Own business: production of polymer pipes. Polymer pipes

Lines for the production of plastic pipes

Today, the vast majority of developers have refused to install metal pipes in new buildings (both multi-storey and private houses), since their installation is extremely expensive and labor-intensive, and the pipes themselves are unreliable. The same applies to the replacement of worn-out metal pipes - they are everywhere replaced by polypropylene, plastic, polyethylene, or PVC pipes, which are today the most optimal replacement for metal pipes.

For more than 15 years, he has been supplying to companies located both in Russia and in the countries of near and far abroad. The number of partners who trust us with the supply of equipment increases many times every year, and the experience gained during the work allows us to provide high-quality advice to all entrepreneurs who decide to establish (or expand) the production of pipe products.

Pipe production equipment: general information

The advantages of polymer pipes produced on the equipment supplied by us cannot be overestimated:

- such pipes weigh much less;
- their installation is several times easier;
- no special conditions are required for the installation of polymer pipes;
- polymer pipes are not affected by corrosion;
— the period of operation is not less than 50 years;
- significant savings;
— the hydraulic resistance of such pipes is an order of magnitude less;
- the structure and biological characteristics of polymers do not allow deposits to form on the walls of such pipes, which is a significant problem for metal pipes.

Below we will consider polypropylene pipes production line, as well as plastic and polyethylene pipes, PVC pipes, since the production processes of all four types of products differ minimally. Let's list the necessary pipe production equipment, as well as manufacturing features.

In general, the manufacture of pipes from polypropylene is a fairly simple process and does not require a lot of labor. So, from the moment of delivery (polypropylene, polyethylene, PVC pipes) to the enterprise, to the full-fledged production of finished products at full design capacity, as a rule, it does not take more than a month (taking into account the time required for training and training of personnel).

However, for the manufacture of pipes, it is necessary to have specialized equipment - a line configured for the production of a specific type of pipe. Usually, pipe production equipment(extrusion) are made based on the requirements. Particular attention should be paid to the quality of the raw material for the manufacture of pipes, the presence of appropriate markings, the specified range of pipes to be produced on this equipment, the thickness of the pipe walls, productivity, energy efficiency, etc.

Pipe production equipment: main components

The fundamental element of the line for the production of any type of pipes is the extruder - it is with the help of the extruder that the production of pipes is carried out, the remaining elements of such lines can be classified as auxiliary. The extrusion process begins with the supply of plastic (in granular or powder form) to the feed hopper of the extruder. Further, the material enters the extruder barrel, which is made of high-strength nitrided steels, and is a helical screw device. Along the perimeter of the cylinder there is a large number of various sensors, with the help of which the required temperature and pressure indicators are maintained. Inside the cylinder, the material is melted, and its plasticization is achieved due to high pressure, after which the material melt is fed into the die (extrusion head) of the required shape, at the exit of which the final solidification of the material that has become the finished product occurs.

In addition to the above elements, the extruder necessarily has an electric motor and automatic control devices, thanks to which the entire pipe production line is directly controlled from the operator's control panel. Depending on the specific conditions of production, in plastic pipe production lines additionally, various additional equipment can be included. Such equipment includes loading elements that, without human intervention, supply material to the feeding hopper; automatic die and tube head changer, etc.

Pipe production equipment: brief characteristics

In order to obtain a high-quality finished product at the exit of the extruder that fully meets the stated requirements, its surfaces (both internal and external) must be calibrated without fail, especially for pipes. To perform accurate calibration in the line for the production of pipes, a specialized device is provided - a calibrator (most often a vacuum one). During calibration, the tubular billet is pulled through the calibrator, after which it acquires the necessary parameters. In order for the workpiece to be pulled evenly, a special device is installed, the main purpose of which is to maintain a given pipe thickness - such devices are caterpillar or track type.

Having calibrated the diameter of the pipe blank, it is necessary to cut the blank correctly so that the finished pipe has a given length: for evenness of the edge, the cut is made at the end of the line. The cut is performed by a special device, most often a guillotine type or a circular saw. After cutting off a given length, with the help of the last device in the line - a stacker, it is thrown to a given place. Note that with the help of (polypropylene, polyethylene, PVC pipes), pipes with diameters of 16-1000 mm are manufactured at a productivity (depending on the source material and the final diameter of the pipes) 80 - 1500 kg / h.

