The supports serve to absorb the force from the pipelines and transmit them to bearing structures or soil, as well as to ensure organized joint movement of pipes and insulation during temperature deformations. When constructing heat pipelines, two types of supports are used: movable and fixed.

Movable supports take the weight of the heat pipe and ensure its free movement on building structures during temperature deformations. When the pipeline moves, the movable supports move with it. Movable supports are used for all installation methods, except channelless. At channelless installation The heating pipe is laid on untouched soil or a carefully compacted layer of sand. In this case, movable supports are provided only in places where the route turns and where U-shaped compensators are installed, i.e. in areas where pipelines are laid in channels. The moving supports experience mainly vertical loads from the mass of the pipelines

Based on the principle of free movement, sliding, rolling and suspended supports are distinguished. Sliding supports are used regardless of the direction of horizontal movements of pipelines for all installation methods and for all pipe diameters. These supports are simple in design and reliable in operation.

Roller supports used for pipes with a diameter of 175 mm or more during axial movement of pipes, when laying in tunnels, collectors, on brackets and on free-standing supports. The use of roller bearings in non-passable channels is impractical, since without supervision and lubrication they quickly corrode, stop rotating and begin to work essentially as sliding supports. Roller bearings have less friction than sliding bearings, but when poor care the rollers warp and may jam. Therefore, they need to be given the right direction. For this purpose, ring grooves are provided in the rollers, and guide strips are provided on the base plate.

Roller bearings(rarely used, since it is difficult to ensure rotation of the rollers. Roller and roller bearings work reliably in straight sections of the network. At turns in the route, pipelines move not only in the longitudinal, but also in the transverse direction. Therefore, the installation of roller and roller bearings in curved sections is not recommended. in this case use ball bearings. In these supports, the balls move freely along with the shoes along the backing sheet and are kept from rolling out beyond the support by the projections of the support sheet and the shoe.

If, due to local conditions for laying heat pipelines relative to load-bearing structures, sliding and roller supports cannot be installed, suspended supports are used. The non-rigid suspension design allows the support to easily rotate and move along with the pipeline. As a result, as you move away from the fixed support, the angles of rotation of the hangers increase, and the distortion of the pipeline and the stress in the rods under the influence of the vertical load of the pipeline increase accordingly.

Suspended supports, compared to sliding ones, create significantly lower forces along the pipe axis in horizontal sections.

motionless The pipelines are divided into independent sections by supports. With the help of fixed supports, pipes are rigidly fixed at certain points of the route between compensators or areas with natural compensation for temperature deformations, which, in addition to vertical loads, perceive significant horizontal forces directed along the axis of the pipeline and consisting of unbalanced internal pressure forces, resistance forces of free supports and the reaction of compensators . The forces of internal pressure are of greatest importance. Therefore, to facilitate the design of the support, they try to position it on the route in such a way that the internal pressures in the pipeline are balanced and are not transferred to the support. Those supports to which reactions internal pressure are not transmitted, are called unloaded fixed supports; the same supports that must absorb unbalanced forces of internal pressure are called unloaded supports.

Exist intermediate and end supports. The intermediate support is subject to forces from both sides, and the end support from one side. Fixed pipe supports are designed to withstand the greatest horizontal load under various operating modes of heat pipelines, including with open and closed valves

Fixed supports are provided on pipelines for all methods of laying heating networks. The magnitude of temperature deformations and stresses in the pipes largely depends on the correct placement of fixed supports along the length of the heating network route. Fixed supports are installed on pipeline branches, at locations shut-off valves, stuffing box compensators. On pipelines with U-shaped expansion joints, fixed supports are placed between the expansion joints. When laying ductless heating networks, when self-compensation of pipelines is not used, it is recommended to install fixed supports at the bends of the route.

The distance between the fixed supports is determined based on the given pipeline configuration, thermal elongation of sections and the compensating ability of the installed expansion joints. Fixed fastenings of pipelines are carried out using various structures, which must be strong enough and rigidly hold the pipes, preventing them from moving relative to the supporting structures.

