Regarding SIS communication to DCS
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I have always believed that SIS and DCS are two separate systems that do not communicate with each other, but I have recently discovered that this is incorrect. There’s a question here: for example, in the case of a pressure transmitter, if the high-pressure threshold is set as an interlock point, and it’s also desired to view the real-time pressure value on the DCS, from what I remember, either two pressure transmitters are used connected by a pipe, or one pressure transmitter is used in the SIS along with a two-way safety barrier. I wasn’t aware that this can be achieved through communication; what exactly is communicated in such cases?
Generally MODBUS 485. In some control systems, those from the DCS/SIS family can be used directly without the need for communication, such as DELTAV
Indeed, SIS (Safety Instrumented System) and DCS (Distributed Control System) can communicate with each other, although their main functions and purposes are different. SIS is primarily responsible for the security of the system, while DCS focuses more on process control and efficiency. Regarding the pressure transmitter issue you mentioned, generally speaking, if it is necessary to meet both the safety interlock requirements of the SIS and the need to monitor pressure values in the DCS, the following approaches can be used: 1. Use two pressure transmitters – one connected to the SIS system for handling safety interlocks, and the other connected to the DCS system for data monitoring and control. 2. Use a single pressure transmitter but separate the signals via a safety barrier: In this approach, the signal generated by one transmitter is sent to a safety barrier, from which two signals are output – one to the SIS system and the other to the DCS system. As for the method of achieving this through communication, it may refer to exchanging information via data buses or networks: Using fieldbuses such as FOUNDATION Fieldbus or Profibus allows a device to send information to both the SIS and DCS systems simultaneously. - OPC (OLE for Process Control) or other industrial Ethernet protocols are used to enable data exchange between systems. Through these communication methods, SIS and DCS can share certain sensor data without the need for physically separating the devices. Doing so may reduce costs and simplify installation, but it is essential to ensure that all safety and isolation measures comply with relevant standards and requirements. .
In terms of the process, after communication is established, it is possible to observe whether the solenoid valve is powered or not; the measured data can be compared with those from the DCS to determine if there are any issues with the instruments in either system.