Specification of equipment for the production of pipes, depending on the purpose of the finished products

Today, the production of polymer pipes for various purposes is very promising: first of all, this is facilitated by the ever-growing popularity of such pipes, their reliability and quality. At the same time, polymer pipes can vary significantly, depending on the area of ​​\u200b\u200bthe planned application. The most popular is the division of polymer pipes (respectively - and equipment for their production) into pipes of low and high pressure. Polymer pipes are also distinguished by the type of material used for their manufacture: polypropylene, polyethylene, PVC.

Visually, the manufacturing features of pipes can be determined by color and marking: the starting material for gray pipes is most often polypropylene; for black - polyethylene; pipes made of PVC most often have an orange or yellow-pink color; the presence of blue or blue longitudinal stripes indicates that such pipes are intended for water supply (cold); white pipes, as well as the corresponding markings applied to them, indicate that these pipes are intended for hot water supply; yellow-painted pipes are produced for gas pipelines.

Completion of lines for the production of pipes

In addition to the basic elements that we described above, they are equipped with pipe heads, a packing table, as well as vacuum-water baths. The presence of the above elements allows in a short time to organize high-quality, continuous, efficient production of pipes from any polymeric materials. Note that depending on the direction of the line for the production of pipes from a particular material (plastic, polypropylene, polyethylene, PVC), a specific type is selected, as well as the performance of the extruder. For example, if you need a line for the production of pipes from soft raw material, a single screw extruder will be the best option. If the feedstock is hard, a 2-screw extruder is best suited.

Starting Your Own Pipe Manufacturing Business

Anyone who decides to start their own pipe production business, or is thinking about expanding existing capacities, needs to know that today the domestic market for the production of metal-plastic pipes is in the middle stage of development. This means that, despite the relatively large number of companies involved in extrusion of metal-plastic pipes or plastic pipes, there is still room for new producers. At the same time, competition in the Russian market for the production of PVC pipes is steadily increasing: new companies appear, and those already present regularly expand production. It should be noted that extrusion equipment, like most elements of equipment for the production of PVC pipes, is of considerable cost, and the production process itself will definitely require the involvement of qualified specialists (at least at the initial stage of starting production to train own personnel).

When arranging heating systems for private houses and for intra-apartment wiring between radiators and main heating risers, polymer pipes are increasingly used.

Polymer pipes for heating

The following materials are used for their manufacture:

• polypropylene (PP);
• cross-linked polyethylene (PEX);
• metal-plastic (PEX-AL-PEX).

The installation of piping made of polymeric materials is distinguished by a high level of performance culture. The necessary tool fits in a small special suitcase, and the performers do not have such high professional requirements as electric or gas welders.

The figure below shows the heating main of an autonomous heating system, assembled from polymer pipes and fittings.

The use of polymer pipes for the installation of heating systems

Application

Growth trends in the consumption of polymer pipes for domestic heating are observed both in the outer European and in the domestic Russian markets. In 2015, more than 70% of pipeline communications in European countries were plastic pipes. In Russia, the transition to plastic pipes is carried out at a rapid pace:

• In 2010, the share of polymer pipes in domestic heating systems was 48%, steel - 52% of the total moldings of pipelines installed during the year;
• In 2015, already 68% were plastic pipes (almost 300,000 linear meters of polymer communications were installed in a year) and only 32% were steel pipes.

Coil of XLPE pipe (PEX-pipe)

Meticulous statisticians have calculated that during the thirty-year period of the development of cross-linked polyethylene technology, more than 5 billion linear meters of PEX pipes were installed in European countries alone.

The modern market is saturated with polymer pipes and fittings for their connections during the installation of heating mains. However, long-term trouble-free operation of pipelines of heating systems can only be ensured by using high-quality plastics made from conditioned chemical raw materials in compliance with all technology requirements.

Unfortunately, the market is full of cheap counterfeit products, which are not easy to recognize by external signs. The quality of counterfeit products is simply incomparable with the products of the leaders in the production of polymer heating pipes.

Recognized global brands among plastic pipe manufacturers are:

1. Germany: " Rehau, Wefatherm, Aquatherm.
2. Italy: " Valtec.
3. Sweden: " Wirsbo.
4. Belgium: " Henco.
5. Czech Republic: " FV-Plast", "Ecoplastic".
6. China: " Dizayn, Blue Ocean.
7. Korea: " Hydrosta.
8. Turkey: « Pilsa", "Firat", "TEBO", "Kalde".
9. Russia: " Politek, PRO AQUA, Heisskraft.
10. Kazakhstan: " Jakko.

The products of these concerns fully comply with the quality criteria adopted for polymer pipes when used as an alternative to steel heating communications.

