Hydraulic resistance coefficient of HDPE pipe. Parameters of polypropylene pipes: frost resistance, service life, roughness. Outer diameter dn, mm

Hydraulic calculation of a conventional household pipeline performed using the Bernoulli equation:

(z 1 + p 1 /ρg + α 1 u 2 1 /2g) - (z 2 + p 2 /ρg + α 2 u 2 2 /2g) = h 1-2 -.

For hydraulic calculation of a pipeline, you can use the hydraulic pipeline calculation calculator.

In this equation, h 1-2 is the loss of pressure (energy) to overcome all types hydraulic resistance, which is per unit weight of the moving fluid.

h 1-2 = h t + Σh m.

• h t - friction head loss along the flow length.
• Σh m - total pressure loss at local resistance.

You can calculate the friction head loss along the flow length using the Darcy-Weisbach formula

h t = λ(L/d)(v 2 /2g).

• Where L- length of the pipeline.
• d is the diameter of the pipeline section.
• v is the average speed of fluid movement.
• λ is the coefficient of hydraulic resistance, which in general depends on the Reynolds number (Re=v*d/ν), and the relative equivalent roughness of the pipes (Δ/d).

Values ​​of equivalent roughness Δ of the inner surface of pipes different types and types are listed in Table 2. And the dependences of the hydraulic resistance coefficient λ on the Re number and relative roughness Δ/d are listed in Table 3.

In the case when the movement mode is laminar, then for pipes of non-circular cross-section hydraulic resistance coefficientλ is found using formulas specific to each individual case (Table 4).

If the turbulent flow is developed and functions with a sufficient degree of accuracy, then when determining λ, you can use formulas for a round pipe with the diameter d replaced by 4 hydraulic radii of the flow R g (d=4R g)

R g = w/c.

• where w is the area of ​​the “live” cross-section of the flow.
• c- its “wetted” perimeter (the perimeter of the “live” section along the liquid-solid contact)

Pressure loss in local resistances can be determined by the shapes. Weisbach

h m = ζ v 2 /2g.

• where ζ is the local resistance coefficient, which depends on the configuration of the local resistance and the Reynolds number.

In a developed turbulent regime, ζ = const, which allows us to introduce the concept of equivalent length of local resistance into calculations L eq. those. such a length of a straight pipeline for which h t = h m. In this case, pressure losses in local resistances are taken into account by adding the sum of their equivalent lengths to the actual length of the pipeline

L pr =L + L eq.

• where L pr is the reduced length of the pipeline.

The dependence of pressure loss h 1-2 on flow is called pipeline characteristics.

In cases where the movement of liquid in a pipeline is ensured by a centrifugal pump, then to determine the flow rate in the pump-pipeline system, a pipeline characteristic is built h =h(Q) taking into account the difference in elevations ∆z (h 1-2 + ∆z at z 1< z 2 и h 1-2 - ∆z при z 1 >z 2) superimposed on the pressure characteristic of the pump H=H(Q), which is given in the pump data sheet (see figure). The intersection point of such curves indicates the maximum possible flow rate in the system.

Pipe range.

Values ​​of equivalent roughness coefficients ∆ for pipes made of various materials.

Dependence of the hydraulic resistance coefficient on the Reynolds number and equivalent pipe roughness.

• ∆ is the absolute roughness of the pipe.
• d. r - diameter. pipe radius. respectively.
• ∆/d is the relative roughness of the pipe.

Basic formulas for laminar flow in pipes.

Coefficients of some local resistances z.

Pipes and connecting parts for hot and cold water supply systems have a number of advantages:

• resistance to high temperatures;
• high sanitary and hygienic properties;
• noise-absorbing properties;
• absolute corrosion resistance;
• chemical resistance to more than three substances and solutions;
• smooth and time-invariant inner surface of the pipe wall;
• simplicity of installation and repair work.

Material

Polypropylene is an isotactic thermoplastic, the macromolecules of which have a helical conformation, was first obtained in 1954.

Polypropylene is produced by polymerization of propylene gas, which has the chemical formula: CH 2 CHCH 3.

Polypropylene has the following modifications:

• propylene homopolymer (type 1) PPH;
• copolymers of propylene and ethylene (type 2) PPV - block copolymer;
• static copolymer of propylene with ethylene (type 3) random copolymer - originally designated as PPRC - polypropylene random copolymer, later the abbreviation was shortened to PPR.

Pipes and fittings for PRO AQUA water supply are made from the 3rd type of polypropylene - random copolymer.

