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): These devices are 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 equipment 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): These devices are primarily used to facilitate heat exchange between media, with heat being transferred through the walls of 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 different shapes of equipment used in factories, with three main types being common. 1. Square or rectangular equipment: These are made by welding flat plates together; 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 formed by welding several spherical segment plates together. The manufacturing process of ball valves differs from that of other equipment, with 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 specifications. 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 along with 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 based on the design pressure of equipment: Based on the nature of pressure they can withstand, equipment can be divided into two categories: internally pressurized equipment and externally pressurized equipment. A device is considered a pressure vessel when the pressure of the medium inside it is greater than the external pressure; otherwise, it is a non-pressure vessel. 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 temperatures and pressures. 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-metal equipment. Among metal materials, low-carbon steel and ordinary low-alloy steel are the most widely used at present. Most chemical and refining equipment comes into contact with media that are somewhat corrosive; therefore, the materials used must have excellent corrosion resistance. In situations where corrosion is severe or high requirements exist regarding product purity, stainless steel, stainless steel composite plates, or aluminum-based equipment are generally 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 requirements of the production process, there are also many devices made of 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 for classification: 1. Classification is carried out comprehensively based on pressure P, pressure times volume P*V (unit: Mpa.m3), medium properties, application purposes, 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 Hazards from Occupational Exposure to Toxic Substances\". ⑵ Highly hazardous (Level II). Its maximum allowable concentration (C) is 0.1 mg/m3 < C ≤ 1.0 mg/m3. Such as formaldehyde, formic acid, dinitrobenzene, etc. ⑶ Moderate hazard (Level III). Its maximum allowable concentration (C) is 1.0 mg/m3 < C ≤ 10 mg/m3. Such as acetic acid, sulfur dioxide, nitric acid, benzene, acetylene, and so on. 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, it is the responsibility of the process design team at the design unit, or the production technology department at the operating unit, to 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 procedures for assessing toxicity or the criteria for classifying flammable materials. Pressure vessels that fall into category three are: ultra-high pressure vessels ； High-pressure shell-and-tube waste heat boilers, storage and transportation vessels, separation vessels, heat exchange vessels, reaction vessels ； Reactors containing flammable or moderately hazardous media with a PV of 0.5 or greater at medium pressure, pressure vessels containing extremely or highly hazardous media, pressure vessels containing 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 Category 2 are: medium-pressure storage and transportation vessels, separation vessels, heat exchange vessels, and reaction vessels, excluding those in Category 3 ； Enameled pressure vessel ； 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 transport 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