Not every plastic pipe, chosen only because of the low price, is capable of working with hot water coolant under pressure.

The figure below shows a counterfeit plastic pipe that failed in the very first days of operation when it was used in central heating communications.

Failed counterfeit polymer pipe

Quality Criteria

The positive dynamics of demand is accompanied by the constant work of manufacturers to improve the technical characteristics of polymer pipes. The main quality criteria for heating pipes (regardless of the material of manufacture):

1. thermal resistance, which allows to withstand temperature jumps of 105 degrees or more due to the possible ingress of hot coolant from the central heating main;
2. resistance to thermal shocks - sudden temperature changes during sudden heating or cooling of the pipeline;
3. mechanical strength to resist external mechanical damage;
4. abrasive resistance to the damaging effects of mechanical impurities such as scale or rust, sand and other solid particles entering the coolant;
5. smooth inner surface of the pipe walls, which does not allow the accumulation of debris in the zone of local unevenness (protrusion, burr, sink or cavity);
6. resistance to the so-called water hammer - sudden pressure drops of the working medium up to a value of 2.5–3.0 MPa (25-30 atm.);
7. chemical inertness to oxygen in the absence of a water coolant and to the aggression of salt additives in the coolant;
8. high maintainability, which allows replacing a failed pipeline element without dismantling the entire section;
9. low thermal conductivity of the wall material to reduce heat loss during coolant circulation.

Lime deposits are also deposited on the inner walls of plastic pipes, clogging the flow area of ​​pipelines. However, their negative impact is not as catastrophic as for steel communications, in which there is a complex effect of corrosion, abrasive particles, chemical additives, and scale deposits.

For comparison, the figure below shows photographs of corroded steel heating pipes clogged with scale.

The internal section of steel heating pipelines after several years of operation

Manufacturers

Germany

Leaders in the production of plastic pipes for heating and their products used in the Russian construction market:

1. The Rehau company was founded in 1948 in the Bavarian town of Rehau.

The Rehau company supplies the Russian market of heating pipes with plastic pipes PEX (cross-linked polyethylene) and PEX-AL-PEX (metal-plastic) of the Rautitan system of the following range:

• Rautitan stabilizer;

Pipe element Rautitan stabil

• Rautitanflex;
• Rautitan pink

Pipe element Rautitan pink

• Rautitan his, relating to a new generation of pipes for heating systems.

Pipes are available in diameters of 16 mm, 20, 25, 32, 40, 50 and 63 mm.

Rehau pipes are capable of transporting a coolant with a temperature of up to 110 degrees. C, which significantly distinguishes them from analogues of other manufacturers. The Rautitan system itself is based on the use of a so-called compression sleeve for connecting Rehau piping elements.

On the territory of the Moscow Region of the Russian Federation, two enterprises from Rehau operate for the production of pipes - the city of Ramenskoye (opened in 2002) and the city of Gzhel (opened in 2005).

1. Wefa Plastic (Attendorn, Germany) is a manufacturer of Wefaterm polypropylene pipes. Since 2003, it has been producing polypropylene pipes with fiberglass reinforcement. Vefaterm composite pipes are used in all sections of heating mains from the heating boiler to radiators.
2. Aquatherm polypropylene pipes made of PP-R-80 propylene and fittings for them are products of Aquatherm GmbH, founded in 1973 by Gerhard Rosenberg. The company is known for a wide range of sizes of polypropylene pipes and fittings, up to a diameter of 630 mm. For pipelines of domestic heating systems, pipes of the Aquatherm qreen pipe series are produced, capable of withstanding temperatures up to 130 degrees. C.

Polypropylene piping system from Aquaterm

About 200 km (200,000 meters) of Aquaterm pipes are supplied to the Russian Federation annually.

Belgium

Henco Industries, founded in 1992 by Louis Hendrickx. It supplies the world market with metal-plastic heating pipes of the Henco RIXc series (outer diameters 16, 20 and 26 mm), Henco Standart (outer diameters 16, 20, 26 and 32 mm).

Branded pipe from the Belgian manufacturer "Henco Industries"

Henko products are produced only in Belgium, so the "manufacturers" of pipes of this brand from other countries (mainly China) supply counterfeit products that are unsuitable for use.

Sweden

The largest manufacturer of PEX-A cross-linked polyethylene pipes is the Wirsbo concern, which began rolling them back in 1972. Since 1992, the company has been present on the Russian market. The concern's products are used for radiator heating and underfloor heating with a working temperature of 95 degrees. C with a possible increase to 110 degrees. C.

