Names

Which connection is more reliable for HDPE pipes. How to connect HDPE pipes: types of connections (fittings, couplings, welding) and their features. Execution of permanent connections

Polymer pipes are often used both in industry and in the installation of plumbing systems in private construction. Their popularity is due to the ease of installation and low price of products. The reason for such a low cost is the limitation of the operating temperature of HDPE pipes to 65 degrees. Nevertheless, the supply of both cold and hot water to a house or apartment is almost always carried out with their help, so the connection of such pipes is a rather relevant issue.

Peculiarities

In addition to the installation of pipelines, the operational properties of HDPE pipes are reflected in the following areas of application:

protection of electrical cables and cable communication systems laid in the soil from corrosion;
formation of a waterproofing layer for various materials - concrete, metal, wood;
installation of irrigation and sewage systems, as well as gas supply.

Their high popularity is also due to the fact that pipe sections can be connected to each other in several ways, which makes them almost universal.

Kinds

There are several classifications of such connecting elements for HDPE systems. The main one is the classification according to the method of their installation. All connections of HDPE products can be divided into two types: one-piece and detachable.

Permanent connections can be created with or without a fitting. However, a connection without an additional element is less reliable and durable, so it is practically not used.

One-piece

Such joints are used quite rarely and are performed using special welding, performed either as a conventional butt joint, or using an electric coupling. In the first case, with the help of professional welding equipment, the ends of the cut products are heated to a soft plastic state, after which they are pressed against each other and cool in this position until hardening. Such a connection will be strong only if the sections of the two pipes to be connected are not oval, but round in cross section.

To work with an electric clutch, you will also need special equipment that will heat the spiral located in it. Cut pieces of pipes are inserted into both outlets of the coupling, the spiral heats up and melts their connected edges. After the spiral has cooled, the heating apparatus is disconnected from the coupling, and it is left as a connecting element that protects the seam.

Thus, welding of HDPE products can be done end-to-end, socket welding with a fitting, using a press (edge welding) and using electric couplings.

Detachable

Most often, detachable fasteners are used to connect HDPE products. This is done by the method of socket alignment with the help of elastic polymer seals. This method can only be used in non-pressure pipeline systems.

For pipes in which water is supplied under pressure, various fittings are an ideal connection method. Their use increases the life of the entire system, its reliability and resistance to temperature extremes. Fittings are universal and resistant to various aggressive environments. They are used both for connecting hoses with the same internal diameters, and for different-caliber products.

The connection itself can be different.

Flanged. In this case, the brass flange or cast flange is welded to the pipe. Most often, pipes of different materials or wide highways are connected in this way.
Bell-shaped when one end of the pipe enters a fitting extension on the other pipe. Systems correctly connected in this way are the most reliable and resistant to pressure.
Threaded. With such a connection, threads are threaded on pipes and fittings in advance with a special tool. Only systems with low pressure can be connected in this way, as this is not a very reliable method.

Depending on the rigidity of the material, there are flexible and inflexible connections made of metal (brass, steel, cast iron and copper) or polymers (polypropylene, plastic, polyethylene and PVC). According to the diameter of the hose, the method of fastening is divided into connecting pipes of the same size and different ones.

In addition to the connection method, accessories for HDPE pipes are divided into the following types.

Welded. Such elements for HDPE systems are produced either by casting (molded fittings) or by conventional welding of short pieces of pipe (welded fittings). Such welding is called butt welding. The diameter of the elements ranges from 63 to 315 mm.
Electrowelded. In essence, such fittings are just thermistor couplings used where it is impossible to organize conventional welded joints or they are not reliable enough. One of the features of such electric welded elements is the possibility of carrying out work without moving the pipe and creating separate tie-ins into the system. With their help, you can connect hoses of different diameters, as fittings are available in many different diameters. They are not only in the form of conventional couplings, but also in the form of tees, bends and plugs, both with small diameters of 20, 25, 32 mm, and for large systems with diameters of 800, 900 and 1200 mm.

This type of product has a wide application and is used for mounting any branches and plugs that exist. Most often they are installed in gas supply systems or for liquids with a highest temperature of 40 degrees.

