A brief description of pressure steel pipe production technology and its application practice for water conservancy and hydropower projects

The goal of the construction of hydraulic and hydroelectric projects is to expect to gather a large amount of water energy resources, and then turn water energy into other types of energy, and for this kind of engineering construction, the most important of which is the construction of water resources for transmission, and in the process of building the relevant transmission pipeline, the application of steel pipe is indispensable. Therefore, in recent years, the development of China’s pressure steel pipe production-related technology has become increasingly rapid, and has been the focus of attention by the industry.

  The application of “tile rounding” technology

For the “tile rounding” technology, it is a traditional method of rolling pressure steel pipe, which is characterized by the need to roll a single section of the tile first, and finally the implementation of the splicing group round. Among them, the quality control of the ring seam welding is the difficult part of the technology.

  (A) Steel plate inspection and surface pre-treatment

Sampling and inspection are carried out according to the tender documents and relevant national standards. Surface slag, oil, and iron oxide need to be thoroughly removed before application.

  (B) Plate nesting and scribing

In accordance with the requirements of the design drawings, the steel plate nesting drawing is drawn and the scribing is carried out according to the nesting drawing. And the steel plate nesting and scribing should be completed on the scribing platform; after scribing the steel plate, it should be marked out one by one by virtue of punching eyes, paint, and steel markings corresponding to the steel pipe block, section and segment number, as well as the direction of water flow, horizontal and vertical centerline, in addition to the bevel angle and cutting line, and grout hole location; in the case of high-strength steel, the application of saws or chisels must be prohibited In the case of high-strength steel, it is forbidden to use saws or chisels, steel marks, etc. to make markings, and also not to punch holes on the outer side of the coil. In addition, check the accuracy of the scribing line about the inner surface of the coil and the outer surface exposed after the completion of the coil can appear light punching eye mark.

  (C) Steel plate cutting and processing of bevels

In the straight pipe steel plate under the use of CNC cutting machine, and welding bevel is mainly the use of the relevant planing machine to implement the processing, in addition to the high strength steel store, should also be called by virtue of the grinding machine to effectively remove the processing bevel, so as to ensure the overall quality of processing. The bending and tapering of the tube is done with a semi-automatic cutting machine, and the processing bevels need to be removed with an angle grinder. Burrs, slag and notches on the cut side of the steel plate need to be removed by grinding wheels. After finishing the bevel processing, it must be painted with non-toxic bevel anti-rust coating that does not affect the welding performance and quality.

  (D) End pre-bending of the two longitudinal seams of the steel plate

The end pre-bending of the longitudinal seam of the steel plate needs to be completed on the coil by virtue of the precipitation, and for the liner, that is, according to a certain curvature and rolled into a special tire film of the steel concerned. After the completion of the pre-bending, the sample plate should be used to check the steel plate end curvature, and this process must meet the design requirements.

  (E) Steel plate rolling

By virtue of hydraulic plate rolling machine to make the tile cold roll forming, the corresponding steel plate after repeatedly rolled, and finally meet the design curvature. After the completion of tile rolling, it should be placed in a free state on the corresponding inspection platform, so as to facilitate the detection of curvature and pipe mouth flatness, etc.. The curvature should be checked by means of a standard sample, while the data on the unevenness of the pipe mouth should be measured and corrected on a special platform. Thus avoiding the distortion of the arc surface, but also can use the diagonal pulling method to implement the verification.

  (F) Tile rounding

In the rounding process, the tiles of the pipe section should be placed on the rounding plane, and no welding should be done to the temporary members in the specific process of rounding, the longitudinal gap should be adjusted and positioned at the same time, and the adjustment of the last longitudinal seam should meet the requirements of the design perimeter. After the tiles are rolled, they should be placed on the platform in a free state. The curvature check should be based on the standard sample, and the measurement and correction of the unevenness of the pipe mouth and other related data should be done on the special platform.

  (G) Rounding and installation of related support devices

After the end of the longitudinal seam welding, should be lifted on the relevant rounding platform, with the head jack aspect of the rotary rounding tooling to implement rounding, and in the process of rounding also need to the overall roundness of the steel pipe, longitudinal seam misalignment, as well as the flatness of the pipe mouth and other aspects of the technical indicators to implement effective control, after rounding the need to install the steel structure of the relevant support devices.