Turkey

Turkish companies supply polypropylene heating pipes to the Russian market, belonging to the middle price class and practically not inferior in quality to products from German or Belgian manufacturers:

• The Pilsa company, established in 1971, is the undisputed leader in the production of plastic products in Turkey. The company's enterprises use German technologies and equipment, specialists are trained in Germany. Since 2008, Pilsa has been a part of Europe's largest concern for the production of plastic pipelines, the WAVIN GROUP.
• Pipes with the Firat brand are supplied by Fırat Plastik AŞ, established in 1972. The company has huge production areas in Istanbul and Ankara.
• Kalde pipes are supplied by Kalde, founded in 1998 in Istanbul. The company has its own quality control laboratory accredited in Spain and Germany.

View of the Kalde pipe

• Under the TEBO brand, pipes made from PPRC type 3 polymer at the production facilities of TEBO technics come to the Russian market. A distinctive feature of TEVO pipes is the reinforcement of polypropylene with perforated aluminum foil.

Russia

Plastic pipes for heating are produced by several Russian enterprises that have adopted innovative technologies from leading European manufacturers and equipped their workshops with modern equipment. As a result, the names of popular brands appeared on Russian-made polymer pipes:

• Pro Aqua polypropylene pipes, produced in Italy and Germany, are now manufactured at the Egoplast plant (Sergiev Posad district, Moscow region). Moreover, at present, over 85% of the entire range of PP-R pipes and fittings of the Pro Aqua brand is produced in the Russian Federation.

The products of the Chinese company "Shanghai Pro Aqua Co Ltd" have nothing to do with the "native" brand. There are no Pro Aqua branches in China.

• The Swiss company "Santrade Ltd" and the German concern "HEISSKRAFT" together with Russian enterprises for several years have been manufacturing metal-plastic and polyethylene pipes "Santrade" and "Heisskraft", which are not inferior in quality to European counterparts.
• POLITEK PTK LLC is the largest Russian manufacturer of polymer pipes made of PP polypropylene, HDPE low pressure polyethylene and PVC pipes, however, its products are less in demand compared to modern metal-plastic or XLPE pipes.

Kazakhstan

The Jakko company (Jakko) is based in Aktobe. Since 2006 it has been producing polypropylene pipes. In 2009, the second plant for the production of polymer pipes was launched in Karaganda, which made it possible to expand the range of products.

Type of pipe "Jakko"

Jacco products are certified according to Turkish quality standards for polymer pipes, so they are often mistakenly considered a Turkish product.

Video about soldering pipes

The nuances of soldering polypropylene pipes, which help beginners avoid possible mistakes, can be found in this video.

Steel pipes lose to polymer pipes in the price-quality ratio, so the trend of growing interest in polymer pipelines will only deepen. Manufacturers of plastic pipes closely monitor the market, so they are always ready to adjust their product range.

In contact with

Technology Description

Pipes are understood as products of an annular section of a closed profile, cylindrical or corrugated with a diameter of 5 to 1500 mm. Thin-walled products of this type with a wall thickness of 1-1.5 mm and a diameter of up to 25 mm are commonly called hoses. Tubes less than 5 mm in diameter with walls less than 0.5 mm thick are called capillaries. The name "pipe" is generic.

As a rule, pipes are made from high-viscosity grades of polymers. For their production, low-density polyethylene, high-density polyethylene (PE-80, PE-100), rigid and plasticized polyvinyl chloride, ABS plastic, polypropylene, high-impact polystyrene are used.

Depending on the properties of the polymers used, plastic pipes can have not only low density, alkali and acid resistance, but also heat resistance up to 120-150 0 C, high electrical insulating properties, petrol and oil resistance, and do not rust during use. In addition, the throughput of plastic pipes is greater than that of metal pipes, due to insignificant losses to overcome the friction of the liquid on the polymer surface.

Also, the use of polymer pipes usually gives a tangible economic effect: the cost of transportation and installation is reduced by several times compared to steel pipes, a significant service life (about 50 years), and no costs during operation. As a result, installation made of pipes and fittings made of polypropylene will reduce the cost by 15–20% compared to a pipeline made of galvanized steel pipes.

Another important advantage of plastic pipes is the manufacturability of their connection into pipeline systems.

Technology and equipment for the production of pipes

The process of production of plastic pipes is technologically quite simple, relatively easy, energy-efficient and environmentally friendly, and the minimum area required to install and operate one complete line for the production of pipes is about 100 m 2 .

All stages of the technological process of pipe production are inseparable and are carried out on one continuous line.