A random PPR copolymer, obtained by a set of propylene and ethylene molecules in a random combination, is represented by the following graphic formula:

Physical and mechanical properties of polypropylene

The physical and mechanical properties of all varieties differ within small limits, and are not differentiated when the properties of polypropylene are given:

1. Minimum long-term strength - MRS (Minimum Required Strength) - a characteristic of the pipe material, numerically equal to the stress in MPa in the pipe wall, arising under the action of constant internal pressure, which the pipe can withstand for 50 years at a temperature of 20 ° C, taking into account the safety factor, equal to 1.25. This means the ability of the pipe material to maintain such a margin of safety of the pipeline at the end of its expected service life that, subject to the conditions of the operating period, it still guarantees the reliable performance of its operating functions. According to modern designations of pressure pipes made of polypropylene, the MRS indicator in kgf/cm 2 (bar) is indicated after the abbreviated designation of the pipe material. For example, polypropylene random copolymer PPR with a minimum long-term strength MRS = 8 MPa (80 kgf/cm2; 80 bar) will be designated PPR 80.

Standard dimensional ratio - SDR (Standard Dimension Ratio) - a dimensionless indicator characterizing the ratio of the nominal outer diameter of the pipe Dn to the nominal wall thickness S (in the same units of measurement for both quantities in mm or m) The value of the standard dimensional ratio of the pipe is calculated by the formula:

SDR = Dn/S;

The SDR value of the connecting piece will correspond to the SDR of the pipe with which it is mounted. For example, a tee marked SDR 11 is intended for welding with a pipe having the same marking.

1. Nominal pressure - PN (Pressure Nominal) - operating pressure of transported water in a plastic pipeline (in bars) with a temperature of 20°C, which has been in trouble-free operation for 50 years with a minimum long-term strength MRS of 6.3 MPa.

The indicators of pipe types PN, SDR, S are related to each other, their relationship is presented in Table 3.1:

Main characteristics of polypropylene

Distinctive features of polypropylene

Polypropylene is characterized by high resistance to repeated bending and abrasion. Resistance to surfactants (surfactants) of polypropylene is increased, and this is its advantage over polyethylene.

Impact strength with a notch is 5 - 12 kJ/m 2, frost-resistant at low temperatures.

Polypropylene is most widely used in cold and hot water supply systems, internal and external sewerage.

Reinforced polypropylene pipes are produced in stages. Initially, a homogeneous polypropylene pipe is produced by extrusion. Then, in a continuous process, the hard outer surface of the pipe is tightly wrapped with solid or perforated aluminum tape, which is formed into a ring shape by rolling rollers. There are two technologies for welding aluminum tape on a pipe - overlap and butt. Most advanced technology stitching - end-to-end (as in the production of reinforced pipes PRO AQUA). The edges of the tape are fixed relative to each other by ultrasonic welding. Next, the resulting pipe structure is extruded again (a new layer of polypropylene is applied on top of the aluminum shell).

Pipe reinforcement has one of the main goals, which is to sharply reduce the thermal elongation of a thermoplastic pipe, which is significant in homogeneous polypropylene pipes.

It is no coincidence that the developers of reinforced polypropylene pipes, having achieved the industrial implementation of such a reinforced structure, call it “stable”. This means a small dependence on the change in the initial length of the pipe when it is heated or cooled.

Coefficient of linear thermal expansion a (mm/m^°C) for PPR pipes s a = 0.15, and for a reinforced PPR pipe a = 0.03.

Reinforcement scheme and design PPR pipes

Rice. 5.1. a - section of a reinforced PPR pipe;

1 - layer of aluminum. b - design of reinforced PPR pipe; 1 - layer of perforated aluminum; 2, 3 - polypropylene.

Based on socket welding technology, in which the outer diameter of the pipe at normal temperature must correspond to the inner diameter of the connecting part, the pipe wall is increased by 2 - 3 mm and the aluminum shell and outer polymer layer cladding, which is removed before welding using a special tool.

PRO AQUA reinforced pipes are produced in two types: perforated and smooth. The difference between the perforated shell of a PPR-reinforced pipe and a smooth one is that the aluminum shell has frequent perforations - a grid of small-diameter holes.

During the extrusion of a polypropylene pipe, a viscous material flows into these holes and thereby creates adhesion between the polymer and metal. On the surface of pipes of this type, visible “drags” remain, repeating the structure of the applied perforation.

In addition to its temperature stabilizing ability, the reinforcement of PPR pipes also has another important function - the creation of an anti-diffusion barrier that prevents the penetration of oxygen molecules through the pipe wall into the coolant.

