【2026 Control Systems】Basis and Key Points for Identifying Hidden Dangers in PLC Systems
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1. The inspection is based on GB 5226.1-2019 \"Mechanical and Electrical Safety\": The emergency stop circuit must be wired directly; it is not allowed to rely solely on communication for control. ISO 13849-1:2015 \"Mechanical Safety – Safety Components of Control Systems\": Safety circuits should be monitored via dual channels. IEC 61131-2:2007 \"Programmable Controllers – Equipment Requirements\": Analog inputs require RC filtering, with an interference resistance of ≥10V/m. IEC 60204-1:2016 \"Mechanical Safety – Electrical Equipment\": Emergency stops must have mechanical locking and allow for manual reset
2. Key inspection points: Emergency stop function: After power is cut off, must the emergency stop button be able to directly cut off the power supply to the actuator? Additionally, mechanical locking and reset are required before it can be reactivated. Interference resistance: Conduct immunity tests such as surge, EFT, and electrostatic discharge to ensure that the AI signal deviation is ≤±0.5%FS. Firmware and logical security: Firmware versions must be checked against the CVE vulnerability database, and permissions for program uploading/downloading need to be managed in a hierarchical manner.
3. Case: A factory was ordered to convert its PLC emergency stop circuit from a communication-controlled system to a hard-wired one, as this violated GB 5226.1. In another incident, the PLC logic was hacked to disable the emergency stop function, resulting in a compressor explosion and highlighting the importance of industrial control network security.
For reference: In the operation of hazardous chemicals and chemical processing plants, automation systems such as DCS, PLC, SIS, and GDS serve as both the \"brain\" for production control and the \"last line of defense\" for safety protection. During the identification of potential hazards, it is necessary to refer to **standards (GB), international standards (IEC/ISA/API), and industry regulations**, as well as documents such as the \"Guidelines for the Identification and Management of Safety Risks in Hazardous Chemical Enterprises\", to ensure that the entire process of design, operation, and maintenance remains compliant and under control.
Specific requirements: The \"Guidelines for the Identification and Rectification of Safety Risks and Hazards in Hazardous Chemical Enterprises\" specify mandatory items such as DCS/SIS independence, GDS coverage rate, and PLC emergency stop functions.
“Regulations on the Safety Management of Instrumentation Systems in Chemical Enterprises”: Any modification to the interlock logic must go through the MOC process, along with a HAZOP analysis.
\"Guidelines for the Implementation of Process Safety Risk Management in Chemical Enterprises\": The SIS system must undergo full-circuit testing annually.
MOC scope expansion: In addition to logical modifications, it also includes hardware replacement, firmware upgrades, and network structure adjustments.
1. Industrial control network security: In accordance with GB/T 30976-2014 Guidelines for Security Protection of Industrial Control Systems, identify issues such as weak passwords, remote access, and patch management.
2. Emergency plan coordination: Check whether the alarms from the GDS/SIS are linked to the emergency broadcasting system and the dispatch center, to ensure timely transmission of information.