Difference in the operation of cut-off valves between basic process control systems and safety interlock systems
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Dear netizens, the difference between the operation of cut-off valves in basic process control systems and safety interlock systems lies in the fact that the operation in basic process control systems is reversible, whereas that in safety interlock systems is irreversible. Is that understandable?
No, the interlock between DCS and SIS is designed based on SIL level assessments. If it is below SIL1, there is no need for a dedicated SIS; interlocks can be implemented using DCS.
In a DCS system, valves are controlled by operators and background interlocks to open or close them. The solenoids of SIS valves are normally in an energized state; when the SIS interlock is triggered, they lose power and the valve operates. To restore normal operation, it is necessary to reset the SIS system. This process is not irreversible – it’s just that the operator cannot control the valve directly.