PPR pipeline design

The design of PPR pipelines for cold and hot water supply systems is carried out in accordance with the regulations of building codes and regulations 2.04.01-85 “Internal water supply and sewerage of buildings”, taking into account the specifics of polypropylene pipes and the Code of Practice for the design and installation of pipelines made of polypropylene random copolymer SP 40 -101-96.

Hydraulic calculation

Hydraulic calculation of pipelines made of PPR 80 consists of determining the pressure loss (or pressure) to overcome the hydraulic resistance that occurs in the pipe, in connecting parts, in places of sharp turns and changes in the diameter of the pipeline.

Hydraulic resistance coefficient

Hydraulic head loss at local resistance in connecting parts it is recommended to determine according to the following table:

Local hydraulic resistance coefficient for connecting parts polypropylene PP-R 80

Linear Expansion Compensation

Because the polymer materials have an increased coefficient of linear elongation compared to metals, then when designing heating systems, cold and hot water supply, calculations are made of lengthening or shortening of pipelines when temperature differences occur.

The design and installation of pipelines must be carried out so that the pipe can move freely within the limits of the calculated expansion. This is achieved due to the compensating ability of the pipeline elements, the installation of temperature compensators and the correct placement of supports (fasteners). Fixed pipe fastenings must guide pipe extensions towards these elements.

Calculation of changes in pipeline length when its temperature changes is carried out using the formula:

AL = аЧ^ At,

• DL - change in the length of the pipeline when it is heated or cooled;
• a is the coefficient of thermal expansion mm/m “C;
• L is the estimated length of the pipeline;
• At is the difference in pipeline temperature during installation and operation °C (°K).

The magnitude of temperature changes in pipe length can also be determined from Tables 6.2 and 6.3.

Linear expansion table (in mm): pipe PP-R 80 PN10 and PN20 - (a = 0.15 mm/m^°C)

Linear expansion table (in mm): reinforced pipe PP-R 80 PN 25

(a = 0.03 mm/m. °C)

Compensation for thermal elongations is solved constructively, using rotation angles, sliding and fixed supports, as well as ready-made compensators. In fixed supports, the pipe is rigidly secured with a clamp through a rubber gasket, and in sliding supports, clamps allow the pipe to move in the axial direction. Using the example of a design solution for pipeline routing in the form of a rotation angle, we present the calculation of thermal compensation for a horizontal section of a polypropylene pipeline, defining desired length vertical section, which, taking into account the elastic properties of the pipe, will “spring” without destruction in the range of elongation equal to AL.

Figure 6.1. Design diagram of the L-shaped compensator:

• BUT - fixed support;
• SO - sliding support;
• L n pyx.uch. - length of the spring section from the pipe axis to the edge of the fixed support, mm;
• DL - increase in the length of the horizontal section of the pipeline during heating, mm;
• L C0 is the distance between the edge of the fixed support and the center of the sliding support, as well as between the centers of the sliding supports, mm.

In order to eliminate discrepancies, it is proposed to measure the spring length from the axis of the horizontal section to the edge of the fixed support on the vertical section. The formula for the length of the spring section of the pipeline is:

L n pyx.uch. = K * √ D*AL+D,

• L n pyx.uch.- length of the spring section, mm;
• k - constant characterizing the elastic properties of the pipe = 30;
• D - outer diameter of the pipe, mm;
• DL - increase in the length of the pipeline section when it is heated, mm.

The calculation of the L-shaped compensator is carried out in the following sequence: first, the value of the thermal elongation of the calculation section is determined, then the required length of the spring section perpendicular to it is calculated.

Figure 6.2. Design diagram of U- and U-shaped compensators:

• BUT - fixed support; SO - sliding support;
• Lnpyxyn - length of the spring section from the pipe axis to the edge of the fixed support, mm;
• b - width of the compensator (insert), distance between the track axes, mm;
• AL 1, D L 2 - increase in the lengths of horizontal sections of pipelines when they are heated, mm;
• L H0 - distance between the edges of fixed supports, mm;
• L C0 - distance between the center of the sliding support and the axis of the pipe elbow, mm;
• L C01, L C02 - distances between the edge of the fixed support and the edge of the sliding support, mm.

When solving thermal compensation of a pipeline section using a U-shaped pipe compensator, you can use 2 methods of placing it between fixed supports:

• median (exactly in the middle) placement between the supports, in which the lengths of both equally spaced pipeline branches on both sides of it are equal, i.e. the design of an equal-arm compensator is obtained;
• displaced placement that occurs during design decisions when the lengths of pipeline branches due to design features object and pipeline routing turn out to be different, i.e. the design of a multi-arm compensator is obtained.

