A brief introduction to the differences between SIS systems and DCS systems
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The last edit to this post was made by 955559 on 2018-9-25 at 22:04. 1. What is a Safety Instrumented System (SIS)? In IEC61508, a Safety Instrumented System is referred to as a Safety Related System or an Emergency Shutdown System (ESD); the device that is controlled is called an EUC (Equipment Under Control). IEC61511 defines a Safety Instrumented System (SIS) as an instrumented system used to perform one or more Safety Instrumented Functions (SIF). A SIS is composed of sensors (such as various switches and transmitters), logic controllers, and end components (such as solenoid valves and electric doors). IEC61511 further specifies that a SIS may or may not include software. Furthermore, when the manual operations performed by operators are considered an integral part of the SIS, it is necessary to specify clearly in the Safety Requirement Specification (SRS) the effectiveness and reliability of these human operations, and to include them in the performance calculations of the SIS. Looking at the development process of SIS, its control unit has gone through three stages: electrical relays (Electrical), electronic solid-state circuits (Electronic), and programmable electronic systems (Programmable Electronic System), namely the E/E/PES stages. http://www.hbconsen.com/upLoad/news/month_1809/201809041137284793.png The functions of a SIS safety instrument system can be safety instrument protection functions, safety instrument control functions, or both. It should be noted that the safety instrument control function mentioned here refers to one that operates in Continuous Mode and possesses a specific SIL, and is used to prevent dangerous situations from occurring or to mitigate their consequences; it is a concept entirely different from conventional PID control functions. SIS may include or exclude software, and a part of SIS may also be human actions. http://www.hbconsen.com/upLoad/news/month_1809/201809041138145378.jpg The release of IEC61508/IEC61511 represents a milestone for the use of safety control systems in the process industry. First, various specific applications of the instrumentation system, such as the ESD safety interlock/emergency shutdown system (ESD is part of the SIS). SIS consists of field instruments, logic processors, and actuators; a conventional ESD system is merely the logic processor part of SIS. ), FGS, BMS, HIPPS… are all unified under the concept of SIS ； Secondly, a reliability assessment criterion based on performance, using SIL as a guideline, is proposed ； Furthermore, a life-cycle framework is established to define the technical activities and functional security management activities at each stage. In this way, the application of SIS forms a complete system that includes: design concepts and methods, selection criteria for instrumentation equipment (based on empirical usage and IEC61508 compliance certification), rules for system hardware configuration and software programming, system integration, installation and commissioning, operation and maintenance, as well as functional safety assessment and auditing. Document No. 116 issued by the State Administration for Work Safety: On November 13, 2014, the State Administration for Work Safety issued the \"Guiding Opinions on Strengthening the Management of Safety Instrumented Systems in the Chemical Industry (State Admin. Work Safety [2014] No. 116)\”. These guidelines cover various aspects such as production, design, and management. HAZOP analysis, SIL level assessment, safety system verification, evaluation of the safety level of safety systems in existing installations, and safety system upgrades – these tasks will become increasingly common and important in the coming years! 2. What is a DCS system? A DCS system, also known as a Distributed Control System, is a next-generation instrument control system based on microprocessors. It follows the design principle of distributing control functions while centralizing display and operation, thereby combining autonomy at the local level with comprehensive coordination. The Distributed Control System is abbreviated as DCS; it can also be translated literally as “distributed control system” or “distributed computer control system”. http://www.hbconsen.com/upLoad/news/month_1809/201809041141567230.jpg DCS adopts the basic design principle of decentralized control and centralized operation and management, and features a multi-layered, hierarchical structure with cooperative autonomy. Its main feature is its centralized management and decentralized control. Currently, DCS has found extremely wide application in various industries such as power, metallurgy, and petrochemicals. DCS hardware architecture: http://www.hbconsen.com/upLoad/news/month_1809/201809041142598459.jpg(1) Field control units are generally located away from the control center, installed in locations close to the field. Their highly modular structure allows them to be configured as process control units with anywhere from a few monitoring points to hundreds of monitoring points, depending on the requirements for process monitoring and control. The structure of a field control unit consists of numerous function-specific plug-ins (or cards) that are installed in a plug-in box in a certain logical or physical order. The various field control units, as well as those units and the control management level, are connected via buses to enable information exchange. The hardware configuration of the field control unit requires the following steps: plugin configuration – configure hardware devices such as host plugins (CPU plugins), power supply plugins, I/O plugins, and communication plugins according to the system’s requirements and the scale of control ； Hardware redundancy configuration: Implementing redundancy for critical devices is an important method for enhancing the reliability of DCS systems. DCS systems can typically provide redundancy for host cards, power supply cards, communication cards and networks, as well as key I/O cards. Hardware installation: Different DCS systems have specific requirements regarding the logical or physical order in which various plugins are installed within their plugin boxes. Furthermore, field control units are usually divided into basic and extended types. The basic type features various plug-ins installed in a plug-in box, but more often an expandable structure is required; that is, a field control unit also includes several digital input/output expansion units, which are connected to each other via a bus. In essence, the structural form and configuration requirements of the field control unit are consistent with those of the hardware configuration of modular PLCs. http://www.hbconsen.com/upLoad/news/month_1809/201809041143391939.jpg(2) Operation station: The operation station is used to display and record process data from various control units; it serves as an interface through which humans can interact with information related to the production process. A typical operation station includes a host system, display devices, keyboard input devices, information storage devices, and print output devices, etc. It primarily provides powerful display functions (such as the display of analog parameters, system status, various types of graphics, etc.), alarm functions, operation functions, report printing functions, configuration and programming functions, and more. Additionally, the DCS operation station is also divided into an operator station and an engineer station. In terms of system functionality, the former is primarily used for general production operations and monitoring tasks, offering functions such as data collection and processing, display of monitoring screens, fault diagnosis, and alarm generation. In addition to the general functions of an operator station, the latter should also have capabilities such as system configuration and modification of control objectives. In terms of hardware, in most systems the engineer station and the operator station are combined, with only an engineer keyboard used to distinguish between them. The three major domestic SIS systems are Hollyland, Zhejiang University Control System, and Kangjisen; all of them basically have SIL certification as well as TUV certification. . . Of course, there are also brands such as Triconex, HIMA, Siemens, Moore, ICS, ABB, and Emerson abroad.
