Suggestions for instrument interlock management in the refining and petrochemical industry

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Instrument interlocks in refining and chemical enterprises are the core control systems that ensure the safe operation of equipment in the intelligent industry. In the current management, there are still prominent issues such as some interlocks not being activated as required, incomplete parameter information, and inaccurate classification, all of which affect the reliability of the system. To strengthen the safety barrier, enterprises should conduct a thorough inspection of all interlocks that are not in use, improve the records related to interlock management, and classify them scientifically based on their importance (into levels A/B/C), to ensure that all control measures are properly implemented. At the same time, special attention must be paid to regulating the statistics of interlock circuit information for newly installed and modified devices, and ensuring that the records in the equipment management system are consistent with the actual situation. Class A interlock circuit 1: An interlock circuit that can cause the device to stop operating once activated ； 2. Interlock circuits that, upon activation, can cause the core process units of the plant to stop operating, feed supply to be interrupted, production to experience fluctuations, and result in unplanned cycles of operation in the plant ； 3. Interlock circuits that can cause the shutdown of critical plant units at the company level following an action ； 4. Interlock circuits used in applications such as the isolation of materials related to major hazard sources of level 1 and 2, emergency pressure relief of equipment, and environmental protection facilities; a failure of these circuits can lead to risks such as massive leaks of flammable, toxic, and harmful materials, environmental pollution, pressure surges, and equipment overpressure ； 5. If a SIL classification is to be performed, the level should be SIL2 or higher. Class B interlock circuits: Interlock circuits that, upon activation, can cause the shutdown of non-core process units of the equipment, production fluctuations, or abnormal production conditions ； 2. An interlock circuit that, after an action occurs, can cause the shutdown of other units and pumps besides the company-level critical units ； 3. If a SIL classification is to be performed, the level should be SIL1 or higher. For interlock circuits of category C: 1. Interlock circuits other than those of categories A and B (such as equipment startup, reset conditions, etc.) ； 2. In case of SIL classification, the level should be SIL1 or below.