Methods for joining polypropylene pipes
If the task is to equip heating with plastic pipes of small diameter (up to 63 mm), in practice there are two ways to connect such pipes:
- socket welding - in this case, one pre-expanded end of the pipe is placed in the other;
- socket welding - here the ends of two elements are connected to each other using a coupling.
In the case of joining pipes with a large diameter (from 63 mm), they resort to the use of butt welding. This installation method does not require additional connecting elements, while maintaining an excellent degree of pipe fixation. Fittings of suitable size (sleeve welding) can also be used. In the presence of pipes with a diameter of 40 mm, it is more convenient to use manual welding, but larger elements are usually joined using a special apparatus that pre-aligns.
Immediately before starting the installation of the heating system, it is worth once again carefully considering the entire process of assembling the pipeline. This will avoid unwanted nuances at the time of operation that affect the final assembly quality of the heating system.
Scheme of the process of connecting polypropylene pipes
Here we outline the main nuances of how to connect plastic heating pipes:
- The optimal heating time of the soldering iron is 5 seconds.
- The recommended melting temperature of polypropylene is 270°C. This parameter can be achieved using a special toggle switch installed on the welding machine.
- It should be noted that the technology for joining pipes of the heating system will vary depending on the place and season. So, during sub-zero temperatures or when installing a heating structure outdoors, the heating time of the soldering iron pipe should be slightly increased or the temperature should be raised to melt polypropylene products.
- In the case of joining pipes of a larger diameter, the melting time of the material will also increase slightly.
- The recommended time for fixing elements of large diameter between themselves after heating is 30 seconds or more.
Next, you need to consider in detail, in fact, the technology of soldering pipes made of polypropylene:
- After reaching the required temperature, the nozzles of the soldering iron for polypropylene pipes - for the outer and inner dimensions of the cross section of the pipes - are simultaneously put on and heated by the connecting parts (coupling, pipe).
- At the moment of the heating process, "flares" are formed on the heating elements.
- As a result of the heating process, both parts are removed from the nozzles and docked with each other by uniform gentle pressure on them from both sides towards each other and fixing in this position. Any rotations and unnecessary movements during the connection of the elements are unacceptable, as this may disrupt the resulting seam.
- The connected elements should be held for 30 seconds for a more reliable adhesion of the parts of the heating system. It must be added that the rim must be even along the entire length of the connection.
After complete cooling, the connected parts are ready for use.
Welding process parameters
Ways of joining pipes made of metal-plastic and PEX-pipes
Metal-plastic elements and PEX pipes are often joined using the same method. Here we will describe in detail the technology of installing a heat pipe from the above materials.
The connection of metal-plastic pipes is carried out in two ways:
- using compression fittings;
- using press fittings (pressure testing of heating pipes).
Pipe connection with compression fittings
This type of fitting is more convenient to use. Compression fittings can also be used to assemble cold water supply systems. Installation of a pipeline that conducts hot water is also carried out by builders using the mentioned fittings.
When assembling the above-mentioned pipelines, there is no need for special equipment for stitching metal-plastic and polypropylene. In order to connect the parts of the pipes together, you only need a pair of wrenches and pruning shears.
The heating elements are connected according to the following algorithm of actions:
- Initially, a compression nut is placed on the end of the pipe from the docking side.
- Next, a split-type ring should be put on behind the nut, while the edge of the ring must be placed at a distance of 1 mm relative to the pipe cut.
- Then the pipe is pushed up to the stop and fixed on the fitting fitting. In this case, chamfering of the pipe is not required.
- The crimp nut is installed with wrenches.
Compression Fitting Parts and Assembly Procedure
When tightening the nut, it is not recommended to apply excessive force, as there is a high probability of cutting the pipe.
Docking pipes using press fittings
Press-type fittings for metal-plastic pipes, as well as cross-linked polypropylene, make it possible to reliably connect parts of the heating system. Unfortunately, such a construction cannot be separated in the future. To perform installation in this way, you will need to use a special press tool.
In order to connect the previously mentioned heating elements using fittings, you should follow the following instructions:
- A clamping threaded sleeve must be put on the end of the pipe.
- Then an expander with the desired cross section is placed into the pipe until it stops.
- The handles of the expander are slowly connected to each other and fixed in this position for a short time.
- The fitting nipple is inserted into the pipe. Due to its unique molecular composition, the pipes will shrink, which will help to tightly fix the fitting to the pipe.