Rice. 1. Line for the production of polymer pipes.

The granulated polymeric material is fed by a pneumatic loader into the extruder hopper, where it is heated, plasticized and fed under pressure in the form of a melt into a direct-flow molding head, from which the molded pipe enters the calibrator and then into the cooling bath. To remove the pipe, a pulling device is used, the gripping elements of which correspond to the profile of the product. The thickness of the pipe wall and the correctness of its geometric shape are controlled by a non-contact measuring device. For applying inscriptions by embossing or printing, a counting and marking device is used. Pipes with a diameter of more than 50 mm are cut into segments of a given length by a circular or guillotine saw moving along the pipe at the speed of its removal, and stacked by a manipulator. Pipes with a diameter of less than 50 mm are wound into coils by a pull-winding device.

Extruders. Mainly single screw presses with screw length (25-30)D are used. The use of long worms helps to reduce the pulsation of the melt and improve the quality of products. In the production of thin-walled products, extruders with axial movement of the screws are used, which makes it possible to adjust the gap between the end of the screw and the head. In modern units used for the production of pipes with a diameter of more than 1000 mm and a wall thickness of more than 25 mm, high-performance twin-screw extruders are used.

Rice. 2. Single screw extruder.

Pipe profile forming. Molding is carried out due to the flow of the polymer melt through the annular gap of the head. For this, straight-through, angular and Z-shaped forming heads are usually used.

Rice. 3. Direct-flow ring head for pipes and hoses:
1 - fitting for compressed air supply; 2 - body; 3 - adjusting screws; 4 - fastening device; 5 - cable for holding sliding plugs in the calibrating device; 6 - pipe billet; 7 - channel for entering the compressed air pipe; 8 - matrix; 9 - mandrel holder; 10 - mandrel.

Direct-flow heads are most widely used (Fig. 2). The body of the head consists of two parts, between which the radial grate of the mandrel holder is fixed. A forming ring (mouthpiece) is inserted into the front part of the body, which is attached to the body with a flange. At the head inlet, a grate and a bag of filter meshes are inserted. A splitter and a mandrel are fixed on the grate of the mandrel holder. The mandrel holder grate has a fitting for supplying compressed air into the pipe. The polymer melt from the cylinder of the eketruder passes through a package of filter meshes, a grate, and then flows in the annular gap between the branch pipe and the mandrel divider and enters the holes of the mandrel holder grate, where it is divided by ribs into several parallel flows. In order to avoid stagnant zones, the ribs of the mandrel holder grid are made into a streamlined shape.

After the grate of the mandrel holder, the melt again enters the annular channel formed by the second part of the body and the mandrel. The final dimensions of the melt takes in the forming channel, while to ensure an equal thickness of the pipe along the perimeter, the forming ring (mouthpiece) can be moved by screws in radial directions relative to the mandrel.

The length of the forming channel is usually taken as a multiple of the channel depth h and should be equal to l/h =15 - 30.

Rice. 4. Forming head for making large diameter pipes.

Mold head designs must meet the following general requirements:
1) uniform flow of the melt along the perimeter of the head;
2) the absence of junction lines;
3) smooth transition from one section of the channel to another;
4) uniform heating of the melt along the perimeter;
5) absence of stagnant zones;
6) the shape of the channel is selected from the operating conditions and the scope of the pipes.

In addition to design factors, the quality of manufactured pipes is influenced by technological parameters - temperature, flow rate and melt extraction rate. During the flow, the orientation of the polymer molecules occurs, which depends on the viscosity of the melt and the flow rate. As the melt temperature increases, the orientation and relaxation time decrease, so the shrinkage of the pipes in the axial direction decreases.

The melt flow velocity in the head mainly affects the anisotropy of the pipe properties. As the speed increases, surface roughness may appear, as there is a periodic breakdown of the melt from the surface of the forming channel.

When forming a pipe profile, the melt is removed from the head using a pulling device. If the melt is withdrawn at a rate greater than the melt exit rate, the pipe wall thickness decreases and the axial orientation of the pipe increases.

Pipe calibration. To give the profile of the extrudate the specified dimensions and exclude its deformation in the cooling device, the pipes are calibrated, i.e. pre-cooled to provide the melt with a certain configuration and dimensions. As a rule, pipes are sized according to their outer diameter, since this is important for joining and joining in future use. Thin-walled hoses and capillaries are also sized according to the internal size.

