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I. Process structural characteristics, classification, and condition upon arrival at the site of tower and vessel-type process equipment 1. Structure and process function: Towers are process equipment with a cylindrical welded structure, consisting of a cylinder body, a head (or cover), and supports; they are non-standard devices designed and manufactured to meet the requirements of specific production processes. A tower is a vertical device used for separation processes such as distillation, extraction, absorption, and purification, and it is widely applied to mass and heat transfer between gas-liquid and liquid-liquid phases. Classified by the structure of the internal components, towers can be divided into plate towers and packed towers. A container that holds materials inside without any chemical reactions or other physical or chemical processes; it usually has no internal facilities or only simple auxiliary structures, and is also known as a tank. Containers are classified by type into vertical (with the axis vertical) and horizontal (with the axis horizontal) types. Most towers are classified as pressure vessels. 2. Arrival condition of the tower at the site: The arrival condition is determined based on the size constraints of railway transportation; however, depending on the mode of transport and road conditions, the arrival condition of the equipment may be determined without being constrained by such size limits. The delivery status is divided into full delivery, phased delivery, and partial delivery. The total length of the equipment delivered is less than 20m, and the diameter is less than 3.8m ； The equipment delivered in segments has a diameter of less than 3.8 meters and a length of over 20 meters ； The equipment delivered in segments has a diameter of over 3.8m. II. Installation Technology for Tower Equipment (I) General Principles for Tower Installation or On-site Welding Construction 1. Before installing or assembling the tower on site, it is necessary to inspect and verify the manufacturing quality of the equipment, semi-finished products, and components to ensure that they meet the required standards. And the welding materials are inspected and accepted. 2. The on-site assembly of the tower shall be carried out in accordance with the design drawings, layout plans, and requirements of the construction plan. 3. The tower is installed or assembled on the foundation. It shall be carried out after the foundation has been accepted as qualified. 4. For the installation of towers that are considered pressure vessels subject to supervision (either by overall placement or by relocating them), as well as on-site welding (completing the final circumferential welds on site or carrying out overall welding), the construction unit must possess the licensing qualifications required by the relevant regulations set forth in the \"Regulations on the Safety Supervision of Special Equipment\". (II) General installation procedure for the entire tower structure upon arrival: on-site inspection and acceptance of the tower, positioning it at the location specified for lifting; fabrication and installation of lifting lugs, as well as setup of lifting equipment; acceptance of the foundation and placement of shims; overall lifting, alignment, tightening of foundation bolts, securing the shims in place, and secondary grouting. (III) On-site alignment and installation procedure for tower equipment delivered in sections 1. Methods of aligning and installing tower equipment delivered in sections: there are two methods, namely horizontal installation and sectional alignment and installation from bottom to top on the foundation. 2. Welding procedure for horizontal assembly: Set up wooden supports or roller frames (idlers) and other assembly fixtures on-site → Weld together the various sections of the tower (in the order of upper shell → middle shell → lower shell → bottom shell including the skirt) to form a single tower unit → Conduct non-destructive testing on the circumferential welds welded on-site. After the tower components are welded together, they are installed in accordance with the same procedure as that used for the fully assembled tower that arrives on site. 3. Install the structure section by section from bottom to top: foundation inspection and shimming → lifting and positioning the lowest section of the tower (the section with a skirt) and aligning it → lifting the second section (in order from bottom to top) and aligning it → welding the circumferential welds between sections, followed by non-destructive testing → lifting section by section until the highest section (the section with a top head) is installed, aligning it → welding the circumferential welds between sections, followed by non-destructive testing → performing overall alignment, tightening the foot bolts, securing the shims in place, and carrying out secondary grouting. The non-destructive testing of the circumferential welds welded on-site can also be carried out after all sections of the tower have been fully assembled and welded. (IV) On-site welding procedure for segmented tower vessels after delivery 1. General procedure for shell welding: Weld the upper and lower end caps on a steel platform → Weld the tube sections → Weld the tube sections together with the end caps → Weld between the tube sections → Weld the skirt base to the lower end cap → Weld the segmented shells together; mark a reference circle within the segmented shells, mark positions for internal fixing elements, make holes and weld the pipes → Weld the internal fixing elements and external reinforcement rings → Weld the shell as a whole. 