In the first case of calculation, the AL value is equal for both pipeline branches and the total elongation is equal to: AL, = 2AL.

In the second case, the value AL is calculated independently for each branch and the elongation is the sum of the calculated elongations: AL, = AL + AL,

• AL = L 1 + L ;
• lion soi so’
• AL = L 2 + L
• rights co2 co

The width of the compensator b (insert), regardless of the length of its branches, is assigned structurally and is equal to 11 - 13 D. The insert is always attached in the middle with a clamp (rigid fastening).

Thermal elongation A L of the calculated sections of pipelines plus a certain guaranteed gap between the approaching upper parts of the compensator (about 150 mm) should not exceed the width of the compensator. Otherwise, the distance between the fixed supports of the calculation sections should be reduced.

The calculation of a U-shaped compensator is carried out similarly to the calculation of an L-shaped one.

If the design dimensions of pipe L and U-shaped compensators are taken according to calculation, then O-shaped compensators for various diameters plastic pipes are produced with calculated fixed values ​​of their geometric dimensions.

O-shaped compensator

Figure 6.3. Diagram of an O-shaped, loop-shaped compensator:

• BUT - fixed support; SO - sliding support; D - outer diameter of the pipe, mm;
• b - distance between the walls of the compensator along the internal diameter, mm;
• L hq - distance between the edges of fixed supports, mm.

Basic principles of laying polypropylene pipelines

In places that provide their protection from mechanical damage (shafts, grooves, channels, etc.), the possibility of their thermal elongation must be ensured. If impossible hidden gasket pipelines they should be protected from mechanical damage and fire.

Connections to plumbing fixtures may be laid openly.

The distance between pipes and building structures must be at least 20 mm.

At places of passage through building construction walls and partitions, polypropylene pipes should be laid in metal cases or sleeves.

The inner diameter of the sleeve should be 20 - 30 mm larger than the outer diameter of the pipeline passing through it. This gap is filled with soft non-flammable material, facilitating free movement of the pipeline along the axis. The edge of the sleeve should protrude beyond the building structure by 30 - 50mm.

It is prohibited to place butt joints of either a detachable or non-detachable nature in the sleeve.

In case of laying pipelines in a layer of concrete or cement-sand mortar It is prohibited to embed detachable threaded connections.

Fastening PPR pipelines

When divided into separate sections, by distributing points of rigid attachment. Thus, uncontrolled movement of pipelines is prevented and their reliable fixation is guaranteed. Rigid fastening points are calculated and carried out taking into account the forces that arise during the expansion of pipelines, as well as additional loads.

Sliding or guiding fasteners must allow the pipe to move in the axial direction without mechanical damage pipes.

The distance between sliding supports when laying a pipeline horizontally is determined according to table 6.4:

The distance between the supports depending on the temperature of the water in the pipeline

Fixed supports must be placed so that temperature changes the lengths of the pipeline section between them did not exceed the compensating capacity of the bends and compensators located in this section and were distributed in proportion to their compensating capacity.

In cases where temperature changes in the length of a pipeline section exceed the compensating capacity of the elements limiting it, it is necessary to install an additional compensator on it.

In order to avoid transferring their weight to the pipeline, shut-off and water valves must be firmly fixed to building structures.

Installation of PPR pipelines

The traditional method of connecting pressure pipelines made of polypropylene is welding, which consists in heating the parts to a viscous-flowing state, connecting them under some pressure, and then cooling the parts until a permanent connection is formed - a weld.

The most commonly used welding method is socket welding, which involves joining the ends of pipes through an intermediate piece into a socket.

Welding machine

To weld small-diameter pipes, a set of welding equipment is used (shown in Fig. 7.1), which includes:

• welding machine with clamp (power 1500 W);
• replaceable heaters (D 20, 25, 32 and 40 mm);
• cutter for cutting pipes up to 40 mm;
• level;
• roulette;
• metal suitcase; instructions for use.

To weld plastic parts with diameters greater than 40 mm, a special welding machine is used, which is supplied in a special case. General form welding machine (power 1500 W) is shown in Figure 7.2.

Tool preparation

Depending on the temperature environment heat heating element lasts 10 - 15 minutes. The operating temperature on the surface is reached automatically. The heating process is completed when the temperature control lamp goes out or lights up (depending on the type of welding machine).

ATTENTION:

Welding tools must be kept clean. If necessary, clean the narrative sleeve and mandrel with solvent using a coarse cloth.

