Classification of petrochemical static equipment

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Classification of petrochemical static equipment. Petrochemical static equipment (also known as stationary equipment, chemical equipment, process equipment, non-customized equipment, or non-standard equipment) is simply referred to as “static equipment”. Containers used in petrochemical production for heat transfer, storage, and chemical reactions. Due to the various requirements of the production process, there is a wide range of equipment with different shapes. To understand their common characteristics and patterns, they are scientifically classified according to certain principles. I. Classification by the principle of operation of the equipment in the production process 1. Reaction equipment (code R): This type of equipment is primarily used as containers for carrying out physical and chemical reactions of the medium. Most devices carry out the process reactions under conditions of heating and pressure in the presence of a catalyst ； Or devices in which, with direct contact between the media, physical heat exchange processes and chemical reaction processes occur. Such as reaction kettles, reactors, decomposition pots, decomposition towers, polymerization kettles, autoclaves, synthesis towers, shift converters, cooking pots, gas generators, etc. 2. Heat exchange equipment (code E): This type of equipment is primarily used to facilitate the heat exchange between media; heat is conducted through the walls of the equipment containing the media. There are heat exchange equipment such as plate-type, tube-type, shell-and-tube type, and spray-type. Such as heat exchangers, coolers, evaporators, heaters, vulcanization kettles, disinfection kettles, dyeing machines, drying cylinders, preheating kettles, steam boilers, electric steam generators, etc. 3. Separation equipment (code S): Separation equipment is primarily used as containers for achieving fluid pressure balance in media and for gas purification, as well as for other material separation processes. Such as separators, filters, oil collectors, buffers, washers, absorbers, copper washing towers, drying towers, stripping towers, steam drum deaerators, etc. 4. Storage equipment (code C, where the spherical tank is coded as B): These devices are primarily used for storing raw materials such as gases, liquids, and liquefied gases that are used in production. Such as various types of storage tanks (spherical tanks, gas holders, etc.). II. Classification by equipment shape: There are many shapes of equipment used in factories, and the common ones fall into three main types. 1. Square or rectangular equipment: These are made by welding flat plates; they are simple to manufacture, but have poor pressure resistance, so they are only used for small storage tanks at atmospheric pressure. 2. Spherical equipment: It is assembled by welding several spherical segment plates together. The manufacturing process of spherical segments differs from that of other equipment and has certain special technical requirements. Spherical equipment has a large volume, can hold a large amount of material, operates under high pressure, and requires stringent technical standards. With the development of the petrochemical industry, there is a greater need for tanks to store liquid or gaseous materials. Therefore, spherical devices have seen increasingly widespread use in recent years. 3. Cylindrical equipment: These are vertical or horizontal containers composed of a cylindrical shell and various types of shaped end caps (elliptical, hemispherical, butterfly, conical). Due to different usage purposes, their internal structures vary. Devices of this shape are easy to manufacture and have good pressure resistance, which is why they are the most widely used. III. Classification by the design pressure of the equipment: Based on the nature of the pressure to which the equipment is subjected, it can be divided into two categories: equipment under internal pressure and equipment under external pressure. When the pressure of the medium inside a device is greater than the external pressure, it is referred to as a internally pressurized device; otherwise, it is an externally pressurized device. Classified by the design pressure of the equipment: 1. Ultra-high pressure equipment: P≥100 MPa; 2. High pressure equipment: 10≤P＜100 MPa; 3. Medium pressure equipment: 1.6≤P＜10 MPa; 4. Low pressure equipment: 0.1≤P＜1.6 MPa; 5. Atmospheric pressure equipment: P＜0.1 MPa; 6. Vacuum equipment: Negative pressure. In petrochemical plants, many devices operate under high temperature and high pressure conditions. For example, the operating pressure in ammonia and urea synthesis plants can reach 38.8 MPa, with temperatures around 430°C. There are also low-temperature and low-pressure equipment in petrochemical plants. Polyethylene production