Compilation of specifications and expert interpretations regarding the installation of level gauges and emergency shut-off valves in tank areas, as well as interlock requirements

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Requirements specified in GB50074-2014 \"Code for Design of Oil Depots\": 15.1 Automatic control systems and instruments 15.1.1 Storage tanks with a capacity greater than 100 m3 shall be equipped with remote liquid level measurement instruments, and the following requirements shall be met: 1 The continuous liquid level measurement signals shall be transmitted to the automatic control system in either analog form or via communication methods； 2 High and low liquid level alarms should be installed in the automatic control system ； 3 The set height for the high liquid level alarm in storage tanks shall comply with the relevant provisions of the current industry standard \"Design Code for Tank Areas in Petrochemical Storage and Transportation Systems\" SH/T 3007 ； 4 The set level for the low liquid level alarm in storage tanks should be such that cavitation does not occur in the pumps. For external floating roof and internal floating roof storage tanks, the set level for the low liquid level alarm (measured from the bottom of the tank) should be at least 0.2m higher than the height at which the floating roof touches the bottom of the tank. 15.1.4 The level measurement instruments used for high and low high/low level alarm signals in storage tanks shall be separate continuous level measurement instruments or level switches, and alarms and interlocks shall be provided in the automatic control system. Interlock requirements: 15.1.2 The following storage tanks shall be equipped with high-level liquid level alarms and interlocks; the high-level liquid level alarm shall be capable of simultaneously interlocking to close the control valve of the tank’s inlet pipeline: Storage tanks for Class A B and Class B liquids with a turnover rate of more than 6 times per year and a capacity of 10,000 m3 or more ； Class A B and Class B liquid storage tanks with a turnover rate of 6 times or less over 2 years, and a capacity of more than 20,000 m3 ； 3 Storage tanks for liquids of toxicity grades I and II. 15.1.3 External floating roof tanks and internal floating roof tanks with a capacity of 50,000 m3 or more shall be equipped with a low-low liquid level alarm. The set height for the low-low liquid level alarm (measured from the bottom of the tank) should not be lower than the height at which the floating roof touches the bottom of the tank; the low-low liquid level alarm should also be capable of triggering the shutdown of the pump. 15.1.4 The level measurement instruments used for high and low high/low level alarm signals in storage tanks shall be separate continuous level measurement instruments or level switches, and alarms and interlocks shall be provided in the automatic control system. "Explanation of the provision: 15.1.4 “Separate level continuous measurement instrument or level switch” refers to a level measurement instrument that, in addition to the “requirement for a remote-level measurement instrument”, is also installed specifically for providing alarms and interlocks for high and low levels in the storage tank. " Setting and interlock requirements: 15.1.2 The following storage tanks shall be equipped with high-high liquid level alarms and interlocks; the high-high liquid level alarm shall be capable of simultaneously interlocking to close the control valve of the tank’s inlet pipeline ； 15.1.7 For the important process pumps, fire pumps, tank agitators and other electric equipment, as well as control valves in Class I oil depots, in addition to being operable on-site, they should also be able to be controlled and have their status displayed from the control room. For the important process pumps, fire pumps, tank agitators and other electric equipment, as well as control valves in secondary oil depots, in addition to being operable on-site, it is also desirable that they can be controlled and their status monitored from the control room. 15.1.11 The start-up and stop-off of the fire pumps in Class 1 oil depots, as well as the opening and closing of the control valves on the fire water pipelines and foam liquid pipelines, shall all be capable of being controlled remotely from the fire control room. The main control panel shall display the operating status of the pumps and the valve position signals of the control valves. "Explanation of the provision: 15.1.7 This provision allows for real-time monitoring of the status of electric equipment, enabling timely handling of any abnormalities. 15.1.11 This provision is intended to ensure the rapid activation of the fire suppression system in order to extinguish fires promptly. " Requirements specified in 02GB 50737-2011 \"Code for Design of Oil Storage Facilities\": 11.1 Automatic control systems and instruments; 11.1.2 Each oil tank shall be equipped with continuous level measurement instruments as well as high-level and low-level switches, and shall comply with the following provisions: 1 The accuracy of the level gauges shall be better than ±1mm ； The 2-channel continuous level gauge should have the functions of high-level alarm, low-level alarm, and interlock to close the tank inlet valve at extremely high levels; the set height for the low-level alarm (measured from the bottom of the tank) should not be less than 2 meters ； 3 The high level switch should have the function of interlocking to close the oil tank inlet valve when the level is too high ； 4 The low-low level switch should have the function of interlocking to stop the oil pump and closing the pump outlet valve when a low-low level is reached; the setting height of this switch (measured from the bottom of the tank) should be no less than 1.85 m ； "Explanation of the provision: 11.1.2 Liquid level is the most important parameter that needs to be monitored in oil tanks; therefore, it is required that \"a continuous liquid level measuring instrument shall be installed in each oil tank.\" The high liquid level interlock to close the inlet valve prevents oil spillage when oil is being filled into the tank, and it is a necessary safety measure. The low liquid level switch is installed to prevent the floating roof legs from dropping to the bottom of the tank. In a floating roof tank, the floating roof generally floats on the surface of the oil and is in direct contact with it, which helps to prevent the evaporation of oil vapor. Moreover, there is no gas space except at the sealing rings, thus greatly eliminating the possibility of an explosive environment. During use, it should be noted that, except for maintaining the oil tank, care must be taken to prevent the floating roof from touching the bottom. Once the floating roof settles to the bottom, a gas space is created between the oil surface and the floating roof. In the case of crude oil, the presence of this gas space means there are explosive gases present, which **increases the risk of fire. In the large oil depot fire that occurred in the north in 2010, several oil tanks with a capacity of 10×104 m3 were exposed to the flames from a distance of just over 10 meters; however, only tank No. 103 caught fire and was ultimately destroyed. The main reason for this was that the floating roof of that tank had dropped to the ground at that time, and there was only a small amount of oil inside the tank. Under the influence of the flames, the oil and gas present in the gas phase easily ignited and caused the fire. The typical height of the floating roof legs is 1.8 m; therefore, it is specified that the setting height of the \"very low liquid level switch (from the tank bottom plate) shall be no less than 1.85 m\"” ； Considering that there is a processing time of 10 minutes to 15 minutes after an alarm is triggered, it is specified that \"the set height for the low liquid level alarm (from the bottom of the tank) should not be less than 2 meters.\" "Requirements: 11.1.10 The start and stop of fire pumps, as well as the operation of control valves on fire water pipes and foam pipelines, shall be able to be controlled programmatically from the fire control room. The main control panel shall be able to display the operating status of the pumps and the valve position signals of the electric valves. 