Calculation of water pressure losses in the pipeline is performed very simply, further we will consider in detail the calculation options.

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

Have you been lucky enough to drill a well right next to your house? Amazing! Now you can provide for yourself and your house or cottage clean water, which will not depend on the central water supply. And this means no seasonal shutdown of water and running with buckets and basins. All you have to do is install the pump and you're done! In this article, we will help you calculate the pressure loss of water in the pipeline, and already with these data, you can safely buy a pump and finally enjoy your water from the well.

It is clear from school physics lessons that water flowing through pipes experiences resistance in any case. The value of this resistance depends on the flow velocity, the diameter of the pipe and the smoothness of its inner surface. The resistance is the smaller, the lower the flow velocity and the larger the diameter and smoothness of the pipe. Pipe smoothness depends on the material from which it is made. Pipes made of polymers are smoother than steel pipes, and they also do not rust and, importantly, are cheaper than other materials, while not inferior in quality. Water will experience resistance, even moving along a completely horizontal pipe. However, the longer the pipe itself, the less significant the pressure loss will be. Well, let's start the calculation.

Head loss in straight pipe sections.

To calculate the loss of water pressure in straight sections of pipes, he uses a ready-made table, presented below. The values ​​in this table are for pipes made from polypropylene, polyethylene and other words beginning with "poly" (polymers). If you are going to install steel pipes, then you need to multiply the values ​​\u200b\u200bgiven in the table by a factor of 1.5.

Data are given for 100 meters of pipeline, losses are indicated in meters of water column.

How to use the table: For example, in a horizontal water pipe with a pipe diameter of 50 mm and a flow rate of 7 m 3 / h, the loss will be 2.1 meters of water column for a polymer pipe and 3.15 (2.1 * 1.5) for a steel pipe. As you can see, everything is quite simple and clear.

Head loss due to local resistances.

Unfortunately, pipes are absolutely straight only in a fairy tale. In real life, there are always various bends, dampers and valves that cannot be ignored when calculating the pressure loss of water in a pipeline. The table shows the head loss values ​​for the most common local resistances: 90 degree elbow, rounded elbow and valve.

Losses are given in centimeters of water column per unit of local resistance.

To determine v - flow rate it is necessary Q - water consumption (in m 3 / s) divided by S - cross-sectional area (in m 2).

Those. with a pipe diameter of 50 mm (π * R 2 \u003d 3.14 * (50/2) 2 \u003d 1962.5 mm 2; S \u003d 1962.5 / 1,000,000 \u003d 0.0019625 m 2) and a water flow rate of 7 m 3 / h (Q \u003d 7 / 3600 \u003d 0.00194 m 3 / s) flow rate
v=Q/S=0.00194/0.0019625=0.989 m/s

As can be seen from the above data, pressure loss on local resistances quite insignificant. The main losses still occur in horizontal sections of pipes, therefore, in order to reduce them, carefully consider the choice of pipe material and their diameter. Recall that in order to minimize losses, you should choose pipes made of polymers with maximum diameter and smoothness of the inner surface of the pipe itself.

Pipes and fittings for hot and cold water supply systems from have a number of advantages:

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

Material

Polypropylene is an isotactic thermoplastic whose macromolecules have a helical conformation and was first obtained in 1954.

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

Polypropylene has the following modifications:

• propylene homopolymer (type 1) PPH;
• copolymers of propylene and ethylene (type 2) РРВ - 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 water supply PRO AQUA are made from the 3rd type of polypropylene - a 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 that occurs 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 is understood as the ability of the pipe material to maintain such a margin of safety of the pipeline by the end of the expected service life that, subject to the conditions of the operational period, it still guarantees the reliable performance of its working functions. According to modern designations of pressure pipes made of polypropylene, the MRS indicator in kgf / cm 2 (bar) is put down 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 / cm 2; 80 bar) will have the designation PPR 80.

Standard dimensional ratio - SDR (Standart 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 both values ​​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 fitting will correspond to the SDR of the pipe with which it is mounted. For example, a tee marked SDR 11 is designed for welding with a pipe bearing the same marking.

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

Indicators of pipe types PN, SDR, S are interconnected, their ratio is presented in table 3.1:

The main characteristics of polypropylene

Distinctive features of polypropylene

Polypropylene is characterized by high resistance to repeated bending and abrasion. The resistance to surface-active substances (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 has received the greatest distribution in systems of cold and hot water supply, the internal and external sewerage.

