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The construction of pillars and ring beams adopts the method of manual well digging. 8 foundation pits are evenly excavated around the chimney, double-row scaffolding is set up, and the fall chain is installed to accurately hang the pillar steel cage. The concrete is poured and vibrated in sections to ensure that no segregation occurs during the concrete tamping process, thereby ensuring the concrete engineering volume of the pillars.
After the pillars are completed, the ring foundation groove of the 600 mm×600 mm ring beam is excavated for steel bar connection and concrete pouring. Chimney reinforced concrete sleeve construction: The chimney outer cylinder wall is constructed with reinforced concrete sleeves to ensure that the foundation construction platform can withstand loads and safety standards, handle the construction level method, and design and manufacture a set of assembled construction platforms.
Its characteristic is that the platform is combined according to the change of chimney radius. It is placed along the circumference of the chimney. Its hanging points are respectively loaded on the double hoop at 50 m, 90 m and 125 m elevations according to the construction height of the concrete sleeve, and the safety rope of the construction platform is tied to the signal platform. The lifting and lowering of the construction platform are operated by hand hoists.
The construction workers use the construction crane to go up and down, and two shaking and pulling rods are symmetrically installed on the signal platform as vertical transportation channels for tools, materials, etc. According to the design requirements, the surface of the original chimney was 2-mold, the surface area of the old chimney was cleaned, and the leaks were repaired. 1,150 expansion bolts were buried as the "shear key" for the combination of new and old concrete.
In order to ensure the surface quality of the new sleeve, the P1015 steel mold was welded with a 300 mm × 1,500 mm steel plate during construction to solve the problem of template leakage. Since the new chimney jacket is constructed under the operating environment of the old chimney, in order to solve the problem of excessive roundness of the old chimney, the wall thickness of the new chimney sleeve has been adjusted within a certain range.
To ensure its roundness, the following measures are taken: cement mortar is used to level the upper surface of the ring to ensure that the steel formwork is at the same height; the formwork surrounding purlin is made in sections and bolted; the roundness of the new chimney is controlled by controlling the curvature of the purlin and supporting long and short different braces, so that the quality of the reinforced concrete jacket of the new chimney is good.
According to the design requirements, a 5 m high trumpet diffuser is installed on the top of the chimney. The diffuser is made of 8 mm thick stainless steel, the outside is insulated with ultra-fine glass wool, and surrounded by 2 mm thick stainless steel. The diffuser consists of 6 pieces, each weighing about 2 t. In order to ensure the safe and smooth installation of the diffuser head, the following lifting scheme was adopted after repeated demonstration: 4 cantilevered single-hole derricks were symmetrically placed at 124 m on the chimney wall, with a height of 15 m. The cantilevered derrick bracket was loaded at 124 m on the chimney, and the 4 single-hole derricks were connected as a group by cross trusses and combined beams.
To ensure the overall stability of the system during the lifting process, the suspended bracket was loaded at the chimney wall, and the concrete strength was tested by sampling on site. The anchor bolt diameter and bracket layout size were determined through planning and calculation. Since the 6 diffusers were assembled at high altitude, in order to ensure the assembly process was foolproof, simulated assembly was carried out on the ground in advance, and each diffuser flange interface was assembled and numbered.
A circular track was specially made with I-beams according to the upper diameter of the diffuser head, and a pulley was installed for in-place assembly. In order to reduce the wear of the diffuser head on the new jacket during the hoisting process, 3 ordinary rollers are installed on each diffuser head to convert the sliding friction into rolling friction, which is convenient for hoisting and protects the surface quality of the new jacket. Due to the meticulous and thoughtful preparatory work in the early stage, the decoration was removed, and the ladder and signal platform were installed; the original plan required the use of controlled blasting to remove the decoration part 5 m from the top of the old chimney, and the lining of broken bricks and concrete should not be damaged to ensure that it can be smoke-proof during the removal process. After sampling the top, it was found that the concrete cylinder wall and the lining were widely adhered. After discussion with the Design Institute, pneumatic tools were used to remove the decoration part, which not only met the design requirements, but also ensured the construction environment requirements. The installation of ladders and signal platforms met the construction standard requirements of stainless steel chimneys.
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