03GB 50160-2018 \"Code for Fire Protection Design of Petrochemical Enterprises\" – Requirements: 6.2.23 Storage tanks for flammable liquids shall be equipped with level gauges and high-level alarms; where necessary, automatic interlock systems to shut off the feeding facilities shall also be installed ； An automatic dehydrator should also be installed. Interlock requirements: 6.3 Above-ground storage tanks for liquefied hydrocarbons, combustible gases, and oxidizing gases ； 6.3.11 Liquefied hydrocarbon storage tanks shall be equipped with level gauges, thermometers, pressure gauges, safety valves, as well as high-level alarms and automatic interlock shutdown mechanisms for extremely high levels to cut off feed. "Explanation of the provision: 6.3.11 of NFPA 58, the Liquefied Petroleum Gas Code, stipulates that: “A high liquid level alarm shall be provided on refrigerated liquefied petroleum gas containers.” “Refrigerated liquefied petroleum gas containers should be equipped with a high liquid level flow cut-off device, which should be independent of all instruments. ”Even for storage tanks at room temperature, such a requirement provides greater safety. The automatic interlock shutdown device for high liquid levels is the most effective means to prevent oil tanks from overflowing; it is widely used nowadays and represents a reasonable setup. "Setup and interlock requirements: 6.3.14 Full-pressure liquefied hydrocarbon storage tanks should be equipped with a secondary dehydration system that includes anti-freezing measures, and an emergency shut-off valve should be installed at the base of the tank. 6.4 Loading and unloading facilities for flammable liquids and liquefied hydrocarbons 6.4.1 An easily operable emergency shut-off valve shall be installed on the inlet pipeline for flammable liquids (except lubricating oils), at a distance of 10 m from the edge of the loading dock ； 6.4.2 When there are no buffer tanks on the station, an emergency shut-off valve that is easy to operate should be installed on the loading and unloading pipelines at a distance of more than 10 m from the loading/unloading crane positions ； 7 Pipeline Layout 7.2 Process and Utility Pipelines 7.2.15 For pipelines leading from liquefied hydrocarbons and flammable liquids with an operating temperature equal to or above their auto-ignition point to the pump inlet, a shut-off valve should be installed near the base of the equipment. When the volume of the equipment exceeds 40 m3 and the distance between it and the pump is less than 15 m, this shut-off valve should be a remotely operated valve with a manual function; the control button for this remotely operated valve should be located at a distance of no less than 15 m from the pump. 7.4.7 When the length of an inter-plant pipeline exceeds 5 km, emergency shut-off valves as well as flow and pressure monitoring devices shall be installed on the pipelines located within the enclosure walls or land boundaries of the enterprises upstream and downstream of it. 8.4.5 Vertical above-ground storage tanks for flammable liquids shall be equipped with a fixed or mobile fire cooling water system; the supply range, supply intensity, and installation method of such a system shall comply with the following provisions: 5 The control valves shall be located outside the fire dike, at a distance of not less than 15 m from the wall of the tank to be protected. The fire cooling water pipes installed behind the control valve and on the storage tank should be made of galvanized steel pipes. 8.10.10 The installation of fixed fire cooling water pipelines for fully pressurized and semi-frozen liquefied hydrocarbon storage tanks shall comply with the following provisions: 2 The fire cooling water system may use manual or remotely controlled valves; when the volume of the storage tank is 1000 m3 or greater, remotely controlled valves shall be used ； 3 The control valve should be located outside the fire dike, at a distance of not less than 15m from the wall of the tank to be protected ； "Explanation of the provision: 6.3.14 Installing emergency shut-off valves at the base of storage tanks can reduce losses in the event of an accident in the piping system. 7.2.15 This provision is intended to allow for the timely shutdown of the material flow in the event of a fire in the downstream equipment directly connected to the tank. For example, if an accident and fire occur in the pump located downstream of the liquefied hydrocarbon tank in a plant’s product refining unit, it becomes impossible for personnel to approach the pump in order to shut off the isolation valve. Moreover, there is no isolation valve on the pipeline near the base of the tank between the pump and the tank, which results in the liquefied hydrocarbon in the tank being completely burned out before the fire can be extinguished, causing significant losses. API Std 2510, \"Design and Construction of Liquefied Petroleum Gas (LPG) Facilities\", specifies that isolation valves on liquefied hydrocarbon pipelines should be located as close as possible to the tanks, preferably at the tank wall nozzles. For ease of operation and maintenance, the installation location of the shut-off valve should be easily accessible. When the volume of a liquefied hydrocarbon tank exceeds 10,000 gal (≈38 m3), all isolation valves located on pipes below the highest liquid level in the tank must be able to close automatically or via remote control within 15 minutes of a fire breaking out. The control system for the shut-off valve shall be protected against fire, and the shut-off valve shall be operable manually. In accordance with API standards, the volume of the liquefied hydrocarbon equipment has been adjusted to 40 m3. Given the higher likelihood of accidents involving pumps for flammable liquids whose operating temperature is equal to or above their auto-ignition point, there is a need to impose the requirement of installing shut-off valves near the base of the equipment in the inlet pipes leading to pumps for such flammable liquid devices. " 04GB 17681-1999 \"Technical Requirements for the Acceptance of Safety Monitoring and Early Warning Systems in Flammable and Explosive Tank Areas\" – Requirement 5.5: Liquid storage tanks must be equipped with level detection instruments, and at least two different types of such instruments shall be installed on each tank. Storage tanks holding flammable and explosive materials should be equipped with high and low liquid level alarm circuits; where necessary, they should also have an interlock system linking the liquid level to relevant process parameters. 05AQ 3036-2010 \"Code for the Installation of On-site Safety Monitoring Equipment in Tank Areas for Major Hazardous Chemicals\" – Installation requirements: 6.3.1 Storage tanks shall be equipped with level monitors that have the capability to issue alarms when the liquid level is too high or too low. Interlock requirements: 6.3.7 Large combustible liquid storage tanks (over 5000 m3) and pressure storage tanks for hazardous chemicals (over 400 m3) shall be equipped with separate high-high liquid level monitoring, alarm, and interlock control systems. Setup requirements: Setup requirements for 5 interlock control equipment 5.1 Interlock automatic control equipment can be installed to regulate parameters such as the temperature, liquid level, pressure of storage tanks, as well as the ambient temperature, based on actual conditions; this includes systems for automatic shutdown or transfer of materials, as well as spray cooling equipment. 06SH/T 3007-2014 \"Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems\" – Requirements: 5. Tank areas for atmospheric and low-pressure storage; 5.4 Selection and installation of instruments; 5.4.1 Tanks with a capacity greater than 100 m3 shall be equipped with remote transmission instruments for continuous level measurement. 5.4.2 High and low liquid level alarms shall be provided in the automatic control system, and they shall comply with the following requirements: a) The set point for the high liquid level alarm in the storage tank shall not be higher than the designed maximum liquid level of the tank ； b) The set level for the low liquid level alarm in the storage tank should not be lower than the designed low liquid level for storage in that tank. 5.4.5 The high and low level alarm signals for the storage tank, as well as the level measurement instruments, shall be provided by separate continuous level measurement devices or level switches; the alarm signals shall be transmitted to the automatic control system. 6 Pressure Storage Tank Area 6.3 Selection and Installation of Tank Instruments 6.3.2 For measuring the liquid level in pressure storage tanks, one set of remote transmission instruments and one set of local indication instruments should be installed; glass plate level gauges should not be used as local indication instruments. 6.3.3 Level measurement remote transmitters shall be equipped with high and low level alarms. The set level for the high liquid level alarm should be the designed maximum liquid level of the storage tank ； The set level for the low liquid level alarm should ensure that the pump will not experience cavitation within 10 to 15 minutes from the onset of the alarm. Interlock requirements: 5.4.3 Storage tanks for liquids of toxicity levels I and II, storage tanks for flammable liquids of categories A B and A C with a capacity of 3000 m3 or more, and storage tanks for other liquids with a capacity of 10000 m3 or more shall be equipped with high-high liquid level alarms and interlocks. The high-high liquid level alarm shall trigger the interlock to close the control valve of the tank’s inlet pipeline. 5.4.4 The raw material storage tanks of the unit should be equipped with a low-low liquid level alarm, and this alarm should be linked to shut down the pump. 5.4.5 The high and low level alarm signals for the storage tank, as well as the level measurement instruments, shall be provided by separate continuous level measurement devices or level switches; the alarm signals shall be transmitted to the automatic control system. 6 Pressure Storage Tank Area 6.3 Selection and Installation of Tank Instruments 6.3.4 Pressure storage tanks should be equipped with a separate set of level measurement instruments or level switches dedicated to detecting extremely high liquid levels and triggering the interlock to shut off the valves controlling the feed pipes to the tank. The set level for the high liquid level alarm should not be higher than the level at which the liquid volume reaches 90% of the tank’s calculated capacity. "Explanation of the provision: 5.4.1 Liquid level is the most important parameter that needs to be monitored in storage tanks; therefore, this provision requires that \"storage tanks shall be equipped with remote liquid level measurement instruments.