On the safety design of chemical plants

You can take a look at the \"Code for Fire Protection Design of Petrochemical Enterprises GB50160-2008\"; it should be helpful to you

The design must be thorough, management must be effective, and the key is to have a strong sense of responsibility!

The design of safety accessories must be reasonable, and the appropriate types should be selected; this includes safety valves, venting systems, condensate removal facilities, level gauges, pressure gauges, temperature indicators, etc. Additionally, the relevant safety distances must also meet the required standards

It is very necessary to conduct a detailed safety analysis of the process.

Safe design of petrochemical plants: In view of the hazards present in petrochemical plants, this approach focuses on various aspects such as the selection of process routes and engineering design (including process system design, instrumentation and automatic control design, equipment design, plant layout design, piping design, civil engineering design, water supply and drainage design, ventilation design, and fire protection design) to ensure the safety of these plants, thereby emphasizing the importance of safe design. Petrochemical plants primarily use petroleum, natural gas, coal, and their derivatives as raw materials for processing, in order to produce various products for society. The raw materials and products of the facility are mostly flammable, explosive, and toxic substances, which means there is a potential risk of fire, explosion, and poisoning in the facility. According to the 1992 Houston Process Plant Safety Forum held by the American Institute of Chemical Engineers (AICHE), the frequency of fires in the hydrocarbon processing industry, as well as the economic losses resulting from such fires, have been on the rise over the past 30 years. Statistics also show that, among the nearly 100 major accidents in the global petrochemical industry over the past 30 years with losses exceeding 10,000×10³ US$, facilities accounted for nearly 60% of them. Incidents such as the Caprolactam plant fire in Fliborough, UK, in 1974, the explosion at the La Mede refinery in France in 1989, and the fire at the Milford Haven refinery in the UK in 1994 were all extremely shocking. This is not only due to the characteristics of petrochemical plants, such as more complex processes, harsher operating conditions, numerous constraints, and concentrated equipment, but also due to social, economic, and managerial factors, which can be summarized as follows: (1) An emphasis on economic scale, with factories (plants) becoming increasingly large ； (2) Reduced land for construction leads to crowded equipment layout and increased asset density ； (3) To eliminate bottlenecks, increase capacity and efficiency, save energy, and improve the environment, add equipment or facilities to the existing installations ； (4) Increased production workdays and long-term operation result in equipment that does not receive timely maintenance or replacement ； (5) A reduction in staff, with high turnover among operational managers. Furthermore, whether technology, equipment, and training are kept up to date is also one of the reasons. How to achieve design safety, how to identify various potential hazards in petrochemical processes, how to estimate deviations from process conditions, and how to take measures at the fundamental stage of project construction (design) to prevent problems before they occur, are all topics of widespread concern. A common practice abroad these days is to, in addition to emphasizing inherently safe design, implement Hazard and Operability Studies (HAZOP) as part of project design. These studies involve analyzing process deviations in order to systematically and qualitatively identify process hazards and potential consequences, thereby allowing for the implementation of appropriate measures. In project management, the (Health and Safety Executive) procedures are implemented to review and verify safety, health, and environmental protection aspects at various stages of the project. In addition, a safety assessment of the project can also be conducted at the owner’s request. At present, there is no complete set of safety analysis methods and management systems for the design of petrochemical plants in our country. Requirements related to safety, hygiene, and environmental protection are often scattered across various **regulations and standards at different levels, which makes implementation and management cumbersome. Moreover, many requirements related to safety, hygiene, and environmental protection in the design process are not covered by existing standards or cannot be incorporated into them. In project management, emphasis is placed only on the “preliminary” review, while the “post-implementation” phase is neglected, often resulting in half the effort yielding half the results. To ensure the safety of device design, it is first necessary to strictly and correctly implement **regulations and standard requirements (especially mandatory standards).** What else should designers do? Based on my own studies and experiences, I present this for discussion among colleagues in the field of petrochemical plant design and production safety. 