Welding of pipelines: technology

When decorating a home or making repairs in the home, you can create the piping system independently. If we are talking about steel communications, it is possible to use the electric welding. As a result, possible to obtain a solid compound which is obtained by the flow of thermochemical processes, using electrodes-conductors.

Whatever welding jobs they require from the master of experience and knowledge, which are used in the process. If you are just a student, then you can start to see the theoretical side of the question. As for steel, polypropylene tubing also requires the appropriate equipment for welding. However, practice shows that the latter technology is much easier than the one, which will be discussed in the article.

Preparation before works

The welding of the pipeline starts with surface preparation. It is important to make sure that it is dry and smooth. The next step is to select the current source. Depends on the quality of education. It can be compact inverters or heavy transformers. With their help, the high voltage can be converted to low secondary circuits.

For households, the most preferred option would be welding. In the operation of the transformer simpler. It has advantages in reliability of operation and durability. The inverter apparatus has a less impressive size also allows you to adjust the modes of operation.

Varieties of welded joints

When welding piping systems today use the following connection types:

• Butt;
• Lap;
• Gusset;
• T-connection.

The position of the joint can be vertical or horizontal, ceiling or bottom. The best situation is considered lower, so if possible re-welding it is necessary to give preference to this method. Welding of pipelines for laying communications usually involves the use of butt joints. Edges it is important to carry out throughout the thickness. For thick-walled pipes are double stitching – external and internal. To reduce the influx of the metal from the inside with the execution of the work electrode must be hold at an angle of 45 ° to the horizontal plane.

Recommended

Staff evaluation: system and methods

Personnel Assessment allows you to identify how competent the employees involved in the enterprise, and it is the performance of their work – the most significant factor affecting the efficiency of the company. To clarify the impact of performa...

How to start your own business: important aspects.

Many people, tired of working for someone else, are increasingly thinking about how to start your own business. Someone wants to open a salon, someone store, and someone enough and vegetable stalls. Before you throw in the pool with his head, it is i...

Business activities. its essence and basic functions

The Entrepreneurial activity of the citizen – is undertaken at your own risk and independent activity, which aims to systematically profit through the sale of works, goods, services, use of the property. The citizen engaged in such activities, ...

What else is important to bear in mind when preparing

Before the manual welding should be trained. It is important to check the compliance of the pipe requirements. The products must fit, they must not be deformed, they should not be defects. You need to make sure that there is no difference in the thickness of the walls.

The material of the pipes shall conform in chemical composition. Edges should be cleaned of dirt and rust. The end is measured as the angle of edges and the magnitude of the scene. According to the norms, the magnitude of the blunting may be equal to the limit from 2 to 2.5 mm. as for the angle of the bevel edge, it can be 70 °. If there were inconsistencies with the requirements, it is necessary to carry out the machining of the edges.

Setting the tacks

The welding of technological pipelines must assume the installation of tack. They represent a component part of the seam, and to run using an electrode that will be applied when the joint. If we are talking about the pipe diameter not exceeding 300 mm, are 4 potholders, they should be distributed around the circumference as uniformly as possible.

When dealing with a more impressive tube diameter, the mitts are placed in increments of 250 mm the recommended length of tack equal to 50 mm, while its width is 4 mm.

Features of electric welding

Welding of pipelines should be carried out according to a specific algorithm. It is important to pay special attention to rotary joints. If cooking is necessary in difficult conditions, then the hand should be held a small mirror. If necessary, the electrode end is necessary to bend, doing the work undamaged part.

A Fairly common situation is welding at an angle of 30 ° toward the surface of the product. Trim the seam is then carried out circumferentially. It can be single layer at the junction of products from low-alloy steels. Additional strength can be achieved by performing a re-weld. The more impressive will be the wall of the pipe, the more passes should be made, they must be 2 or greater.

In a circle should cook for large diameter pipe. Their link is accessed before half of the seam. Then the areas are cleaned from slag and covered the following seam at a distance of 1.5 cm from the previous one. To complete the work required by the connection of a gain with a small overlap. Without clearing from the slag of work done on is not recommended, so as to achieve a good result is not obtained.

Quality control

Executing the welding of pipelines, at the final stage you should make sure thatthe quality of the welds turned out perfect. Invisible cracks can be detected using a soap solution, which is applied with a brush on the weld joints. After the system air is supplied. If there neproverennye seams or places, then you will be able to notice the bubbles.

Rotary welding method

The welding of technological pipelines usually involves the maximum number of welds made in the flat position. This indicates that you can use the rotary method. If the pipe has a wall thickness of 12 mm, it is possible to do triple stitch. First layer welded with the electrode, the thickness of the rod which varies from 2 to 4 mm. All subsequent layers can be welded with electrodes of the more impressive diameter.