Reinforced polypropylene pipes are produced in stages. Initially, a homogeneous polypropylene pipe is made by extrusion. Then, in a continuous process, solid outer surface the pipes are tightly covered with a solid or perforated aluminum tape, the annular shape of which is given 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 tubular structure is again extruded (a new layer of polypropylene is applied over the aluminum shell).

The reinforcement of the pipe pursues one of the main goals, which is to sharply reduce the temperature elongation of the thermoplastic pipe, which in homogeneous polypropylene pipes appear to a large extent.

It is no coincidence that the developers of reinforced polypropylene pipes, having achieved the industrial implementation of such a reinforced structure, call it the term “stable”. This implies a small dependence of 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 a PPR pipe a = 0.15, and for a reinforced PPR pipe a = 0.03.

Reinforcement scheme and design of PPR pipe

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

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

Based on the technology of socket welding, in which outside diameter pipes 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 with a special tool.

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

In the process of extruding 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 to the eye “sinks” remain, repeating the structure of the applied perforation.

Reinforcement of PPR pipes, in addition to the temperature stabilizing ability, 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.

Design of PPR pipelines

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

Hydraulic calculation

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

Hydraulic resistance coefficient

Hydraulic head loss due to local resistance in fittings is recommended to be determined according to the following table:

Coefficient of local hydraulic resistance for fittings made of polypropylene PP-R 80

Linear expansion compensation

Since polymeric materials have an increased coefficient of linear elongation compared to metals, when designing heating systems, cold and hot water supply, they calculate elongations or shortenings of pipelines when temperature drops occur.

Design and installation of pipelines must be carried out so that the pipe can move freely within 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 fixings must guide pipe extensions towards these elements.

The calculation of the change in the length of the pipeline with a change in its temperature is made according to the formula:

AL = аЧ^ At,

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

The magnitude of temperature changes in the length of the pipe 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 \u003d 0.03 mm / m. ° C)

Compensation for thermal elongations is solved constructively, using angles of rotation, sliding and fixed supports, as well as ready-made expansion joints. In fixed supports, the pipe is rigidly fastened with a clamp through rubber gasket, and in sliding bearings, retainers allow the pipe to move in the axial direction. Using the example of a design solution for tracing a pipeline in the form of a rotation angle, we will calculate the thermal compensation of a horizontal section of a polypropylene pipeline by determining the required length of the vertical section, which, taking into account the elastic properties of the pipe, will “spring” without destruction in the interval of elongation equal to AL.

Fig 6.1. Calculation scheme of L-shaped compensator:

• BUT - fixed support;
• CO - sliding support;
• L n pyx.ac. - the length of the spring section from the axis of the pipe 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 - distance between the edge of the fixed 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 count the spring length from the axis of the horizontal section to the edge of the fixed support in the vertical section. The formula for the length of the spring section of the pipeline is:

L n pyx.ac. = K * √ D*AL+ D,

• L n pyx.ac.- 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 during its heating, mm.

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

Fig 6.2. Calculation scheme of U- and U-shaped compensators:

• BUT - fixed support; CO - sliding support;
• Lnpyxyn is the length of the spring section from the pipe axis to the edge of the fixed support, mm;
• b - compensator width (insert), distance between track axes, mm;
• AL 1 , D L 2 - increase in the length of the horizontal sections of pipelines during their heating, 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 the thermal compensation of a pipeline section using a pipe U-shaped compensator, 2 methods of its location between fixed supports can be applied:

• median (exactly in the middle) placement between the supports, in which the lengths of both pipeline branches equally spaced on both sides of it are equal, i.e. the design of an equal-shoulder 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-shoulder compensator is obtained.

In the first case of calculation, the value of AL is equal for both branches of the pipeline 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 \u003d 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 constructively and is equal to 11 - 13 D. The insert is always fastened in the middle with a clamp (rigid fastening).

Thermal elongation A L of calculated sections of pipelines plus some 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 calculated sections should be reduced.

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

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

O-shaped compensator

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

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

Basic principles of laying pipelines from polypropylene

In places providing their protection from mechanical damage (mines, strobes, channels, etc.), at the same time, the possibility of their thermal elongation should be provided. If hidden laying of pipelines is not possible, 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.

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

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

It is forbidden to place butt joints in the sleeve, both detachable and non-detachable.

In the case of laying pipelines in a layer of concrete or cement-sand mortar it is forbidden to monolithic detachable threaded connections.

