For laying external pipelines for the purpose of transporting the working medium, both to industrial facilities and to the residential sector, pressure pipes made of polyethylene are widely used. All features related to the characteristics and installation of these pipes are discussed in this article.

PE pressure pipe

Features of PE products

Scope of use

PE pipes are used to transport the working medium, which is:

• drinking and technical water;
• various gases;
• liquid chemical compounds that do not affect polyethylene.

The products are mainly used for:

1. Cold water supply.
2. Sewer systems.
3. Transportation of natural gas.

In addition, polyethylene non-pressure pipes can be used when installing a protective route for power cable due to its property not to conduct electricity.

Main characteristics

Pressure polyethylene pipes are produced using polyethylene, which is characterized by high density, of the following class:

• PE 100;
• PE 80;
• PE 63.

PE pipes in coils

In order to solve all possible problems in the organization of water supply, pipes are produced in various diameters from 16.0 mm to 1600.0 mm and are designed to work with a medium under pressure from 0.40 to 2.0 MPa. Products are painted black and marked with blue stripes. Products are supplied in straight lengths of 12 m or other standard length. At the same time, pressure polyethylene pipes less than 110.0 mm in diameter are supplied in coils having a length of 50 m to one kilometer.

Although the polyethylene pipe products mainly used for transmission cold water, worker temperature Range operation of products is plus 40ºС. Therefore, it is quite possible to use pipes (made of special high-tech polyethylene) for organizing heating or hot water supply systems. For sewerage, non-pressure coupling pipes made of polyethylene are more often used.

Advantages

Polyethylene products are in constant demand. Their popularity is due to many positive features when compared with cast iron and metal products. First of all, they are characterized by:

• longer period of operation. Guarantee period polyethylene pipes defined at age 50;
• non-susceptibility to corrosion during transportation of water and aggressive chemical working environment;
• very light weight, which reduces the cost of transporting products;
• convenient delivery in coils, thanks to which expendable materials and significantly increases the installation efficiency;
• the presence of several ways of connecting pipes, including butt welding.
• the ability to repeatedly dismantle and re-lay the pipeline at minimal cost;
• ease of disposal and recycling of products;
• high elasticity, due to which the installation of a line of any configuration is greatly facilitated;
• ability to withstand variable ground loads, including earthquakes. For laying in the ground, products do not need additional protection;
• smooth inner surface;

Thanks to this design feature, it is possible to use pipes with a smaller diameter, while providing the necessary hydraulic properties. The throughput of PE pipes is 15% higher than steel pipes.

• low elasticity of the material, therefore, polyethylene water pressure pipes are not subject to water hammer;
• resistance against low temperature (when the working medium freezes, the pipe does not collapse);
• ecological purity and bacteriological safety.

Installation of PE pipes

Connection types

Reliable connection of products can be carried out in several ways:

1. Butt welding.
2. With the use of special couplings with embedded electric heaters.
3. With flange connections.
4. The flared method.
5. With the use of a compensating clutch.

Flange and socket connections are detachable. Other connections cannot be disconnected.

Butt welding procedure

This method is used to connect polyethylene pipes with a diameter of 63.0 mm or more. To obtain a reliable joint, you must:

1. Fix the parts to be welded in a special machine for butt welding.
2. Clean the ends of the pipes from dirt and dust.
3. Treat the surfaces of the products to be welded with a facing device.
4. After obtaining a uniform chip (no more than 0.50 mm thick), check the mutual parallelism of the pipes.
5. By using heating device heat the ends of the parts until the pipe surface begins to melt.
6. Close the melted surfaces and gradually increase the contact pressure.
7. Wait some time for complete welding and cooling of the seam.

Butt welding

Welding with electrical couplings

Although this method is more expensive, since special couplings are required, in which electric heating elements are embedded, it is widely used in conditions where it is impossible to perform butt welding due to limited space. This technology is used for pipeline products not large diameter.

