Is the SIL certification for control valves applied to the entire unit, or only to the components that generate signals?
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Is the SIL certification for control valves applied to the entire unit, or only to the part that generates signals? For example, in the case of a SIL2 split-type temperature sensor, since the temperature sensing element itself has a SIL2 rating, is it also required that the RTD or thermocouple have a SIL2 rating? For a SIL2 control valve, is it required that the solenoid valve, positioner, limit switch, and actuator all have SIL2 certification?
The SIL certification for instrument valves is usually applied to the entire system, including all its critical components. In your example, if a device such as a temperature sensor is rated at SIL2, then all components that are directly related to it and affect its safety functions, such as RTDs or thermocouples, should theoretically also meet the SIL2 standards. Similarly, for a SIL2 control valve, its key components such as solenoids, positioners, limit switches, and actuators must all meet the SIL2 certification requirements in order to ensure the safety integrity level of the entire system. .
Ask the senior instrumentation engineer at the factory
Overall, all components, including valves, must have SIL2 certification!
These temperature sensors and thermocouples do not require certification. But some institutions have done it, and they use this as an example.
The SIL rating of the instrument valve is overall, not referring to just one individual instrument.
Overall. I have a question: the pump in the equipment is even less reliable, and for the circuit that controls the starting and stopping of the pump as well as the equipment, there is no requirement that either the pump or the equipment meet the SIL2 standard; in fact, the function of this entire circuit isn’t being fulfilled!
Overall certification: All accessories are required, except for the valve body and actuator