Welding parts into a socket

The socket welding process includes simultaneous heating of the parts to be joined, technological holding, removal of the parts from the nozzles, their mating and subsequent natural cooling of the welded parts. For each outer diameter, corresponding pairs of nozzles are selected. Welding order:

Nozzles of the appropriate diameter are installed on the welding machine, and the working surfaces of the nozzles must be degreased with acetone or an aqueous solution of alcohol. In cases where polymer residues from previous welding stick to the nozzles, it is necessary to clean the working surfaces.

1. The welding machine is connected to the network and is expected to be ready for operation.
2. The technology-appropriate welding temperature for PPR is 260 - 270 °C.
3. The pipe is cut at right angles to the pipe axis using a special cutter.
4. Before welding, if necessary, the end of the pipe and the socket of the fitting are cleaned of moisture, dust and dirt and degreased.
5. A mark is applied to the pipe at a distance equal to the depth of the socket plus 2 mm.
6. The ends of the parts are smoothly inserted into the nozzles by axial movement without rotating.
7. The regulated warm-up time to a viscous-flow state is maintained (according to table 7.1).
8. The parts are removed from the attachments and mated with each other within 1 - 2 seconds. During this operation, rotational movements of the parts relative to each other are not allowed; only minor adjustments to the final arrangement of the parts are possible in the final stage of welding.
9. The welded joint and parts are cooled naturally.

For reinforced polypropylene pipes, before welding, the end of the pipe is cleaned by stripping, and a thin polymer layer is removed along with the foil. As a result, the resulting outer diameter of the pipe must correspond, within tolerances, to the standard outer diameter of this standard size.

ATTENTION:

• During operation, if necessary, the replaceable heaters are cleaned of adhering material;
• to ensure high-quality connection of parts, damage to the coating of the nozzles should be avoided;
• It is strictly forbidden to cool the device with water, otherwise the thermal resistances may be damaged.

Technological parameters of socket welding of parts made of random copolymer PP (outside air temperature 20 °C)

Welding thermoplastics is accompanied by the obligatory extrusion of a melt of material called flash at the weld site. During socket welding, the bead comes out onto the outer surface of the pipe and inner surface connecting piece

It should be noted that grades of polypropylene various manufacturers differ from each other in compositional composition, therefore, in the case of welding pipes and parts different manufacturers To obtain a guaranteed connection, it is necessary to carry out test welding before starting the main work.

Pipeline testing cwater supply systems

Internal cold and hot water supply systems must be tested by hydrostatic or manometric method in compliance with the requirements of GOST 24054-80, GOST 25136-82 and these rules.

The test pressure value for the hydrostatic test method should be taken equal to 1.5 times the excess operating pressure.

Hydrostatic and pressure testing of cold and hot water supply systems must be carried out before installing water taps.

Systems are considered to have passed the tests if, within 10 minutes of being under test pressure using the hydrostatic test method, no pressure drop of more than

0.05 MPa (0.5 kgf/cm 2) and drops in welds, pipes, threaded connections, fittings and water leaks through flushing devices.

At the end of the hydrostatic test, it is necessary to release water from the internal cold and hot water supply systems.

Manometric tests of the internal cold and hot water supply system should be carried out in the following sequence:

• fill the system with air at a test excess pressure of 0.15 MPa (1.5 kgf/cm 2);
• if installation defects are detected by ear, the pressure should be reduced to atmospheric pressure and the defects eliminated;
• then fill the system with air at a pressure of 0.1 MPa (1 kgf/cm2),
• hold it under test pressure for 5 minutes.

The system is considered to have passed the test if, when it is under test pressure, the pressure drop does not exceed 0.01 MPa (0.1 kgf/cm2).

Heating systems

Testing of water heating and heat supply systems must be carried out with the boilers and expansion vessels turned off using the hydrostatic method with a pressure equal to 1.5 operating pressure, but not less than 0.2 MPa (2 kgf/cm2) at the lowest point of the system.

The system is considered to have passed the test if, within 5 minutes of being under test pressure, the pressure drop does not exceed 0.02 MPa (0.2 kgf/cm2) and there are no leaks in welds, pipes, threaded connections, fittings, heating devices and equipment .

The test pressure value using the hydrostatic test method for heating and heat supply systems connected to heating plants must not exceed the maximum test pressure for heating devices and heating and ventilation equipment installed in the system.

Manometric tests of heating and heat supply systems correspond to manometric tests of internal cold and hot water supply systems and are carried out in the same sequence (clause 8.1).