\" 5.4.2 The purpose of setting high (low) liquid level alarms is to predict that the liquid level in the tank will rise (fall) to the specified limit levels; operators are required to complete the task of switching to another tank within a specified time after hearing the alarm, in order to prevent accidents. 5.4.3 The interlock to close the inlet valve at high liquid levels can prevent overflow when feeding the storage tank; more stringent safety measures are required for the three situations listed in this clause. " 07SH 3136-2003 \"Code for Safe Design of Spherical Storage Tanks for Liquefied Hydrocarbons\" – Requirements: 5.3.1 Spherical storage tanks for liquefied hydrocarbons shall be equipped with local and remote level gauges; however, glass plate level gauges should not be used. The level gauge used should be safe and reliable, and the number of openings in the spherical storage tanks for liquefied hydrocarbons should be minimized as much as possible. 5.3.2 Liquefied hydrocarbon spherical storage tanks shall be equipped with a high liquid level alarm and a high-high liquid level interlock. A low liquid level alarm should be installed if necessary. Interlock requirements: 5.3.2 Liquefied hydrocarbon spherical storage tanks shall be equipped with high liquid level alarms and high-high liquid level interlocks. A low liquid level alarm should be installed if necessary. 5.3.3 For spherical liquefied petroleum gas storage tanks loaded and unloaded by tank trucks under intermittent operation, an automatic high liquid level interlock emergency shutdown feed cut-off device shall be provided. For single-component liquefied hydrocarbons or spherical storage tanks used in the continuous operation of refining and petrochemical production units, the interlock requirements shall be determined based on the needs of the upstream and downstream process streams. Settings and interlock requirements: 6.1 Emergency shut-off valves – Emergency shut-off valves should be installed at the liquid inlet and outlet of the liquefied petroleum gas spherical storage tank, and their location should be as close as possible to the spherical tank. 08AQ3053-2015 \"Safety Technical Specifications for Vertical Cylindrical Welded Steel Storage Tanks\" – Requirements: 12.2.2 For storage tanks holding flammable liquids, level gauges as well as high and low level alarm devices, and high-high level alarm devices must be installed in accordance with the specifications and operational requirements; the alarm signals and level information must be transmitted to the control room. Storage tanks that are operated frequently should be equipped with automatic interlock emergency shut-off devices. Large tanks should be equipped with low and high liquid level alarm devices, high-high liquid level alarm devices, and emergency shut-off devices. Interlocking measures should be implemented between the high-high liquid level alarm and the emergency shut-off device, and interlocking buttons for the emergency shut-off valves should be provided outside the fire dike as well as at the control room operation stations. When a high level alarm or a fire occurs in the storage tank, it is possible to remotely or manually close the feed cut-off valve; once the cut-off valve is closed, the feed pump should be automatically shut down via interlock. Interlock requirements: 12.2.2 For large tanks equipped with level control accessories, high and low level alarm devices, as well as high-high level alarm devices and emergency shut-off devices shall be installed. Measures shall be taken to interconnect the high-high level alarm device with the emergency shut-off device; in addition, interlock buttons for the emergency shut-off valves shall be provided outside the fire dike and at the control room operation stations. When a high level alarm or a fire occurs in the storage tank, it is possible to remotely or manually close the feed cut-off valve; once the cut-off valve is closed, the feed pump should be automatically shut down via interlock. Installation requirement: 6.13 A main shut-off valve should be installed near the tank body on the inlet and outlet pipes of the material in the shut-off valve tank. For large storage tanks, valves equipped with pneumatic, hydraulic, or electric actuators should be used. When the actuator is of electric type, its power cable, signal cable, and electric actuator shall be provided with fire protection. The cut-off valve should have automatic and manual shutdown functions, with manual shutdown including remote manual shutdown and on-site manual shutdown. 09 General Administration of Work Safety Document No. 3 [2014] 68, “Notice on Further Strengthening the Safety Management of Chemical Tank Areas”: Requirements: (1) Further improve the monitoring and control facilities in chemical tank areas. In accordance with regulatory requirements, high and low liquid level alarms are installed for the storage tank; automatic interlocks are employed to shut down the tank’s feed valve when the liquid level is too high, and to stop material transfer when the liquid level is too low. Ensure that the alarm systems for leaks of flammable, explosive, toxic, and harmful gases are in good working condition. Emergency shut-off valves must be installed on key storage tanks such as those for large-scale liquefied gases and highly toxic chemicals. Setup and interlock requirements: (1) Further improve the monitoring and control facilities in the chemical tank area. In accordance with regulatory requirements, high and low liquid level alarms are installed for the storage tank; automatic interlocks are employed to shut down the tank’s feed valve when the liquid level is too high, and to stop material transfer when the liquid level is too low. Ensure that the alarm systems for leaks of flammable, explosive, toxic, and harmful gases are in good working condition. Emergency shut-off valves must be installed on key storage tanks such as those for large-scale liquefied gases and highly toxic chemicals. Circular No. 10 An Jian Zong Guan San [2013] 76, “Notice on Further Strengthening the Safety Design Management of Hazardous Chemicals Construction Projects”: Requirements: (14) The design unit shall determine the standards and specifications to be applied for a particular project, based on the characteristics of the hazard sources associated with that project and the scope of application of relevant standards and regulations. For construction projects involving the \"two key aspects and one major issue,\" they must meet at least the requirements of the following current standards and specifications, with the strictest safety provisions taking precedence. (19) Newly built chemical plants must be designed with automated control systems. It should be determined whether a safety instrumented system is needed based on the results of the hazard and risk analysis of the process. For large and medium-sized new projects involving hazardous chemical processes that are under strict supervision, the design of safety instrument systems shall be carried out in accordance with relevant standards such as \"Functional Safety of Safety Instrument Systems in the Process Industry\" (GB/T21109) and \"Design Code for Safety Instrument Systems in Petrochemical Industries\" (GB50770). (22) Emergency shut-off devices that can be operated automatically or remotely by hand should be installed on the pipelines for feeding and discharging materials from toxic material storage tanks, cryogenic storage tanks, and pressure spheres. Interlock requirements: (19) Newly built chemical plants must be designed with automated control systems. It should be determined whether a safety instrumented system is needed based on the results of the hazard and risk analysis of the process. For large and medium-sized new projects involving hazardous chemical processes that are under strict supervision, the design of safety instrument systems shall be carried out in accordance with relevant standards such as \"Functional Safety of Safety Instrument Systems in the Process Industry\" (GB/T21109) and \"Design Code for Safety Instrument Systems in Petrochemical Industries\" (GB50770). (22) Emergency shut-off devices that can be operated automatically or remotely by hand should be installed on the pipelines for feeding and discharging materials from toxic material storage tanks, cryogenic storage tanks, and pressure spheres. Order No. 40 of the State Administration of Work Safety, “Interim Provisions on the Supervision and Management of Major Hazard Sources of Hazardous Chemicals”: Requirement in Article 13 – 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 a comprehensive safety monitoring system in accordance with the following requirements in order to improve control measures: (1) Major hazard sources must be equipped with systems for continuous collection and monitoring of data 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 should 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) Automated control systems for chemical production facilities and equipment with major hazard sources that meet safety production requirements ； 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) is