Initially, the joint should be divided into 4 parts. The welding is performed in the first and second sectors are positioned at the top of the tube. The tube is then rotated, and the master will have to make a junction of the third and fourth sectors. The pipe on the next step, turn again and cook 1 and 2 sector. When repeat turn the second layer is superimposed in sectors 3 and 4. The last layer should be placed in the same direction, the pipe should be rotated.

Automated welding

The welding Process of the pipeline can be carried out on large-scale production, which is important for high performance. Under such conditions, manual welding would be time consuming, so we are using welding machines. All the process will happen automatically.

Welding is the welding wire, which is unwound from the coil and fed into the working area. In the working area in the automatic mode serves another and shielding gases. If the work is automated it can not be used welding machine.

Alternative welding methods

Welding and pipeline installation can be carried out with the help of gas welding. This method involves heating the edges to the melting temperature. Simultaneously, the melted welding rod and the metal used to fill the seam. As a result, possible to obtain a sufficiently strong seam that will have a protruding cushion.

Welding gas is carried out using a mixture of oxygen and acetylene. The main tools are the torch and a cutting torch. In the body first there are two channels by which gases are fed into the mixing chamber. The master thus controls the flow of gas when welding different materials.

Welding of steel pipelines can be carried out using an induction method. This technology involves heating of the elements of the eddy currents. Edges connect the pressure rollers. This type of welding is used in industries and in mechanical engineering.

Recommendations on the selection of electrodes

When welding of pipelines GOST 16037-80 must be respected. They prescribed more and features array of electrodes. The latter are metal rods made from welding wire. Its thickness can vary from 2 to 5 mm. Surface is covered with plaster, which is applied with a thick or thin layer. In the latter case, the mass of the coating ranges from 1 to 2% by weight of the core. If we are talking about a thick layer, then its weight can vary from 20 to 30%.

As the primary task of the coating is the formation of slag, which has the appearance of non-alloy lower weight compared to metal. The slag floats to the top when welding, creating a protective coating. After the pipe welding slag should be down. As soon as the crust will become brittle, you can remove it pretty easy.

The Electrodes are now available with different types of coatings, the latter of which was created to solve certain problems. For example, the cellulosic coating used for welding of pipelines of impressive diameter. With such electrodes it is possible to create circular and vertical seams.

In the market you can find the electrodes with rutile coating, which is easily ignited and forms a slag crust high brittleness. With these electrodes you can create a presentation joints, corner joints, set of potholders and boil for root seams. This allows you to connection, beautiful appearance.

The Technology of welding of pipelines may involve the use of electrodes with rutile-acid coating. This material is characterized by ease of separating peel, and electrode consumption is small, which allows you to save. Rutile-Celulose coating is suitable to perform welds in all positions that can be directed upward, what is the most difficult.

The Seam is with higher viscosity can be obtained with basic coating electrode. As a result, possible to form compounds which do not crack. The material is perfectly suitable for thick-walled pipes and products, which will be used in difficult conditions.

Repair welding method

You can perform a repair of pipelines welding. To do this, the defective area must be cleaned mechanically. May be cleaned by sandblasting, abrasive wheels, shlifmashiny and circular wire brushes.

Repair welding involves the welding on the defective areas. Damage can be caused by corrosion on the surface can develop scratches, scuffing and risks. In order to clarify the wall thickness,should be measuring and visual inspection. Valid, and no additional physical methods that are not destructive.

The Defect, the depth of which is 0.2 mm, can be eliminated by the method of grinding. Norms for pipeline welding in this case involve the use of manual method with the use of electrodes with main type of coating. For seam welding of the first filling it is recommended to use electrodes whose diameter is 3.2 mm. For facing and filling joints the diameter of the electrode can vary between 3 to 4 mm.

Technological process of welding of the pipeline involves the calcination of the electrodes. Acceptable use of electrodes, calcined in stationary conditions. Thus to the place of production, they must be transported in sealed containers. Storage of electrodes in accordance with state standards this should be carried out in a heated dry room, the temperature does not fall below +15 °C.

The Defective area before welding should be preheated by electric heating devices. You can use an induction method, which provides uniformity of heating. It is acceptable to use the gas burners or heaters. Welding can be performed using the inverter method. Welding is performed with direct current reverse polarity.

The Ignition arc is produced at the edges of the sample defect area. Welding of filling layers rectilinear or circular shape is narrow roller. Used scheme – anti-symmetric. The direction of movements in each of the next seam needs to be inverted. Width of first filling layers may vary from 4 to 6 mm. All subsequent layers have a width of 8 to 10 mm.

Conclusion

With the appropriate equipment welding piping system you can carry yourself. However, it is important to choose the right electrodes, it should take into account the properties of the materials that underlie the pipes. For example, to connect carbon steel pipe, you should be welding materials with a basic or rutile coating.

If the welds performed on pipes of galvanized steel, it is necessary to prepare electrodes for welding of galvanized pipes. As the main features of welding when working with galvanized pipes acts the boiling point of zinc. It is lower compared to that which is true for steel. This indicates that the zinc coating will evaporate when heated.