Surface heating systems must be tested, usually using the hydrostatic method. Manometric testing can be carried out at negative temperature outside air.

Hydrostatic testing of surface heating systems must be carried out (prior to installation). mounting windows) pressure of 1 MPa (10 kgf/cm 2) for 15 minutes, while the pressure drop is allowed no more than 0.01 MPa (0.1 kgf/cm 2).

For surface heating systems combined with heating devices, the test pressure value should not exceed the maximum test pressure for heating devices installed in the system.

The test pressure value of panel heating systems, steam heating and heat supply systems at manometric tests should be 0.1 MPa (1 kgf/cm2). Test duration -5 min. The pressure drop should be no more than 0.01 MPa (0.1 kgf/cm2).

The system is recognized as having passed the pressure test if, within 5 minutes of being under test pressure, the pressure drop does not exceed 0.02 MPa (0.2 kgf/cm 2 ] and there are no leaks in welds, pipes, threaded connections, fittings, heating devices.

Pipeline insulation

Thermal insulation of water supply pipelines is carried out in accordance with the requirements of SNiP 2.04.14-88 (section 3).

When installing cold water supply systems, it is necessary to protect pipelines from condensation. Determination of quantity minimum thickness insulation for polypropylene pipes can be produced according to table 9.1:

Determination of insulation thickness for cold water supply

Transportation and storage of PPR pipes

According to SP 40-101-96, transportation, loading and unloading of polypropylene pipes must be carried out at an outside temperature of at least - 10 ° C. Their transportation at temperatures up to - 20 °C is allowed only when special devices are used to secure the pipes, as well as special precautions are taken.

Pipes and connecting parts must be protected from impacts and mechanical stress, and their surfaces from scratches. When transporting, PPRC pipes must be laid on flat surface Vehicle, protecting from sharp metal corners and edges of the platform.

PPRC pipes and fittings delivered to site in winter time, before their use in buildings must first be kept at a positive temperature for at least 2 hours.

Pipes should be stored on racks in indoors or under a canopy. The height of the stack should not exceed 2 m. Pipes and connecting parts should be stored no closer than 1 m from heating devices.

Safety requirements

When in contact with an open fire, the pipe material burns with a smoky flame, forming a melt and releasing carbon dioxide, water vapor, unsaturated hydrocarbons and gaseous products.

Welding of pipe connecting parts should be carried out in a ventilated area.

When working with welding machine You must follow the rules for working with power tools.

Normative references

1. GOST R 52134-2003 “Thermoplastic pressure pipes and connecting parts for them for heat supply and heating systems. Are common technical specifications" It lists all the necessary foreign standards. GOST contains requirements for pipes made of polyethylene, unplasticized and chlorinated polyvinyl chloride, polypropylene and its copolymers, cross-linked polyethylene (classified as thermoplastics in this standard) and polybutene.
2. SNiP 2.04.05-91* “Heating. Ventilation and air conditioning", Appendices to it, as well as SP 41-102-98 "Design and installation of pipelines for heating systems using metal-polymer pipes" and SP 40-101-96 "Design and installation of pipelines made of polypropylene "Random copolymer".
3. SNiP 41-01-2003 came into force on January 1, 2004; the developers tried to take into account the requirements of the main foreign standards and the changes that have occurred in the market.
4. TU 2248-039-00284581-99 - General requirements for pressure pipes made of cross-linked polyethylene are defined in Russia.
5. TU 2248-032-00284581-98 - general requirements for pipes made of polypropylene copolymers.

Foreign regulatory framework:

Due to the fact that the law “On technical regulation» has led to instability in the regulatory framework and the classification of a number of provisions and documents as advisory, it makes sense to list a number international standards regulating the most important parameters thermoplastics. These norms, as a rule, are reflected in new Russian regulatory documents.

International standard 1EO 15874 defines the requirements for pipelines for hot and cold water supply made of polypropylene, ISO 161-1:1996 - nominal outer diameters and nominal pressures for pipes made of thermoplastics, ISO 4065:1996 - wall thickness; ISO 9080:2003 contains a method for determining long-term hydrostatic strength, ISO 10508:19995 contains requirements for pipes and fittings.

Over the past ten years, polypropylene pipes have become popular among professional builders, and for those people who are organizing their apartments or country house. When going shopping, many are faced with the problem of choosing a product, since there are a lot of polypropylene pipes on the market. But, first of all, the parameters of polypropylene pipes must correspond to the parameters of your engineering system.