Compression (crimp). Such detachable fasteners are produced for combining pipes without the use of welding. Compression elements consist of a polyethylene rigid or flexible body with sealing rings at the ends, clamping connections, a pressing sleeve and cap nuts. The dimensions of such fittings start from just 16 mm, and end with a standard riser line diameter of 110 mm. Usually, when installing water supply and sewerage, fittings with a diameter of 50 mm are used, since inlet and outlet pipes of this particular diameter are installed in most houses and apartments.

In addition to all of the above classifications, the fittings themselves are divided into several types, depending on what role they play in the water supply or sewerage system.

Plugs - for permanent or temporary closing of the path to the flow of water and gas.
Clamps crimp and fix the pipe.
Tees or crosses - for arranging branches from the main pipeline and connecting additional devices.
Couplings - elements of connection of two segments.
Adapters - for assembling pipes from different materials into one system, for example, HDPE with metal.
Elbows are needed for angular rotation of pipes and changing their direction. Standard elbows are available in 45, 56 and 90 degree angles and can be made to order if a different degree of bend is required.
Saddles are used to create branches.
Overlays cut new pipes into the previously installed system.

Mounting

Of all the types of connection of polyethylene parts for installation on their own, compression fittings are most often chosen. The choice of this type of components is associated with the lack of expensive equipment for their installation. You just need to connect all the details of such a mount with your bare hands.

The installation process itself is as follows.

Pipe cutting. The polyethylene pipe is cut with special scissors at a right angle. The edge must be free of all burrs and rounded off. A special mark is applied to the surface of the pipe, which shows how deep the pipe must be inserted into the socket of the fitting.
Mounting disassembly. Before inserting the pipe ends into the polymer connector, loosen and remove their plastic caps. Putting the assembled fitting on the end of the pipe is strictly prohibited, as the parts will not be connected correctly and there is a high risk of leaks.
Compound. The end of the pipe is lubricated with ordinary soap or wetted with water, a nut removed from the fitting is put on it. A pressing sleeve is placed on the pipe. The white clamping ring is installed so that its thick part is directed to the pipe, and the rubber ring can either be placed in a special recess of the fitting or put on the pipe itself.

The pipe is inserted into the fitting body, the ring and sleeve are moved close to it. The clamping nut is first tightened by hand, and then tightened with a special tool. After installing all connections, it is necessary to check the system by supplying water to it under the maximum permitted pressure.

Installing a water supply system using HDPE pipes is quite simple, even beginners can assemble a simple water supply system on their own.

However, there are some typical mistakes that it is better to know about in advance in order to avoid them.

Do not buy products from different materials. Water supply hoses can be made from different types of polymers, which will reduce the tightness of their connection. As a result, you can get a crack or leak near the fitting.
A mistake is both excessively strong tightening of the nut, and its weak fixation. In the first case, you can not only break the thread on the product, but also get a microcrack in the body, which is invisible at first glance. After water is supplied to the system, such a crack will begin to expand, and the fitting body will eventually burst. In the second case, the waterproofing ring will be loosely pressed, and water may seep over the edge of the joint.

In household networks, they usually put the most inexpensive option with manual control. Nevertheless, devices with a gearbox are also widely used, which make it possible to facilitate manual effort when changing the position of the lever. With a line width of 150 mm and above, only mechanical drives are used and they are not manually blocked.

Modern plumbing is rarely made of metal. He has worthy competitors - polymers, which are gradually replacing him in many areas. One such material is low density polyethylene. Pipes for pressure pipelines are made from this material, that is, for water pipes and even for gas pipelines. This type of material is becoming increasingly popular, as the connection of polyethylene pipes is easy to do with your own hands. You just have to follow very simple rules.

Advantages and features of the application

Polyethylene pipes are made from low pressure polyethylene. This material is abbreviated as HDPE. It is characterized by increased strength and elasticity, has good performance properties:

chemically neutral, can be used for food transportation;
smooth walls prevent the formation of plaque inside;
not subject to corrosion;
low coefficient of thermal expansion - about 3% at maximum heating (up to + 70 ° C);
they normally react to the freezing of water inside, due to elasticity they increase in diameter, and after thawing they take on their original dimensions.

