Installation process of the Safety Instrumented System SIS

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This post was last edited by 955559 on 2018-12-4 09:56. The installation process for the SIS system in chemical plant safety: According to **Document No. 116 issued by the Safety Supervision Bureau, as of January 1, 2018, all newly built chemical plants and hazardous chemical storage facilities that fall under the category of “two key areas and one major hazard” must be equipped with SIS systems that meet the required standards. For the safety instrument systems of other newly built chemical processing units and hazardous chemical storage facilities, starting from January 1, 2020, it is necessary to comply with the requirements of functional safety standards and design safety instrument systems that meet those requirements. http://www.hbconsen.com/upload/image/20181008/15389648428752882.jpg First, let’s introduce the SIS system for chemical process safety, commonly referred to as the chemical SIS system. When it comes to the hazards associated with chemical manufacturing enterprises, these generally include acidic and alkaline gases, liquids, or corrosive solutions. During their transportation, storage, and in chemical reaction processes, there are risks such as fires or explosions caused by excessive temperatures, as well as leaks of harmful gases and corrosive liquids. If a chemical process safety instrumented system SIS is installed, it will immediately issue warning signals and take emergency actions such as initiating emergency braking, shutting down the process, or closing valves, in order to prevent the occurrence of such hazards or accidents. I. HAZOP analysis http://www.hbconsen.com/upload/image/20181012/15393126737589292.jpg HAZOP analysis refers to Hazard and Operability Analysis. The HAZOP analysis method involves using scientific procedures and approaches to identify, analyze, and evaluate potential hazards in engineering projects or production facilities from a systematic perspective. It helps to identify issues related to the design of the facilities as well as their operation and maintenance procedures, and it provides suggestions for improvements aimed at enhancing the safety and operability of the process. This method serves as a basis for making decisions regarding the establishment of basic disaster prevention measures and emergency response plans. In other words, before installing a chemical process safety SIS system, HAZOP analysis is used to identify potential hazards in the production processes and equipment operation. II. SIL Classification SIL classification was first established by the International Electrotechnical Commission (IEC), with IEC/TC65 being responsible for its implementation. The standardization technical committee responsible for SIL technology is the \"National Technical Committee for Measurement, Control, and Automation in Process Industries\" (SAC/TC124), with the Secretariat located at the Comprehensive Technical and Economic Research Institute for Instruments and Meters in the machinery industry. SIL certification is divided into 4 levels in total: SIL1, SIL2, SIL3, and SIL4, covering both the product and system levels. Among them, the requirements for SIL4 are the highest. http://www.hbconsen.com/upload/image/20181006/15387911188971922.jpg Relevant technical personnel and experts utilize analyses such as HAZOP/LOPA to seamlessly integrate SIF identification with SIL grading services. Taking into account the industry characteristics, the properties of the process equipment, the nature of the enterprise, and management requirements, appropriate risk management and SIL classification methods are employed. Third-party experts or technicians conduct analyses using methods such as HAZOP/LOPA, thereby providing seamless integration with SIF identification and SIL classification services. Taking into account the industry characteristics, the properties of the process equipment, the nature of the enterprise, and management requirements, appropriate risk management and SIL classification methods are employed. In essence, it uses the results of HAZOP analysis to determine the accurate SIL level for your production equipment and processes, providing reliable risk data for the subsequent design of safety instrumented systems. III. Design of the Safety Instrumented System (SIS): Based on the data obtained from the aforementioned HAZOP analysis and SIL level determination, a comprehensive design plan for the safety instrumented system of your enterprise is developed. When designing chemical SIS systems, in addition to testing their safety and integrity, it is also necessary to ensure that such systems possess confidentiality and independence. Of course, future maintenance work also needs to be taken into consideration during the design phase; therefore, I will now go into detail about the principles of such systems. http://www.hbconsen.com/upload/image/20180929/15381921798008009.jpg (1) One of the principles that should be followed when designing a system is to ensure its independence. Generally, when such a system is put into practical use, it is separated from other device systems, mainly to ensure that the system can handle