Safety in the Plant
Interlocks minimise opportunities for human error
Interlocking systems are vital to ensure that process operations occur in the correct sequential order, reports Sean Ottewell. Minimising the possibility of human error, they protect workers from injury and property from damage.
Verriegelungssysteme sind von elementarer Bedeutung, um sicherzustellen, dass Prozessschritte in der richtigen Reihenfolge ablaufen, berichtet Sean Ottewell. Indem sie die Gefahr von menschlichen Fehlern minimieren, verhindern sie Verletzungen und Sachschaden.
Les systèmes à emboîtement sont vitaux pour s’assurer que les opérations de traitement sont effectuées dans le bon ordre séquentiel, relate Sean Ottewell. En minimisant les risques d’erreur humaine, ils protègent les ouvriers contre les blessures et les biens contre l’endommagement.
T
rapped-key interlocks 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°). 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: using the special tamperproof tool (provided), the interlock cover is removed and the set screws adjusted; and the valve is then operated again to its shut tight (closed) position and the screws are retightened (reset) in the new position. Meanwhile, Netherlocks has
launched a series of practical training courses aimed at enabling technicians to develop basic skills on installing, setting and troubleshooting valve interlocks.
Fig. 1. The operator has to liaise with the loading manager and wait for authorisation from the control room before coupling the hose and starting to unload.
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