requires ultra-high pressure equipment with pressures of 100–300 Mpa, and such equipment must be manufactured from monolithic high-strength forgings. IV. Classification by equipment structural materials: The materials used in manufacturing equipment must meet the requirements of both the operating conditions and the manufacturing processes. They are generally divided into two main categories: metal equipment and non-metallic equipment. Among metal materials, low-carbon steel and ordinary low-alloy steel are the most widely used at present. Most chemical and petroleum refining equipment comes into contact with moderately corrosive media; thus, the materials used must exhibit excellent corrosion resistance. Consequently, in situations where corrosion is severe or where strict product purity requirements apply, stainless steel, stainless-clad steel plates, or aluminum equipment are typically employed. Under low-temperature and deep-freezing operating conditions, aluminum, aluminum alloys, or copper and copper alloys are generally used for equipment. There are also devices made of cast iron. Depending on the needs of the production process, there are also many pieces of equipment made from non-metallic materials. Non-metallic materials can be used as equipment linings or as separate components. Commonly used non-metallic materials include polyvinyl chloride, fiberglass-reinforced plastic, stainless graphite chemical enamel, acid-resistant bricks, rubber linings, and so on. V. Classification by supervision and management: In order to strengthen the technical management and supervision of pressure vessels, these vessels are divided into three categories in accordance with the **Ministry of Labor’s ‘Regulations on Technical Supervision of Pressure Vessels’**. Principles of classification: 1. Classification is carried out comprehensively based on pressure P, pressure multiplied by volume P*V (unit: MPa·m³), medium characteristics, application, as well as design and manufacturing features ； 2. The toxicity level of the medium is classified into four grades in accordance with the provisions of GB5044 “Classification of the Hazard Levels of Toxic Substances in Occupational Exposure”. ⑵ Highly hazardous (Level II). Its maximum permissible concentration (C) is 0.1 mg/m³ < C ≤ 1.0 mg/m³. Such as formaldehyde, formic acid, dinitrobenzene, etc. ⑶ Moderate hazard (Grade III). Its maximum permissible concentration (C) is 1.0 mg/m3 < C ≤ 10 mg/m3. For example, acetic acid, sulfur dioxide, nitric acid, benzene, acetylene, etc. ⑷ Minor hazard (Level IV). Its maximum allowable concentration (C) is C > 10 mg/m3. Flammable and explosive media. Flammable media, also known as explosive hazard media, refer to those whose gas or liquid vapors and mists, when mixed with air, form explosive mixtures, and whose lower explosion limit is less than 10%, or whose difference between the upper and lower explosion limits is at least 20%. For example, the lower explosion limit of hydrogen is 4%, and the upper limit is 74.2% ； The lower explosive limit of ethanol is 3.28%, and the upper explosive limit is 18.95%. 3. When the medium in a pressure vessel is a mixture, the process design team of the design unit, or the production technology department of the operating unit, shall determine whether the toxicity level of the medium constitutes that of a flammable medium, based on the composition of the medium and in accordance with the toxicity assessment procedures or the classification criteria for flammable media. Pressure vessels that fall into category three are: ultra-high pressure vessels ； High-pressure shell-and-tube waste heat boilers, storage and transport containers, separation containers, heat exchange containers, reaction containers ； Reactors for flammable or moderately hazardous media with a medium pressure PV of 0.5 or greater, pressure vessels for extremely or highly hazardous media, pressure vessels for flammable or moderately hazardous media with a PV of 10 or greater, and shell-and-tube waste heat boilers. Pressure vessels for extremely or highly hazardous media with a low pressure PV of 0.2 or greater. Pressure vessels belonging to the second category are: medium-pressure storage and transportation vessels, separation vessels, heat exchange vessels, and reaction vessels other than those in the third category ； Enameled steel pressure vessels ； Low-pressure shell-and-tube waste heat boilers, storage vessels for flammable or moderately hazardous media, reactors for flammable or moderately hazardous media. Pressure vessels belonging to the first category include low-pressure storage and transportation vessels, separation vessels, heat exchange vessels, and reaction vessels, excluding those of the second and third categories. VI. Classification by equipment weight (G) category: 1. Small equipment: G≤40t; 2. Medium-sized equipment: 40t＜G≤80t; 3. Large equipment: G＞80t