situations on its own in case of emergencies. Therefore, if this principle is not followed in the design of such systems, the equipment used in the chemical industry will be unable to implement shutdown procedures or safety interlocks in response to unexpected situations, which in turn **increases the risks associated with these industries. (2) The second principle to be followed when designing a system is to ensure the safety of both the equipment and the personnel. To ensure that the system adheres to this principle during design, excitation should be used to maintain it in the event of a power outage. (3) The third principle to be followed when designing a system is to ensure the complexity and integrity of such a system structure. The main purpose of following this principle is to enable such a system to maintain the operational capacity of relevant equipment in emergency situations, thereby preventing accidents that could result in losses for the chemical industry. Of course, attention should also be paid to the quality of the intermediate steps during the design process. IV. Installation of the Safety Instrumented System SIS http://www.hbconsen.com/upload/image/20181006/15387933889224470.png (1) Design and configuration of sensors: Principle for independent setup of sensors: In a primary safety instrumented system, the sensors can be shared with the process control system ； A secondary safety instrumented system has sensors that are separate from the process control system, while a tertiary safety instrumented system also has sensors that are separated from the process control system. Principle for redundant sensor configuration: In a Level 1 safety instrumented system, a single sensor can be used ； Secondary safety instrument system, utilizing redundant sensors ； For a Class 3 safety instrumented system, redundant sensors should be used. Redundancy scheme for sensors: When system safety is a primary concern, an “or” logical structure should be employed ； When focusing on the availability of the system, a “AND” logical structure should be used ； When both the security and availability of the system need to be ensured, a three-to-two logic structure should be used directly ； The sensors of safety instrumented systems should be of flameproof type. (2) The design and setup of the final actuator can be an independently installed on-off valve, or it can be a control valve shared with the process control system. Principles for the redundant configuration of valves. For the primary safety instrumented system, valves that are in use can be employed; for the secondary safety instrumented system, redundant valves should be used ； If a single valve is used, the accompanying solenoid valve shall be provided with direct redundancy ； Class 3 safety instrumented system, utilizing redundant valves, with redundant solenoid valves as well ； For valves with a redundant configuration, one control valve and one on/off valve can be used. The final actuator is a device with low reliability and risk in the safety instrument system. Under normal operating conditions, the safety instrument system is static and passive; its output remains unchanged, and the final actuator stays in its original state, making it difficult to determine whether there is any dangerous fault. Under normal operating conditions, process control systems are dynamic and active; the actuating elements change in response to changes in the control signals, and they do not remain in one position for an extended period of time. (3) Design of logic operators – The logic operators in safety instrumented systems can be composed of relay systems, programmable electronic systems, or a combination of both. Programmable electronic systems can be programmable logic controllers (PLCs), distributed control systems (DCS), or other specialized systems. Principles for the technical selection of logic operators: Relay systems are used in applications with few input/output points and simple logical functions, while programmable electronic systems are used in situations with many input/output points, complex logical functions, and the need for data communication with process control systems. The independent operation principle of logic operators is that a Level 1 safety instrumented system should be separated from the process control system ； The secondary safety instrumented system should be separated from the process control system ； A Class 3 safety instrumented system must be separated from the process control system. Redundancy principle for logic operators: In a Class 1 safety instrumented system, a single logic operator can be used ； For secondary safety instrumented systems, redundant or fault-tolerant logic operators are recommended; the central processing unit, power supply units, and communication systems should be configured redundantly, as well as the input/output modules ； For a Class 3 safety instrumented system, redundant or fail-safe logic operators should be used, and the central processing unit, power supply units, communication systems, and input/output modules shall be configured redundantly. http://www.hbconsen.com/upload/image/20180926/15379313836554380.jpghttp://www.hbconsen.com/upload/image/20181114/15421774406414854.jpg