The technology for performing the procedure is as follows:

Modern devices ensure that the entire welding cycle is carried out independently with guaranteed quality. In addition, all information on the operation is documented in an electronic protocol.

Thus, polyethylene pipe products are optimal and sufficient effective option for the organization of water supply or sewerage system.

In order to form and install water supply and drainage networks, it is necessary, first of all, to use water channels made of polyethylene pipes, taking into account all the advantages of such water channels over steel or cast iron products. A significant drawback of pipes made of metal, especially for steel products, is their lack of long term operation due to exposure to corrosive processes.

When installing any piping system, its operating characteristics will be determined by how scrupulously and carefully the workers adhered to the technique of installing gutters, no matter what material they were made of - metal or plastic. Each type of pipe has its own rules and installation technologies. Laying pipelines from polyethylene pipes has significant differences. First, you need to measure the width of the trench. It should perfectly provide convenience during installation and installation of the pipeline. The main thing to consider: the width of the ditch should be approximately 40-50 cm larger than the diameter of the pipes. Such conditions must be met when laying sewer pipes and when laying water pipes. If the laying of drains is carried out in strong or dense soil, then it is imperative to arrange a sand embankment about 10 centimeters wide.

It is imperative to remove any stones from the bottom of the trench, and the bottom must be made smooth and even. Care should be taken to ensure that the ground at the bottom is not frozen. If the soil for laying the pipeline from polyethylene pipes is loose, then it may be necessary to apply technologies to create the effect of strengthening the earth. If there is a possibility of soil displacement, then in order to ensure the static position of water channels in the ground, geotextiles are laid out at the bottom of the ditch.

Most often, the installation of a pipeline made of polyethylene pipes begins with the laying of a special pillow, which is a certain material, namely gravel or sand. The thickness of such a pillow can be varied depending on the characteristics of the soil, but on average it is 10-15 centimeters. It is necessary to seal the pillow only in the vicinity of the manhole. In places where water channels are attached to each other, workers make pits. When, during the analysis of the soil, its ability to strong internal friction is clarified, in this case the pillow can not be laid. Then, at the base of the track, the hardened soil is removed, and softer soil is laid out in its place. The excavated soil can later be used to backfill the pipeline, but it must first be ensured that it does not contain large stones. You can also fill up the water supply pipe with sand or fine gravel. First, the pipe is backfilled along the entire perimeter, at a height of more than 15 cm from it. extreme point. If you have to make the soil more dense, then backfilling is done in small layers of 20 centimeters. In no case should you compact the earth directly above the drain.

After installation pipeline made of polyethylene pipes backfilling is most often carried out with seized earth, but it is first necessary to clear it of stones if they exceed 6 cm in size, and if there are boulders, then 30 cm.

Pipes made of polyvinyl chloride are attached to each other most often with glue in the socket. However, it should be borne in mind that gluing requires scrupulous cleaning of surfaces and applying adhesive base very carefully. The butt edges must not be bent. AT last years For installation and fastening of drains made of polyethylene materials, bell-shaped solderings have become very popular, which are sealed with rubber cuffs of various profiles. In such a case, drains are made with sockets that contain circular grooves inside. Attach if necessary polyethylene pipe to steel or cast iron, then flange connections must be used. Where they are laid sewer systems from polyethylene gutters through the walls of wells, fasteners with a single rubber ring are used as sleeves.

Welding is carried out mainly by the contact method, it is carried out in a socket or end-to-end with shaped compartments. When welding polyethylene pipes it is necessary to strictly observe and monitor the diameters of the drain and their circumference.

They are used in systems whose maximum operating pressure is not more than 0.16 MPa.

Polyethylene pipes low pressure simple and easy to install.

Not so long ago, pipes made of various materials. Along with asbestos-cement products, non-pressure reinforced concrete products were also actively used.

But this area of ​​water supply and sewerage began to be actively conquered by non-pressure polyethylene pipes.

The main factors that significantly influence the choice of low-pressure polyethylene pipes are their highest performance:

• no corrosion;
• excellent resistance to various chemicals;
• long service life;
• simplicity and ease of installation;
• relatively low cost.