1. Hazard factors of installations: There are many types of petrochemical installations, and due to differences in technical approaches, raw materials, products, and process conditions, the hazard factors vary. These can be summarized as follows: 1.1 Poisoning risk: During petrochemical production, workers may be exposed to toxic substances in the form of raw materials, finished products, semi-finished products, intermediates, reaction by-products, and impurities. Through the mouth, nose, and skin, these substances can cause pathological changes in the body’s physiological functions and normal structures. In mild cases, this can disrupt the body’s normal responses and reduce a person’s ability to make correct judgments and take appropriate actions during production; in severe cases, it can even lead to death. 1.2 Fire and explosion hazards: Mixtures of combustible gases, oil and gas, and dust with air, when their concentration reaches the explosive limit, can cause fires and explosions if ignited. The radiant heat from the fire and the shock waves generated by the explosion can cause damage to people, equipment, and buildings. In particular, explosions caused by steam clouds formed by large leaks of flammable gases or oil and gas are often devastating. There are many such examples, such as the explosion of the ethylene air separation unit at Fushun Petrochemical Company in 2001, the explosion of the high-pressure polyethylene unit at Beijing Yanshan Petrochemical in 2000, and the hydrogen explosion at the high-pressure hydrogenation unit of Daqing Petrochemical Company in 1967; the losses resulting from these incidents were extremely severe. 1.3 Reactive hazards Chemical reaction processes can be divided into endothermic and exothermic types. Generally, exothermic reactions are more dangerous than endothermic reactions, especially oxidation reactions that involve strong oxidizing agents ； Halogenation reaction involving the introduction of halogen atoms into organic molecules ； Nitration reaction involving the substitution of hydrogen atoms in compounds with nitro groups ； Once out of control, it can lead to serious consequences. Furthermore, some of the raw materials used in petrochemical processes are highly reactive, and even slight carelessness can pose a threat to safety. 1. 4 Negative pressure operation: Negative pressure operations can allow air and moisture to enter the system, either by forming explosive gas mixtures or by causing dangerous reactions in materials sensitive to oxygen and water, as a result of the oxygen and water vapor present in the air. Such as the vacuum tower system in the atmospheric and vacuum distillation units of oil refining. 1.5 High-temperature operation: Operating flammable liquids at temperatures above their flash point or boiling point can result in the formation of explosive vapor clouds in the event of a leak ； The operating temperature of flammable liquids is equal to or above their autoignition point; once they leak, they can ignite spontaneously or serve as a source of ignition ； A high-temperature surface is also a source of ignition; combustible liquids splashing onto it can cause a fire. For example, in 2001, the Maoming coking plant experienced a major fire and severe casualties due to the use of incorrect pipeline materials, which allowed high-temperature residue oil to leak out. 1.6 Low-temperature operation: Not designed for low-temperature conditions; the intrusion of low-temperature media causes low-temperature brittle failure of equipment and pipelines. Such as damage to the low-temperature equipment in air separation, and low-temperature brittle fracture at -195°C in the low-temperature methanol washing process of large-scale fertilizer slag gasification. 1.7 Corrosion Corrosion is a common factor that leads to the damage of equipment and pipelines, thereby causing fires. The importance of a material’s corrosion resistance, in terms of optimizing its performance, is second only to its mechanical properties. Its corrosion resistance is often determined through experience and testing, as there are no established standards for this purpose (however, there are existing standards for selecting materials for units used in Sinopec’s processing of high-sulfur oil). Furthermore, the diversity of corrosion types and the influence of ever-changing environmental conditions add an element of unpredictability to the risk of corrosion. For example: fires in the oil drills at Tianjin Petrochemical, corrosion caused by high-temperature sulfur, and corrosion caused by low-temperature sulfur. 1.8 Leakage Leakage is an important pathway for hazardous substances within equipment pipelines to be released into the atmosphere. The static and dynamic seals of equipment pipelines fail; in particular, periodic changes in temperature and pressure, as well as the presence of corrosive media, can easily lead to seal failure. Weak points in the equipment pipelines, such as bellows expansion joints, glass level gauges, and failures in the dynamic seals of moving equipment, can lead to serious accidents once they are damaged. The major fire caused by a mechanical seal leak in the hydrogenation unit of Zhenhai Refining & Chemical Company. Incidents such as pipeline leaks of high-temperature and high-pressure threaded locking rings in hydrocracking units in 1996. 