One moment to remember! If you need pipes that are resistant to freezing (for example, for), look at the description or technical specifications when choosing. Not all types of copolymers that are used for the production of pipes tolerate freezing well. So be careful.

The main disadvantage of polyethylene pipes is the restrictions on the temperature of the transported medium: it should not be higher than + 40 ° C, that is, only cold water supply can be made from HDPE, they cannot be used for hot water and, moreover, heating.

Another point: polyethylene does not tolerate UV radiation. With constant exposure to the sun, the material loses elasticity, and, after a while, breaks (some manufacturers make HDPE pipes resistant to ultraviolet radiation, but they are more expensive). Therefore, open laying of water pipes from plastic pipes is very undesirable. But it is very possible to lay a pipe in a trench from a well or well to the house, to make cold water distribution around the house. This is a fairly economical and convenient solution, since the installation and connection of polyethylene pipes is not a very complicated matter. If we are talking about a detachable connection, then no equipment is needed for it. All you need is fittings and hands.

Which polyethylene pipes are better

For the production of water pipes, two grades of polyethylene are used - PE 80 and PE 100. The hundredth polyethylene is denser and more durable than the eightieth. For water supply systems of a private house, the strength of PE 80 is more than enough - they can withstand pressure up to 8 atm. If you like a large margin of safety, you can take them from PE100. They work fine even at 10 atm.

What you should pay attention to is the country in which this product is produced. Quality leaders are European manufacturers. High precision execution guarantees high reliability of the system. Average quality and prices are from Turkish companies, in a cheaper price segment, Chinese manufacturers. Their quality, as usual, is also much lower. It is difficult to give advice here, everyone selects at their own discretion (or what is in the region).

Types of HDPE pipe connections

There are several types of connection of polyethylene pipes:

detachable (on fittings or couplings);
one-piece - by welding:
- using a special welding machine;
- electric couplings - a heater is built into such couplings, when an electric current is applied to it, polyethylene is heated and fused.

Weld mainly pipes of large diameters, which are used to create main pipelines. Pipes of small diameters - up to 110 mm, used in private construction, are mostly connected using fittings. Couplings are used more often during repair work, as their installation takes more time.

Fittings for polyethylene pipes are shaped parts (tees, crosses, angles, adapters, couplings), with the help of which the required system configuration is created. Since self-connection of polyethylene pipes is carried out more often with the help of fittings, let's talk about them in more detail.

Assembly on compression (crimp) fittings

On one or two sides of the fitting (sometimes on three), a whole system is installed that provides the connection. The fitting itself consists of:

How reliable is the connection

Despite the apparent unreliability, the connection of polyethylene pipes on compression fittings is reliable. Properly made, it can withstand operating pressures up to 10 atm and above (if these are products of a normal manufacturer). Watch the video for proof.

This system is good for easy self-assembly. You probably appreciated it already from the video. Just the pipe is inserted, the thread is tightened.

Summer residents, in addition to the ability to do everything with their own urks, like it because, if necessary, everything can be disassembled, hidden for the winter, and reassembled in the spring. This is in case the wiring is done for irrigation. The collapsible system is also good because you can always tighten the digging fitting or replace it with a new one. The disadvantage is that the fittings are bulky and internal wiring in a house or apartment is rarely made of them - the appearance is not the most pleasant. But for the water supply section - - it is difficult to find better material.

Assembly order

The pipe is cut strictly at 90 °. The cut should be even, without burrs. Dirt, oils or other contaminants are also unacceptable. Before assembly, chamfers are removed from the sections of the connected sections. This is necessary so that the sharp edge of the polyethylene does not damage the sealing rubber ring.