Life time

1. The service life of polypropylene pipes is 50 years in a cold water supply system. IN heating system, as well as in the hot water supply system, they will last 25 years, while maintaining all their original characteristics.

2. You need to know that the maximum service life of polypropylene pipes depends on the correct combination of two important factors: pressure and temperature. At high temperature and low pressure, or vice versa, pipes can last a long time. This is even indicated in special tables. But if both the pressure and temperature are high, then the pipes will not last long.

3. What can be done to make the pipes last as long as possible? In order for the service life to be maximum, that is, 50 years, the temperature should be no more than 60-75 degrees or the pressure should be no more than 4-6 atmospheres. In general, a polypropylene pipe will last as long as it can withstand without destruction, taking into account the reliability factor of the influence of constant temperature and pressure on it. And if you follow everything operational parameters, which are indicated in building codes, polypropylene pipes will last a long time.

Polypropylene pipes and frost

Polypropylene pipes can be used at temperatures up to 40 degrees below zero. They have high frost resistance. They will not crack in frost and will not defrost in winter even at shallow burial depths. Even if the water in the pipes freezes, they do not collapse, but only increase slightly in size; when they thaw, they return to their previous size. The only thing you need to be wary of is putting too much external pressure on the pipe, which could cause it to burst. Despite the temperature norms, the temperature hot water in the heating system may exceed the specified 95 degrees in some regions. First of all, this applies to regions with a sharply continental climate: Yakutia, the Far East and Siberia. If the temperature is 52 degrees below zero, then to heat buildings at such a high temperature, the water in the heating mains must be heated much above the boiling point. And at the same time, polypropylene pipes may suffer. Therefore, there is only one conclusion: polypropylene pipes can be safely used in heating and water supply systems everywhere except in the coldest regions.

Roughness and diameter

1. When designing a pressure pipeline system important have it hydraulic calculations. Using them, the diameter of the pipes is calculated and pumping equipment is selected that ensures the desired operating mode of the above system for the entire service life.

2. Polypropylene pipes have a fairly smooth internal surface and low hydraulic losses. This allows the installation of polypropylene pipes of smaller diameter than steel pipes. Installation turns out to be more economical and compact.

3. The equivalent roughness coefficient for polypropylene pipes is 0.003-0.005 mm. For new steel pipes - 0.2 mm. Therefore, it becomes clear why, when replacing steel pipe instead of polypropylene, choose a pipe with a smaller diameter.

In the process installation work heating or plumbing systems, it is necessary to calculate the diameter of the polypropylene pipe. Thanks to these calculations, heat loss and unnecessary energy costs can be avoided. This calculation is made using special formulas.

Hydraulic calculation

1. During the hydraulic calculation of polypropylene pipes, the pressure loss (pressure) is determined, aimed at suppressing the hydraulic resistance that occurs inside the pipe.
2. In addition to the pipe, hydraulic resistance can also arise in places where the polypropylene pipe turns quite sharply and where its diameter expands or, on the contrary, narrows.
3. To carry out a hydraulic calculation of a polypropylene pipe, it is necessary to use special nanograms.
4. Hydraulic head losses in various connecting parts can be determined using the table presented.

Inner diameter of polypropylene pipe

From internal diameter The pipe depends on the volume of water that it can pass through itself in a certain time. In the vast majority of cases, before installing a pipeline, it is the internal, and not the external, diameter of polypropylene pipes that is calculated. If you do not calculate the permeability and diameter of polypropylene pipes, then, in the worst case, periodically people living on the most upper floors multi-storey buildings, will remain without water.

Formula for calculating the internal diameter of pipes

The permeability of a polypropylene pipe can be calculated using the formula shown in the figure, in which:

• Qtot means the total peak water flow;
• Pi equals the value 3.14;

under V this refers to the speed at which water flows through polypropylene pipes. The speed of water flow in thick pipes is from 1.5 to 2 meters per second, in thin pipes - from 0.7 to 1.2 meters per second.

Pipe diameter for a private house

It is advisable to calculate the internal diameter of polypropylene pipes if plumbing system will be built in a large apartment building. IN small apartment or a private home, you can easily do without such calculations. In this case, polypropylene pipes with a diameter of 20 millimeters will be sufficient.

Thermal elongation

When designing and carrying out installation work, it is necessary to take into account the thermal elongation of pipelines. Unreinforced polypropylene pipes have significant thermal expansion. Polypropylene pipes reinforced with aluminum or fiberglass have a coefficient of linear expansion that is five times less than non-reinforced pipes. You should always remember this when starting to install a particular system.

