Relationship between chemical process DCS and safety interlock SIS systems
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A chemical DCS system is used to control the process itself, while a SIS system is intended for safety interlock control. Does it also serve to control the process? It just focuses on different aspects... In my understanding, companies with high safety requirements use SIS systems. Similar to DCS control systems, the control room can monitor parameters such as temperature and pressure at the site, and it is also possible to adjust valves based on these values. Better safety interlocks for pumps, valves and other equipment in emergency situations... A beginner in the SIS system seeking advice
SIS is a plant-level monitoring system, while DCS is a distributed control system. In my understanding, SIS focuses more on key control points, whereas DCS places greater emphasis on operational control
DCS allows for manual control by central control units or individual devices, while SIS is a plant-level monitoring and control system for the entire production process. For example, without affecting normal production, you can turn a pump on or off, or adjust the temperature, pressure, and liquid level of a reactor, but this will not have a significant impact on the overall process parameters. As for SIS, if an abnormality is detected in a certain device or process area, it may lead to adjustments in the overall production process parameters or trigger safety interlock controls, thereby interrupting normal production activities and providing time for subsequent manual maintenance
DCS is primarily used for operational control, including some interlock functions, while SIS is mainly used for safety interlocks – it applies to equipment and monitoring points where serious accidents could occur. Its interlock capabilities are much more advanced than those of DCS. The typical safety level in chemical plants is SIL2; SIL4 seems to be used in the nuclear industry. SIS systems are generally developed by German companies