The structures of fixed supports consist of two main elements: load-bearing structures (beams, reinforced concrete slabs), to which the forces from the pipelines are transferred, and the supports themselves, with the help of which the pipes are fixedly secured (welded gussets, clamps). Depending on the installation method and installation location, fixed supports are used: thrust, panel and clamp. Supports with vertical double-sided stops and front ones are used when installing them on frames in chambers and tunnels and when laying pipelines in through, semi-through and non-through channels. Panel supports are used both for channelless installation and for laying heat pipes in non-passable channels when placing the supports outside the chambers.

Panel fixed supports are vertical reinforced concrete panels with holes for the passage of pipes. Axial forces are transmitted to the reinforced concrete shield by rings welded to the pipeline on both sides, reinforced with stiffeners. Until recently, asbestos was laid between the pipe and the concrete. Currently, the use of asbestos packings is not permitted. The load from the pipelines of heating networks is transferred through the panel supports to the bottom and walls of the channel, and in case of channelless installation - to the vertical plane of the ground. Panel supports are made with double symmetrical reinforcement, since the acting forces from the pipes can be directed in opposite directions. At the bottom of the shield, holes are made for the passage of water (if it gets into the channel).

Calculation of fixed supports.

Fixed supports fix the position of the pipeline at certain points and perceive the forces arising at the fixation points under the influence of temperature deformations and internal pressure.

Supports have a very important influence on the operation of the heat pipeline. There are frequent cases of serious accidents due to improper placement of supports, poor design choices or careless installation. It is very important that all supports are loaded, for which it is necessary to verify their placement along the route and their height position during installation. When laying without channels, they usually refuse to install free supports under pipelines in order to avoid uneven settlements, as well as additional bending stresses. In these laying pipes are laid on undisturbed soil or a carefully compacted layer of sand.

The bending stress arising in the pipeline and the deflection boom depend on the span (distance) between the supports.

When calculating bending stresses and deformations, a pipeline lying on free supports is considered as a multi-span beam. In Fig. T.s.19 shows a diagram of the bending moments of a multi-span pipeline.

Let's consider the forces and stresses acting in pipelines.

Let us accept the following notation:

M- power moment, N*m; Q B , Q g - vertical and horizontal force, N; q V , q G- specific load per unit length, vertical and horizontal, H/m;..N - horizontal reaction on the support, N.

The maximum bending moment in a multi-span pipeline occurs at the support. The magnitude of this moment (9.11)

Where q - specific load per unit length of the pipeline, N/m; - span length between supports, m. Specific load q determined by the formula
(9-12)

Where q B - vertical specific load, taking into account the weight of the pipeline with coolant and thermal insulation; q G - horizontal specific load, taking into account wind force,

(9-13)

Where w - wind speed, m/s; - air density, kg/m3; d And - outer diameter of pipeline insulation, m; k - aerodynamic coefficient equal to an average of 1.4-1.6.

Wind force should be taken into account only in open-laying above-ground heat pipelines.

The bending moment occurring in the middle of the span is

(9.14)

At a distance of 0.2 from the support the bending moment is zero.

The maximum deflection occurs in the middle of the span.

Pipeline deflection boom
, (9.15)

Based on expression (9-11), the span between free supports is determined

(9-16) from where
,m(9-17)

When choosing the span between supports for real pipeline diagrams, it is assumed that under the most unfavorable operating conditions, for example, at the highest temperatures and pressures of the coolant, the total stress from all acting forces in the weakest section (usually a weld) does not exceed the permissible value [].

A preliminary estimate of the distance between supports can be made based on equation (9-17), taking the bending stress 4 equal to 0.4-0.5 permissible voltage:

Fixed supports perceive the reaction of internal pressure, free supports and

compensator.

The resulting force acting on a fixed support can be represented as

A - coefficient depending on the direction of action of the axial forces of internal pressure on both sides of the support. If the support is unloaded from the internal pressure force, then A=0, otherwise A=1; R- internal pressure in the pipeline; - internal cross-sectional area of ​​the pipeline; - coefficient of friction on free supports;
- difference in lengths of pipeline sections on both sides of the fixed support;
- the difference between the frictional forces of axial sliding compensators or the elastic forces of flexible compensators on both sides of the fixed support.