   The application of “overall rolling” technology

In the overall rolling process, the steel plate rolled before the need to do the preparatory work and the overall steel pipe rolled after the need to do the finishing work and the conventional tile rounding the same work, but the difference is that the overall rolled tile rolling from the section tile rolling directly into a single section of the tile implementation of the overall rolled, the tile in the free state of the vertical group rounding changed into a suspended overall horizontal group rounding, the The welding of the longitudinal seam in the process of rounding is changed from multiple vertical operations to a single operation level.

  (i) Steel plate assembly and welding

In the case of multiple steel plates that are formed into one section of steel pipe, the steel plates are butt-joined and cross-seam welded by means of a special platform. After the grouping between the steel plates, the first point is to make the butt longitudinal seam to complete the front welding, and then turn the steel plate 180° to complete the reverse welding, and then finally pre-bend the ends of the steel plate with the pre-bending die. In the specific operation process, the use of submerged arc automatic welding welding method to complete the longitudinal seam welding, the use of nondestructive detection method to complete the quality inspection of the weld.

  (II) Steel pipe overall coiling

With a special spreader to lift the steel plate after the completion of welding, according to a certain rate directly transported to the coil machine to implement the coil, in the steel plate after calendering can be under the relevant auxiliary support device to follow the corresponding curve path, and then use the coil machine to implement the closing of the seam, and steel pipe rounding. In the specific operation, the arc sample is used to detect the relevant curvature of the coiled plate, and the longitudinal seam is welded by virtue of the relevant welding method of submerged arc automatic welding.

  (iii) Steel pipe gripping and leveling

The use of special spreader or gripping device, after the completion of the coil steel pipe from the coil machine or auxiliary support device to take out the designated location, but also to complete the welding of the longitudinal seam of the implementation of nondestructive testing. And in turn to complete the installation of support devices, rounding, installation of related welding accessories and other aspects of follow-up operations.

A comprehensive comparison between the two fabrication technologies

  (A) Technology

Compared with the overall rolling technology, the tile group rounding is not only complicated, but also very frequent transit, and the production efficiency is not very high. The overall rolling technology, its procedures are very simple, in the actual production process, as long as the broken head of the tile pre-bending twice, the tile can be rolled only once. At the same time, generally speaking, the processing of the longitudinal seam of the steel pipe, are used flat welding station related to the submerged arc for welding aspects of the automatic welding method, which greatly improves the production efficiency, especially in carrying out complete sets of steel plate grouping and welding, rolling work.

  (B) Quality assurance

Tile group round technology in the process of welding the longitudinal seam of the steel pipe, mainly through the vertical welding station to achieve, however, its welding quality not only can not be effectively guaranteed, in response to this phenomenon, can take the welding method of rich argon welding to promote the quality of longitudinal seam welding work, however, this welding method will have a great impact on the human body. And the overall rolled technology, mainly using good submerged arc automatic welding method, welding quality is very high. However, its disadvantages are mainly reflected in the steel pipe rolling is mainly with the help of a single section of long steel plate, therefore, it will be subject to the constraints and influence of a number of factors, such as the coil roller spacing, the choice of different auxiliary support methods, etc., can not be effective control of the precision of the steel pipe closing seam.

  (C) engineering applications

At present, the tile group round technology has become increasingly mature, in the domestic and international water conservancy engineering applications have been very wide; and “overall roll system” due to the slow promotion, manufacturing restrictions, special equipment development, and equipment space requirements are relatively large, can not be indoor operations and other related factors, in the specific application of It has been greatly restricted in the specific application.

  Conclusion.

Pressure steel pipe as an important component of water conservancy and hydropower projects, the quality of its good or bad directly on the quality of the project has a direct impact on the high or low. “Tile group round” technology has been widely recognized by the engineering community, its process is more flexible, and the operation process has matured, in the future for a long time will remain the mainstream of the production of pressure steel pipe. The application of the whole rolled technology is still limited by many aspects, but there is no steel pipe longitudinal seam problem, can better control the quality

I believe that in the future the large-scale and high-strength pressure steel pipe production in the application will be more widespread.

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