Today, when repairing water pipes and heating systems, instead of metal pipes, they install polypropylene counterparts. This is due to the durability, lightness and easy maintenance of the material, as well as the ability to carry out installation on their own quickly and reliably.
The specifics of soldering polypropylene pipes
The principle of soldering polypropylene pipes is based on the thermoplasticity of the material. The polymer under the influence of temperatures above +200℃ quickly softens, it also takes several seconds to harden under normal conditions. During the contact of the melted edges of the workpieces, a polyfusion process occurs, the result of which is a monolithic connection of the elements. Thermal impact on the end parts of the pipes does not lead to changes in the quality characteristics of the material.
Another option involves the use of special fluids that cause a similar process due to the chemical reaction of polypropylene with active ingredients (organic solvents). This approach is otherwise called “cold welding”. This do-it-yourself technology for soldering polypropylene pipes is easy to implement, but has limitations in application, which is reflected in its relatively low popularity compared to polyfusible.
Methods for connecting polypropylene pipes
The assembly of the pipeline from polypropylene blanks is carried out in two ways: direct and by means of additional connecting elements for various purposes. The first option is relevant for elements whose diameter exceeds 40-63 mm, since the products have fairly thick walls. Here it is important to observe several conditions:
- identical dimensions in cross section, thickness;
- exact match of end edges;
- strict alignment.
The socket welding method is used for thin-walled (up to 4.5-5 mm) products with an outer diameter of 16 to 40-63 mm. Such blanks are relevant for plumbing and heating systems in the residential sector. Here, for the assembly of highways, additional connecting fittings are used, one or all of the pipes of which are made of a thermoplastic polymer. It is worth noting that the inner and outer diameters of the parts used should be close in values, but differ upwards in favor of the second size.
Couplings according to their purpose are classified into several main groups:
- size adapters;
- connectors at different angles;
- splitters from one to several channels;
- elements with a threaded tip for the formation of collapsible units;
- taps, valves.
For the soldering of polypropylene pipes in hard-to-reach places and in general using coupling technology, compact equipment is used that is available to a home master. Here the essence of welding lies in the fact that the blanks are inserted into an additional connector. The method, compared with the direct (docking) one, is easier to implement, therefore it is often performed without the involvement of professional help.
What is required for installation work
Work with polypropylene pipes consists in cutting blanks, preparing end edges for installation, heat treatment of elements and forming a joint. The implementation of the project requires a small arsenal of soldering tools:
- measuring instruments, locksmith square and marking materials (pencil, marker);
- roller pipe cutter or special scissors;
- rags with a degreaser;
- apparatus for soldering certain polypropylene pipes;
- thick gloves with anti-slip coating.
The cutting tool must be comfortable, serviceable. The blade is checked for defects, sharpening. If possible, the shortcomings are corrected, if not, they acquire new scissors. It is also important to monitor the perpendicularity of the cut, which must be clean and even. Such requirements exclude the use of a hacksaw blade (saw, jigsaw) or grinder.
To ensure a tight and reliable connection between polypropylene blanks, it is necessary to prepare the working edges. The process includes removing dust, dirt, burrs, moisture, and degreasing surfaces. To do this, you can use a ready-made general construction compound or alcohol (ethyl, isopropyl).
For large-scale projects with large diameter pipes, mechanical, electro-hydraulic equipment is used. The composition of such devices includes a frame, a control unit, grippers with a seal, a trimmer, a disk heating element, a dynamometer. Fixation, displacement and adjustment of the position of polymer blanks is carried out by mobile centralizers. They are operated manually by means of a lever. Another option involves the presence of a hydraulic drive.
The welding machine for working with pipes of small diameter and thickness is structurally represented by a stand, a handle, an adjustment unit, a heating element in the form of a narrowed plate (xiphoid) or a pin (cylindrical). Special nozzles (sleeve-mandrel) of various diameters are attached to the latter. As a rule, it is permissible to install several interchangeable gear at the same time (under holes or in the form of clamps) in order to carry out continuous installation of highways from channels of different sizes. A hex wrench is included for fastening parts.
How to solder polypropylene pipes
Instructions for soldering any polypropylene pipes by means of thermal action on products require compliance with standardized or manufacturer-recommended time intervals. They apply to heating and the formation of a nodal connection between the elements of the highway. The process itself is carried out differently depending on the equipment used and the dimensions of the pipeline elements.