For water supply and sewerage, three varieties are produced:

• non-pressure smooth HDPE pipe;
• non-pressure corrugated HDPE polyethylene pipe;
• spiral wound non-pressure pipe.

Non-pressure smooth pipe

Connection of a non-pressure smooth pipe with clamp fittings.

Smooth non-pressure polyethylene pipes are orange in color and are produced in the following sizes:

• diameter from 20 to 560 mm;
• length from 500 to 1300 mm.

Types of products based on the ring stiffness class:

• SN2 - installation depth no more than 1 meter;
• SN4 - installation depth no more than 6 meters;

Installation of this product is carried out in a socket. One side of the HDPE pipe has a socket in which it is located. Sewerage installation is very simple, for this you need to insert one product into the socket of another. If you need to connect elements with different diameters There are special adapters for this. For ease of installation, various tees, couplings and angles are provided.

It also doesn't cause problems. Fastening to the ceiling or wall is carried out using the simplest latches (clamps), which are fastened with screws to the wall or ceiling.

Corrugated non-pressure pipes

Sewerage installation is very simple, for this you need to insert one product into the socket of another.

This type of HDPE pipes is also used for sewerage and drainage systems. This variety without pressure pipes can be made from polyethylene, polypropylene and combinations thereof.

Polyethylene pipes of this type have differences in design and production technology. These products are produced in a two-layer version and have a smooth inner surface and a corrugated outer surface. The outer wall of the product, which has a black color, guarantees high protection against ultraviolet radiation, it also serves to provide the necessary ring rigidity of the HDPE pipe and its resistance to deformation. White color, which has an inner wall, facilitates visual diagnostics of the sewer system.

This product is available in the following ring stiffness classes:

• SN4 - installation depth no more than 4 meters;
• SN6 - installation depth no more than 6 meters;
• SN8 - installation depth no more than 8 meters;
• SN16 - installation depth no more than 16 meters.

Produced in sizes:

• diameter - from 110 to 1200 mm;
• length - 6 or 13 m;
• profile width - from 6 to 41 mm;
• wall thickness - from 1.2 to 5 mm.

Here are some positive factors:

A rubber gasket is installed inside the corrugation, which prevents its displacement during installation.

1. High impact resistance (even at low operating temperatures).
2. Good chemical and mechanical resistance.
3. High ring stiffness as a result of the use of special grades of polyethylene in the production and optimal design.
4. Ease of installation: the connection is made with a rubber gasket (o-ring) and a socket or butt welding. A rubber gasket is installed inside the corrugation, which prevents its displacement during installation. Due to its special shape, the rubber gasket prevents not only leakage from the product, but also the ingress of ground water into it.
5. High versatility, due to the possibility of using a wide range of fittings, which allows you to connect to any type of pipe.
6. The light weight of the product makes it convenient to store, mount and transport.
7. The excellent flexibility of the product makes it possible to bypass various obstacles when laying the piping system without much difficulty.
8. Long service life at low cost of operation.
9. Excellent value for money.

Features of installation and installation

For pipes with a diameter of 250-1200 mm, the sealing ring is inserted into the groove of the first corrugation.

This product is designed for underground installation with a maximum depth of up to 16 m and a minimum depth of at least 1 m. It is very important to choose the right backfill material for the formed trench. The granulometric composition of this material should densely fill corrugated products, that is, the particle size should not exceed the width of the profile.

Connection using a sealing ring and a coupling is carried out as follows: for a product that has a diameter of 250 to 1200 mm, install the sealing ring in the groove of the first corrugation. For a product that has a diameter of 110 to 200 mm, into the groove of the second corrugation. After that, we install the coupling, while the force must be constant and equally distributed.

One of the important advantages of corrugated non-pressure pipes is that they can be joined by butt welding. This became possible due to the sufficient wall thickness and the distance between the corrugations. Welding is a complex process that should only be carried out by an authorized and qualified person. However, it should be remembered that butt welding is used to seal pipes and cannot provide the same ring stiffness like a clutch.