26. Compensation for thermal elongations of pipelines of heat supply systems. Basics of calculation of flexible expansion joints.

In heating networks, gland, U-shaped, and, more recently, bellows (wavy) expansion joints are most widely used. In addition to special compensators, they are used for compensation and natural angles turns of the heating main - self-compensation. Compensators must have sufficient compensating capacity
to perceive the thermal elongation of the pipeline section between the fixed supports, while the maximum stresses in the radial expansion joints should not exceed the permissible ones (usually 110 MPa). It is also necessary to determine the response of the compensator used in calculating loads on fixed supports. Thermal elongation of the design section of the pipeline
, mm, determined by the formula

, (2.81)

Where

=1.2· 10ˉ² mm/(m о С),

- calculated temperature difference, determined by the formula
, (2.82)

Where

L

Flexible expansion joints Unlike stuffing box valves, they are characterized by lower maintenance costs. They are used for all installation methods and for any coolant parameters. The use of stuffing box expansion joints is limited to a pressure of no more than 2.5 MPa and a coolant temperature of no higher than 300°C. They are installed when laying underground pipelines with a diameter greater than . 100 mm, for overhead installation on low supports of pipes with a diameter of more than 300 mm, as well as in cramped places where it is impossible to place flexible expansion joints.

Flexible expansion joints are made from bends and straight sections of pipes using electric arc welding. The diameter, wall thickness and steel grade of the expansion joints are the same as the pipelines of the main sections. During installation, flexible expansion joints are placed horizontally; Vertical or inclined placement requires air or drainage devices that make maintenance difficult.

To create maximum compensation capacity, flexible expansion joints are stretched in a cold state before installation and secured in this position with spacers. Size

compensator stretch marks are recorded in a special report. The stretched expansion joints are attached to the heat pipeline by welding, after which the spacers are removed. Thanks to pre-stretching, the compensation capacity is almost doubled. To install flexible compensators, compensatory niches are arranged. The niche is a non-passable channel of the same design, the configuration corresponding to the shape of the compensator.

Stuffing box (axial) expansion joints are made from pipes and sheet steel of two types: single-sided and double-sided. The placement of double-sided expansion joints goes well with the installation of fixed supports. Stuffing box compensators are installed strictly along the axis of the pipeline, without distortions. The packing of the stuffing box compensator consists of rings made of asbestos printed cord and heat-resistant rubber. It is advisable to use axial expansion joints when laying pipelines without channels.

The compensating ability of stuffing box expansion joints increases with increasing diameter.

Calculation of flexible compensator.

Thermal elongation of the design section of the pipeline
, mm, determined by the formula

, (2.81)

Where
- average coefficient of linear expansion of steel, mm/(m o C), (for standard calculations it can be taken
=1.2· 10ˉ² mm/(m о С),

- calculated temperature difference, determined by the formula

, (2.82)

Where - design coolant temperature, o C;

- calculated outside air temperature for heating design, o C;

L- distance between fixed supports, m.

The compensating capacity of stuffing box expansion joints is reduced by a margin of 50 mm.

Reaction of the stuffing box compensator - frictional force in the stuffing box packing determined by the formula, (2.83)

Where - operating pressure coolant, MPa;

- length of the packing layer along the axis of the stuffing box compensator, mm;

- outer diameter of the branch pipe of the stuffing box compensator, m;

- coefficient of friction of the packing on the metal is assumed to be 0.15.

Technical characteristics of bellows expansion joints are given in table. 4.14 - 4.15. Axial reaction of bellows expansion joints consists of two terms

(2.84)

Where - axial reaction caused by wave deformation, determined by the formula

, (2.85)

where  l- temperature elongation of the pipeline section, m;  - wave rigidity, N/m, taken according to the compensator passport; n- number of waves (lenses). - axial reaction from internal pressure, determined by the formula

, (2.86)

Where - coefficient depending on the geometric dimensions and thickness of the wave wall, equal on average to 0.5 - 0.6;

D And d are the outer and inner diameters of the waves, respectively, m;

- excess coolant pressure, Pa.

