Does the overspeed protection system act directly on the valve solenoid, or does it control the valve after entering the SIS?
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Recently, I have been looking into information on overspeed protection systems. For those used in turbine technology, it is recommended that they use a three-out-of-two voting mechanism to generate a signal that directly acts on the shut-off valve. There is another approach, where no such voting mechanism is used; instead, a signal is sent to the SIS, which then carries out the voting process to close the valve. What do people do in practical applications? What I saw before was another type: in that case, the overspeed protection system would carry out a two-out-of-three voting process, send an interlock signal to the SIS, and it would still be the SIS that shut down the valve.
In practical applications, the handling method of the overspeed protection system (SPS) may depend on specific industrial standards and safety requirements. Some systems perform a two-of-three voting mechanism within the SPS to directly control the shut-off valve ； In other cases, the SPS merely sends signals to the Safety Instrumented System (SIS), which then carries out further logical processing and controls the valves. The choice of approach usually depends on the specific security requirements of the project, system complexity, and reliability considerations. .