2. Shell assembly method: Depending on the site conditions, either horizontal or vertical installation methods can be used. The vertical installation method can be divided into overall installation (lifting) after sectional assembly, and sectional assembly from bottom to top using a foundation. It is similar to the method of alignment and installation for tower units delivered in segments. 3. Principles for segmenting construction using the vertical installation method: to facilitate on-site work and minimize work at heights as much as possible ； Complies with on-site lifting capacity ； The interfaces should be located on a straight cylindrical section made of the same material and having the same thickness, and should be kept away from nozzles. III. Preparation and Inspection of Product Welding Test Plates (I) Requirements for the Preparation of Product Welding Test Plates 1. The raw materials used for the test plates must be of qualified quality, and they should have the same steel grade, the same specifications, and the same heat treatment condition as the materials used for the containers. The test plate should be placed at the extension of the longitudinal weld of the tube section, and welded simultaneously with the tube section. 2. The test plate shall be welded by the welder who welds the container, under the same conditions and using the same welding process as that employed for the container. For containers that require heat treatment, the test plates should be heat-treated together with the containers. 3. Identification marks of the test plate, including: work order number or container number ； Material steel grade ； Welder’s stamp number. 4. Test plate size: It should meet the requirements for the type and quantity of specimens needed for the test. Dimensions of the butt joint test plate: the length should be 300 mm or more, and the width should be 250 mm or more. 5. After the visual inspection of the weld joints of the test plates shows they are satisfactory, they must undergo 100% radiographic testing to confirm their quality. (II) Qualification criteria for product welding test plates (see \"Inspection of Mechanical Properties of Welding Test Plates for Steel Pressure Vessel Products\" NB/T 47016-2011): 1. Qualification criteria for the tensile test of test plates: The tensile strength of the tensile test specimens shall be greater than or equal to one of the following values: the value specified in the product drawings ； Minimum standard tensile strength value for steel ； For welded joints composed of steels of different strength grades, it is the smaller of the lower limit values of the standard tensile strengths of the two steels. 2. For the bending test of the test plate, there shall be no single crack or defect on its tensile surface that is longer than 3 mm in any direction. 3. The normal-temperature impact test of the test plates shall be carried out in accordance with the specifications in the drawings or relevant technical documents. IV. Pressure Testing and Airtightness Testing (I) Pressure Testing of Containers 1. Hydrostatic Testing (1) Medium requirements: Clean fresh water should be used; when water is used as the medium for containers made of austenitic stainless steel, its concentration shall not exceed 25 mg/L. (2) Qualification standard: No leakage ； No visible deformation ； No abnormal noises were heard during the test. Containers made of materials with a strength greater than 540 MPa were inspected via surface non-destructive testing, and no cracks were found. 2. Pneumatic pressure test: (1) Conditions: A pneumatic pressure test can be carried out under special conditions such as when it is not possible to fill the container with water (liquid) or when residual test liquid is not allowed. However, safety measures should be in place, approved by the technical head of the testing unit, with on-site supervision by the safety department. (2) Medium requirements: It should be dry and clean air, nitrogen, or other inert gases; oil-free gases must be used for pressure testing of degreased containers. (3) Qualification standard: No air leakage ； No visible deformation. (II) Airtightness test of the container 1. Test conditions: It may be carried out only after passing the hydraulic pressure test. For towers that have undergone a pressure test, if the pressure test results are satisfactory and the design drawings do not specify otherwise, a leak test is not required. The requirements for the test medium are the same as those for the pneumatic pressure test. 2. Qualification standard: leak-free and seepage-free.