When calculating self-compensation, the main task is to determine the maximum voltage at the base of the short arm of the route rotation angle, which is determined for rotation angles of 90° formula
; (2.87)

for angles greater than 90°, i.e. 90+  , according to the formula
(2.88)

where  l- lengthening of the short arm, m; l- short arm length, m; E- modulus of longitudinal elasticity, equal on average for steel to 2·10 5 MPa; d- outer diameter of the pipe, m;

- the ratio of the length of the long arm to the length of the short one.

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HEATING NETWORKS - BUILDING STANDARDS AND RULES - SNIP 2-04-07-86 (approved by Decree of the USSR State Construction Committee dated 30-12-86 75) (edited... Relevant in 2018

DETERMINATION OF LOADS ON PIPE SUPPORTS

1. The vertical standard load on the pipe support F_v, H, should be determined by the formula

where Gv is the weight of 1 m of pipeline, including the weight of the pipe, thermal insulation structure and water (for steam pipelines, the weight of water is taken into account when hydraulic test), N/m;

l - span between movable supports, m.

Notes 1. Spring supports and hangers of steam pipelines Dу >= 400 mm in places accessible for maintenance can be calculated for vertical load without taking into account the weight of water during hydraulic testing, providing for this special devices for load bearings during testing.

2. When placing a support in pipeline assemblies, the weight of shut-off and drainage valves, compensators, as well as the weight of pipelines in adjacent sections of branches attributable to this support must be additionally taken into account.

3. The diagram of loads on the support is shown in the drawing.

Scheme of loads on the support 1 - pipe; 2 - movable pipe support

2. Horizontal standard axial F_hx, N, and lateral F_hy, N, loads on movable pipe supports from friction forces in the supports must be determined using the formulas:

where mu_x, mu_y are the friction coefficients in the supports, respectively, when the support moves along the axis of the pipeline and at an angle to the axis, taken according to the table. 1*of this application;

G_h - weight of 1 m of pipeline in working condition, including the weight of the pipe, thermal insulation structure and water for water and condensate networks (the weight of water in steam pipelines is not taken into account), N/m.

Table 1*

Friction coefficients

Note. When using fluoroplastic gaskets under sliding supports, the friction coefficients are assumed to be 0.1

With a known rod length, the friction coefficient for a rigid suspension should be determined by the formula

where l is the thermal elongation of the pipeline section from the fixed support to the compensator, mm;

l_t - working rod length, mm.

3. Horizontal lateral loads, taking into account the direction of their action, must be taken into account when calculating supports located under flexible expansion joints. and also at a distance<= 40Dу трубопровода от угла поворота или гибкого компенсатора.

4. When determining the standard horizontal load on a fixed pipe support, the following should be taken into account:

4.1. Friction forces in movable pipe supports N, determined by the formula

where mu is the coefficient of friction in the movable pipe supports;

Gh - weight of 1 m of pipeline in working condition (item 2), N/m;

L is the length of the pipeline from the fixed support to the compensator or the angle of rotation of the route during self-compensation, m.

4.2. Friction forces in stuffing box compensators, , N, determined by the formulas

, (6)

, (7)

, (8)

d_ic - internal diameter of the stuffing box compensator housing, m.

When determining the value using formula (6), the value is taken to be no less than 1 x 10(6) Pa. The largest of the forces obtained from formulas (6) and (7) is taken as the calculated one.

4.3. Unbalanced internal pressure forces when using stuffing box compensators, N, on pipeline sections with shut-off valves, transitions, rotation angles or plugs, determined by the formula

4.4. Expansion forces of bellows expansion joints from internal pressure, H, determined by the formula

, (11)

4.5. Stiffness of bellows expansion joints, H, determined by the formula

where R is the rigidity of the compensator when it is compressed by 1 mm, N/mm;

Compensating capacity of the compensator, mm.

The values ​​of R, , are taken according to the technical specifications and working drawings for compensators.

4.6. Expansion forces of bellows expansion joints when installed in combination with stuffing box expansion joints in adjacent areas, N, determined by the formula

(13)

4.7. Elastic deformation forces for flexible expansion joints and self-compensation, determined by the calculation of pipes to compensate for thermal elongation.

4.8. The friction forces of pipelines when moving a pipe inside a heat-insulating shell or the friction forces of the shell on the ground during channelless laying of pipelines, determined according to special instructions depending on the type of insulation.