- The pipe is securely pressed onto the fitting using a manual or hydraulic press.
Pressing with a special tool
Features of the installation of polypropylene pipes
Installation of additional equipment
When installing polypropylene pipes, it is necessary to take into account the thermal expansion factor
This is important on heating systems and hot water pipes. To do this, it is necessary to install compensators on propylene pipes.
The main functions of compensators:
- Absorption of temperature changes and strong pressure surges in the heating and water supply system.
- Maintaining the integrity of the entire system.
- Increasing the reliability of the plastic pipeline.
You can also distinguish between compensators by the material from which they are made.
You can use metal expansion joints, they are:
- axial bellows compensators KSO;
- compensators bellows surge arresters;
- shear compensators (KSS);
- rotary compensators (KSP);
- universal compensators (KSU).
Universal expansion joints are usually installed on small structures.
There are devices with a flexible connection made of elastic materials. The most commonly used are U- and L-shaped structures, as well as loop-shaped compensators and "snakes".
Compensators: loop-shaped (left) and U-shaped (right)
Threaded connection with metal pipes (American)
The connection of plastic pipes using the threaded method does not provide a great connection strength. In this case, welding of elements of this design gives greater tightness. If it is impossible to avoid a threaded connection for some reason, then American women for polypropylene pipes are quite suitable.
This is a special detachable combined fitting, which has a metal thread on one side and a polypropylene base on the other. On the one hand, it will be screwed to the metal, and on the other, it will be welded to the plastic.
American can be used multiple times
Use of flanges
Such a connection is made using adapter bushings welded to the ends, or cap steel flanges (profile and smooth) with a thread on one side. They are installed without welding. Of the advantages, there is a high reliability of joints that can withstand high temperatures and pressures up to 16 atm. The connection can be made on a pipeline of different diameters from 2 to 120 cm.
Docking begins with pulling the flange on the pipe and putting on a rubber gasket. It is installed at a distance of no more than 10 mm from the end. The flange is moved to the gasket, another pipe is prepared in the same way
The bolts are tightened carefully so that the plastic does not crack.
Flange connection of plastic pipes
Welding a polypropylene pipe with fittings
Main stages:
- preparation of the necessary tool.
- pipeline planning.
- pipe cutting.
- welding of pipes and fittings.
Fittings and accessories are usually attached to plastic pipes by welding. This will require a special soldering iron with several nozzles that are suitable in size to the diameters of the pipe and fittings. Before starting welding, it will be necessary to clean the area where the fitting enters it. To do this, the aluminum foil is removed if a pipe with an aluminum layer is used.
Soldering a polypropylene pipe with a fitting
Then the fittings for polypropylene pipes and the pipe itself are evenly heated with a soldering iron with an appropriate nozzle and connected to each other.
When gluing pipe parts and fittings, rotation of the parts must be avoided. The soldering of the elements must be securely fixed at the time of their cooling. Otherwise, the connection will not be tight and will leak during operation.
With a combined connection with a metal water pipe, a different connection method will be required, including both welding and a threaded connection. Typically, such a combined connection is required when connecting plumbing equipment.
First of all, before starting work, turn off the risers and drain the water in the system. After that, the old water supply is dismantled.
To speed up the dismantling of the old water supply, you can simply use the grinder - cut the old metal pipes into pieces.
The soldering process is shown in detail in the video below.
After the dismantling work is completed, it is necessary to remove the old valves, clean the part of the water supply line leading to the riser with a cable and proceed with the installation of a new valve. This will help to avoid a blockage in the water supply on this old section of water supply.
Before installation, it is necessary to put the filter on the mixer. This will prolong the life of the washing machine, which can be connected to the water supply system in this place.
After all this, you can install a combined fitting. The threaded metal part is attached to the mixer, and the plastic part is welded to the pipes.
Welding and installation of a separate part of the piping system
When soldering a water main made of polypropylene, they always try to install individual sections of the water supply in a place with a large free space and at a convenient height. To do this, you will need basic tools, a line drawing and the correct order of work.
Usually the most difficult side to solder is located on the wall with two corner fittings, so it is welded first and fixed with clips or dowel sleeves. After that, from the corner fittings, further installation of the line sections is carried out, proceeding to soldering work directly near the walls.For ease of installation, it is necessary to provide in advance a place for installing the soldering iron on a stand or organize its suspension.
