MECHANICAL VALVE INTERLOCKS PREVENT PROCESS VALVE CONTROL ERRORS

The new QL and GL mechanical valve interlocks from Smith Flow Control ensure potentially hazardous valve operations are performed in the correct sequence, eliminating the possibility of operator error or deliberate sabotage. They can be integrated with any size of ball, plug, gate, butterfly and globe valve. Mechanical interlocks are typically used to support ‘Permit to Work’ procedures such as safety relief valve changeover, pig trap loading and retrieval, or filter changeover. Because they simply replace the original handwheels or levers, the QL and GL interlocks are easily retro-fitted to operational plant without requiring shut-down. In addition, their fitting does not compromise the certified pressure envelope of host valves. Fitting kits can either be bespoke, to match the topworks of a specific make and model of valve, or as universal fittings. The latter option allows the interlocks to be re-sited and re-used if the original plant is decommissioned. A novel feature is on-site lock re-coding, which allows plant managers to quickly adapt interlocking sequences to changes in process logic. Designed for long-term operation in the harshest of onshore and offshore conditions, the QL and GL interlocks are made from 316 stainless steel and are also available to order in Duplex and SuperDuplex*. The standard finish is a bright yellow polyester powder coat (to RAL1021) which has high visibility for locating control valves in poor conditions. Operation is by cast stainless steel ‘coded card’ keys, which simply push in and pull out of anti-ingress and weather sealed apertures in the lock body. Lock mechanisms are totally maintenance-free.