To give the calibrated product the required shape with its subsequent preservation, the process must begin at a temperature close to the melting temperature of the thermoplastic T 1 ≤ T melt and end when the melt solidifies, that is, at a temperature below the softening temperature T 2 Calibration can be carried out using compressed air or vacuum.

During OD calibration using compressed air, the tubular melt billet is squeezed out of the die and enters the metal sleeve of the calibrator. When compressed air is supplied inside the pipe, it partially expands along the diameter, as a result of which the pipe at the exit from the head fits snugly against the cooled walls of the calibrating sleeve. To prevent destruction (bloating) of the extrudate, the nozzle in this case is attached close to the head, and coolant is supplied to the jacket of the calibrating nozzle. To prevent melt sticking, the packing sleeve is cooled to a temperature which must always be below the glass transition or melting temperature. In this case, a layer of solid polymer is formed on the surface of the pipe, which, after leaving the nozzle, must withstand the internal air pressure, as well as the friction forces arising in the nozzle.

The calibration pressure is selected depending on the diameter of the pipe, its wall thickness, as well as on the properties of the polymers and the temperature of the melt. Usually it is selected experimentally when starting the installation. At the same time, it should be taken into account that at low pressure, the appearance of the pipes worsens (surface ripples form), and at excessively high pressure, the strength decreases due to an increase in the friction coefficient and the appearance of microcracks.

To create pressure inside the pipe, the end of it is closed with a stopper or bent several times at an angle of 180 0. The use of a cork worsens the quality of the inner surface of the pipe and increases the force of its friction during calibration.

Inflating with compressed air allows you to create a high pressure inside the pipe. This calibration method is used in the production of pipes with a diameter of more than 100 mm and a wall thickness of more than 5 mm.

When calibrating with a vacuum, it is necessary to ensure tightness between the extrudate and the sleeve at the inlet, so the diameter of the forming mouthpiece is made somewhat larger than the diameter of the sleeve. The pipe acquires the required dimensions as a result of pressing the extrudate against the walls of the sleeve under the influence of the pressure difference between atmospheric air and vacuum. Since it is impossible to create a large pressure difference (∆P does not exceed 0.05 MPa), this method is not applicable when calibrating thick-walled pipes.

Rice. 5. Vacuum calibrator.

When calibrating with plates, the tubular blank is inflated by compressed air supplied inside the pipe, or by creating a vacuum in the calibrating chamber. In this case, a set of sizing plates is placed in a sealed chamber in which a vacuum is created. In the same chamber, nozzles are installed for spraying water or completely filled with water. The water level is maintained by drain pipes. The distance between the plates at the inlet is made small so that the melt does not swell under the action of vacuum. As the pipe is withdrawn, the temperature of the melt decreases and the distance between the plates increases. Cold plate calibration speeds up the cooling process and reduces friction.

When calibrating by inside diameter, the calibrator is attached directly to the mandrel of the head. Through a tube passing through the mandrel, cooling water is supplied to it. The pipe pulled through the calibrator is cooled and smoothed. Using this method, it is possible to obtain products with a wall thickness of up to 0.2 mm and with a section of any shape corresponding to the configuration of the forming slot of the head.

When sizing products, rapid cooling should be avoided to minimize residual stresses and uneven shrinkage, which are often the cause of microcracks. It is necessary to coordinate the wall thickness of the product, the speed of its removal from the head, the length of the calibrating sleeve and the thermophysical properties of the processed polymer material (thermal conductivity, thermal diffusivity).

For more uniform cooling of the pipe, water mist is also injected through the mandrel into it. In this case, heat is removed not only through the calibrating sleeve, but also inside the product.

Operational heating of calibrated pipes above T p may be accompanied by a spontaneous change in their diameter due to highly elastic deformation.

Pipe cooling carried out by irrigating them with water or passing through a water bath. The main requirement for this operation is uniform and rapid cooling of the melt.

In the baths, intensive mixing of the liquid is provided, for which bubbling tubes, spray nozzles are installed, or a spiral flow of water is created around the pipe. Intensive mixing is also necessary to remove air bubbles that settle on the pipe surface and disrupt heat transfer. Otherwise, the surface becomes defective (with pockmarks). The temperature of the cooling water is usually selected according to the polymer as well as the pipe requirements. Pipes of good quality are obtained if the temperature of the melt on the inner surface after leaving the bath is reduced to the melting or pour point. Therefore, it is necessary to ensure a certain speed of pipe retraction by the pulling device. The length of the bath and the frequency of water exchange are determined taking into account the wall thickness of the product.

pulling device designed to remove the product from the forming head and move it through the cooling bath. The most widely used devices are caterpillar type. Depending on the diameter of the pipe, its wall thickness, cross-sectional configuration, the pulling elements can be an endless belt with elastic pads or roller chains with tracks that follow the contour of the product. The number of such "caterpillars" can be 2, 3, 4 or 6, also depending on the size of the pipe. The pulling device must be equipped with a continuously adjustable drive and a device for estimating the linear speed of the retracted product. The latter is especially important, because, firstly, it allows compensating for the swelling of the extrudate, and secondly, the ratio of the rate of removal of the product to the rate of extrusion of the extrudate depends on the so-called degree of pipe drawing and its properties in the longitudinal and transverse directions.