required ； Interlock requirements: Article 13 Hazardous chemicals 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 a safety monitoring and control system in accordance with the following requirements to enhance control measures: (3) Install emergency shut-off devices for key facilities within major hazard sources, such as toxic gases, highly toxic liquids, and flammable gases ； 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) is required ； 12 Safety Supervision General Administration Document No. 3 [2016] 62 **Notice from the General Administration of Safety Supervision on Issuing Guidelines for Curbing Serious Accidents Involving Hazardous Chemicals and Fireworks and Firecrackers – Requirements: (4) As of January 1, 2017, all hazardous chemical storage areas that constitute Class I or Class II major hazard sources and do not have an emergency shutdown (emergency isolation) function must cease to be in use ； Document No. 13 Su An Jian [2009] 109, \"Opinions on Standardizing the Technical Renovation of Automatic Control Systems in Chemical Enterprises\", sets the following requirements: 1. New production units or storage facilities that fall within the scope of renovation must be equipped with automatic control systems; safe and reliable automatic control instruments and interlock protection systems should be used, along with necessary detection and alarm systems for leaks of toxic, harmful, flammable, and explosive gases, as well as fire alarm systems. For investment projects with a scale of 100 million RMB or more, as well as those equipped with production facilities involving high-risk processes (such as cracking, hydrogenation, polymerization, fluorination, nitration, peroxidation processes, etc.), emergency shutdown systems must be installed in addition to automated control systems. 2. Existing production units involving hazardous processes must complete the transformation to automatic control technology within the specified time frame, in order to achieve automatic control of the process flow as well as automatic alarm functions for key parameters such as temperature and pressure. Systems with high risk or under specific conditions must be equipped with distributed control systems and emergency shutdown systems to enable remote operation. Hazardous chemical manufacturing enterprises must complete the renovations before renewing (obtaining) their safety production licenses. 3. The existing storage facilities within the scope of the renovation must complete the upgrade to automatic control technology within the specified time frame. Storage areas for highly toxic and flammable/explosive chemicals must be equipped with alarms for excessive levels of liquid, temperature, and pressure, as well as gas leak detection alarms and fire alarm systems ； Key storage tanks such as liquefied gases and highly toxic liquids, which constitute major hazard sources, must be equipped with emergency shut-off devices. Sinopec An [2010] No. 635, dated November 17, 2010: “Interim Provisions on the Safety Technology Management of Liquefied Hydrocarbon Spherical Tank Areas in Sinopec Group”. Requirements for installation: 3.2.4 Instrumentation and automation; 3.2.4.1 An instrumentation control system shall be installed in liquefied hydrocarbon spherical tank areas to carry out tasks such as data collection, monitoring, alarm generation, and process control during production. Control systems can include programmable logic controllers (PLC), distributed control systems (DCS), supervisory control and data acquisition systems (SCADA), and fieldbus control systems (FCS), among others. When safety interlock requirements are present in tank farm operations, safety interlock circuits and safety instrumented systems should be installed. The measuring elements (including sensors, transmitters, etc.), logic controllers, and actuating elements (including solenoid valves, control valves, shut-off valves, etc.) in the safety interlock circuit must all meet the Safety Integrity Level (SIL) requirements. 3.2.4.3 Liquefied hydrocarbon spherical tanks shall be equipped with local and remote level gauges. Local level gauges can be magnetic flap level gauges, steel belt level gauges, radar or servo level gauge indicators mounted beside the tank; glass tube (plate) level gauges should not be used. When the local level gauge is a radar or a servo tank-side indicator, the spherical tank shall also be equipped with a different type of remote level measuring instrument. Interlock requirements: 3.2.4.4 Liquefied hydrocarbon spheres should be equipped with low and high level alarms, as well as interlocks that shut off feeding when the level reaches extremely high values. The sensing elements for the high liquid level interlock should be installed separately; ultrasonic, tuning fork, float, or capacitive level switches can be used. It is advisable to combine these with the high liquid level signals from radar and servo-type remote level gauges to implement a \"three-out-of-two\" interlock system that shuts off feeding. Settings and interlock requirements: 2 Terminology 2.2 An emergency shut-off valve is a valve installed on the inlet and outlet pipelines of spherical tanks, capable of closing quickly and tightly in the event of an accident or abnormal condition. The allowable leakage rate for such valves should meet ANSI B16.104 (FCI 70-2) CLASS V or a higher standard. The valve shall have the capability to be closed thermally, manually, and remotely manually (via a remote control with a handle). 3.2.4 Instrumentation and automatic control 3.2.4.4 Liquefied hydrocarbon spheres should be equipped with high and low liquid level alarms, as well as interlocks that shut off feed when the liquid level reaches extremely high levels. The sensing elements for the high liquid level interlock should be installed separately; ultrasonic, tuning fork, float, or capacitive level switches can be used. It is advisable to combine these with the high liquid level signals from radar and servo-type remote level gauges to implement a \"three-out-of-two\" interlock system that shuts off feeding. 3.2.4.5 Emergency shut-off valves a) Emergency shut-off valves shall be installed at the liquid inlet and outlet of liquefied hydrocarbon spherical tanks; the actuating mechanism for these valves can be pneumatic, hydraulic, or electric (pneumatic type is preferred). When the actuator of the shut-off valve is a pneumatic actuator, a single-acting cylinder actuator (fault-safe type) should be selected ； If a pneumatic double-acting cylinder actuator is used, an emergency air tank should be provided. When the actuator is of electric type, its power supply should be provided by an electrical UPS, and its power cables, signal cables, and electric actuator should be protected against fire. b) Emergency shut-off valves should be distinguished from process control valves. Its sealing structure shall be of fire-resistant design and comply with ANSI/API STD607 standards ； The allowable leakage rate shall meet ANSI B16.104 (FCI 70-2) CLASS V or higher. c) Outside the fire dike of the liquefied hydrocarbon sphere tank area, as well as at the control room operation stations (hard or soft switches), emergency shutoff valve interlock buttons should be installed. In the event of a high liquid level alarm in the spheres or a fire, operators can remotely or manually shut down the emergency shutoff valve; once the valve is closed, it automatically triggers the shutdown of the feed pump. The shutdown time of the emergency shut-off valve is as follows: Nominal size DN (mm) – Complete shutdown time (s): ≤50: ≤5; 65–350: ≤10. The emergency shut-off valve must be able to shut off automatically when the temperature of the fusible element automatic shut-off device reaches 75±5°C. e) The selected emergency shut-off valve shall be fail-safe. 15 “Regulations on Safety Technology Management for Liquefied Hydrocarbon Spherical Tank Areas in Sinopec”: Requirements: 4.4 Instrumentation and Automation 4.4.1 An instrumentation control system shall be installed in liquefied hydrocarbon spherical tank areas to carry out tasks such as data collection, monitoring, alarm generation, and process control during production. Control systems can include programmable logic controllers (PLC), distributed control systems (DCS), supervisory control and data acquisition systems (SCADA), and fieldbus control systems (FCS), among others. 