1.9 Open flames: An arc or spark 0.5 mm long is sufficient to ignite hydrogen. The open-flame heating equipment (heating furnaces) in the device, as well as high-temperature surfaces, and any possible arcs, static sparks, sparks generated by impact or friction, and flying embers from chimneys, all have sufficient energy to ignite explosive mixtures. For example, during the construction of the new power plant at Zhenhai Refining & Chemical Company in 2001, a fire broke out in the turbine building. 2. Safety considerations in the selection of the process route. The safety of the process method is the foundation for the safety of plant design; therefore, during the project initiation and feasibility study phases, due attention should be paid to the safety aspects of the process route. 2.1 Try to use materials with low risk. To obtain a certain end product, the raw materials or auxiliary materials are not always unique. Where possible, materials that are free from danger or have low risk should be given priority. 2.2 Try to ease the severity of process conditions. The severity of process conditions can also be changed. For example, catalysts or better catalysts can be used, as well as dilution and the use of gas-phase feed instead of liquid-phase feed, in order to reduce the intensity of the reaction. 2.3 Simplify to avoid interference and ensure intrinsic safety: The probability of process accidents is related to the factors that influence them; the more parameters there are, the greater the interference. In cases where a single device performs multiple functions, can multiple devices be used, each handling one function, in order to improve production reliability? Improve the reliability and intrinsically safe level of equipment, automation, and electrical systems. 2.4 Minimize the amount of hazardous materials stored. The greater the quantity of hazardous materials stored, the greater the losses and impact in the event of an accident. For example, using membrane distillation in place of distillation columns, continuous reactions instead of batch reactions, flash drying instead of tray dryers, and centrifugal extraction instead of extraction columns. 2.5 Reducing production waste: Whether raw materials, additives, solvents, carriers, catalysts, etc. used in the process are necessary, and whether their use can be reduced ； Can it be recycled and reused? ； It is possible to make comprehensive use of waste, carry out harmless treatment of it, reduce production waste, make the most of available resources, and minimize environmental pollution. 3. Safety in engineering design – Process system design. The task of ensuring safety in process system design is to effectively control hazardous materials and the entire production process. 3.1.1 Description of material hazards: The hazards associated with a material can usually be described using its Safety Data Sheet. The key information includes the following: general fire hazard characteristics such as flash point, ignition temperature, explosion limits, relative density, boiling point, melting point, and water solubility. Classification of fire hazard (see GB50160/GBJ16); health hazards: maximum allowable concentrations of harmful substances in the workplace (see TJ36), acute toxicity (LC50 or LD50) and onset conditions, chronic poisoning conditions and consequences, carcinogenicity. Classification of toxicity hazard levels (see GB5044). Reactivity hazards: stability under environmental conditions, intensity of reaction with water, sensitivity to heat or mechanical shock. Reactivity hazard class (refer to NPPA704) – storage and transportation requirements. Methods for extinguishing accidents, emergency measures. 3.1.2 Process Conditions The essence of a normal production process is the relative balance of various process parameters. If any parameter changes outside its specified range, the balance is disrupted, which can lead to accidents. How to control and adjust process conditions, and what emergency measures to take in case of loss of control in order to minimize and avoid losses. Various reactions, including the main reactions and side reactions, as well as possible harmful reactions and measures to prevent their occurrence. Optimization software is used to control and adjust the production process. 3.1.3 Coordination between combined operation units: Petrochemical plants are essentially combinations of various process operation units. How to achieve secure connection between units and avoid mutual interference ； When a certain unit encounters an accident or failure, how to isolate it, how the other units should continue to operate, and how to achieve a smooth shutdown. A combined unit is a combination of several original conceptual units, resulting in a relatively higher asset density; it is particularly important to ensure proper coordination in the design of the process system. 