Major hazard sources of level I and II should be equipped with SIS

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I. Method for determining whether a unit should be included in the SIS: Whether a unit needs to be part of the SIS is determined in two ways. One method involves conducting a Hazard and Operability Study (HAZOP) on the unit’s processes, flow diagrams, equipment, piping, instruments, etc., to assess whether it has SIL1, SIL2, or SIL3 circuits; if such circuits exist, then an SIS is necessary, otherwise it is not. Secondly, the managers (owners or insurance companies) have the right to decide on their own whether to use a SIS; they can make this decision without conducting a HAZOP analysis. If the managers decide that a SIS is necessary, it is also up to them to determine the SIL level, as stated in IEC61511. If SIS is not needed, then it can be omitted, with the risks and disaster consequences borne by the decision-makers themselves. Among them, a series of directive documents, notices, and guiding opinions issued by the former **Work Safety Supervision Bureau (which are equivalent to laws) fall into the second category; examples include Document No. An Jian Zong Guan San [2014] 116, Order No. 40, and others. II. **Instructions from the Ministry of Emergency Management (including the former **General Administration of Work Safety): 1. “Guiding Opinions of the General Administration of Work Safety on Strengthening the Management of Chemical Process Safety Instrumented Systems” (An Jian Zong Guan San [2014] No. 116): Article 1: Chemical process safety instrumented systems (SIS) include safety interlock systems, emergency shutdown systems, as well as detection and protection systems for toxic and harmful gases, flammable gases, and fires. The safety instrumented system is independent of the process control systems (such as distributed control systems, etc.). It remains in a dormant or inactive state during normal production, but can act instantly and accurately once a situation that could lead to a safety accident occurs in the production facility, thereby stopping the production process safely or bringing it into a predetermined safe state. It must have high reliability (i.e., functional safety) as well as proper maintenance and management. If the safety instrumented system fails, it can often result in serious safety accidents; indeed, most of the major chemical (hazardous chemicals) accidents that have occurred in developed countries in recent years have been related to failures in the safety instrumented systems or improper installation of those systems. Based on the consequences and risks arising from the failure of safety instrument functions, these functions are classified into different safety integrity levels (SIL1-4, with level 4 being the highest). Safety instrumented systems of different grades have varying technical requirements in terms of design, manufacturing, installation and commissioning, as well as operation and maintenance. Article (III) requires further improvement of the technical standards and certification system for chemical process safety instrument systems. Accelerate the formulation and revision of the technical standard system for chemical process safety instrumented systems. In accordance with \"Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems\" (GB/T20438) and \"Functional Safety of Safety Instrumented Systems in the Process Industry\" (GB/T21109), a functional safety certification service system for relevant personnel, products, and organizations is being established step by step. Article (XIII) requires that, as of January 1, 2018, all newly constructed chemical processing units and hazardous chemical storage facilities involving the \"two key areas and one major concern\" must be designed with safety instrument systems that meet the specified requirements. 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. Article (XIV) requires that chemical enterprises and hazardous chemicals storage units dealing with operational production units or facilities that fall under the category of “two key items and one major item” shall, on the basis of conducting comprehensive process hazard analyses (such as Hazard and Operability Studies), determine the functions of safety instruments and the requirements for risk reduction through risk analysis, and promptly assess whether the existing safety instrument functions meet those risk reduction requirements. 2. \"Criteria for Identifying Major Potential Hazards in Production and Operation of Chemicals and Hazardous Chemicals (Trial)\\" (Safety Supervision Administration Order No. 3 [2017] 121): Article 5 requires that chemical storage areas that constitute level 1 or level 2 major hazard sources must have an emergency shutdown function in place ； The hazardous chemical storage areas that constitute Class I and Class II major hazard sources involving toxic gases, liquefied gases, and highly toxic liquids are not equipped with independent safety instrument systems. Interpretation of Article 5: In chemical storage areas that constitute major hazard sources of Grade 1 or Grade 2, due to the severe consequences that can result from accidents, emergency shutdown systems must be installed in each storage tank to enable emergency isolation. For storage tanks directly connected to upstream production units, if installing an emergency shut-off device could lead to abnormalities such as overpressure in the production units, an emergency switching mechanism can be employed to prevent issues like excessive liquid levels or overpressure in the tanks, thereby fulfilling the function of emergency shutdown. Interpretation of the fifth standard for key counties: (1) For chemical storage areas that constitute major hazard sources of level 1 or level 2, emergency shut-off valves must be installed at both the inlet and outlet of each storage tank; otherwise, it is considered a serious safety hazard. (2) For hazardous chemical storage areas that constitute Class I or Class II major hazard sources, if a main emergency shut-off valve is installed on the main inlet and outlet pipelines of the storage area but not on each individual storage tank, it is considered a serious safety hazard. (3) For hazardous chemical storage areas that constitute level 1 or level 2 major hazard sources, if an emergency switching mechanism is installed between storage tanks of the same purpose to prevent situations such as overfilling or overpressure in the tanks, they are not considered to be major safety hazards. (4) For chemical storage areas that constitute level 1 or level 2 major hazard sources, if the storage tanks do not have an emergency shutdown function, but the enterprise has conducted HAZOP analyses and SIL assessments and the results show that safety requirements are met, such areas may not be considered major hazards. (5) Chemical storage areas that are classified as major hazard sources of level 1 or 2 and involve toxic gases, liquefied gases, or highly toxic liquids do not have an independent safety instrumented system, which is considered a serious safety hazard. 