4.4.3 Liquefied hydrocarbon spheres should be equipped with local and remote level gauges. Local level gauges can be magnetic flap level gauges, steel belt level gauges, or radar or servo level gauge indicators mounted beside the tank. When the local level gauge is a radar or a servo tank-side indicator, the spherical tank shall also be equipped with a different type of remote level measuring instrument. Interlock requirements: 4.4.4 Liquefied hydrocarbon spheres should be equipped with low and high level alarms, as well as interlocks that shut off feeding at extremely high levels. The sensing elements for the high liquid level interlock should be installed separately, and options such as ultrasonic sensors, tuning fork sensors, float switches, and capacitive level switches can be used. Requirements: 4.4.5.4 The control of the emergency shut-off valve shall allow for remote control from the control room as well as local control on-site. The time required for it to close is specified in the following table: Nominal diameter DN (mm) – Time to full closure (s): ≤50: ≤5; 65–350: ≤10. Source: Sinopec [2011] Jian 518, Specifications for the selection and design of emergency shut-off valves for liquefied hydrocarbon spheres. Requirements: 3.1 The emergency shut-off valve is designed specifically for installation on the inlet and outlet pipelines of liquefied hydrocarbon spheres, serving as a valve that can quickly and completely shut off and isolate flammable and toxic materials in the event of fires or leaks within the tank area. When the liquid level in the spherical tank reaches or exceeds the high-high level limit, the emergency shut-off valve can be used to prevent the material from overflowing the tank. No other fittings or valves shall be installed between the emergency shut-off valve and the tank outlet except for the connecting pipes, and the spacing therebetween shall meet the requirements for piping installation, valve maintenance, and the process. The emergency shut-off valve shall have automatic and manual shutdown functions, with the manual shutdown function including remote manual shutdown from the control room and on-site manual shutdown. 4.5.11 An on-site operation switch for the emergency shut-off valve shall be installed outside the fire hazard area of the liquefied hydrocarbon sphere tank area; the signal from its contacts is sent directly to the solenoid valve of the pneumatic actuator, or to the ESD actuation terminals of the electro-hydraulic or electric actuator, so as to enable manual shutdown of the emergency shut-off valve on site in emergency situations. On November 20, 2018, Sinopec issued Document No. Anfei 477, titled \"Guidelines for the Rectification of Atmospheric Pressure Storage Areas for Flammable and Combustible Liquids at Sinopec\". Interlock requirements: 4.1.4 The emergency shut-off valves on the feed pipes to the storage tanks should be interlocked with the high liquid level alarm instruments of those tanks ； Settings and interlock requirements: 4.1 Emergency shut-off valves 4.1.1 Emergency shut-off valves shall be installed on the inlet and outlet pipelines of storage tanks containing extremely hazardous liquids (Class I) and highly hazardous liquids (Class II), storage tanks for flammable liquids of Class A B and Class B A with a capacity of 3000 m3 or more, storage tanks for other flammable liquids with a capacity of 10000 m3 or more, as well as on the pipelines of tank farms that constitute major hazard sources of Class I or Class II. The emergency shut-off valve should be able to be closed remotely from the control room. 4.1.2 Emergency shut-off valves for storage tanks in refineries, petrochemical plants, and petrochemical fiber plants should preferably be pneumatic valves and should have a fail-safe shutdown function ； Electric valves can be used as emergency shut-off valves for storage tanks in crude oil depots, refined oil depots, and pipeline auxiliary stations. 4.1.3 The emergency shut-off valves on the inlet and outlet pipelines of the storage tank can share the same process control valves. 4.1.4 The emergency shut-off valve on the tank feed pipeline shall be interlocked with the tank high liquid level alarm instrument. 4.1.8 The time required for the emergency shut-off valve to open or close completely via a pneumatic or electric actuator shall not exceed 180 seconds. 4.2.1 Storage tanks for bulk hydrocarbons, liquefied hydrocarbons, and liquid ammonia shall be equipped with an independent Safety Instrumented System (SIS). 18【2016】No. 39: Sinopec’s “Guidelines for the Campaign to Rectify Hazards in Tank Areas” – Requirements regarding interlocks: IV. Low-low liquid level interlocks and high-high liquid level interlocks 1. Storage tanks with a volume of more than 100 m3 shall be equipped with continuous liquid level measurement and transmission instruments for high, high-high, low, and low-low liquid levels. However, whether interlocks should be installed to shut off the inlet and outlet valves or to stop the pumps depends on the effects that such interlocks would have; the following regulations must be complied with: (1) Storage tanks that are classified as major hazard sources of level 1 or 2 shall be equipped with high-high liquid level interlocks to shut off the inlet valve. It is also necessary to verify that the design pressure of the inlet pipes and related pipelines meets the requirements of the most severe operating conditions (such as the head at the pump’s shut-off point), and that appropriate safety measures are in place. (2) When the high liquid level interlock of a storage tank containing a certain material shuts down the feed valve, in order not to affect the normal operation of the upstream units (facilities), an alarm should be triggered and the feed valve of another storage tank should be opened promptly. (3) For tanks whose automatic interlock shutdown due to low-low liquid level can cause significant disruptions such as shutdowns and restarts in downstream facilities or stations (such as feed tanks and intermediate feed tanks in processing units, as well as tanks at oil transfer stations), a secondary alarm should be implemented when the liquid level reaches low-low levels; this alarm should trigger the closure of the discharge valve, while simultaneously activating another tank’s discharge valve. (4) For tanks in which automatic interlock shutdown of the pump is triggered when the low-low liquid level is reached, and which do not cause significant disruptions such as stops and restarts to downstream operations (loading onto vehicles or ships) – such as finished product tanks in refining enterprises or storage tanks in oil depots – it is possible to use interlocks to close the discharge valve or to shut down the pump when the liquid level reaches the low-low level. Setup and interlock requirements: 2. For storage tanks that are classified as major hazard sources of level 1 or 2, in addition to high and low liquid level alarms, corresponding alarms and interlock protection measures should also be installed for low-low liquid level and high-high liquid level. For storage tanks that require a separate SIS system, tank base valves should be installed on their inlet and outlet pipelines (emergency shut-off valves must have fire protection measures, be capable of manual operation, and also have fire protection features); the SIS system is used to interlock and shut off feed in emergency situations such as high liquid levels in the tank or fires ； For storage tanks that do not require a separate SIS system, the tank bottom valves on their inlet and outlet pipelines should be control valves equipped with manual operation capabilities; in emergency situations such as high liquid levels in the tank or fire accidents, feed can be shut off through interlocks in the basic process control system. 19Q/SH 0749-2018 \"Technical Standards for the Storage and Transportation of Liquefied Hydrocarbons\" – Requirements for installation and interlocking: 12.2.5 The selection of level measurement instruments shall comply with the following provisions: a) Two servo level gauges shall be installed in low-temperature vertical storage tanks for level measurement ； A separate servo level gauge should be installed in the low-temperature vertical storage tank, to enable interlock functions for high and low levels by using the level alarm signals from those two servo level gauges. b) The spherical tank shall be equipped with a servo level gauge and a radar level gauge separately for level measurement; in addition, a level switch shall be installed to provide interlock protection against high levels based on the level alarm signals from these two gauges ； An additional level switch is installed to provide a low-low level interlock with the level alarm signals from the two level gauges used by the supervisor. f) The emergency shut-off valve (ESDV) should preferably be equipped with a pneumatic single-acting actuator or an electro-hydraulic actuator. g) The selection of emergency shut-off valves at the base of liquefied hydrocarbon spheres shall comply with Sinopec Document Jian 518, \"Specifications for the Selection and Design of Emergency Shut-Off Valves for Liquefied Hydrocarbon Spheres\" ； The fire shield for the emergency shut-off valve at the base of the spherical tank should be a rigid fire protection shield suitable for outdoor use; such a shield must be able to keep the temperature inside it below 80°C for 30 minutes in the presence of hydrocarbon fires at 1093°C. Letter No. 27 [2018] issued by the General Office of the Work Safety Supervision Administration, Department 3** Office of the Work Safety Supervision Administration, February 7, 2018 Requirements for installation and interlocking: (I) Jiangsu Tianjiayi Chemical Co., Ltd. (13 items): 5. The DCS and SIS pressure transmitters of some dinitration reactors share the same pressure sampling point. 6. The benzene tank area and methanol tank area, which constitute secondary major hazard sources, are not equipped with emergency shut-off valves at the base of the tanks. 8. The cabinet room and monitoring room were improperly located within the nitration plant. (II) Kunpeng Chemical Co., Ltd. in Xiangshui County (15 items): 6. The distillation system does not have automatic control. 11. The doors and windows of the control room and cabinet rooms face devices with fire and explosion hazards. 