3.1.4 Sealing and sealing systems Production systems that continuously emit flammable, toxic gases, dusts, or acid mists should be designed to be sealed, and mist and dust removal or absorption facilities should be installed. For low-boiling flammable liquids, toxic liquids, or those that can undergo oxidation, decomposition, autopolymerization, or deterioration in reaction with oxygen and water in the air, inert gas sealing should be employed, along with anti-corrosion measures. 3.1.5 Reducing the entry of hazardous materials into the fire scene: While ensuring stable production, minimize the residence time of materials within the equipment, and use distillation equipment with a small liquid storage capacity. Emergency isolation valves should be considered for the bottom of large-scale equipment, high-displacement pumps, the inlets of pumps operating at high temperatures (≥ flash point, ≥ auto-ignition temperature), the inlets of liquefied hydrocarbon pumps with a discharge rate greater than 8 m³/h, and the outlets of liquefied hydrocarbon tanks, in order to cut off flow in case of an accident and thereby reduce the amount of material that could leak out. The best way to extinguish a gas fire is to cut off the gas supply. Therefore, accident isolation valves should be installed on the combustible gas pipes at the boundary of the gas processing unit. 3.1.6 Overpressure protection of equipment: Both GB150 and the (Safety Technical Regulations for Pressure Vessels) require pressure vessels to be equipped with overpressure protection ； Positive displacement pumps and equipment requiring overpressure protection must be equipped with safety pressure relief devices. When medium corrosion, coking, and blockages cause the safety valve to fail, it is advisable to use a combination of safety valve rupture discs, or to implement steam shielding and steam (or electric) heating. For equipment subject to sudden overpressure or rapid increases in pressure due to heating, automatic pressure relief systems or combinations of detonating tubes and rupture disks should also be installed. 3.1.7 Pressure relief and venting: The pressure relief from the safety valves of flammable media should be directed to the flare system; since the released gases contain liquids, a liquid separation tank should be installed in the facility ； The flare header should be capable of handling the maximum discharge volume from any single incident. Accidents in the emissions from the vent flares of petrochemical plants. The venting of liquefied hydrocarbon equipment and pipelines should go into the flare system. The release of toxic and corrosive substances must be treated in a harmless manner. The drainage from equipment and pipelines should be collected in a sealed manner. 3.1.8 Purging and displacement: Purging and displacing the equipment and pipelines within the unit during start-up, shutdown, and maintenance operations creates conditions for safe start-up, shutdown, and repairs. Incomplete purging, an imperfect purging system, or unsuitable purging media can create conditions for fires. The fixed purge system should have measures to prevent the backflow of hazardous media. 3.1.9 Isolation from the system: Shut-off valves should be installed at the boundaries for the hazardous materials entering and leaving the device, and \"8\"-shaped blind plates should be placed on the device side to prevent mutual interference in the event of a fire or maintenance work on the device. For equipment handling flammable and toxic media, when it is necessary to shut down the unit during operation for maintenance and cleaning, double valves or valves equipped with blind plates should be installed. 3.1.10 Utility Supply: In the event of a water supply interruption, the cooling system shall be able to maintain normal cooling for more than 10 minutes. For other items such as fuel and instrument air, accident supply sources or emergency reserves should be considered. 3.1.11 Handling of extreme operating conditions: Fires and other accidents can easily occur during the startup, shutdown, or emergency shutdown of the equipment. The process system should not only provide normal operating procedures but also outline procedures for starting up and shutting down, as well as steps to take in cases of water or power outages, ensuring that the entire production process proceeds in an orderly manner. Such as the accident response plans for large petrochemical facilities. 3.2 Instrumentation and Automatic Control Design: Instruments serve as the operator’s eyes, while the automatic control system acts as the hub for regulating and controlling the equipment. 3.2.1 The power system shall be equipped with emergency power and gas supplies to ensure sufficient time for dealing with accidents. 3.2.2 Selection of instruments and controllers should be fail-safe to ensure that the production system remains safe in the event of a failure. After automatic stop, the instrument circuit should be prevented from automatically returning to normal operation without confirmation and reset. Avoid using multi-functional instruments that may lead to misjudgments. 