Comparative table of linear expansion of pipes from various materials

The issue of thermal expansion is largely resolved correct use supports and choice of pipeline configuration. One of general rules installation is the desire to create as flexible as possible elastic system with a minimum of rigid short nodes that have little ability to deform. Ignoring instructions for compensating for linear pipeline expansions causes high longitudinal stresses in the pipe walls and thereby significantly reduces the service life of the system. Incorrectly selected distances between pipeline fasteners also negatively affect service life. An arbitrary increase in the distance between the supports can lead to an increase in the deflection of the pipe and pinching it on the supports, which eliminates straightness and the possibility of free extension or shortening of the pipeline during operation, and also creates additional forces on the structure of the supports.

Thermal lengthening/shortening of the pipelineΔl, mm, regardless of its diameter, is determined by the formula

Δ l = α/Δ t ,

where α is the linear elongation coefficient,

Δt is the difference between temperatures during operation and during installation.

If the temperature of the pipeline during operation is higher than the installation temperature, then the length of the pipeline increases, and vice versa.

To eliminate errors in calculations, it is advisable to denote elongation with a plus sign (+Δl) and shortening with a minus sign (-Δl).

The longitudinal force arising in a rigidly fixed section of the pipeline does not depend on its length, therefore it is necessary to take into account the influence of thermal stresses in any fixed section of the pipeline.

The pipeline must be freely lengthened or shortened without overstressing the material of the pipes, connecting parts, pipeline seams, as well as moving (sliding) and fixed (dead) supports. This is ensured thanks to the compensating ability of pipeline elements (self-compensation) and compensators, as well as correct placement movable and fixed supports.

Fixed supports must direct the linear thermal expansion of the pipeline towards the compensating elements. The distances between supports are calculated based on regulatory documents(SP 40-101-96, SP 40-102-2001 and technical catalog of the Egoplast company “Pipeline system for water supply and heating”, part 1) depending on the material, outer diameter, pipe wall thickness, temperature and weight transported substances. In this case, it must be ensured that the straightness of the pipeline is maintained for the entire design period of operation. If the calculation was made incorrectly or was not done at all, then a negative result will not be long in coming.

Roughness and diameter

When designing pressure pipeline systems, their hydraulic calculations are of decisive importance. They serve as the basis for calculating pipe diameters and selecting pumping equipment, which ensure the required operating mode of these systems throughout the entire service life. The quality of the hydraulic calculations performed determines the efficiency of both the pipeline itself and the entire complex of structures associated with it. Polymer pipes have a very smooth internal surface and low hydraulic losses, which allows the use of smaller diameter pipes than steel pipes. Installation becomes more compact and economical. From the table below it can be seen that the equivalent roughness coefficient of a polypropylene pipe is two orders of magnitude lower compared to a steel pipe. Therefore, when the customer has a question: “Why was a smaller diameter chosen when replacing a steel pipe with a polypropylene one?”, you can provide this table, even if you do not have a hydraulic calculation of the system at hand.

Pipeline equivalent roughness coefficient depending on pipe material

Insulation

To prevent the occurrence of excess stress and damage to polypropylene pipes on building structures, they must be sealed in insulation. To avoid the appearance of condensation on pipes in cold water supply systems, the installation of pipelines must also be done in insulation. Insulation of hot water supply system pipelines reduces heat losses to the environment.

Welding and fastening

In pipelines made of polypropylene, a welded connection practically does not reduce the reliability of the system; the number of connecting and installation elements does not matter if all welding rules are observed. When welding polypropylene pipes and fittings, it is necessary to comply with the recommendations and requirements set out in the “Installation Guide for Polypropylene Pressure Pipe Systems”.

The resistance coefficients of polypropylene fittings are lower than those of cast iron. Shut-off valves It is highly reliable, there is no effort from tightening the threads. When placing pipes on walls and ceilings, it is not recommended to use fixed supports. Fixed supports, as a rule, fix heavy pipe assemblies or heavy pipeline elements that do not have their own fastenings (for example, filters or taps).

When carrying out installation work, it is not allowed to use a pipe (gas) wrench to tighten combined polypropylene fittings. Usage given key leads to destruction of fittings. Compliance with all these regulatory rules will ensure reliable and trouble-free operation of the pipeline system throughout the entire design period of its operation.

With production technology analysis and analysis current state and market forecast you can find in the marketing research report of the Academy of Industrial Market Conditions: "Market of polypropylene pipes in Russia."

Yu. D. Oleynikov, Ph.D., Egoplast company, head of the Heating department