12. The ESD system does not have dual-circuit power supply. (III) Jiangsu Dahua Chemical Industry Co., Ltd. (11 items): 4. The DCS control room of the facility is not of explosion-proof design, and its doors and windows face Workshop No. 1, which is at risk of fire and explosion. 8. The tank farm, which constitutes a major hazard source of level 1, is not equipped with emergency shut-off valves at the base of the tanks. 9. The procedures for disabling the instrument interlock were not followed. (IV) Jiangsu Yongtai Technology Co., Ltd. (9 items): 3. The tank areas that constitute first-level major hazard sources have numerous safety hazards, such as the emergency shut-off valves not being installed at the base of the storage tanks ； The storage tanks are not equipped with on-site level indicators; some of them have only one static grounding point ； (II) Jiangsu Sierbang Petrochemical Co., Ltd. (9 items): 4. The interlock devices for pumps at the plant site did not have the interlock indication marked in a prominent position on the coupling guards. 7. The gland openings of some instrument junction boxes are not sealed, and they are not explosion-proof ； The static bonding wires of individual instrument bodies and junction boxes have come loose. (III) Jiangsu Hailirui Technology Development Co., Ltd. (17 items): 8. The units involving hazardous chemical processes that are under strict supervision do not have emergency shutdown systems. 17. The control room is located within the production facility. (IV) Jiangsu Xincheng Chemical Co., Ltd. (13 items): 6. The units involving hazardous chemical processes that are under strict supervision do not have automated control systems in place, nor is emergency shutdown functionality available. (1) Jiangsu Zhongneng Silicon Industry Development Co., Ltd. (12 items): 3. The control measures for major hazard sources are inadequate; for example, since the company constitutes a first-class major hazard source, the assessment in the current status evaluation report places the acceptable social risk curve in the area where risks should be minimized as much as possible. The potential risks present were not analyzed as required, nor were any measures to address those risks established. 7. The safety instrument systems are inadequate; for example, units involving hazardous chemical processes do not have emergency shutdown systems that are independent of the process control system, as required. Document No. 21 An Jian Zong Guan San [2017] 121, \"Criteria for Identifying Major Potential Hazards in Production Safety Incidents in Chemical and Hazardous Chemicals Production and Operation Units (Trial)\\": Requirements regarding installation and interlocking: IV. Plants involving hazardous chemical processes that are under strict supervision do not have automated control systems; the systems do not possess emergency shutdown functions, and the automated control systems and emergency shutdown systems installed are not in use. V. The hazardous chemical storage areas that constitute Class I and Class II major hazard sources do not have an emergency shutdown function ； 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. X. Operating chemical plants lack proper design and have not undergone safety design assessments. 13. The side of the control room or cabinet room that faces devices with fire and explosion hazards does not meet the fire and explosion prevention requirements of the ** standards. 14. The chemical production facilities do not have dual power supply systems as required by **standards, and the automation control systems lack uninterruptible power supplies. 19. Newly developed production processes for hazardous chemicals are put into industrial production directly, without undergoing pilot tests, scale-up tests, or industrial trials ； The chemical process used for the first time in the country had not undergone safety and reliability assessments organized by the relevant provincial people’s government departments ； No trial production plan has been established for the newly installed unit, so it has not been put into operation with materials fed in ； Fine chemical enterprises have failed to conduct reaction safety risk assessments as required by regulatory documents. Notice No. 22 An Jian Zong Guan San [2014] 68 on Further Strengthening the Safety Management of Chemical Tank Areas – Requirements for Installation and Interlocking: (1) Further improve the monitoring and control facilities in chemical tank areas. In accordance with regulatory requirements, high and low liquid level alarms are installed for the storage tank; automatic interlocks are employed to shut down the tank’s feed valve when the liquid level is too high, and to stop material transfer when the liquid level is too low. Ensure that the alarm systems for leaks of flammable, explosive, toxic, and harmful gases are in good working condition. Emergency shut-off valves must be installed on key storage tanks such as those for large-scale liquefied gases and highly toxic chemicals. (II) Strengthen the production and operation management of chemical tank areas. Under normal operating conditions, it is strictly prohibited to allow any space to form between the floating disk of an internal floating roof tank and the material contained within it. In special cases where operation at an extremely low liquid level is necessary, it is essential to ensure that the feed flow rate is below the specified limit when resuming feeding, in order to prevent accidents caused by static electricity. When high or low level alarms occur, immediate action must be taken. (VI) Tank farms dealing with hazardous chemicals under strict supervision shall conduct hazard and operability analyses on a regular basis. Guiding Opinions on Strengthening Leak Management in Chemical Enterprises, No. 23 An Jian Zong Guan San [2014] 94: Requirements for installation and interlocking: (VIII) Improve the automated control system. For production facilities involving hazardous chemical processes and chemicals that are under strict supervision, automated control systems, safety interlocks or emergency shutdown systems, as well as detection and alarm systems for leaks of flammable and toxic gases, must be installed in accordance with safety requirements. The emergency stop system and safety interlock protection system must meet the functional safety level requirements. Appropriate safety technical measures must be implemented for hazardous chemical storage systems, such as high and low liquid level alarms, high-high and low-low liquid level interlocks, as well as emergency shutdown devices. 24 General Administration of Work Safety Document No. 3 [2013] 88: Guidelines for Strengthening Safety Management in Chemical Processes, dated July 29, 2013. Requirements for installation and interlocking: (V) Establish a risk management system. Enterprises should establish a risk management system for chemical processes, defining the scope, methods, frequency, and responsible parties for risk identification, specifying the requirements for applying the results of risk analysis and implementing improvement measures, and conducting risk identification and analysis throughout the entire production process. For the production and storage facilities involving highly regulated hazardous chemicals, highly regulated hazardous chemical processes, and major hazard sources of hazardous chemicals (collectively referred to as \"two key areas and one major hazard\"), risk identification and analysis should be carried out using the Hazard and Operability Study (HAZOP) technique, generally once every 3 years. For the risk identification and analysis of other production and storage facilities, depending on the degree of complexity of those facilities, methods such as safety checklists, job hazard analyses, preliminary hazard analyses, Failure Mode and Effects Analysis (FMEA), and HAZOP techniques, or combinations of several such methods, can be used; this analysis can be carried out every 5 years. When there are significant changes in the enterprise’s management structure, personnel composition, production facilities, etc., or when a production safety accident occurs, it is necessary to conduct risk identification and analysis promptly. Enterprises should involve all their staff in risk identification and analysis, striving to achieve comprehensive coverage of such activities. (7) Establish acceptable risk standards. Enterprises shall, in accordance with the requirements of the Interim Provisions on the Supervision and Management of Major Hazard Sources of Hazardous Chemicals (Order No. 40 of the State Administration of Work Safety), determine their own acceptable risk criteria based on relevant regulations or by referring to international standards. For the unacceptable risks identified through the analysis, enterprises should promptly formulate and implement measures to eliminate, reduce, or control these risks, so as to keep them within an acceptable range. Document No. 25 Su Ying Ji [2019] 53: Notice from the Provincial Emergency Management Department on the Issuance of the “Basic Requirements for Inherent Safety Diagnosis and Management”. Issued by the Office of the Jiangsu Provincial Emergency Management Department on June 6, 2019. Requirements regarding installation and interlocking: I. The diagnosis of major hazards shall be carried out in accordance with the “Standards for Identifying Major Safety Hazards in Chemical and Hazardous Chemicals Production and Operation Units (Trial)” (An Jian Zong Guan San [2017] No. 121); major hazards must be identified accurately, without any omissions or misjudgments. 