3.2.3 Interlocking and shutdown systems: For critical operational stages, alarm, interlocking, and emergency shutdown systems should be installed. (ESD) When an emergency stop could have a significant impact on production, the signal system should be equipped with a 3-out-of-2 voting system. When control system failures could lead to serious accidents, a n:1 or even 1:1 redundant control system should be installed. During production operation, the instruments and shutdown circuits should be capable of being detected. 3.2.4 Field Instruments: Instruments, analytical instruments, and controllers located in explosive hazard areas shall be equipped with appropriate explosion-proof designs or positive pressure ventilation systems. 3.2.5 In-depth monitoring of harmful gases: Monitoring and alarm systems should be installed in areas where harmful gases or vapors are released. 3.2.6 Instrument cables: In areas at risk of fire and explosion, instrument cables should be made of non-flammable materials or flame-retardant materials. 3.3 Equipment Design Process equipment is the core element for carrying out a process; all individual operational steps are carried out through specific equipment. Therefore, the reliability of this equipment is crucial for the safe operation of the facility. The main aspects of equipment design include manufacturing materials, mechanical design, manufacturing processes, and process control systems. 3.3.1 Material selection: It is necessary to be familiar with the manufacturing process, external environment, failure modes, and material processing properties. Corrosion is a significant factor leading to equipment failure and fires; therefore, corrosion-resistant materials and appropriate corrosion margins should be selected carefully. 3.3.2 Mechanical design shall be able to meet the stress requirements imposed on the equipment under severe temperature and pressure conditions. Pay special attention to the vibration loads generated by the power units on the container, as well as the alternating loads resulting from periodic changes in temperature and pressure. Stress analysis of high-temperature and high-pressure hot-wall reactors. The piping for large reciprocating compressors follows API618. Section 3.3) specifies the acoustic simulation calculation and analysis of pressure pulsations, as well as the use of fault diagnosis techniques. 3.3.3 In equipment manufacturing design, it is most important to assess the quality control procedures for equipment materials and the quality procedures for the manufacturing process, in order to verify that the manufacturing meets the design requirements. The following safety issues should be considered in the design. (1) Pressure vessels shall strictly comply with the \"Regulations on Safety Supervision of Pressure Vessels\", and ventilation facilities for vessel cleaning shall be installed ； Install erosion and anti-static protection facilities ； The internal components should prevent the accumulation of liquid ； Dead zones in the flow within the container should be avoided ； Vertical container support structures shall be provided with fire protection. (2) Rotating equipment: Rotating equipment used to handle flammable and toxic media should employ double-end sealing or a sealing system with better performance ； Cast iron materials and components that can react with the medium (and/or lubricant) must not be used ； The inlets of each stage of the compressor should be equipped with liquid separation facilities ； Large pumps and compressors should be equipped with vibration suppression devices. Advanced dry gas seal technology and floating ring seal technology are employed. (3) Open-flame equipment: The furnace chamber shall have air, nitrogen, or steam purging ports ； Gas stoves should be equipped with a pilot light ； Large open-flame heating equipment should be equipped with flame monitors. 3.4 Electrical Design: Electricity is the primary power source for equipment production, and a continuous and reliable power supply is an essential guarantee for the safe operation of such equipment. (1) For critical continuous production processes, dual power supply should be used ； (2) Critical equipment that could lead to explosions, fires, poisoning, and casualties in the event of a sudden power outage must be equipped with a backup power supply. (3) When starting high-power motors, it is necessary to ensure that the starting current does not exceed the peak current allowed by the power supply system, or soft-start devices should be used. (Voltage conversion technology). (4) The structure, classification, and grouping of electrical equipment in explosive hazardous environments shall comply with GB50058. (5) Cables and cable assemblies installed overhead in fire-hazardous environments shall be of flame-retardant type. (6) Buildings and equipment shall have possible lightning protection and grounding measures ； Equipment and pipelines that may generate static electricity should have measures to prevent the accumulation of static charge. (7) Safety facilities such as fire alarms, emergency lighting, and evacuation lighting should be equipped with a backup power supply. 3.5 Equipment Layout Design The equipment layout includes the arrangement of devices, structures, and passages, ensuring the smooth progress of processes, compliance with safety spacing requirements, facilitating operation, maintenance, and firefighting tasks, as well as enabling easy evacuation of personnel. 