Of course, there are also brands such as Triconex, HIMA, Siemens, Moore, ICS, ABB, and Emerson abroad. This Conixen is a product from Triconex; it’s not domestically produced! ! !
Domestic options like Zhejiang University Zhongkong or Hollyland are also good
Recently, my company plans to install a safety instrumented system/SIS system; I am currently learning about it and researching the market conditions. I found that Kangjisen’s SIS systems offer a good cost-performance ratio. I also referred to other posts on forums regarding Kangjisen – thank you for any feedback!:lol
Essentially, it doesn’t explain the differences between DCS and SIS, so I’m still quite confused. Are the interlock systems and emergency shutdown systems in enterprises considered DCS or SIS?
Emergency shutdowns and interlocks are all included in the SIS; the equipment also needs to be classified according to SIL criteria
The DCS system is used for process control, maintaining process parameters within acceptable ranges; actuators such as control valves operate continuously. In contrast, although the controllers and sensors in the SIS system also work continuously, the actuators only act when process parameters reach certain limits and the control function is triggered. Moreover, the sensors and actuators of the DCS system are separate and independent from those of the SIS system.
Strictly speaking, DCS systems and SIS systems are two separate systems. A DCS system is designed for process control; its role is to monitor and control the process parameters involved in production. It displays, records, and issues alerts regarding these parameters through operation stations, allowing operators to take actions based on this information in order to ensure the smooth progress of the production process. Without a DCS system, the production process cannot proceed. The SIS system, also known as a Safety Instrumented System, is, as the name implies, a device designed to ensure the safety of industrial processes. Like the DCS system, it consists of sensors, controllers, and actuators. In operation, when an abnormality occurs in the process for some reason and the SIS sensors detect that the process parameters have reached preset limits, the safety controller of the SIS system issues control commands to the corresponding actuators according to predefined control logic. These actuators then take action to prevent the process from continuing along a dangerous trajectory, thereby avoiding or reducing the risk of accidents and ensuring process safety. It is precisely because of the important role played by the SIS system that its sensors, controllers, and actuators are required to have extremely high reliability; they are products that have undergone SIL certification, which is different from DCS systems. Furthermore, not all process operations require the installation of a SIS system; it is only after conducting a process safety analysis of the operation that it can be determined whether a SIS system is needed and what the SIL level of that system should be.
Strictly speaking, DCS systems and SIS systems are two separate systems. A DCS system is designed for process control; its role is to monitor and control the process parameters involved in production. It displays, records, and issues alerts regarding these parameters through operation stations, allowing operators to take actions based on this information in order to ensure the smooth progress of the production process. Without a DCS system, the production process cannot proceed. The SIS system, also known as a Safety Instrumented System, is, as the name implies, a device designed to ensure the safety of industrial processes. Like the DCS system, it consists of sensors, controllers, and actuators. In operation, when an abnormality occurs in the process for some reason and the SIS sensors detect that the process parameters have reached preset limits, the safety controller of the SIS system issues control commands to the corresponding actuators according to predefined control logic. These actuators then take action to prevent the process from continuing along a dangerous trajectory, thereby avoiding or reducing the risk of accidents and ensuring process safety. It is precisely because of the important role played by the SIS system that its sensors, controllers, and actuators are required to have extremely high reliability; they are products that have undergone SIL certification, which is different from DCS systems. Furthermore, not all process operations require the installation of a SIS system; it is only after conducting a process safety analysis of the operation that it can be determined whether a SIS system is needed and what the SIL level of that system should be.
I’ve learned that all cases of two types of hazards and one serious hazard need to be entered into SIS