5. The horizontal axial load on the fixed pipe support should be determined:

to the end support - as the sum of the forces acting on the support (clause 4);

On the intermediate support - as the difference in the sums of forces acting on each side of the support; in this case, a smaller sum of forces, with the exception of unbalanced forces of internal pressure, spacer forces and the rigidity of bellows expansion joints, is accepted with a coefficient of 0.7.

Notes: 1. When determining the total load on pipeline supports, the stiffness of bellows expansion joints should be taken taking into account the maximum deviations of rigidity values ​​allowed by the technical conditions for expansion joints.

2. When the sums of forces acting on each side of the intermediate fixed support are the same, the horizontal axial load on the support is determined as the sum of the forces acting on one side of the support with a coefficient of 0.3.

6. The horizontal lateral load on the fixed pipe support should be taken into account when turning the route and from pipeline branches.

For double-sided pipeline branches, the lateral load on the support is taken into account from the branches with the highest load.

7. Fixed pipe supports must be designed for the greatest horizontal load under various operating modes of pipelines, including with open and closed valves.

With a ring diagram of heating networks, the possibility of coolant movement from any direction must be taken into account.

Determination of vertical and horizontal load on a fixed support.

Determination of vertical load

Loads acting on fixed supports are divided into vertical and horizontal. Vertical loads include weight ( R in ) and compensation (P k), if the pipeline is located in a vertical plane).

R V - ql, H, Page 37 (37)

Where q – weight of 1 m of pipeline (weight of pipe, insulating structure and water);

q = q tr + q from + q in N/m;

l– span between movable supports, m.

1st section: P in = 1217 * 13.0 = 15821 N

Section 7: P V = 843*11.6 = 9778.8 N

We will similarly calculate other sections of pipelines.

If the fixed support is located in a pipeline assembly, then it is necessary to take into account the additional load from fittings and stuffing box expansion joints.

In the thesis project, it is necessary to determine the loads on 2-3 fixed supports (according to the instructions of the supervisor). For given supports, determine the vertical load.

Horizontal loads on fixed supports are more diverse. They arise under the influence of the following forces:

forces of elastic deformation of flexible expansion joints or self-compensation when they are stretched in a cold state or during thermal elongation of pipelines;

internal pressure forces when using unbalanced stuffing box compensators;

friction forces in stuffing box expansion joints during thermal elongation of the pipeline;

friction forces in movable supports during thermal elongation of pipelines laid in channels and above ground;

friction forces of the pipeline on the ground during channelless installation.

Frictional force in moving supports.

N Page 38 (38)

Where μ – sliding friction coefficient; accept for sliding supports μ = 0.3 – steel on steel; μ = 0.6 – steel on concrete; for roller, roller, ball and suspension bearings μ = 0,1;

q - weight of 1 m of pipeline, N/m;

L 1 – length of the pipeline from the fixed support to the compensator or from the fixed support to the turn (for self-compensation), m.

1 section: = 0.3*1217*130 = 47463 N

Section 7: = 0.3*843*120 = 30348 N

Internal pressure force

N Page 38 (39)

where P slave is the working pressure of the coolant, Pa;

f 1 and f 2 - larger and smaller pipe cross-section, m.

At pipe turns of 90° and with closed valves f 2 = 0.

Section 1: P ind = 1.6*(58 – 0) = 92.8 N

Section 7: P ind = 1.6*(40 – 0) = 64 N

Table 12

Axial forces act on each fixed support from the left and right. Depending on the direction of the reactions, the forces are partially balanced or summed up.

Fixed supports that perceive partially balanced horizontal axial forces are called unloaded (intermediate). They are located between adjacent straight sections of pipelines. Unbalanced (end) supports are located at pipeline turns or in front of the plug and perceive horizontal forces acting on one side.

When calculating loads, it is necessary to consider all possible operating modes of the pipeline from cold to operating conditions.