3.5.1 Equipment layout shall meet the requirements of the process regarding equipment arrangement (such as pump filling heads, elevation differences between equipment rooms) ； The fire separation distances between equipment rooms, as well as between equipment and buildings, shall comply with the provisions of GB50160 ； Continuous ignition sources (open-flame heating equipment) and hazardous release sources should be avoided from being placed in close proximity to each other ； High-risk equipment and ordinary-risk equipment should be arranged separately as much as possible ； The equipment should be arranged in an open or semi-open area as much as possible, in order to minimize the size of the area at risk of explosion ； Unless required by the process, when the equipment is arranged in multiple layers, it should not exceed three layers ； Air coolers are generally not installed above equipment whose operating temperature is equal to or greater than the auto-ignition temperature of the medium ； Safety spray and eye wash stations should be installed near medium and equipment that may cause accidental injury to humans. Such as methanol plants. 3.5.2 Layout of buildings and structures Buildings that may generate sparks or use open flames (such as control rooms, power distribution rooms, laboratories and maintenance areas, office buildings) should be located in non-explosive hazard areas; if they are within Zone 2, they should be raised 0.6 m above the outdoor ground level ； The vertical arrangement of the facility should facilitate the discharge of leaks and fire-fighting fluids, thereby reducing their residence time in the facility area. Such as the explosion-proof facilities in foreign control rooms. 3.5.3 Channel setup: An annular channel should be provided around the device ； The fire access routes of the facility shall run through the facility area, with no fewer than two intersections connecting to the surrounding roads ； The areas separated by roads for the installation should ensure that there are no dead corners in firefighting operations ； The distance between the equipment joint platform and the adjacent evacuation passage of the framework should not exceed 50 m. 3.6 Pipeline Design Pipeline design consists of three parts: pipeline layout, pipeline fittings, and pipeline machinery. Poor design and mistakes can pose risks to safe production and even lead to disasters. 3.6.1 Pipe layout: Except for the necessary flange connections, welding should be used as much as possible for pipe connections ； Small-diameter branch pipes on the pipeline should be connected to the main pipe using reinforced pipe fittings ； Pipelines transporting liquefied hydrocarbons or corrosive media on pipe bridges should be arranged in the lower layer ； Oxygen pipelines should be arranged away from oil pipelines. For pipes carrying hazardous media that cross roads, in addition to the required clear height, no valves, flanges, or bellows shall be installed above them ； Various valves used for handling accidents, such as emergency venting, accident isolation, fire suppression steam, and fire suppression risers, should be installed in safe, visible locations that are easy to access. 3.6.2 Pipeline Equipment The pipeline equipment selected shall be capable of withstanding the forces generated under the most severe temperature and pressure conditions during operation ； The use of piping fittings shall not exceed the limits permitted by the specifications, and materials not allowed under those specifications must not be used ； For pipelines carrying corrosive media, careful selection of corrosion-resistant materials and appropriate corrosion margins is necessary ； For the connection of pipes of different grades, flange connections should be used as much as possible to avoid welding of dissimilar steels ； For pipelines carrying hazardous media, it is advisable to avoid using bellows expansion joints in order to ensure the flexibility of the pipelines ； For valves used in pipelines carrying highly toxic and liquefied hydrocarbons, valves with threaded valve caps must not be used; high-pressure valves should employ a pressure-sealing structure or an even better sealing mechanism. When a soft seal is used for the accident isolation valve, it should be fire-resistant ； The pipeline sealing (flange temperature and pressure rating, pipe connection type, sealing surface type, gasket material and structure type, bolt and nut materials) should be selected appropriately ； The adoption of new equipment should be subject to evaluation by **or industry-approved technical authorities. 