5. In accordance with the “Notice of the **General Administration of Work Safety on Publishing the List of Key Hazardous Chemical Processes Subject to Strict Supervision” (An Jian Zong Guan San [2009] No. 116), the “Notice of the **General Administration of Work Safety on Publishing the List of Key Hazardous Chemical Processes Subject to Strict Supervision in the Second Batch and Making Adjustments to Some Typical Processes Among Those in the First Batch” (An Jian Zong Guan San [2013] No. 3), as well as standards such as GB/T50770, GB/T20438, and GB/T21109, and based on the recommendations arising from HAZOP analysis, a list is prepared to assess the compliance of the safety functions related to automatic control systems (including DCS, PLC, ESD, SIS) in production facilities that utilize key hazardous chemical processes under strict supervision; any non-compliance issues are listed separately. 6. In accordance with the requirements of documents such as the Interim Provisions on the Supervision and Management of Major Hazard Sources of Hazardous Chemicals (formerly Order No. 40 issued by the State Administration of Work Safety) and the Guiding Opinions of the State Administration of Work Safety on Strengthening the Management of Safety Instrumented Systems in the Chemical Industry (An Jian Zong Guan San [2014] No. 116), a list should be prepared to assess the compliance of safety functions such as automated control systems, safety instrumented systems, emergency shutdown systems, and emergency isolation devices in the production units (storage facilities) that constitute major hazard sources; any non-compliances should be listed separately. (1) Automatic control of raw material and product storage tanks as well as plant storage tanks: 1. Flammable liquid storage tanks, toxic liquid storage tanks, cryogenic storage tanks, and pressure vessels with a volume of 100 m3 or more shall be equipped with remote transmitters for continuous level measurement and local level indicators, as well as high-level alarms. Floating roof storage tanks and storage tanks equipped with extraction pumps shall also be fitted with low-level alarms ； Pressure vessels containing flammable and toxic media are equipped with high liquid level or high pressure interlocks to stop feeding. If the design plan or HAZOP analysis report requires the installation of an automatic interlock to shut down the pump and close the discharge valve at very low liquid levels, such requirements must be met. 2. For liquid raw material and product storage tanks containing 16 types of hazardous chemicals that are explosive by nature and with a volume of less than 100 m3, a high liquid level alarm should be installed. If the design plan or HAZOP analysis report specifies the need for a high-high liquid level alarm that triggers the interlock to shut off the feed valve, as well as a low-low liquid level alarm that triggers the interlock to stop the pump, these requirements must be met. 3. Storage tanks for liquids of toxicity grades I and II, storage tanks for flammable liquids of categories A B and A C with a capacity of 1000 m3 or more, and storage tanks for other flammable liquids with a capacity of 3000 m3 or more shall be equipped with high-level liquid level alarms and interlocked control valves to shut off the inlet pipes of the tanks. 4. Liquid storage tanks in hazardous chemical tank areas that constitute primary or secondary major hazard sources shall be equipped with high and low liquid level alarms, as well as high-high and low-low liquid level interlock systems to shut off the control valves of the inlet and outlet pipelines urgently. 5. Storage tanks for flammable or toxic liquids should be equipped with high liquid level alarms, as well as interlocks that shut off feeding when the liquid level reaches an extremely high level. The high-level tank of the unit should be equipped with an alarm for high liquid levels, and interlocks should be in place to shut off feeding when the level is too high; an overflow pipe should also be installed. Interlocks to stop the extraction pump or shut down the discharge system should be provided in case of low liquid levels. 7. Hazardous chemical storage areas that are classified as Class I or Class II major hazard sources and involve toxic gases, liquefied gases, or highly toxic liquids shall be equipped with an independent safety instrumented system. The sensing elements and actuating elements of each circuit should be installed independently, with the Safety Instrumented Level (SIL) being no lower than Level 2. 9. Flammable liquid and highly toxic liquid storage tanks equipped with high-level interlock functions shall be fitted with two types of level gauges or level switches based on different principles; the high-level interlock measuring instrument and the level gauge for the basic control circuit shall be installed separately. The liquid level measurement of the pressure storage tank should be equipped with a set of remote transmission instruments and local indication instruments; in addition, another set of liquid level measurement instruments or level switches dedicated to detecting extremely high or extremely low liquid levels and triggering interlocks to shut off the tank’s feed (discharge) valves should be provided. 14. Major hazard sources of Class 1 and Class 2 hazardous chemicals shall be equipped with an emergency shutdown system, and key facilities such as toxic gases, highly toxic liquids, and flammable gases within these major hazard sources shall be fitted with emergency isolation devices. The safety functions of the emergency shutdown (emergency isolation) system can be implemented either through basic process control (DCS or SCADA) systems or through Safety Instrumented Systems (SIS). For systems with a safety integrity level (SIL) of 1, the safety functions of their emergency shutdown systems can be implemented either through basic process control systems (DCS or SCADA) or through safety instrumented systems (SIS). For systems with a safety integrity level of 2 or higher, the emergency shutdown functions must be implemented through safety instrumented systems (SIS). Document No. 26 Guo Ban Fa [2016] 88: Notice from the General Office of the State Council on Issuing a Comprehensive Plan for the Safe Management of Hazardous Chemicals. Requirements regarding installation and interlocking: (1) The chemical process safety instrument system (SIS) includes 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 in the production plant or facility that could lead to a safety accident occurs, thereby safely stopping the production process or automatically bringing it into a predetermined safe state. It must possess high reliability (i.e., functional safety) as well as proper maintenance and management. 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. (11) Design and implement toxic, hazardous, and flammable gas detection and protection systems in strict accordance with relevant standards; to ensure their reliable operation, such systems should be independent of the basic process control system. (12) Starting from January 1, 2016, qualified chemical enterprises such as large-scale enterprises and those wholly owned by foreign investors that construct new chemical plants or hazardous chemicals storage facilities related to the \"two key areas and one major project\" must design safety instrument systems that comply with relevant standard requirements, in accordance with the provisions of these guiding principles. (13) Starting from January 1, 2018, all newly constructed chemical processing units and hazardous chemical storage facilities related to the \"two key areas and one major project\" must be designed with safety instrument 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. (14) Chemical enterprises and hazardous chemicals storage units that operate production facilities or plants classified as “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 these risk reduction requirements. (15) Enterprises shall, on the basis of assessment, formulate management plans for safety instrumented systems and regular inspection and testing plans. For safety instrument functions that do not meet the requirements, relevant maintenance plans and corrective action plans must be developed, with the assessment and improvement of the safety instrument system to be completed by the end of 2019. Other chemical processing units and hazardous chemical storage facilities shall be implemented in accordance with the requirements of these guidelines. 