Fixing PPR pipelines

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

Sliding or guide fasteners must allow movement of the pipe in the axial direction, while excluding mechanical damage to the pipe.

The distance between sliding supports for horizontal laying of the pipeline is determined according to table 6.4:

Distance between supports depending on the temperature of the water in the pipeline

Fixed supports it is necessary to place it so that the temperature changes in the length of the pipeline section between them do not exceed the compensating capacity of the bends and compensators located in this section and are distributed in proportion to their compensating capacity.

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

Shutoff and water fittings in order to avoid transferring their weight to the pipeline must be firmly fixed on building structures.

Installation of PPR pipelines

Traditional connection method pressure pipelines from polypropylene is welding, which consists in heating the parts to a viscous state, connecting them under some pressure, and then cooling the parts until an integral connection is formed - a weld.

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

Welding machine

The kit is used for welding small diameter pipes. welding equipment(shown in Fig. 7.1), which includes:

• welding machine with a 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.

For welding 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

temperature dependent environment heat heating element lasts 10 - 15 minutes. Working 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 heating sleeve and the mandrel with solvent using a coarse cloth.

Socket welding

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

Nozzles of the appropriate diameter are installed on the welding machine, while 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 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. The end of the pipe and the socket of the fitting before welding, if necessary, are cleaned of moisture, dust and dirt and degreased.
5. A mark is applied to the pipe at a distance equal to the socket depth plus 2 mm.
6. The ends of the parts, by axial movement, without rotating, are smoothly inserted into the nozzles.
7. The regulated warm-up time to a viscous state is maintained (according to Table 7.1).
8. Parts are removed from the nozzles, and within 1 - 2 seconds are mated with each other. During this operation, rotational movements of the parts relative to each other are not allowed, only a slight adjustment of the final location of the parts in the final stage of welding is possible.
9. Cooling of the welded joint and parts is carried out in a natural way.

For reinforced polypropylene pipes, before welding, the end of the pipe is cleaned by stripping, while the 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 size.

ATTENTION:

• During operation, if necessary, replaceable heaters are cleaned of adhering material;
• to ensure high-quality connection of parts, damage to the nozzle coating 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 PP random copolymer (outside air temperature 20 °C)

Welding of thermoplastics is accompanied by the obligatory extrusion of a melt of a material called flash in the place of the weld. In socket welding, the flash comes out to the outer surface of the pipe and inner surface connecting piece

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

Piping tests cwater supply systems

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

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

Hydrostatic and manometric tests of cold and hot water supply systems should be carried out before the installation of water fittings.

Systems are considered to have passed the test if, within 10 minutes of being under test pressure in 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 leakage through flushing devices.

Upon completion 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 with a test overpressure of 0.15 MPa (1.5 kgf / cm 2);
• if mounting defects are found by ear, the pressure should be reduced to atmospheric pressure and the defects should be eliminated;
• then fill the system with air at a pressure of 0.1 MPa (1 kgf / cm 2),
• keep it under test pressure for 5 minutes.

The system is recognized as having passed the test if, when it is under test pressure, the pressure drop does not exceed 0.01 MPa (0.1 kgf / cm 2).

Heating systems

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

The system is recognized as having passed the 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 joints, fittings, heating appliances and equipment .

The value of the test pressure in the hydrostatic test method for heating and heat supply systems connected to heating plants should not exceed the limiting test pressure for heaters 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, as a rule, by the hydrostatic method. The manometric test may be carried out at negative temperature outside air.

Hydrostatic testing of surface heating systems must be carried out (before 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 appliances, the value of the test pressure should not exceed the limiting test pressure for the heaters installed in the system.

The value of the test pressure of surface heating systems, steam systems heating and heat supply during manometric tests should be 0.1 MPa (1 kgf / cm 2). Test duration -5 min. The pressure drop should be no more than 0.01 MPa (0.1 kgf / cm 2).

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 appliances.

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 systems, it is necessary to protect the pipelines from the formation of condensate. The determination of the minimum insulation thickness for polypropylene pipes can be made 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 air temperature of at least -10 °C. Their transportation at temperatures up to -20 °C is allowed only with the use of special devices that ensure the fixation of pipes, as well as taking special precautions.

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

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

Pipes should be stored on racks in closed rooms or under a canopy. The stack height should not exceed 2 m. Pipes and fittings should be stored no closer than 1 m from heating devices.

