Technical Instructions for the Construction of Vertical Cylindrical Welded Steel Storage Tanks

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Technical Instructions for the Construction of Vertical Cylindrical Welded Steel Storage Tanks I. Project Overview: A 10,000 m³ vertical cylindrical steel welded storage tank with a dome shape; the diameter of the tank body is 30 m, and the total height of the tank walls is 14.2 m. The thickness of the tank bottom plate is 6 mm and 10 mm respectively, the thickness of the wall plates at each layer ranges from 8 mm to 20 mm, the thickness of the top plate is 6 mm, and the total weight of the tank is 250 t. The installation of the wall panels at each layer of the tank body and the tank roof is carried out using a hydraulic lifting device in a top-down construction method. II. Construction Preparation 1. Materials for the project and those for construction measures (1) Main materials for the project The main materials used in this project include: mid-span plate at the bottom of the tank, δ=6mm, 36t ； Side panel δ=10mm, 14t ； Tank wall plate δ=8~20mm, 160t ； Top plate of tank δ=6mm, 40t. (2) Materials for the measures: The main materials used for these measures include those for the formwork of the top and side panels, materials for expansion rings, as well as materials for support pipes and curved clamps. That is, materials such as steel plates, pipes, and sleepers. 2. Main Equipment The main construction equipment includes: truck cranes, hydraulic lifters, welding machines, hydraulic pumps, gas welding equipment, etc. 3. Preparation and conditions for on-site work: (1) Re-measure and inspect the elevation, slope, and diameter of the storage tank foundation, and carry out the acceptance procedures for intermediate handover. (2) Re-measure the geometric dimensions of the tank semi-finished products and steel structural members, verify the material quality certificates, and carry out the acceptance procedures for intermediate handover at the same time. (3) The crane access roads at the construction site are unobstructed, and all necessary forms and materials for various measures are readily available. (4) The elevator, hydraulic pump, hydraulic pipes, hydraulic oil, and power cables are all fully equipped. III. Labor Organization: For the installation of the 10,000 m³ storage tank, 12 riveters, 12 welders, 4 sanders, 2 gas welders, 3 signal workers, 2 maintenance electricians, and 1 fitter are required. IV. Main Construction Techniques 1. Construction Procedure The main procedure for installing storage tanks using hydraulic lifting equipment is to first carry out the welding of the tank bottom plate ； Then, the assembly welding of the top wall panel and the roof slab is carried out ； Proceed with the installation of the lifting equipment ； Finally, proceed with the assembly and welding of the wall panels from the second layer down to the bottom layer. 2. Welding of the base plate: Once the foundation has been approved, the installation of the base plate can proceed. The welding procedure for the bottom plate is as follows: weld the short seams first, then the long seams; the turtle-shell joints between the side plates and the mid-span plates are to be welded after the bottom wall plates are installed. 3. Roof panel assembly: Start with the assembly of the top wall panels and the corner steel members used for framing; thereafter, assemble the roof panel on the bottom of the tank, install the jigs, and lift the hydraulic lifting equipment as well as the expansion rings into the tank. Once everything is in place, proceed with the assembly and welding of the roof panel. 4. Wall panel assembly: A hydraulic lift is used to raise the already assembled top wall panels and roof panel, during which the second layer of wall panels is assembled and their longitudinal seams are welded. Subsequently, lap welding at the joints between the two layers of wall panels as well as welding of the internal and external seams is carried out. Once the welds of the wall panels after welding have passed non-destructive testing, the expansion rings inside the tank can be loosened, the lifting device can be placed beneath the second layer of wall panels, and preparation can begin for assembling the third layer of wall panels. Follow the aforementioned procedures and methods until the welding of the wall panel assemblies for the following layers is completed. 5. Welding of the bottom wall panels to the bottom plate: First, weld the lower wall panels to the bottom plate, and then weld the side panels to the middle plates. 6. Fitting installation and tank testing: First, all the manholes, material inlet pipes, inspection holes, ventilation holes, light-transmitting holes, connection pipe holes, ladders on the tank, as well as all welded components attached to the tank, are welded together. Finally, the tank is subjected to a water filling test and a airtightness test. V. Quality Standards 1. Mainly comply with construction specifications: (1) \"Specifications for the Construction and Acceptance of Cylindrical Welded Steel Storage Tanks\". (2) Code for Construction and Acceptance of Welding Works for Field Equipment and Industrial Pipelines. 2. Key points for quality inspection: (1) The local unevenness after the welding of the bottom plate shall not exceed 50 mm. (2) The out-of-roundness of the wall panel shall not exceed 20 mm. (3) The misalignment of the wall panels shall not exceed 3 mm. (4) The local unevenness of the top plate after welding shall not exceed 30 mm. (5) The verticality of the tank wall shall not exceed H/1000. VI. Precautions (1) Measures should be taken to prevent deformation of wall panels and ceiling panels during stacking, handling, and lifting. (2) Hydraulic lifters and associated equipment must be inspected before use, and they require a dedicated operator. (3) Before lifting the tank, carefully check whether the clamping plates on the expansion ring are firmly welded. (4) Hitting the tank body is strictly prohibited during the lifting process.