Spiral non-pressure pipes

Thanks to geometric shape profile of the pipe wall, helical pipes have the highest resistance to deformation for non-pressure networks.

A spiral non-pressure product is used for the construction of a non-pressure sewerage and drainage network, often with a large diameter (more than 1000 mm). This type of non-pressure pipe is made of polyethylene by winding a continuously produced profile onto a rotating drum. cylindrical shape with simultaneous welding of coils to each other. Due to the geometric shape of the pipe wall profile, it has the highest resistance to deformation.

This product has several types:

1. SPIROLINE has a ring stiffness of SN2, SN4, SN6, SN8, SN16, which allows it to be laid to a depth of up to 16 m. A wide range of internal diameters - from 500 to 2400 mm. The length of the segment is from 0.5 to 13.5 m.
2. KORSIS has a ring stiffness of SN4, SN8, which allows it to be laid to a depth of up to 8 m. The inner diameter is from 800 to 2400 mm. The length of the segment is from 0.5 to 13.5 m.
3. VEHOLIGHT has ring stiffness SN2, SN4, SN8. Inner diameter - from 280 to 800 mm and from 360 to 3000 mm. The length of the segment is from 0.5 to 13.5 meters.

The connection is made by directly screwing one product into another with further end welding. These polyethylene pipes can also be mounted using various fittings (branch, transition, tee, tank, well).

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Construction of a pipeline from polyethylene pipes

Most of all pipelines laid in cities date back to the Soviet era. The deterioration of heating mains, sewerage, gas and water communications reaches 70%, which is due to the material from which the pipes are made. This is a steel that is subjected to intense corrosive attack. The construction of gas pipelines from polyethylene pipes is becoming more popular today. As the service life expires, various pipelines many accidents happen high pressure pipes break, numerous leaks form, which lead to significant water losses. Performance indicators are deteriorating: due to a decrease in the cross-section of pipes, their throughput is reduced, water is polluted, and its biological indicators are reduced.

Advantages of polyethylene pipes

Pipes made of polyethylene (PE) are modern alternative to their obsolete physically and morally metal predecessors. They have a number of indisputable advantages in comparison with products made of steel or cast iron.

1. The absence of corrosion damage, which minimizes the cost of installation, maintenance and repair.
2. Ease of use: Polyethylene products are easy to cut, so they can be easily adjusted to size both on the construction site and in the field when laying pipelines.
3. High throughput due to the fact that the inner walls of PE products are smooth.
4. Pipes made of polyethylene have an elastic structure of the inner walls, on which scale does not form as a result and they are not clogged from the inside with various suspensions contained in the liquid.
5. Polyethylene is chemically inert, successfully resists aggressive effects, therefore, it does not need additional special protection.
6. Polyethylene is not electrically conductive, so it is not afraid of stray currents that destroy metal pipes.
7. The bending radius of a polyethylene pipe can be up to 10 of its outer diameters, depending on temperature, which reduces the cost of connecting parts and facilitates the design and construction of pipelines.
8. Polyethylene pipe has high flexibility: the minimum bending radius is 25 pipe diameters at 200°C.
9. Significantly less weight than metal pipes which facilitates assembly and installation.
10. PE pipes are resistant to temperature changes and have high sanitary and hygienic characteristics.

Scheme of deformation of polyethylene pipes depending on the type of soil.

Important note. Freezing of the soil leads to the movement of pipelines in a vertical plane. These movements are uneven, resulting in deformations (bends). Prediction of these states should determine how much the bending radius of a polyethylene pipe depends on the level of temperature decrease. In order to determine the bending radius, it is necessary to make special calculations. Or refer to special tables, which indicate the minimum bending radius for a particular type of pipe.

The minimum bending radius of a polyethylene pipe is recommended by the manufacturer for each type and grade of pipes. If it is not possible to obtain the desired bending radius, then bends, tees, etc. should be used.