3.6.3 Piping machinery must ensure that the piping has sufficient flexibility under design conditions. Especially for pipes connecting high-temperature, thick-walled, large-diameter pipes to sensitive equipment such as pumps, compressors, turbines, air coolers, etc., the forces and moments acting on the equipment outlets must meet the requirements of the equipment manufacturer ； In addition to considering flexibility, the connections of reciprocating compressors should also undergo pulse vibration analysis ； When two or more devices operate as backups for one another or are switched between each other, the effects of stress analysis and vibration analysis under different operating conditions must be taken into account ； Cold tightening can reduce the force exerted by the pipes on the fixing points of the equipment during operation, but pipes connecting rotating equipment must not be tightened in this way ； The pipe support structure should be reliable and reasonable. Vibrating pipeline supports should not be anchored to the plant building or equipment. For two-phase flow pipelines and other pipelines subject to impact loads, the supports should take the effect of impact forces into account ； The openings in the pipes should be reinforced. 3.7 Civil engineering design: The fire resistance ratings of control rooms, power distribution rooms, and production buildings shall meet the requirements of GBJ16. The control room, facing the side of the equipment containing hazardous materials, should be a solid wall made of non-combustible material without any doors or windows ； For Class A and B factories with explosion hazards, lightweight structures should be used, and the pressure relief area must meet the requirements of GBJ16 ； The safe evacuation routes for buildings and frameworks shall comply with the regulations ； When flammable liquid equipment is installed in multi-story buildings, facilities should be in place to prevent such liquids from leaking to the lower floors ； For large power foundations, vibration isolation measures should be adopted to consider the impact on the plant building ； Load-bearing steel structures and prestressed reinforced concrete structures in fire hazard areas shall be provided with fire protection, and their fire resistance rating shall not be less than 1.5 hours ； In earthquake-prone areas, building design must also comply with the requirements of seismic codes ； When the foundation of a low-temperature cold storage tank comes into contact with the soil, measures should be taken to prevent the 0°C temperature line from passing through the soil layer. 3.8 Water supply and drainage design: Sewage systems in production facilities are particularly prone to fires. Plant-wide production wastewater shall not pass through the process unit boundaries ； The combustible liquid separation tank for production wastewater in the plant equipment area must be equipped with a cover made of non-combustible material ； The manhole covers for wastewater from Class A and Class B facilities must be sealed. 3.9 Ventilation design: Factories that emit harmful gases or vapors must be equipped with ventilation systems, and the number of air exchanges per hour should meet the requirements specified in TJ36 regarding the maximum allowable levels of harmful substances in workshop air ； The intake openings for mechanical ventilation must ensure that the concentration of harmful gases or dust in the air being exhausted does not exceed 30% of the maximum allowable level of such substances in the workshop air ； Facilities where a large amount of harmful gases or vapors may be generated suddenly should be equipped with an emergency ventilation system. 3.10 Fire protection design: The main elements of the fire protection design for facilities are various fixed installations; however, the roads surrounding these facilities, as well as the fire access routes and fire hydrants along the roads, will facilitate the entry and exit of fire trucks and the retrieval of water ； The fire protection water pipes of the facility should be arranged in a circular pattern; there should be no fewer than two inlet pipes, and the circular piping system should also be divided into several pipe sections using valves. Large-scale equipment installations should be protected by high-pressure water cannons. When the framework platform for Class A and Class B equipment is higher than 15 cm, a vertical fire supply pipe must be installed. Equipment that is prone to serious accidents if it cannot be cooled in a timely manner after catching fire should be equipped with a water spray or water mist system. In pump rooms for flammable liquids and compressor rooms for Class A gases, when their volume is less than 500 cubic meters, fixed sieve-tube steam fire extinguishing systems shall be installed. Fixed steam fire extinguishing systems shall be installed in the furnace chamber of the heating furnace and in the elbow boxes with plugs. The flange connections of equipment whose operating temperature is equal to or greater than the auto-ignition point of the medium shall be protected by annular steam strainer tubes. Dry powder or foam fire extinguishers should be installed in the equipment production area, while gas fire extinguishers should be available in the control room. Fire alarm buttons should be installed around Class A and Class B plant areas. Alarm panels for temperature, smoke, flame, etc. are installed in the control room, which should also be equipped with a dedicated telephone for fire alarms ； When the plant control room is built together with other buildings, a separate fire compartment shall be provided, along with an automatic fire alarm system.

You can find out by looking at the citation guidelines in the safety assessment report or the special section on safety facility design.