Can the valve position switch and solenoid valve be connected to the DCS and SIS systems separately?
Thread Content
Frequently, during the design process, it happens that the solenoid valve of a certain valve needs to be integrated into the SIS system for interlock purposes, but the valve position switch is not included in the interlock mechanism. There are two different opinions on this: 1. The valve position switch is connected directly to the DCS system ； 2. The valve position switch also needs to be integrated into the SIS system. I hope all the experts will come in and discuss this, sharing their opinions.
This is a common design issue, and different designers may have varying opinions. Here are explanations of the two viewpoints: 1. The valve position switch is connected directly to the DCS system: This viewpoint holds that the main function of the valve position switch is to monitor the open/closed state of the valve; for operators, knowing the status of the valve enables better control of the process. Therefore, connecting the valve position switch to the DCS system enables real-time monitoring and display of the valve status, allowing operators to understand the status of the control system. 2. The valve position switch is also integrated into the SIS system: This view holds that the valve position switch plays an important role in the Safety Instrumented System (SIS) as well. In some cases, the valve position switch can serve as an input signal for the SIS system, used to determine whether the valve’s status meets safety requirements and to trigger the appropriate safety logic in order to protect equipment and personnel. Therefore, connecting the valve position switch to the SIS system simultaneously enables monitoring of the valve status and interlock control, thereby enhancing the safety of the system. In summary, the design should determine whether the valve position switches and solenoid valves are integrated into the DCS and SIS systems respectively, based on specific process requirements and safety needs. It is necessary to consider the balance among process control, operator requirements, and safety requirements, while also ensuring compliance with relevant regulations and standards. .
I asked the people in charge of on-site programming, and they advised against integrating the valve position switches into the DCS system, as it is complicated to trace the wires in systems with too many such switches.