Safety Requirements

Upon contact with an open flame, the pipe material burns with a smoky flame with the formation of a melt and release carbon dioxide, water vapor, unsaturated hydrocarbons and gaseous products.

Welding of pipe fittings 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 “Pressure pipes made of thermoplastics and fittings for them for heat supply and heating systems. General specifications". It lists all required foreign standards. GOST contains requirements for pipes made of polyethylene, unplasticized and chlorinated polyvinyl chloride, polypropylene and its copolymers, cross-linked polyethylene (referred to as thermoplastics in this standard) and polybutene.
2. SNiP 2.04.05-91* “Heating. Ventilation and air conditioning”, Annexes 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 was put into effect on January 1, 2004, the developers tried to take into account the requirements of the main foreign standards and the changes that have occurred on the market.
4. TU 2248-039-00284581-99 - general requirements for pressure pipes from 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 field of the regulatory framework and the classification of a number of provisions and documents as advisory, it makes sense to cite a number of international standards governing the most important parameters thermoplastics. These norms, as a rule, are also reflected in the new Russian regulatory documents.

International standard 1EO 15874 defines the requirements for pipelines for hot and cold water supply from 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 the long-term hydrostatic strength, ISO 10508:19995 - requirements for pipes and fittings.

Thermal elongation

When designing and implementing installation work it is necessary to take into account the thermal elongation of pipelines. Non-reinforced polypropylene pipes have significant thermal expansion. For polypropylene pipes reinforced with aluminum or fiberglass, the coefficient of linear expansion is five times less compared to unreinforced pipes. This should always be remembered when starting the installation of a particular system.

Comparative table of linear expansion of pipes from various materials

The issue of thermal expansion is largely solved correct use supports and choice of piping configuration. One of general rules installation is the desire to create the most flexible elastic system with a minimum of rigid short knots that have a low ability to deform. Ignoring the instructions for compensating for linear expansions of the pipeline 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 adversely affect the 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 lengthening or shortening of the pipeline during operation, and also creates additional forces on the design of the supports.

Thermal expansion/shrinkage of pipelineΔ l , mm, regardless of its diameter, is determined by the formula

∆l = ∆/∆t,

where α is the coefficient of linear elongation,

Δt is the difference between the 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 exclude the appearance of errors in the calculations, it is advisable to denote the elongation with a plus sign (+Δl), and the shortening with a minus sign (-Δl).

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

The pipeline must be freely extended or shortened without overstressing the material of pipes, fittings, pipeline seam, as well as movable (sliding) and fixed (dead) supports. This is ensured by the compensating ability of the pipeline elements (self-compensation) and compensators, as well as correct placement movable and fixed supports.

Fixed supports should direct the linear thermal expansion of the pipeline towards the compensating elements. Distances between supports are calculated based on normative documents(SP 40-101-96, SP 40-102-2001 and Egoplast technical catalog "Pipeline system for water supply and heating", part 1) depending on the material, outer diameter, pipe wall thickness, temperature and mass transported substances. At the same time, the straightness of the pipeline should be maintained for the entire estimated period of operation. If the calculation is made incorrectly or it was not made 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 the diameter of pipes and selecting pumping equipment, which provide the required mode of operation of these systems during the entire period of operation. The quality of the performed hydraulic calculations determines the efficiency of both the pipeline itself and the entire complex of structures associated with it. Polymer pipes have a very smooth inner 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 bring this table, even if you do not have a hydraulic calculation of the system at hand.

Equivalent roughness coefficient of pipelines depending on the pipe material

Insulation

To prevent the occurrence of excessive stresses and damage to polypropylene pipes on building structures, they must be embedded in insulation. To avoid the appearance of condensate on pipes in cold water systems, the installation of pipelines must also be carried out in insulation. Insulation of pipelines of the hot water supply system reduces heat losses to the environment.

Welding and fasteners

In polypropylene pipelines, a welded joint practically does not reduce the reliability of the system, the number of connecting and mounting elements, subject to all welding rules, does not matter. When welding polypropylene pipes and fittings, it is necessary to follow the recommendations and requirements set out in the “Installation Manual for Polypropylene Pressure Piping Systems”.

Drag coefficients polypropylene fittings lower than cast iron. The shut-off valves are highly reliable, there is no effort from tightening the thread. 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 fasteners (for example, filters or taps).

During installation work, it is not allowed to use a pipe (gas) wrench to tighten combined polypropylene fittings. Usage given key leads to destruction of the fittings. Compliance with all these regulations ensure reliable and trouble-free operation of the pipeline system during the entire estimated period of its operation.