If the melt is withdrawn at a rate greater than the melt exit rate, the tube wall thickness decreases and the axial orientation of the tube increases. The strength increases in the longitudinal direction and decreases in the transverse direction. Accordingly, with shrinkage, everything happens the other way around: the transverse increases, while in the axial direction, the shrinkage decreases significantly.

Pipe cutting carried out with saws of various designs (circular, tape). During the cutting process, the saw moves along with the pipe and returns to its original position after the cycle is completed.

Rice. 6. Cutting device.

Stacker drops finished pipes of a given length as they arrive from the cutting device onto a special rack for further sorting or packaging by the operator.

In the production of non-pressure pipes made of polyethylene or PP-pipes of small diameter, instead of a stacker, an automatic winder can be used, which, having a winding drum adjustable in diameter, an electric drive and a meter counter system, makes it possible to obtain finished coils at the exit.

Production of corrugated pipes.

Corrugated pipes are used for laying sewer and drainage lines. Due to the corrugated (profiled) surface, the pipe has a small wall thickness, having a sufficiently high crushing strength, i.e. It has transverse rigidity and at the same time longitudinal flexibility. When laid underground, it withstands ground pressure, while having an insignificant mass (low weight) of one linear meter of pipe and fits into trenches quite easily.

Corrugated pipes can be single-layer or multilayer, when the corrugated part has a smooth polymer layer from the inside to reduce hydraulic resistance, fig. 7. At the same time, the pipe remains flexible. In some cases, to provide higher rigidity and thermal conductivity, a third layer of polymer is applied to the outer surface of the corrugations.

Rice. 7. Corrugated pipe.

The installation for the production of corrugated products consists of an extruder with a direct-flow tube head with an elongated mandrel and an unheated mouthpiece (Fig. 8).

Rice. 8. Scheme of the process of corrugating pipes.
1 - mandrel; 2 - mouthpiece; 3 - half-form; 4 - cable; 5 - cork; 6 - product.

The extruder must be run on rails to compensate for thermal expansion when barrel temperature changes. In the immediate vicinity of the head, there is a corrugator designed like a double-circuit outlet device, on each track of which a half-mould with a channel for cooling water is fixed. In the working area, the half-moulds are closed. The thin-walled tubular billet enters the zone of closed half-molds of the corrugator, is pressed against the cooled surfaces under pressure of compressed air and hardens, retaining the shape given to it. To maintain pressure inside the inflated sleeve, a floating plug is placed in it, attached to the mandrel with a cable. The corrugator thus performs two functions. The first - like a calibrator, it gives the product the required geometric shape, the second - is a diverting device with smooth adjustment of the speed of movement of the half-moulds.

A feature of the technology for the production of corrugated products is that to ensure the completeness of the formation of corrugations, the process is carried out at the maximum allowable temperature for the processed material. In addition, since the molding of the blank sleeve occurs on the unheated section of the head, a significant pressure arises in it, reaching 30-40 MPa.

The development of iron processing technologies can be fully traced by considering the history of the use of cast iron and steel for the manufacture of pipes. The history of cast-iron pipelines is usually counted from the creation of underground pipelines at Versailles (1662 by master R. Salem, designed by architect A. de Ville), after which cast iron became the main material for water pipes and sewers. In Russia, cast-iron pipes were used for the reconstruction of the Rostokinsky water pipeline in Moscow (1858 by A. Delvig). The first Russian oil pipeline was built on the Baku-Batumi oilfields (1897-1907 by V.G. Shukhov) with a length of 835 km.

The volume of pipe production is an indicator of the technological and technical state of the heavy industry of any state, and the level of domestic consumption of pipe products is an indicator of the dynamics of the entire economy.