General technological methods for welding polypropylene pipes
How to solder polypropylene pipes of large diameter? The butt welding process includes two steps. Workpieces are pre-installed and fixed on the equipment in a predetermined position. The edges of both parts at once are processed with a trimmer (a special rotating disk). Then it is replaced with a heating flat element. After its elimination, after a certain technology time, the workpieces with melted edges are pressed against each other to carry out the polyfusion process.
Sleeve welding technology requires attention regarding the time for melting the walls and compressing the elements.
Below is a table of soldering temperatures for thin-walled polypropylene pipes, which is especially worth relying on for a novice master.
|Outer Diameter (mm)|
|Heat Treatment Section (mm)||13||fourteen||16||eighteen||twenty||23||26|
|Melt timer (sec)||5||7||eight||12||eighteen||24|
|Node Adjustment Timer (sec)||four||6||eight|
|Connection commit timer (sec)||6||ten||twenty||thirty|
|Polymerization timer (sec)||120||240||360|
The joint is formed by means of the inner wall of the fitting and the outer wall of the pipe. The sections are subjected to thermal impact by means of special nozzles for soldering equipment, heated to a temperature of +260℃. Next, the workpieces are inserted into each other and hold the fixation for the minimum required time.
Features of working with pipes with aluminum reinforcement
Polypropylene has the property of warm expansion, which limits the use of the material in conditions with high temperature, temperature fluctuations. The disadvantage is corrected by reinforcing the pipes with aluminum or fiberglass. In the case of the first, there are no difficulties during soldering and operation of the highways.
Metal reinforcement can be installed on the inside of the products or under the outer shell. The outer layer with aluminum foil must be removed before soldering. There are three reasons for this:
- additional heating is required;
- metal-plastic blanks have a larger outer diameter than without reinforcement or with fiberglass;
- aluminum with a polymer in the process of welding form a weak connection.
To carry out the work, a shaver is used — a duralumin hollow cylinder with steel blades located inside. Additionally, for ease of use, a removable handle in the form of a rod can be inserted. Here, a limitation on the thickness of the cut and the depth of the treated area is provided in advance, so there is no need to track the parameters.
Internal stripping is carried out to exclude direct contact of aluminum with the transported liquid. This can lead to the activation of electrochemical processes, the destruction of the reinforcing foil, the delamination of the pipe, and the depressurization of the contact assembly. Here, trimmers are used to prepare workpieces for welding. This device is similar in structure to a shaver, only the blades are located on the inner end.
Specificity of work in conditions of negative temperatures
Carrying out installation work at low temperatures involves making changes to the key time periods of heating and fixing workpieces. But installation features are not limited to this. The impact of frost on the polymer is reflected in the hardness of the material — it becomes brittle, which complicates cutting, requires more attention during transportation.
The issue of fragility is solved only by the accuracy of the work. It is better to cut in a heated room. Limiting values of admissible temperatures are in the range of 0-+5℃. Lower rates lead to crystallization processes that do not bypass polymeric materials. In such conditions, there is a high risk that the pipes will begin to crumble.
Thermal exposure guidelines are based on room conditions. The lower the thermometer reading, the longer it takes to heat the polypropylene. Based on practice, the masters recommend first bringing the material to +20℃, then using a normalized timer. At the same time, it is impossible to heat the device above +260℃, as this may adversely affect the quality of the pipes.
There is an opinion that all standards when working in the cold should be increased to 50%. This is absolutely not applicable to commit time. The connection of the elements here must be carried out in an accelerated mode, so that a full-fledged polymerization process is possible with rapid cooling. Delay in this case will lead to the fact that the assembly will be of poor quality, will not last long due to early depressurization.
Effect of errors on welding quality
Experts note that the most common mistakes are neglecting the requirements for pipe preparation and time standards. Often skip degreasing, inattentive to the condition of the edges, cleanliness and dryness. Such errors lead to a violation of the solidity of the connection.
Overheating of the walls of polypropylene pipes leads to a narrowing of the inner diameter of the nodal connection. It also occurs with excessive compression. It is usually impossible to clean the duct. And such a malfunction, along with distortions, is the cause of a rupture or clogging of the channel.
In rare cases, early failure of the assembled line is justified by dissimilar materials relative to the manufacturer. This happens even after professional installation. The reason is that each manufacturer works according to its own technology, uses its own recipe. As a result, the pipes may have different rates of heating, fixing and cooling. Therefore, it is worth using blanks with fittings from one manufacturer.