Thanks to its technological and performance characteristics polyethylene pipes received wide application: they are used in the construction of new pipelines and in the repair of old communications that have served their time.

Scope of polyethylene pipes

Polyethylene products are widely used in modern construction.

They are used in the construction of water pipes, sewerage, gas pipelines. PE pipes are used in pressure and gravity sewerage, serve as protective cases for electrical and telephone wires.

With the help of polyethylene pipes, the reconstruction of old networks is carried out. Replacement can be carried out with the destruction of worn-out communications, but it is possible to lay new ones in parallel with the old ones, which does not require stopping the water supply to the population and blocking the sewerage system. Reconstruction of wells and other communication and plumbing structures depends on the degree of their deterioration. Individual parts may be subject to partial replacement (necks, shut-off valves etc.), if necessary overhaul with a complete replacement of pipelines.

Installation of polyethylene pipes for sewerage

Sewer networks are internal and external. Their purpose is to collect and transport sanitary and storm waste water, which has different chemical composition. Any sewer problems dramatically affect the quality of life.

Elements and assembly for polyethylene pipes of internal sewerage

Polyethylene pipes for sewerage began to be produced not so long ago, and today they fully meet the high requirements due to their inertness to the effects of mineral acids, alkalis and other aggressive substances. PE sewer pipes have a large throughput due to the absence of internal roughness. When arranging external systems sewers use frost-resistant PE pipes. Installation of internal sewerage does not require pipes with such high performance characteristics.

Sewer pipes are attractive to specialists working on the arrangement of such systems in that their installation is much easier in comparison with traditional sewer networks. Installation of internal sewer communications using polyethylene pipes does not require complex special equipment. Small-diameter polyethylene pipes are mounted using compression fittings.

Equipment outdoor sewerage produced by butt welding: special welding equipment allows installation, reducing the number of joints up to five times in comparison with metal sewer pipes

Connection of water polyethylene pipes

PE products are connected in three main ways:

1. butt welding,
2. socket welding with embedded electric heaters
3. installation with compression fittings.

A detachable connection is also possible, which is carried out by steel clamping flanges. Installation of bends and branches of pipelines is carried out using welded or cast fittings.

Different connection methods are used depending on the working conditions. If there are conditions for the placement of welding equipment, then butt welding is necessary. Butt welding is used when working with pipes large diameters(from 630 mm).

The limited working space (wells, chambers, trenches) requires electrofusion welding using embedded heaters.

If it is necessary to connect pipes with a diameter of up to 63 mm, compression fittings are used, which creates detachable structures. This connection is easy to use, has high performance, does not require complex special equipment. The connection of internal piping systems is most often carried out in this way. Their installation is available even to non-professionals.

Laying pipelines

Laying polyethylene pipelines carried out in two main ways. These are the traditional laying of pipes in an open trench and trenchless laying - a method of deep directional drilling.

Polyethylene pipelines for open method fit into a trench, the width of which is determined by the need to create conditions for work. Water supply and sewerage equipment requires a trench width of 40 cm more than the outer diameter of the pipeline. These parameters are most often specified in the project. Long-length polyethylene pipes are often laid in a trench dug with a narrow-reach chain excavator. In this case, the width of the trench decreases.

The trench must be properly prepared. Its arrangement depends on the condition of the soil. If the bottom of the trench is hard and dense, then a pillow device is necessary. The bottom is covered with a layer (about 10-15 cm) of sand or other granular material and leveled. At a distance of 2 meters from the manhole, the pillow is rammed. There should be no stones, lumps at the bottom frozen ground. When working with loose soil, which has a risk of displacement, it is necessary to strengthen the bottom. In such cases, the bottom of the trench is reinforced with geotextiles.

With a flat trench bottom with optimal soil characteristics, a cushion is not needed. You can get by with a small excavation of the earth at the base of the pipe to its width and replace it with a softer one.