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

Yu. D. Oleinikov, Ph.D., Egoplast Company, Head of Heating Department

In the process of carrying out installation work of heating or plumbing systems, it is necessary to calculate the diameter of the polypropylene pipe. Thanks to these calculations, it is possible to avoid heat losses, as well as unnecessary energy costs. 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 arising inside the pipe.
2. Hydraulic resistance, in addition to the pipe, can also occur in places where the polypropylene pipe turns sharply enough and where its diameter expands or, conversely, narrows.
3. To carry out the hydraulic calculation of a polypropylene pipe, it is necessary to use special nanograms.
4. You can determine the hydraulic pressure loss in various connecting parts using the table below.

Inner diameter of polypropylene pipe

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

Formula for calculating the inner diameter of pipes

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

• Qtotal means the total peak water flow;
• Pi equals 3.14;

under V 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

Calculation of the inner diameter of polypropylene pipes is advisable to do if plumbing system will be built in a large apartment building. AT small apartment or a private house, you can easily do without such calculations. In this case, polypropylene pipes with a diameter of 20 millimeters will suffice.

Code of Practice for the Design and Installation of Polypropylene Pipelines

"Random copolymer"

SP 40-101-96

2. Piping design

2.1. The design of pipeline systems is associated with the choice of the type of pipes, fittings and fittings, the performance of hydraulic calculations, the choice of the laying method and conditions that ensure compensation for thermal changes in the length of the pipe without overstressing the material and pipeline connections. The choice of pipe type is made taking into account the operating conditions of the pipeline: pressure and temperature, the required service life and the aggressiveness of the transported liquid.

2.2. The range of pipes, fittings and fittings is given in App. 3 .

2.3. Hydraulic calculation of pipelines from PPRC consists in determining the pressure loss to overcome the hydraulic resistance that occurs in the pipe, in butt joints and fittings, in places of sharp turns and changes in the diameter of the pipeline.

2.4. Hydraulic pressure losses in pipes are determined from the nomograms in Fig. 2.1. and 2.2.

Consumption, l / sec.

Friction head loss, mm/m

Rice. 2.1. Nomogram for engineering hydraulic calculation of cold water pipes from PPRC pipes (PN10)

Definition example

Given: PPRC 32PN10 pipe,

fluid flow 1 l/s

According to the nomogram: average fluid flow velocity 1.84 m/s, head loss 140 mm/m

Consumption, l / sec.

Friction head loss, mm/m

Rice. 2.2. Nomogram for engineering hydraulic calculation of cold water pipes from PPRC pipes (PN20)

Definition example

Given: PPRC50 PN20 pipe,

fluid flow 1 l/s

According to the nomogram: average fluid flow velocity 1.1 m/s, head loss 45 mm/m

2.5. Hydraulic head loss in butt joints can be taken equal to 10-15% of the head loss in pipes, determined by the nomogram. For internal plumbing systems, the value of pressure loss due to local resistances, in fittings and fittings, is recommended to be taken equal to 30% of the pressure loss in pipes.

2.6. Pipelines in buildings are laid on suspensions, supports and brackets openly or hidden (inside mines, building structures, furrows, in channels). Hidden laying of pipelines is necessary to ensure the protection of plastic pipes from mechanical damage.

2.7. Pipelines outside buildings (inter-shop or outdoor) are laid on overpasses and supports (in heated or unheated boxes and galleries or without them), in channels (through or without passage) and in the ground (channelless laying).

2.8. It is forbidden to lay technological pipelines made of PPRC in premises belonging to fire hazard to categories A, B, C.

2.9. It is not allowed to lay intrashop technological pipelines from plastic pipes through administrative, amenity and utility rooms, electrical installation rooms, control and automation system panels, stairwells, corridors, etc. In places of possible mechanical damage to the pipeline, only hidden laying in furrows, channels and mines should be used.

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

2.11. The change in the length of pipelines from PPRC with a temperature difference is determined by the formula

L = 0.15 x L x t (2.1)

where L is the temperature of the change in the length of the pipe, mm;

0.15 - coefficient of linear expansion of the pipe material, mm/m;

L - pipeline length, m;

t is the calculated temperature difference (between the temperature of installation and operation), C.

2.12. The magnitude of temperature changes in the length of the pipe can also be determined from the nomogram in Fig. 2.3.

Temperature t, ° С

Change in pipe length L, mm

Example: T 1 = 20 ° C, t 2 = 75 ° C, L = 6.5 m.