During installation, the connection of polyethylene pipes on compression fittings is tightened by hand

Spare parts are put on the prepared pipe in this order: a compression nut is pulled, then a collet, followed by a thrust ring. We install a rubber gasket in the fitting body. Now we connect the body and the pipe with the parts put on it, applying force - we must insert it all the way. We tighten all the spare parts to the body and connect them with a crimp nut. We twist the resulting connection of polyethylene pipes with force by hand. For reliability, you can hold out with a special mounting key. The use of other tightening tools is undesirable: plastic can be damaged.

Saddles and their scope

In addition to fittings, there is another interesting device that allows you to make branches from an already finished pipeline. These saddles are specially designed couplings. This coupling has one or more threaded holes. They usually put a tap in them, and a new branch of the water supply is connected to it.

Sedeki are put on the pipe, fixed with screws. After that, a hole is drilled in the branch with a drill and a thick drill in the surface of the pipe. When it is ready, a crane is installed, a branch is assembled further. So improve the system with minimal effort and cost.

Flange connections and transition to metal

In the water supply system, elements of the system that do not have a threaded, but a flanged connection can be installed. Usually these are taps or other shut-off or control valves. To connect with such elements, there is a special fitting for HDPE. On the one hand there is a standard compression version, on the other - a flanged version. Installation is standard - with a compression nut on one side, gaskets and bolts on the flange side.

When installing a water supply system from polyethylene pipes, questions may also arise about the connection of polyethylene and metal. For these cases, fittings are used, on one side of which there is a thread. It can be external or internal - it depends on the type of device or transition being installed. Such fittings are available in straight lines, in the form of a 90° angle.

The installation is standard - a thread (with winding neatly) on one side and a crimp nut on the other.

Pipes made of polyethylene are a modern high-tech material that is widely used for the construction of pipelines for transporting various media.

This type of pipe is also popular because the installation of pipelines can be performed by a non-specialist. Consider how HDPE pipes can be connected, and what advantages each installation method has.

Polyethylene pipes are widely used in construction and in everyday life.

For example, these products can be used:

For the construction of a pipeline for water supply;
For installation of sewerage systems;
To protect power cables when laying electrical networks;
To create waterproofing shells when laying heating mains;
To protect communication cables;
For the construction of artesian wells;
For use as shaping parts in the construction of monolithic buildings.
To create irrigation systems in greenhouses, etc.

Such a wide application, not least, is due to the ease of installation. Consider the methods of their connection.

Methods used to connect HDPE pipes

All existing ways to connect two polyethylene pipes can be divided into two types.

One-piece connections, i.e. welding.
Detachable connections using fittings.

The latter option is used more often, here are its main advantages:

Saving. There is no need to purchase special equipment for welding or pay for the services of a master.
Availability. A detachable connection can be made where the use of welding is not possible, for example, under water.
Speed. This method allows you to connect parts at high speed.

Making a detachable connection of HDPE pipes

Detachable pipe connection can be made in the following ways:

Socket connection. This method requires elastic seals. Such a connection is most often performed during the construction of a free-flow sewer pipeline.
Flange and fitting connection using special fasteners.

Use of couplings

In the construction of pipelines, couplings for HDPE pipes are widely used.

This part is an element made of polyethylene. For the manufacture of couplings, the extrusion method is used.

This connection method allows you not to use welding machines, that is, it does not require the purchase of special equipment. Moreover, the couplings for HDPE pipes themselves are quite cheap, so their use saves on construction.

Additional benefits of using couplings:

Long service life of several decades.
Fastening reliability.
High resistance to temperature changes, as well as to mechanical stress.
Resistance to aggressive environments.
A wide range of applications, the coupling for HDPE pipes can be used for the construction of a pipeline for almost any purpose.

There are the following types of couplings:

Compression sleeve. This product is available with both external and internal threads. This product is widely used in the construction of heating and gas supply systems. With the help of this part, steel and polyethylene pipes are joined.
For quick and reliable connection of parts of the same diameter, a coupling for HDPE pipes is used.
Reducing clutch necessary to connect pipes with different diameters.

Connecting pipes with compression fittings

The work is carried out according to the following algorithm:

The compression fitting must be disassembled by unscrewing the union nut.
The pipe is cleaned of dirt, a chamfer is made at the end.