When determining the horizontal axial load on the support for each operating mode of the pipeline, the forces acting on the fixed support in one direction are added, and then the smaller one is subtracted from the larger sum of forces, while taking into account possible deviations from the calculated values, frictional forces and elastic deformation forces are subtracted with a coefficient of 0.7, which provides some margin in the design load on the fixed support. If the sum of forces acting on the support on both sides is equal, one of the sums with a coefficient of 0.3 is taken as the calculated one.

V.V. Logunov, General Director;
V.L. Polyakov, chief designer of heating network projects;
M.Yu. Yudin, head of technical support department,
PJSC NPP Kompensator, St. Petersburg;

E.V. Kuzin, Director, ATEKS-ENGINEERING LLC, Irkutsk

Introductory part

The issue of energy efficiency of heating networks is closely related to the technologies and materials used in the construction and reconstruction of heating networks. At the same time, modern energy-saving technologies are becoming increasingly important. Despite the fact that in Russia bellows expansion joints are considered a new product, a change in approach is already clearly visible, from when their use was resorted to because it was impossible to solve the problem of thermal expansion using classical methods, to the moment when in many regions bellows expansion joints became a mandatory condition of the technical specifications for the development of pipeline projects. And today, the question of using bellows expansion joints remains open only in the absence of sufficient information to determine the feasibility of their use in comparison with classical types of expansion joints. In this article we will look at the technical aspects of using bellows expansion joints instead of stuffing box expansion joints.

Comparison of the loads of stuffing box and bellows expansion joints

One of the pressing issues when deciding whether to abandon stuffing box expansion joints is the possibility of preserving existing fixed supports. The solution to this issue is complicated due to significant differences in the regulatory documentation for stuffing box and bellows expansion joints. In this article we will determine which type of compensator, all other things being equal, has a greater axial load on the fixed supports. The axial load from the bellows compensator on the fixed end support is defined as:

P button = P r + P f + P tr

where P r is the expansion force of the bellows compensator, P w is the force from the axial rigidity of the bellows compensator, P tr is the force from the friction of the pipeline in movable supports (sliding supports in areas of channel and above-ground installations, or friction of the heat pipeline on the ground in areas of non-channel installation).

The axial load from the stuffing box compensator is determined by a similar formula:

P button = P C p + P C tr + P tr

where P C p is the expansion force of the gland compensator, P c tr is the force from the friction of the gland of the gland compensator, P tr is the force from the friction of the pipeline in the movable supports (sliding supports in areas of channel and above-ground installations, or friction of the heat pipeline on the ground in areas of channelless installation ).

Any axial expansion joints, be it stuffing box, bellows or lens, due to the absence of a rigid axial connection, transmit a thrust force (from the internal pressure of the medium) acting on the pipeline wall and perceived by the fixed end supports (Fig. 1).

The thrust force is defined as the product of pressure and the area of ​​application of the force. In the case of a bellows compensator, the effective area of ​​the bellows is taken under the force application area, and in the case of a gland compensator, the force application area is determined by the outer diameter of the compensator pipe (Fig. 2).

Accordingly, they can be subjected to hydraulic tests with a test pressure equal to 1.25РN. The thrust force from any axial compensator increases in proportion to the increase in pressure. In RD-3-VEP-2011, the maximum expansion force for bellows expansion joints is given at test pressure. Whereas for gland compensators, as for all others, in GOST R 55596-2013, when calculating the thrust force, the value of the nominal pressure is used. It is this difference in the approach to calculating axial forces that is decisive when deciding to replace the stuffing box compensator with a bellows one.

Let's compare the loads from the stuffing box and bellows compensator for several diameters (DN), for PN = 16 kgf/cm 2, provided that the expansion force will be calculated in two versions: taking into account the test pressure (P pr), and the nominal pressure (PN) (Table . 1). The rigidity of bellows expansion joints will be determined in accordance with RD-3-VEP-2011 (Table 2). The friction force values ​​of the seals of stuffing box expansion joints are given from the drawing books of stuffing box expansion joints (certified value of the friction force) (Table 3). We neglect the friction of the pipeline in the moving supports in this calculation.

Table 1. Expansion force of stuffing box and bellows expansion joints at РN=16 kgf/cm2.

Table 2. Rigidity force of the bellows expansion joint.

Table 3. Friction forces of the stuffing box compensator (series 5.903-13 issue 4).