Trench backfilling

The soil excavated during the trenching, in which there are no stones of 20 mm in size, is used for the initial backfill. It is made for the entire length of the pipe, about 15 cm high from its top. If it is necessary to compact the backfill, the soil must meet certain requirements. Fine gravel (20-20 mm) or crushed stone (4-44 mm) can be used. Soil must not be dumped directly onto the pipeline. Laid to the bottom of the trench and sprinkled pipeline needs to be sealed. The backfilled soil is compacted in layers of 20 cm on both sides of the pipe so that it does not move. The soil is not compacted directly above the pipe.

Backfilling is carried out after compaction and obtaining a compacted layer of about 30 cm on top of the pipe. Backfilling of the trench can be done with excavated soil, the size of the largest stones is allowed no more than 300 mm. Even if there is a layer of protective backfilling with a thickness of about 30 cm, the size of the stones in the soil, which is used for backfilling, cannot be more than 60 mm.

Trenchless pipeline laying

In some cases, when pipeline lines intersect with a railway, a busy highway, a river, and other obstacles, laying an open trench is not possible. The reason may also be the need to minimize the cost of digging a trench. This is the basis for applying the method of trenchless laying of polyethylene pipelines. The method of trenchless laying of horizontally directional drilling (HDD method) has become widespread.

Horizontal drilling is in a special way communication devices without opening the ground. Work begins at the point where the pipe is brought to the surface. Technology guarantees high precision the output of the drill in the proposed place of exit to the surface. The method allows laying underground pipes with a length of more than 100 m and a diameter of up to 630 mm or more. There are two main ways horizontal drilling: managed and unmanaged.

Controlled horizontal drilling is carried out by tunneling machines, through flushing and pilot drilling.

Unguided horizontal drilling is carried out by two methods: 1) without casing (ramming, displacement drilling, auger drilling) and 2) with casing pipes(drilling injection, puncture drilling, impact drilling, ram drilling).

Horizontal drilling methods and trenchless laying of polyethylene pipes are considered the most modern technology. To expand the well, a special drilling extension is used. To improve the wiring, the well is treated with drilling mud, which forms and lubricates the channel itself.

Thus, the characteristics of polyethylene products make it possible to carry out their installation and laying using any currently known method, taking into account the limitations imposed by the minimum allowable radius of their bending.

A pulled or pushed polyethylene pipe is able to repeat the configuration of the old route, which has a radius of curvature of more than 120 diameters of the pipe itself. Hardware such a bending radius practically does not have.

Organization of installation work

Welding is carried out either according to the basic scheme, or by the route method. The basic method is used in cases where the object is located near the welding site, where the pipes are pre-connected, and then they are brought to the pipeline route in finished sections. The length of the section can reach more than 30 m. On site, they are welded into a single thread, which then carefully, so as not to violate the bending radius, must be laid in a trench.

Route welding starts along the trench. Then the installation and welding is carried out by mobile welding units. Pipes of small diameter can be laid manually in the trench. However, pipelayers or cranes are most often used. The finished thread should be lowered without jerks, evenly, having previously secured it with hemp ropes or soft slings, which should be located at a distance of 5-10 meters from each other. The solid welded string must be lowered into the trench carefully so that the critical bending radius is not exceeded during the laying process. Beforehand, you should wait at least 2 hours after welding the last link.

Disadvantages of polyethylene pipes

Problems with polyethylene products are associated with the characteristics of all viscoelastic thermoplastics. Their strength largely depends on the degree of bending and compression, and in general it is relatively small. Polyethylene is sensitive to ultraviolet light, which has to be compensated for with coloring additives (usually soot) and the use of a protective color. The thermal expansion of polyethylene is quite high and it has to be compensated with the help of a constructive L- or U-shaped bend of the pipe.

Today domestic underground pipelines have a length of about 2 million km. Basically, these are steel pipelines. The share of polyethylene pipes accounts for, for example, about 10% of the entire length of gas pipelines. Other networks also have not very high rates for this parameter. However, there is a strong trend towards the fact that modern pipelines are changing in percentage terms in favor of polyethylene pipes.