SFC’s technology makes valve interlock adjustment effortless

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SFC’s technology makes valve interlock adjustment effortlessSmith Flow Control is promoting its trapped-key interlocks, which offer enhanced safety and efficiency for the most difficult process management challenges. Mounted directly to valves, interlocks ensure a process only happens in the correct operational sequence.

Trapped-key interlocks for handwheel-operated valves are different from those for lever-operated valves, as the latter only have a finite movement (normally 90 degrees). Interlocks on handwheel-operated valves, however, usually require several full revolutions between the locked open and locked closed positions.

Because of this, handwheel-operated interlocks need to be able to ‘count’ the number of handwheel turns in order to release keys in the required open and/or closed positions. Similarly, with gate and globe valves, the closed position can vary through the effects of valve seat wear. After a period of use, the closed position on gate and globe valves may have altered. This can mean that when the valve is shut tight, the interlock (closed) key will not release as the valve has travelled past the original set key release position.

Smith Flow Control’s (SFC’s) GL Interlocks are suitable for this scenario as they can be adjusted in-situ in a matter of minutes simply by operating the valve back to the original key release position in two easy steps:

  1. Using the special tamperproof tool (provided), the interlock cover is removed and the set screws adjusted
  2. The valve is then operated again to its shut tight (closed) position and the screws are retightened (reset) in the new position

This simple in-situ adjustment feature is claimed to be unique to SFC’s GL interlock, and provides a fast and efficient method of maintaining valve interlocks on site. To learn more about trapped-key interlocks, please go to

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