Table 4. Total value of loads on the fixed end supports.

As can be seen from table. 4, in most of the cases considered, when calculating the force using a similar method, the load on the fixed end supports from the bellows compensator turned out to be less than the similar load from the stuffing box compensator. Exceeding the load by 1% for DN1000 is also not critical when deciding to replace the gland compensator with a bellows one.

Thus, if you change the existing stuffing box expansion joint to a bellows expansion joint, then in most cases there will be no need to strengthen the existing fixed end supports (all calculations for bellows expansion joints are correct only for bellows expansion joints according to IYANSH.300260.029TU. - Author's note).

(Table 10.1)

moment of resistance of the cross section of the pipe at the design thickness of the pipe wall, cm3, (Table 2.10. SP);

Weld strength coefficient (Table 10.2).

0.8 plasticity coefficient

Equivalent weight load kgf/m (equal to the weight of the pipeline in working condition);

The equivalent weight load for underground laying of pipelines is taken equal to the design weight of the pipeline in working or cold condition.

where q is the weight of one meter of pipeline: the weight of the pipe (qtr), water (qw) (Table 2.11., 2.12. SP), insulating structure (qiz).

The span between movable supports with stuffing box expansion joints is determined by calculation using tensile or compressive stresses (=0.95,=1, respectively).

For compressive stresses, = 1

Tensile stress = 0.95

accepted as settlement

Loads on fixed supports.

Loads on fixed pipeline supports are divided into vertical and horizontal.

Vertical:

l-span between movable supports, m.

Horizontal loads on fixed pipeline supports arise under the influence of the following:

Friction in moving supports during thermal elongation of heat pipes.

Friction in stuffing box expansion joints during thermal elongation of heat pipes.

Horizontal axial loads on intermediate supports are determined taking into account all acting forces on both sides of the support:

Friction forces in moving supports, kgf

Friction forces in stuffing box compensators, kgf

where q is the weight of 1 meter of pipeline, kgf

L is the length of the pipeline from the fixed support to the compensator, m

f-friction coefficient of moving supports (Table 11.1)

The friction forces in stuffing box expansion joints are determined depending on the operating pressure of the coolant, the diameter of the pipe and the design of the stuffing box packing:

kgf

kgf

Coolant operating pressure

length of the packing layer for the stuffing box compensator (4.16)

outer diameter of the gland compensator cup (4.16 )

friction coefficient of packing with metal =0.15

number of compensator bolts(4.16)

Cross-sectional area of ​​packing (4.16 )

the value is taken to be at least 10 kgf/cm2.

The smaller of the forces is taken as the calculated one.

The resulting horizontal forces on the intermediate fixed supports are found as the difference in the total forces on both sides of the support. S=SB-SM, m. In this case, for the safety factor, the smaller of the forces is accepted with a coefficient of 0.7: S=SB-0.7SM, with SB=SM we accept one of the sums with a coefficient of 0.3 S1=0.3St. To. l1=l2=120 m, then S1=S2.

f=0.3 for sliding supports

qtr=62.15 kgf

qв=134.6 kgf

qiz=30.4 kgf

16 kgf/cm2

We take kgf as the calculated value.

S=5451.6+8346.9=13798.5 kgf

As a calculated value we take 13798.5 = 4139.6 kgf

Calculation of thermal insulation of heat pipelines.

The calculation is made at the head section (from the Energy Center to the first branch.)

Initial data:

We determine the thickness of thermal insulation for a two-pipe installation of a heating network with a diameter of dn = 0.426 m in a reinforced concrete non-passable channel with dimensions of 2.54 x 0.93 m (internal) and 2.94 x 1.33 m (external). Place of construction - Moscow Average temperature of the coolant in the supply heat pipe, in the return pipe (from the temperature graph). The depth of the pipeline axis is h = 1.23 m. The average annual soil temperature tgr = 3.2 °C. As thermal insulation we use mineral wool mats, stitched, GOST 2/880-88 grade 100. Cover layer made of fiberglass .

For pipelines with dн = 0.426 m (dу = 400 mm) according to the heat flux density standards and (Table 13.6).

;

.

We accept the thickness of the thermal insulation layer and the covering layer