Netherlocks has updated the design on their partial-stroke emergency shutdown (ESD) and HIPPS valve testing unit, the FAITH. The device is now available with an incorporated emergency override lever, which can be operated in the unlikely – but possible – event of an ESD needing to be performed whilst the valve is being tested.
Typically, testing an emergency shutdown valve involves operating it, and thus halting production. It is not so much a test, as just a planned shutdown. By using a FAITH, when the right key is inserted into the unit the stroke of the actuator is limited to 20 degrees (can be changed on request): this is enough to make sure that the valve has not stuck, and that it can still be operated, but it does not interrupt production. This has the added benefit of allowing the valves to be tested more often, thus negating the need for a powerful, over-dimensioned actuator to be fitted ‘just in case’.
A potential flaw in this method, however, is that an emergency could occur whilst the limit was active, which could be very dangerous indeed. By building in an ESD override lever, Netherlocks has solved this potential problem. In the event of an incident during testing, the lever can be rotated to release the stroke limiter and the valve will close, stopping operations.
Although this may seem to be a very improbable situation, when dealing with issues of safety it always pays to consider and plan for every possible event. The emergency lever also allows the replacement of solenoid valves, quick exhausts and other safety instrumented system (SIS) components without stopping the process.
The device is completely mechanical and maintenance-free, not needing any wiring, PLC or software, although it can optionally be fitted with switches and solenoids to provide a feedback signal.