PID instrument control system

I think the poster did not understand the concepts of three different control systems and control methods. PID is a regulating control method and has no necessary connection with the control system to which it is attached. Even a simple field instrument with PID function can also perform corresponding PID adjustment control. Conventional instrument control systems are generally early single-loop or multi-loop independent instrument controls. DCS is a decentralized control system, which is integrated, synthesized and developed from conventional instrument control systems. It is a collection of information collection, processing, calculation, adjustment, feedback, optimization and other functions in the process industry. It mainly focuses on normal production operations. SIS is a safety instrumented system, which has a different control purpose from DCS. It is a system involving safety alarm interlocking parking.

This time it’s even more troublesome, and I don’t understand it even more. Why is there such a classification in the specification? I don’t know what its use and learning are. * value? I am majoring in craft design

I guess the poster is talking about the selection of instrument control system symbols in the Process Flow Diagram with Control Points (P&ID). In fact, this diagram is jointly completed by the process major and the automatic control major. These issues will be selected and raised by the instrument major according to the regulations of this major. Some hospitals even have the instrument major supplement this part of the content, so the process designers can ignore this matter.

Conventional instrument control systems are generally installed in front of the instrument panel, such as S series and I series instruments, which use a single instrument to complete various control functions. For example, the alarm instrument displays alarm information, the regulator adjusts the circuit, the hand operator controls the valve, and the recorder records process trends, etc. The DCS control system uses a control station and an operating station to replace these panel tables. The control station completes the logic operation function, and the operating station completes the human-machine interface such as display. SIS or ESD are both safety instrument interlocking systems and are independent of the DCS control system. From the perspective of the operating mode of the control system itself, DCS is a dynamic system. It always continuously detects, calculates and controls process variables, and dynamically controls the production process to ensure product quality and output. SIS is a static system. During normal times, it always monitors the operation of the production device. The system output remains unchanged and has no impact on the production process. During abnormal processes, the SIS system operates according to preset logic to safely interlock and stop the production device. From the perspective of the role of the control system, DCS is used for continuous measurement control and operation control management of the production process to ensure the normal operation of the device. SIS is used to monitor the operating status of production equipment and minimize the harm when abnormalities occur. As for the legend symbols, you can check HG/T20505-2000. We apologize for any bias.

Generalized control, including basic process control systems (BPCS: Basic Process Control System) and safety instrumented system (SIS: Safety Instrument System). This is divided according to different functions. The basic process control system is within safety limits to ensure smooth and continuous production. ； When the safety limit is reached, the safety instrumented system performs emergency intervention in the production process to ensure production safety. ； Conventional instruments and DCS are tools to achieve the above control. That is, conventional instruments can be used to achieve basic process control, and DCS can also be used to achieve basic process control. Nowadays, most DCS are used to achieve basic process control. ； Safety instrumented systems can be implemented in DCS or as independent safety instrumented systems. Most are now independent safety instrumented systems. Similarly, it can be implemented with conventional instruments + relays, or with PLC.

The current consensus is that DCS should be independent from the SIS system. Although DCS can realize some or even all functions of SIS, domestic and foreign experts have reached consensus that the two systems need to operate independently.

Very professional. I just need to learn a little bit about craftsmanship.

Thank you, I understand a lot when you say that.

DCS control, SIS security

To put it bluntly, conventional instruments are just digital display meters and controllers. They are obsolete products. Who would design this? Unless the temperature control and electric heating may still be used, there will be an interface to the DCS. Sis, you can directly exclude the pid. sis is a static system and the pid is constantly adjusted by millisecond calculation and will not enter sis. One of my previous considerations was to directly implement the control of the steam turbine into sis, but I guess the manufacturer would have to provide a dedicated module. sis and pid are incompatible things, unless you have the idea like me above. Large-scale unit interlocking protection can be integrated into sis, but generally manufacturers will provide control system communication access. DCS has more pids. At present, the more advanced chemical technology, the more pids there are, hundreds or thousands. It is normal for DCS to be able to respond normally. The key lies in the scene. The cleanliness of your valve selection positioner selection air source.