To chamfer, a beveler should be used, however, in the absence of this tool, you can use a sharp knife.

A mark is made on the pipe with a marker, which should characterize the depth of entry into the fitting.
Before introducing the part, the pipe should be moistened with liquid soap.
The pipe is inserted into the fitting, when performing this action, some effort will have to be applied, since the rubber seal creates resistance.
The fitting nut is tightened.

When tightening the nut, it is important not to overdo it so as not to overtighten the connection.

Making a permanent connection of HDPE pipes

In some cases, it is more advantageous to use the pipe welding method, that is, the formation of a permanent connection. Consider how to connect HDPE pipes by welding. Currently, two methods are used - butt welding and connection using electric couplings.

Electrofusion welding

This type of welding is carried out using a shaped part (coupling) made of polyethylene, into which electric spirals are inserted. When voltage is applied to the spirals, the pipes heat up, and they are welded to the inner walls of the coupling.

Requirements for the process:

Preliminary cleaning of pipes;
The immobility of parts during the period of heating and cooling.

Butt welding

This method of connection is carried out by using a special apparatus in which the edges of the pipes are heated. After heating, the parts to be welded are joined to each other, and when the plastic cools down, a reliable connection will be obtained.

When connecting butt welding, pipes with pronounced ellipticity are not allowed to work.

Requirements for welded joints on polyethylene pipes

The butt weld cannot be located below the level of the outer surface of the pipe.
When welding two segments, their displacement relative to each other should not exceed ten percent of the wall thickness of the pipe used.
The height of the bead on a high-quality weld does not exceed 2.5 mm for pipes with a wall thickness of up to 5 mm, and should be more than 5 mm when using thick-walled pipes (wall thickness 6-20 mm).

conclusions

The choice of one or another pipe connection method should be carried out taking into account the operating conditions of the pipeline - whether it will be pressurized or not, what medium will be supplied through the pipes, etc. The correct choice of pipe connection method will ensure the reliability of the pipeline system.

The technology of connecting HDPE pipes, in contrast to the connections of metal pipelines, can be carried out both by welding and with the help of special parts. And if the tightness of the welding structure is beyond doubt, then the quality of the connection using fittings depends on the correct installation.

HDPE is low pressure polyethylene. HDPE is obtained by polymerization of ethylene organic matter at temperatures up to 120 ͒С under pressure up to 2 MPa in a solution of a special catalyst. The resulting material is also called high-density polyethylene (PVP) because it is denser and stronger than other polymers.

Note! Modifications of HDPE are used in the creation of boats, body armor and the construction of landfills for the processing of hazardous waste, as well as for the manufacture of pipes. The variety of applications proves that LDPE is a very durable and hermetic material.

Advantages and disadvantages of HDPE pipes

The advantages of HDPE pipes include:

Immunity to any kind of solvents. At temperatures up to 80 ͒С, HDPE pipes do not dissolve at all. When this temperature is reached - only in special solvents. Water is harmful only at temperatures above 180 ͒С.
Are not exposed to corrosion. This problem is known for all metal pipes, which, under the influence of water and air, begin to oxidize over time. Corrosion is not terrible for HDPE pipes, since they do not contain metals.
Smooth inner surface. Roughness and unevenness lead to the accumulation of various kinds of pollution. Over time, such dirt can almost completely block the lumen. HDPE pipes are smooth, so nothing interferes with the laminar flow of liquids through them.
Durability. Manufacturers promise that their products can last up to 50 years. It should be borne in mind that this figure was obtained theoretically. High-density polyethylene was put into operation about 60 years ago, therefore, reliable data on such a service life have not yet been received.
Flexibility. HDPE pipes are very flexible, they can even be rolled up. This is an undeniable advantage if they are laid through uneven terrain.
High strength. HDPE is a durable, airtight and at the same time elastic material. It doesn't leak, break, or kink. Due to their flexibility and strength, they have proven themselves even in seismically active areas.

Low pressure polyethylene in the popularity rating among the materials used for the assembly of pipelines occupies a leading position. The secret of such demand is easily explained by the versatility of application and ease of installation of polyethylene pipes.