Product types

The nomenclature of names of positions of pipe production is very extensive. GOST 28548-90 “Steel pipes. Terms and definitions” gives the following classification:

• Seamless steel pipes.
• Welded steel pipes.
• Soldered steel pipes.
• Steel pipes with external or internal protective coating (tires).
• Steel pipes with treated (internal or external) surface.

The classification is based on basic manufacturing technologies. Within each category, the standards define their own requirements, because different industries have their own technical requirements. There are GOSTs for pipes for the chemical, oil and gas or nuclear industries. In addition, modern technologies for protecting the pipe from the effects of external and internal factors significantly expand the number of nomenclature positions.

• especially thin-walled
• thin-walled,
• thick-walled,
• especially thick.

Production technology

There are two basic pipe manufacturing technologies: seamless and welded. Within each technology, there are technological methods that ensure the manufacture of certain standard sizes with the most optimal technical and price parameters.

Seamless technology

The technology is based on the plastic deformation of the workpiece. There are technologies according to the temperature regime of processing in relation to the recrystallization temperature of the iron-carbon alloy (Fe-C):

• Cold-formed.
• Hot-formed.
• Heat-deformed.

According to technological schemes, the following methods of manufacturing a seamless pipe are distinguished:

Forging. It is used for the manufacture of blanks (sleeves) for further processing. In addition, forging is used to manufacture pipes from hard-to-deform steels and alloys. A close method of obtaining a pipe, according to the method of formation and processing conditions, can be considered hot pressing.

Rolling. A manufacturing method in which the workpiece passes through a stand with calibrated rolls. When rolling the sleeve through the rolls, a proportional change in the geometry of the pipe occurs - a decrease in wall thickness and an increase in length. Distinguish:

• cold-rolled pipes (diameter 5 ... 250 mm, wall thickness 0.3 ... 24 mm, GOST 8734-75) are made immediately after forging (piercing) the workpiece, without additional heating. During the rolling process, the part is cooled to a temperature below the crystallization temperature of the Fe-C alloy.
• hot-rolled pipes (diameter 20 ... 550 mm, wall thickness not less than 2.5 mm, with a maximum thickness of 75 mm, GOST 8732-78) are made after additional heating above the heating temperature above the recrystallization temperature by 50 ... 70 ° C . Heat treatment required.
• heat-rolled pipes are manufactured using an intermediate temperature regime, which makes it possible to simplify the subsequent heat treatment regime.

Drawing. A manufacturing method in which the sleeve passes through calibrated holes. Drawing, in terms of names, is associated with the temperature regime of the process, similar to rolling: hot, cold and heat drawn.

Special technologies.. Pressing, centrifugal casting and cutting technologies that do not directly use metal deformation are used to obtain pipes with specific properties or pipes using special materials.

Technologies using welding

Welding of the edges of a sheet or strip deformed into a tube occurs in two ways:

• Pressure welding, under the action of deformation forces, when the heated and prepared edges of the strip are closed in a shaping die (furnace welding).
• Welding of the edges is carried out by an electric arc method in a protective environment or submerged arc. Electric welding differs in the position of the seam relative to the axis of the pipe into straight and helical.

Arc welding has become widespread due to the development of welding technologies and methods of non-destructive automatic control of the quality of the weld.

Position in the industry

In the nineties, the decline in industrial production affected metallurgy and pipe production. The reduction in production volumes by 4.4 times in linear meters and by 2.6 times in weight terms, compared with 1990, has put pipe production on the brink of destruction. The privatized metallurgical industry, until 2000, was subject to restructuring and the limit between the owners. As a result, several financial and industrial groups were formed, which are vertically oriented structures with a fairly independent set of enterprises. Six holdings: Evraz Group, Magnitogorsk Iron and Steel Works (MMK), Severstal Russian Steel, Novolipetsk Iron and Steel Works (NLMK), Metalloinvest and Mechel control about 80% of pipe production. From 2000 to 2007, the production of pipes in Russia increased by 2.7 times in terms of weight and reached the level of 1990 of the last century. The main increase in production was achieved in the segment of production of large-diameter pipes (LDP) for the oil and gas industry.

Industry Outlook

The prospects of the industry should be considered in two segments of pipe production: general purpose pipe production and LDP production. In the first segment, there is strong pressure from manufacturers of high-tech pipes with anti-corrosion coatings and manufacturers of polymer pipes, especially China, Japan and India, which offer large volumes at dumping prices. The re-equipment of production requires about $ 90 billion over 10 years. In the LDP segment, the situation is much better due to the relatively high share of new equipment, which produces 40% of LDP, and participation in government programs for the construction of new oil and gas pipelines, both in Russia and outside it.