Welding of water pipe network
A distinctive feature of the pipeline network is the presence of water in their construction of five specific types of compounds, namely "pipe + pipe", "tube + shift", "shift + flange", "removal of tube + sector", "shift + gate." The number of various compounds on assembly is determined by the degree of blocking of supplied equipment units. The most time consuming of them during installation of pipelines are compounds of the type "flange + shift" due to the fact that the welding of the joints requires additional installation and removal and partial disassembly of units being consolidated.
Welding of flanges to the pipe element is held at venues Pre-assembly of pipe units, which are located in the premises of the place of installation of power lines network. The technology of welding flanges with tube elements. In this first impose the outer seam, then the inner. Outer leg seam exceed the wall thickness of the pipe by 2-4 mm. The inner seam, which seam sealing is performed cathetus equal to the pipe wall thickness, and shall not exceed for economic reasons, regardless of 7 mm diameter pipes.
Welding technique, which determines to a large extent the quality of welds, the welder is selected on the basis of the conditions of formation of the deposited weld metal. The criterion for selection of welding equipment is in the gap junction. If the assembly is provided with no joints or gaps with minimal gaps, it is preferable to perform welding in position in the boat. This ensures adequate penetration without the edges of the molten weld metal flowing into the gap between the inner surface of the flange holes and the outer surface of the pipe. In cases where the gaps in some areas exceed 1.5 mm in the joint, weld in these areas is carried out with the transverse oscillations of the electrode, disposable to the axis of the tube blank at an angle of 25-30 °. This provides the greatest penetration of the base metal flange and its share in the deposited weld metal.
Welding of pipe flanges to the elements is performed on-site installation of network equipment and piping of water and is characterized by two features:
the need to disassemble the previously collected flanged connections for the imposition of the joints;
the presence of local damage pipe ends in a flattening and shortening of edges.
According to experimental data, about 70% of the joints have gaps between the pipe and an inner diameter of flange equal to 4.0-4.5 mm in the length of the perimeter of the circumference of the pipe from 100 to 250 mm. These areas are the joints welded corner joints, legs that exceed the standard rates on the value of the excess clearance in the joints. Capacity of pipe ends in their places of rough cuts made by the MMA welding electrodes with layer-stripping and verification of deposited weld metal.
After that the pump flanges removed, and the edge of the translation were available, subject to replacement surfacing.
The edges are restored by welding and the use of melted inserts, manufactured from wire 1.6-2.5 mm. The reconstruction of the edges are held in the following sequence. The pump is assembled with the bolt-on flange 2, 3, is installed into the place, then checked the build quality of transition 4 with a flange 3 and the fixed parts of the joint, requiring replacement of surfacing, and leveling.
To make the desired shape space surfacing processed by grinding wheels. Validation of surfacing overlay welds is checked by putting on an available flange on the end of the transition. In cases where no such flanges, to test the geometry of deposition using flanged, welded to the pipe before the pump components, which assembled unit by crane lifted and set in position.
After checking the quality of welding and assembly of the flange welding is carried out with the transition of these elements outside seam.
The imposition of the internal weld is performed after disconnecting and removing the flange pump. From the general form of the inner seam, brewed with different gaps, it is clear that with the increase in the gap junction increases and the leg joint. In those areas where gaps exceeding 2.5 mm, welding is done with the use of additives in the form of the electrode or filler wire of 1.6-2.5 mm.
See also:
Welding of Water Pipe Network
Welding of Pipe Heating Systems
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