According to formula 2.1

L = 0.15 x 6.5 x (75 - 20) = 55 mm

t \u003d 75 - 20 \u003d 55 ° C.

According to the nomogram = 55 mm.

2.13. The pipeline must be able to freely lengthen or shorten without overstressing the material of the pipes, fittings and connections of the pipeline. This is achieved due to the compensating ability of the pipeline elements (self-compensation) and is ensured by the correct arrangement of supports (fasteners), the presence of bends in the pipeline at the points of rotation, other bent elements and the installation of temperature compensators. Fixed pipe fixings must guide pipe extensions towards these elements.

2.14. The distance between the supports for horizontal laying of the pipeline is determined from the table. 2.1.

Table 2.1

Distance between supports depending on the temperature of the water in the pipeline

2.15. When designing vertical pipelines, supports are installed at least every 1000 mm for pipes with an outer diameter of up to 32 mm and at least every 1500 mm for large diameter pipes.

2.16. Compensating devices are made in the form of L-shaped elements (Fig. 2.4), U-shaped (Fig. 2.5) and loop-shaped (circular) compensators (Fig. 2.6).

Rice. 2.4. L-shaped element of the pipeline

Rice. 2.5. U-shaped compensator

Rice. 2.6. Loop compensator

2.17. The calculation of the compensating capacity of L-shaped elements (Fig. 2.4) and U-shaped compensators (Fig. 2.5) is made according to the nomogram (Fig. 2.7) or according to the empirical formula (2.2)

where L k is the length of the section of the L-shaped element that perceives temperature changes in the length of the pipeline, mm;

d - outer diameter of the pipe, mm;

L - temperature changes in the length of the pipe, mm.

The value of L k can also be determined from the nomogram (Fig. 2.7).

(2.2)

Rice. 2.7. Nomogram for determining the length of a pipe section that perceives thermal elongation

Example: d n = 40 mm,

According to formula 2.2

According to the nomogram L = 1250 mm

2.18. It is recommended to design internal piping systems in the following sequence:

On the piping diagram, the locations of the fixed supports are preliminarily marked, taking into account the compensation for temperature changes in the length of the pipes by the pipeline elements (bends, etc.);

Check the calculation of the compensating ability of the elements of the pipeline between the fixed supports;

Outline the location of the sliding supports, indicating the distances between them.

2.19. Fixed supports must be placed so that the temperature changes in the length of the pipeline section between them do not exceed the compensating capacity of the bends and compensators located in this section, and are distributed in proportion to their compensating capacity.

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

2.21. Compensators are installed on the pipeline, as a rule, in the middle, between fixed supports dividing the pipeline into sections, the temperature deformation of which occurs independently of each other. Compensation for linear elongations of PPRC pipes can also be provided by preliminary deflection of pipes when laying them in the form of a "snake" on a solid support, the width of which allows the pipeline deflection shape to change with temperature changes.

2.22. When arranging fixed supports, it should be taken into account that the movement of the pipe in a plane perpendicular to the wall is limited by the distance from the surface of the pipe to the wall (Fig. 2.4). The distance from fixed connections to the axes of the tees must be at least six pipeline diameters.

2.23. Shut-off and water fittings must be fixed to building structures so that the forces arising from the use of the fittings are not transferred to the PPRC pipes.

2.24. When laying several pipelines made of plastic pipes in one room, they should be laid together in compact bundles on common supports or hangers. Pipelines at the intersection of building foundations, ceilings and partitions must pass through sleeves made, as a rule, from steel pipes, the ends of which should protrude 20-50 mm from the intersected surface. The gap between pipelines and cases must be at least 10-20 mm and carefully sealed with non-combustible material that allows the movement of pipelines along its longitudinal axis.

2.25. When laying in parallel, PPRC pipes must be located below the heating and hot water pipes with a clear distance of at least 100 mm between them.

2.26. The design of means for protecting plastic pipelines from static electricity is provided in the following cases:

The negative impact of static electricity on the technological process and the quality of transported substances;

Dangerous effects of static electricity on service personnel.

2.27. To ensure the service life of hot water pipelines from PPRC pipes for at least 25 years, it is necessary to maintain the recommended operating modes (pressure, water temperature) specified in appendix. 2.

2.28. Taking into account the dielectric properties of PPRC pipes, metal bathtubs and sinks must be earthed in accordance with the relevant requirements of current regulations.