisms to establish and confirm the status of the equipment. This can also be observed when valves are in the ‘Open’ (‘Remote’ setting) position – The valve is free to operate to ‘Closed’ without hindrance or interruption by the interlock system.

Equipment Status: Valve Open

  • ‘SLU’ Switch Unit Locked in ‘REMOTE’
  • ‘HWL’ Handwheel Drive locked ‘OFF’
  • ‘A’ Key in Control room.

To close valve:

  1. ‘A’ Key into ‘AKE’ positional indicator unit. ‘B’ Key is removed from ‘AKE’ – ‘A’ Key trapped
  2. ‘B’ Key into ‘SLU’ Switch Unit to unlock. ‘SLU’ Unit switched to ‘LOCAL’ (‘B’ & ‘C’ Keys trapped). Operate button to close valve
  3. ‘SLU’ Unit now switched to ‘OFF’ – ‘C’ Key is removed. ‘SLU’ Unit locked in ‘OFF’ position trapping ‘B’ Key
  4. ‘C’ Key into’ AKE’ Unit – remove ‘D’ Key trapping ‘C’ Key. ‘D’ Key is then directed towards continuation of the procedure

The ‘D’ Key will not release unless the valve has completed its full stroke to the CLOSED position.

P12_pic2V3

Equipment Status: Valve Closed

  • ‘SLU’ Switch Unit Locked ‘OFF’
  • ‘HWL’ Handwheel Drive locked ‘OFF’
  • ‘D’ Key in Control room

To close valve:

  1. ‘D’ Key into ‘AKE’ positional indicator unit. ‘C’ Key is removed from ‘AKE’ – ‘D’ Key trapped
  2. ‘C’ Key into ‘SLU’ Switch Unit to unlock. ‘SLU’ Unit switched to ‘LOCAL’ (‘B’ & ‘C’ Keys trapped). Operate button to open valve
  3. ‘SLU’ Unit now switched to ‘REMOTE’ – ‘B’ Key is removed. ‘SLU’ Unit locked in ‘REMOTE’ position trapping ‘C’ Key
  4. ‘B’ Key into’ AKE’ Unit – remove ‘A’ Key trapping ‘B’ Key. ‘A’ Key is then directed towards continuation of the procedure

The ‘A’ Key will not release unless the valve has completed its full stroke to the OPEN position.

P12_pic1V3