3. Article 13 of the Interim Provisions on the Supervision and Management of Major Hazard Sources of Hazardous Chemicals (**Order No. 40 of the State Administration for Work Safety**) requires that hazardous chemical enterprises shall, based on the types and quantities of hazardous chemicals that constitute major hazard sources, as well as the production and usage processes (methods) or relevant equipment and facilities, establish and improve safety monitoring systems in accordance with the following requirements to enhance control measures: (1) Major hazard sources shall be equipped with systems for continuous collection and monitoring of information such as temperature, pressure, liquid level, flow rate, and composition, as well as detection and alarm devices for leaks of flammable gases and toxic and harmful gases; such systems shall also have functions such as remote data transmission, continuous recording, accident early warning, and information storage ； Class 1 or Class 2 major hazard sources are equipped with an emergency shutdown function. The electronic data recorded shall be retained for no less than 30 days ； (II) The automation control systems of chemical production facilities for major hazard sources meet the requirements for safe production ； For Class 1 or Class 2 major hazard sources, an emergency shutdown system is required ； (III) Install emergency shut-off devices for key facilities such as toxic gases, highly toxic liquids, and flammable gases among the major hazard sources ； For facilities handling toxic gases, emergency devices for dealing with leaks must be installed. For major hazard sources of level 1 or 2 involving toxic gases, liquefied gases, or highly toxic liquids, an independent Safety Instrumented System (SIS) must be installed ； 4. Article 21 of the “Notice of the General Office of the State Council on Issuing the Comprehensive Management Plan for the Safety of Hazardous Chemicals” (Guo Ban Fa [2016] No. 88): New chemical processing units must be equipped with automated control systems. Chemical processing units that fall under the category of “two key areas and one major hazard” must be equipped with safety instrumented systems, and major sources of hazardous chemicals must have sound safety monitoring and control systems in place. III. How are the relevant standards and specifications specified? 1. According to Clause 3.2.3 of \"Functional Safety of Safety Instrumented Systems in the Process Industry – Part 1: Framework, Definitions, Systems, Hardware, and Application Programming Requirements\" (GB/T 21109.1-2022/IEC 61511-1:2016), a Basic Process Control System (BPCS) is a system that responds to input signals from the process and its associated equipment, other programmable systems, and/or operators, and generates output signals to ensure that the process and its related equipment operate in the desired manner; however, it does not implement any SIFs. 2. According to Clause 3.2.3 of \"Functional Safety of Safety Instrumented Systems in the Process Industry – Part 1: Framework, Definitions, System, Hardware and Software Requirements\" (GB/T 21109.1-2007 / IEC 61511-1:2003), a DCS system shall not implement any instrument safety functions designated with an SIL level of ≥1. 3. Article 8.2.1 of the \"Code for Design of Safety Instrumented Systems in Petrochemical Industries\" (GB/T 50770-2013): For SIL 1 level safety instrumented functions, logic controllers should be separated from the basic process control system. 8.2.2 For SIL 2 safety instrumented functions, the logic controller shall be separated from the basic process control system. 4. Article 8.2.1 of the “Code for Design of Safety Instrumented Systems in Petrochemical Industry” (GB/T 50770-2013) (Revised draft in 2023, not yet officially promulgated and implemented): For safety instrumented functions classified as SIL 1, the logic controller shall be separated from the basic process control system. In summary, in accordance with current standard requirements, for those SIF circuits related to major hazard sources of level 1 and 2, if their integrity level is SIL1, and given the current standards’ recommendations that such circuits should be installed separately either as a matter of preference or as a requirement, it is likely that in the future they will all have to be installed separately. It is therefore recommended to establish an independent SIS system to fulfill their safety functions. In accordance with **regulatory requirements, Order No. 40 stipulates that primary or secondary major hazard sources must be equipped with an emergency shutdown system ； For major hazard sources of level 1 or 2 involving toxic gases, liquefied gases, or highly toxic liquids, an independent Safety Instrumented System (SIS) must be installed ； Document No. 116: Safety Instrumented Systems (SIS) include safety interlock systems and emergency shutdown systems; all newly constructed chemical processing plants and hazardous chemical storage facilities that fall under the category of “two key areas and one major hazard” must be equipped with safety instrumented systems that meet the required standards. Document No. 88: Safety instrument systems shall be installed in chemical plants classified as “two key items and one major item”.