But as with any other polymer, high-quality installation of HDPE pipes with your own hands can be done only if the technology is strictly observed. We will tell you what nuances to take into account when matching elements. We will explain how to properly bend and straighten them.

Technologically, HDPE pipes can be connected by two main methods - one-piece and detachable.

The first involves the involvement, the second is implemented without using it.

Each fastening method has its own advantages and disadvantages, and therefore the best option for joining polymer pipes is chosen based on specific conditions.

Welded one-piece connections enable maximum sealing, which is especially important when arranging. Detachable connections are easy to install and make it possible to disassemble the pipeline at any time in order to change the configuration of the line or supplement it with new branches.

One-piece connection methods

For joining HDPE pipes, two permanent connection methods are used: by butt welding and by installing an electric welding coupling.

In any case, when implementing these methods, the following requirements are imposed on the connections:

The maximum displacement angle of the welded segments should be no more than 10% relative to the wall thickness of the pipes being joined.
The butt joint should be made above the outer level of the surface of the adjacent segments.
The height of the roller of a well-made seam should vary in the range of 2.5-5 mm.

The optimal value of the height of the roller depends on the wall thickness of the melted product. On thin-walled pipes (up to 5 mm), it should be no more than 2.5 mm. If the wall thickness of the pipes varies between 6-20 mm, then the height of the roller should be no more than 5 mm.

By butt welding of pipes

The creation of an integral connection is carried out by softening the material to the state of a viscous substance so that a diffuse association of its parts occurs. It is used for pipes having a wall thickness of more than 5 mm.

Butt joint using a welding machine is used in the arrangement of pipelines through which liquid is to be transported under high pressure conditions

The connection method using welding is used on straight sections of the water supply system, which is supposed to be operated under pressure. Only it allows to obtain a tight connection with diameters over 200 mm, since it does not create a loss of pipe rigidity, leading to deformation.

Strong welding of HDPE pipes with their own hands is carried out using a special tool. The essence of the method is to heat the ends of the joined elements to a viscous state using a heating nozzle. The softened ends are simply joined together under pressure, after which the joint is simply allowed to cool.

The main difficulty in working with the equipment is the need to control not only the degree of heating of the elements, but also their own movements in order not to spoil the seam and not violate the integrity of the pipes.

When performing welding work, it is important to maintain the temperature regime of the heating elements.

The parameters for holding the time and temperature of the heating elements are determined by taking into account three factors:

The thickness of the walls of the pipeline.
Outlet diameter.
Technical parameters of the soldering device.

Connecting pipes by welding is the most reliable and durable option. With it, you can create a one-piece mount that can withstand the pressure of both non-pressure and pressure.

The main advantage of welding fasteners is reliability, which cannot be achieved using the cold pressing method. Among the "cons" of the welding method is only the inability to disassemble the connection for maintenance work and cleaning the same pipe

Welding is performed in the following sequence:

Communication is cut to the specified size. Trim the parallelism of the plane of the ends. The ends are cleaned with a piece of sandpaper.
A chamfer 2-3 mm wide is removed from the ends. The welding site is thoroughly cleaned and treated with a degreasing agent.
The soldering iron is set to a heating mark of 260 °. While it is warming up, string welding nozzles and wait until their degree of heating reaches the set temperature.
Using a centering mechanism, a fitting and a pipe end are deepened into the cavity of the nozzle. If a centering mechanism is not provided in the soldering iron, the alignment will have to be checked “by eye”, making the docking as accurate as possible.
The centered elements are pushed to the specified mark, connecting under pressure, and withstand the time specified in the instructions for reflow.
After completion of work, the device is moved aside and disconnected from the network. The welding area without displacement and rotation is fixed in a predetermined position until the surface is completely cooled.

When performing welding, it is important not to overdo it. This can provoke the formation of an influx of polyethylene on the inner diameter of the product.

Video #3 Pipe straightening option:

When choosing a method for connecting and aligning polyethylene pipes, the level of pressure of the working medium must be taken into account. This will minimize the negative impact of the pipeline manipulations on its technical characteristics.