The advantages of flexible plastic pipes in operation cause the displacement of aging metal analogues. This process is especially evident in plumbing structures. Polymeric materials are easy to use and at the same time practically inferior to metal in terms of technical and operational qualities. But along with the replacement of the material, the methods of processing it also change. A rather specific operation in terms of technical support is the welding of polyethylene pipes, during which it is necessary to use special fixation and heating devices. With the high-quality performance of this procedure, it is possible to obtain a jointing place of two elements that is tight and resistant to external influences.
Technology Overview
To connect two plastic pipes, the method of joining their surfaces under the action of heating, which is performed by a metal tool, is used. As a result of direct contact with heated surfaces, intense heat transfer is ensured. This property distinguishes technology from heating by air. This method of heat distribution in the plastic mass acts positively from the point of view of forming a reliable structure and does not imply thermal stress with subsequent deformation of the joints. In addition, butt welding of polyethylene pipes allows the formation of joints that are not inferior in strength to the whole structure. The process itself involves heating the end surfaces of two elements to a molten state and their further reduction into one segment. But with all the outward simplicity, this technology requires accuracy of execution, which to a large extent depends on the tools used. It should be noted that modern high-tech devices for plastic welding minimize the influence of the human factor, but do not completely exclude it.
Equipment for welding polyethylene pipes
Even small-scale welding activities of this kind involve the use of a whole group of technical means. The basis of such equipment is a centralizer, which provides clamping of two pipes for further installation operations. Also, a special frame is used to fix the centralizer itself. To activate the work of movable clamps, a hydraulic system is used, which works due to a mechanical drive. However, there are different types of equipment that performs this function. On the market you can also find a universal apparatus for butt welding of polyethylene pipes of different sizes. As part of such devices, kits with nozzles with a diameter of 20 to 75 mm are usually provided. This is the best option if you plan to perform installation activities in the domestic environment. For more complex tasks, you will need a set of several functional parts that form a single welding complex.
Centralizers for pipe welding
At first, this technology was used exclusively in working with pipes, one of which was stationary, that is, it was already part of the communication network. This made the task easier as the accuracy of the connection was improved. Problems arose in working with two movable pipe ends, for which a basic centralizer was introduced. This device, due to which the welding machine for welding polyethylene pipes provides high accuracy of the formation of the joint. It is required first to achieve the alignment of the ends, and then the operator performs their reduction. By design, the centralizer resembles a massive clamp system made of two metal parts. Although such units to some extent belong to universal equipment, they should still be selected for pipes with standard sizes of the target range.
Hydraulic units for welding
In the process of welding, it is envisaged to exert mechanical action on the pipes with the aim of moving them along the axes or to each other. To perform this function, the aforementioned hydraulic unit is used. Usually it makes up a single complex with a centralizer, providing its control. In the simplest configurations, equipment for welding polyethylene pipes only fixes and solders the elements. More sophisticated systems require the user to control the pressure supplied to the hydraulic machine, precisely adjust the pipe ends and directly control the centralizer clamps. All of these functions may fall on the hydraulic unit. Especially to simplify these operations, manufacturers supply equipment with ergonomic control panels, including those with automatic systems.
Trimmers and heaters
The welding operation is foreshadowed by the preparation of the pipes. In particular, with the help of a trimming tool, grinding of the edges and planes of elements is carried out in some way in order to ensure their tight fit. As for the heaters, they are integrated into a complex consisting of a hydraulic machine and a centralizer. By design, this component resembles a large pancake, which is placed between the ends of two pipes, ensuring their heating. Management of this part is also realized through a special remote control. If this unit is used for welding polyethylene pipes in a regular mode, then it is included in a single design with a centralizer. It usually acts as a folding accessory, despite the importance of the heating function. It is also worth noting that heaters must have special Teflon coatings, which allows them to be easily removed after melting the pipes.
Welding preparation
Work begins with the immersion of the pipes in the centralizer and their subsequent fixation. Pipes should be securely fixed so that they can be moved smoothly. As a rule, one part is fixed rigidly, and the other moves due to the efforts of the hydraulic machine. If necessary, welding of polyethylene pipes with their own hands can be performed without trimming. In this case, you should initially clean the mating surfaces with a grinding tool. If in the presence of a miter, then cleaning is done directly on the centralizer, after which the resulting chips are removed from the outside and from the inside. Next, you can begin to perform a control fit. It is important that the pipes fit together with a minimum clearance and deviations in the planes. Small errors are compensated by welding, but in this case, the unevenness of the plastic mass in the connection zone will be ensured.
Pipe heating
Perhaps this is the most crucial stage, since it is used to heat the plastic. First of all, a heated disk should find sufficient temperature. After that, it is located between two ends, which are pressed to ensure preheating. The force should be small, but sufficient so that the material of the two pipes melts and converges tightly. In order to get high-quality welding of polyethylene pipes, it is necessary to control the thermal effect. It can be monitored visually - the optimal mode provides for the melting of the ends, but subject to maintaining the viscosity of the structure. The result of this step should be the formation of a small roller from the molten mass, which will slightly extend beyond the edges of the ends.
Rearrangement
After completing the heating of the ends, it is very important to timely remove the incandescent tool and reconcile the surfaces to be welded. It is important that the pipes maintain the overall integrity of their edges at future junctions. The maximum time period during which this action should be performed takes 25 seconds. But this is true for large pipes whose diameter is 60-75 mm. For household plumbing PVC pipes, this figure is about 5-10 seconds. A high permutation speed is required because the material cools quickly without the support of a heater. As a result, butt welding of polyethylene pipes may lose in quality due to loose adhesion of the ends. On the other hand, rush is also not always good. Violations in the accuracy of the reduction of elements are no less dangerous from the point of view of the formation of a high-quality seam.
Pipe draft
The essence of precipitation is the correct formation of the seam and bringing its grant to the optimum state. After the docking of the ends without a heater is completed, the stage of already complete cooling of the material begins. During this period, the release of plastic mass beyond the edges is also possible - this will be the creation of a quality grant. It is desirable that the formation of a new layer of emerging plastic occurs against the background of its mixing with the grat obtained before the permutation. Thus, a deeper welding of polyethylene pipes with optimally mixed structures of the two materials will be obtained. Usually, to achieve a good result after rearrangement, operators increase the clamping force, which brings the end surfaces closer together.
Material cooling
The final formation of the weld with the fixing of its structure occurs in the cooling stage. The gain of strength in the connection zone is due to the fact that the places of the pipe walls adjacent to the resulting seam increase in thickness. By the way, this means not just the formation of a reliable joint - such areas, as a rule, turn out to be mechanically stronger than the original structure of the material. Artificially increase this figure can be due to more intense heating, which allows welding of polyethylene pipes in the framework of technological limitations. Cooling itself should occur naturally and at room temperature. That is, help to accelerate the cooling should not be, as this may adversely affect the future qualities of the seam. After complete cooling, the pipe should be removed from the welding unit, having previously weakened the clamping force.
Conclusion
Technologically, the process of joining plastic pipes is much simpler than welding metal analogues. However, polyvinyl chloride materials that are popular in our time have appeared recently, therefore, methods for their processing are not so common among home masters. In fact, the welding of polyethylene pipes is easy and practically without investment in consumables. The main thing is to purchase the appropriate equipment. To work with small-diameter pipes, compact devices are offered in which all the main functional parts are already provided. Another thing is that in everyday life the need to perform such operations arises quite rarely, although the quality of the result of such welding cannot be repeated in any popular way.