27 General Administration of Work Safety Document No. 3 [2015] 113 **Notice from the General Administration of Work Safety on the Issuance of the “Key Guidelines for Safety Inspections in Chemical (Hazardous Chemicals) Enterprises” – Requirements regarding installation and interlocking: Equipment and facility management 19. Oil and gas storage tanks that do not meet the following requirements: (1) Storage tanks for liquefied hydrocarbons shall be equipped with level gauges, thermometers, pressure gauges, safety valves, as well as measures for detecting high liquid levels and for automatically shutting off feed when such levels become too high ； Fully cryogenic liquefied hydrocarbon storage tanks should also be equipped with vacuum relief facilities and high/low temperature monitoring, and should be connected to an automatic control system ； (2) The gas holder shall be equipped with upper and lower limit alarm devices, and it is advisable to have automatic interlock cut-off devices for the inlet and outlet pipes ； (3) Emergency shut-off valves should be installed at the liquid inlet and outlet of the spherical LPG storage tank, and their location should be as close as possible to the spherical storage tank ； (4) Spherical storage tanks for propylene, propane, mixed C4, stripped C4, and liquefied petroleum gas shall be equipped with water injection facilities. Article 33 of the Work Safety Law ； Articles 6.3.11 and 6.3.12 of the Code for Fire Protection Design of Petrochemical Enterprises (GB50160) ； Articles 6.1 and 7.4 of the «Code for Safe Design of Spherical Storage Tanks for Liquefied Hydrocarbons» (SH3136) ； 20. Automated control systems are not installed in facilities involving hazardous chemical processes or chemicals that are subject to strict supervision ； Or large chemical plants that involve hazardous chemical processes and do not have an emergency shutdown system in place. Article 9 of the **Implementation Measures for Safety Production Licenses of Hazardous Chemicals Production Enterprises** (Order No. 41 of the State Administration for Work Safety). 25. Production facilities for hazardous chemical processes involving exothermic reactions that do not have a dual power supply, or whose control systems lack an uninterruptible power supply (UPS). Article 38 of the Work Safety Law, the Technical Specifications for Electrical Design of Production Units in Petrochemical Enterprises (SH3038), and the Design Code for Power Supply and Distribution Systems (GB50052). Safety Management 28. The control room or cabinet room shall have doors and windows on the side facing devices with fire and explosion hazards. (Must be rectified by 2017) ； Article 38 of the Law on Work Safety, and Article 5.2.18 of the Code for Fire Protection Design of Petrochemical Enterprises (GB50160). 28API STD 2510-2011 Design and Construction of LPG Installations – Requirements for installation and interlocks: 9.3.4 Emergency Shutoff Valves 9.3.4.1 Emergency shutoff valves shall be provided in the loading-unloading systems for tank cars, trucks, and marine facilities, and they shall incorporate the following means of closure: a. Manual shutdown at the point of installation; b. Manual activation from a location that is accessible in an emergency. A safety analysis shall be conducted to determine whether automatic shutdown in the event of an LPG release or automatic shutdown through thermal activation is necessary. 9.3.4.2 The installation practices for emergency shutoff valves shall comply with those specified in 9.3.4.2.1 and 9.3.4.2.2. 9.3.4.2.1 When hoses or swivel piping are used for transferring liquids or vapors, an emergency shutoff valve shall be installed in the piping of the transfer system, within 20 linear feet of the end to which the hose or swivel piping is connected. If the flow is in only one direction, a check valve may be used in place of an emergency shutoff valve, provided that the check valve is installed in a dedicated storage vessel’s inlet line or vapor return line. When two or more hoses or swivel piping arrangements are used, either an emergency shutoff valve or a check valve (only for unloading lines) shall be installed in each section of the piping. Note: If check valves are used in place of emergency shutoff valves, the owner/operator must have a system in place to ensure the reliability of these devices. 9.3.4.2.2 Emergency shutoff valves or backflow check valves shall be installed in such a way that any break in the piping occurs on the side of the connection where the hose or swivel piping is located, while the valves and piping on the plant side of the connection remain intact. This can be achieved by using concrete bulkheads or equivalent anchoring methods, or by incorporating weak points or shear connections. Refer to NPGA Bulletin 128. 29API RP 2001-2012 Fire Protection in Refineries – Requirements for installation and interlocks: 5.4.3.4 Isolation Valves 5.4.3.4.1 General A key consideration for isolation valves is the ability to isolate certain sections of a process system, thereby minimizing the amount of hydrocarbons that can be released and preventing additional materials from entering from other areas. Isolation valves should be installed at the boundaries between units or within process unit areas, so that equipment can be isolated in case of a fire. Attention should also be paid to ensuring safe access and the ability to manually operate these valves during fires or emergencies. Whenever possible, battery-powered valves should be placed far enough away from areas where fire hazards exist, so that they can still be operated manually safely. If they are located in fire hazard areas, they may need to be capable of remote operation. Isolation valves can also be used to allow for blocking off equipment for maintenance and inspection. During such operations, valves suitable for the pressure levels involved should be used. Isolation valves and drains should be provided for equipment that may need to be accessed or removed during repairs. Refer to API 553. 5.4.3.4.2 Remote-Operated Valves If it is determined through a risk assessment that remote-operated shutoff valves are necessary, they should be considered as part of the PHA and FHA processes. The use of these and other isolation valves should be included in emergency procedures. However, automatic (fire- or heat-activated) self-closing valves should only be used after a hazard analysis or MOC review has been conducted to determine whether their accidental activation could lead to undesirable consequences. Such a review should confirm that the automatic valve system is inherently safe, as closing the valve in a non-fire situation or at the wrong time during a fire could result in unwanted outcomes, such as excessive pressure buildup in the process system or interference with the proper shutdown sequence of equipment or the transfer of products from tanks or vessels during an emergency. The review should also determine the safest option—whether to keep the valve “open” or “closed”—in the event of a power loss if remote-operated shutoff valves are used. Information on emergency valves (ROEIV, EIV, EBV, ROSOV) can be found in API 553 and UK HES Information Sheet CHIS2. 30API 553 -2012 Refinery Valves and Accessories for Control and Safety Instrumented Systems – Requirements for installation and interlocks: 3.9 Emergency Block Valves EBVs Emergency block valves are designed to help control hazardous situations. They serve as emergency isolation devices intended to prevent the uncontrolled release of flammable or toxic materials. If these valves are located within a fire zone, they must be fire-resistant. These valves are classified into types A, B, C, and D. Refer to the definitions of each type in this section. 3.14 Fire Zone This is an area that is unsafe to enter during an emergency. It is defined as an area within a radius of at least 7.6 meters (25 feet) around the source of the leak. 3.43 Type A EBV This is a manually operated, fire-resistant block valve that is installed directly on the equipment. This type of valve is used when ignition is not expected in the event of a leak. 3.44 Type B EBV This fire-resistant block valve should be installed at a distance of at least 7.6 meters (25 feet) from the source of the leak, especially when ignition is possible. It is manually operated and is available in sizes up to DN 200 (8 inches), with pressure ratings up to ANSI CL300. For ease of access, the valve should be reachable from the ground; if ground access isn’t possible, it should be accessible via a platform located no higher than 4.6 meters (15 feet) above the ground level. 3.45 Type C EBV This is a power-operated version of the Type B valve. It is used when the valve size exceeds DN 200 (8 inches) or when a higher pressure rating than ANSI CL300 is required. It should be installed outside the fire zone, at a distance of at least 7.6 meters (25 feet) from the leak source, and no higher than 4.6 meters (15 feet) above the ground level. Controls for this valve should be accessible from its location. 3.46 Type D EBV This is an EBV that includes remote control capabilities. There are no restrictions regarding where this valve can be installed, but the control devices must be at a distance of at least 12 meters (40 feet) from the leak source and must be located outside the fire zone. EBVs installed at elevations higher than 4.6 meters (15 feet) also fall under this category. Both the actuator and those parts of the control cables and tubing that are located within the fire zone must be fire-resistant or designed to function properly during a fire. It is necessary to specify that conduit, tubing, and cable supports must also be fire-resistant. References: Fan Wenjin, “Self-Controlled Systems | Requirements for the Installation and Interlocking of Level Gauges in Standards and Documents” ； Yan Changling, \"Standard Specifications for Installing Emergency Shut-off Valves in Tank Areas (Updated Version)\\" ； Author profile: Fan Yongfeng, male, graduated in 1993 from the Department of Electrical Engineering, Tongji University in Shanghai, majoring in Industrial Electrical Automation. He is currently working at Zhongke Synthetic Oil Engineering Co., Ltd. as Deputy Chief Engineer and Senior Engineer.