Regarding the issue of whether interlock design should be done in a DCS or SIS system

Interlock design refers to a system designed in industrial processes to protect equipment and personnel safety. Under normal circumstances, the interlock system can operate in two different control systems: a Distributed Control System (DCS) or a Safety Instrumented System (SIS). Requirements for interlocking to integrate with DCS: 1. Interlocking should be based on process control requirements, and it should interact with the DCS system to enable process control and monitoring. 2. Interlocks shall be able to be processed and responded to in real time within the DCS, and control measures shall be taken promptly to protect the safety of equipment and personnel. 3. Interlocking should be integrated with other DCS functions (such as alarms, action tracking, etc.) to achieve overall process management. Requirements for interlocking in the SIS: 1. Interlocking shall be controlled and monitored through the independent hardware and logic of the safety instrumented system to ensure high reliability and fault tolerance. 2. The interlock system shall meet the relevant standards and specifications for safety instrumented systems to ensure the compliance and safety of the system. 3. The interlocking system should have appropriate logic and redundancy design to provide a high level of safety protection. The criteria for deciding whether interlock functions should be integrated into a DCS or a SIS system are primarily based on the following principles: 1. Functional requirements: If interlocks need to be integrated with and interact with other process control functions, they are usually incorporated into a DCS system. If interlocking requires independent safety control and monitoring, as well as high reliability in the event of failures, it enters the SIS system. 2. Safety requirements: In accordance with safety standards and specifications, certain safety functions may need to be implemented in the SIS. These functions include emergency shutdown, fire and explosion protection, etc. 3. Equipment type: Some equipment may require special safety controls, such as pressure vessels or equipment for handling hazardous chemicals. The interlocks of these devices usually feed into the SIS system. Although the above are general principles, the final decision usually needs to be determined based on the requirements of the specific engineering project, safety regulations, and the proposed technical solutions. .

In some cases, the Ministry of Emergency Management issues specific regulations requiring the use of a SIS system. For example, Order No. 40 issued by the General Administration of Work Safety stipulates that primary or secondary major hazard sources involving toxic gases, liquefied gases, or highly toxic liquids must be equipped with an independent Safety Instrumented System (SIS). Additionally, LOPA analysis may indicate the necessity of installing a SIS system.

GBT50770，GBT21109