Prefabricated Pipe Dn500 A234 Wp91 Customized Pressure Vessel Power Plant Pipeline

In industrial construction projects, the workload of pipeline construction is large, the requirements for building quality are higher and higher, and the number of pipeline construction tasks is doubled. However, the pipeline construction procedure is complex and the number of components is huge. When the pipeline construction conditions are met, the construction period for pipeline installation is short and the task is heavy, and the phenomenon of rush for construction period often occurs. The industrialized prefabrication of pipeline is very important.

Pipeline factory prefabrication is deeply valued by the same industry because of its advantages of short construction cycle, high production efficiency and high welding qualification rate, which greatly improves the construction efficiency and construction quality.

Factory prefabrication procedure

Four major channels:

1: Main steam pipeline (two high-temperature and high-pressure steam pipelines between the outlet header of the superheater and the high-pressure main valve interface);

2: Hot reheat steam pipes (two high temperature and high pressure steam pipes from the outlet header of the reheater to the interface of the medium pressure main valve);

3: Cold and reheat steam pipes (two high-temperature and high-pressure steam pipes between the steam exhaust port of the high-pressure cylinder and the inlet header interface of the reheater);

4: High-pressure water supply pipeline (the high-pressure boiler supply water pipeline between the outlet of the electric feed pump and the header interface of the inlet of the economizer)

The four major pipelines refer to the main steam pipeline, the reheat hot section steam pipeline, the reheat cold section steam pipeline and the main water supply pipeline in the high temperature and high pressure steam water pipeline.

Factory prefabrication refers to the detailed decomposition of the power station pipeline design drawings provided by the design institute in accordance with the relevant standards and regulations for thermal power plant construction, and the use of equipment, technology, and processes (bending, beveling, welding, heat treatment, Marking, cleaning, painting, protection, inspection) and other advantages for piping. The model of pipeline factory prefabrication has been widely used in power plant construction and has shown many benefits.

The key work of pipeline factory prefabrication is elbows: a large number of standard elbows are used in the layout design of power pipelines, and welds are required at both ends of the elbows. Especially the in-service inspection after the operation of the power station consumes a lot of manpower and material resources. Moreover, the standard elbow has almost no straight section, and the welding seam is located at the arc starting point during welding, which is the place where the fluid scours and the alternating stress is the highest. Therefore, the use of elbows instead of elbows has become the consensus of more and more people in the industry.

The four major power pipes are high-pressure thick-walled pipes, and the traditional bending processes are mostly hot bending and pressing. Hot bending is to use medium and high frequency power to locally inductively heat the circumference of the pipe material to above the phase transition temperature, and then bend the pipe material along the preset track to a certain curvature radius and angle under the action of external force. The disadvantage of this process is that the heating speed is slow, the temperature of the inner and outer walls is uneven, the temperature difference is not well controlled, and an oxide layer is formed on the surface of the tube. High consumption, pollution and low efficiency. Press bending is the pressure of the hydraulic press to press down the pipe material through the upper mold, so that the pipe material is plastically deformed to obtain a curved pipe similar to the shape of the lower mold. The arc made by this simply supported beam principle is not a standard arc, so it is difficult to control and measure the bending radius accurately. During the pressing process, the inner arc side of the tube material is compressed and the outer arc side is pulled, and without compensation measures, it is difficult to control the thinning amount of the pulled surface. Also difficult to control.

With the development of the electric power industry, the specifications of the main steam pipes of the supercritical and ultra-supercritical units have reached ID425X 129, and the specifications of the main pipes of the reheating hot section have reached ID883X72. Materials: ASTM, A335, P92. The defects of the traditional hot bending process are becoming more and more obvious: the thickness of the pipe wall is increased, especially when it reaches more than 10mm, the temperature difference between the inner and outer walls of the pipe during the bending process is too large, and it is difficult to meet the production requirements; the requirements for hydraulic equipment are even higher. It is also difficult to ensure the quality of the elbow, which brings huge challenges to the electric power escort industry.