Compensators for heating networks. This article will discuss the selection and calculation of compensators for heating networks.

Why are compensators needed? Let's start with the fact that when heated, any material expands, which means that the pipelines of heating networks lengthen as the temperature of the coolant passing through them increases. For trouble-free operation of the heating network, compensators are used that compensate for the elongation of pipelines during compression and expansion, in order to avoid pinching of pipelines and their subsequent depressurization.

It is worth noting that to allow expansion and contraction of pipelines, not only compensators are designed, but also a system of supports, which, in turn, can be either “sliding” or “dead”. How usually in Russia regulation of the thermal load is qualitative - that is, with temperature changes environment, the temperature at the outlet of the heat supply source changes. Due to the high-quality regulation of heat supply, the number of expansion-compression cycles of pipelines increases. The service life of pipelines is reduced, and the risk of pinching increases. Quantitative load regulation is as follows - the temperature at the outlet of the heat supply source is constant. If it is necessary to change the heat load, the coolant flow changes. In this case, the metal of the heating network pipelines operates under easier conditions, there are a minimum number of expansion-compression cycles, thereby increasing the service life of the heating network pipelines. Therefore, before choosing compensators, their characteristics and quantity, you need to determine the amount of expansion of the pipeline.

Formula 1:

δL=L1*a*(T2-T1)where

δL is the amount of pipeline extension,

mL1 - length of the straight section of the pipeline (distance between fixed supports),

ma - coefficient of linear expansion (for iron equal to 0.000012), m/deg.

T1 - maximum pipeline temperature (the maximum coolant temperature is assumed),

T2 - minimum pipeline temperature (minimum ambient temperature can be taken), °C

As an example, let’s consider solving an elementary problem of determining the amount of pipeline extension.

Task 1. Determine how much the length of a straight section of a pipeline 150 meters long will increase, provided that the coolant temperature is 150 °C, and the ambient temperature during the heating period is -40 °C.

δL=L1*a*(T2-T1)=150*0.000012*(150-(-40))=150*0.000012*190=150*0.00228=0.342 meters

Answer: the length of the pipeline will increase by 0.342 meters.

After determining the amount of elongation, you should clearly understand when an expansion joint is needed and when it is not needed. To answer this question unambiguously, you need to have a clear diagram of the pipeline, with its linear dimensions and supports marked on it. It should be clearly understood that changing the direction of the pipeline can compensate for elongations, in other words, turning with overall dimensions not less than the dimensions of the compensator, with correct arrangement of supports, is able to compensate for the same elongation as the compensator.

And so, after we have determined the amount of pipeline elongation, we can proceed to the selection of compensators, you need to know that each compensator has a main characteristic - this is the amount of compensation. In fact, the choice of the number of compensators comes down to the choice of type and design features compensators. To select the type of compensator, it is necessary to determine the diameter of the heating network pipe based on bandwidth blow the trumpet required power heat consumer.

Table 1. The ratio of U-shaped expansion joints made from bends.

Table 2. Selection of the number of U-shaped compensators based on their compensating ability.

Task 2 Determining the number and size of compensators.

For a pipeline with a diameter of DN 100 with a straight section length of 150 meters, provided that the carrier temperature is 150 °C, and the ambient temperature during the heating period is -40 °C, determine the number of compensators. bL = 0.342 m (see Problem 1). From the Table. 1 and Table 2 we determine the dimensions of n-shaped compensators (with dimensions of 2x2 m it can compensate for 0.134 meters of pipeline extension), we need to compensate 0.342 meters, therefore Ncomp = bL/∂x = 0.342/0.134 = 2.55, round to the nearest integer in the direction of increasing it, 3 compensators measuring 2x4 meters are required.

Currently, lens compensators are becoming more widespread; they are much more compact than U-shaped ones, however, a number of restrictions do not always allow their use. The service life of a U-shaped compensator is significantly higher than that of a lens compensator, due to the poor quality of the coolant. The lower part of the lens compensator is usually “clogged” with sludge, which contributes to the development of parking corrosion of the compensator metal.

The amount of displacement (compensating capacity) of compensators is usually expressed as a combination of positive and negative numerical values(±). A negative (-) value indicates the permissible compression of the compensator, a positive (+) value indicates its permissible stretch. The sum of the absolute values ​​of these values ​​represents the total displacement of the compensator. In most cases, compensators work in compression, compensating for the thermal expansion of pipelines, less often (refrigerated media and cryogenic products) - in tension.

Preliminary stretching during installation is necessary for the rational use of the full displacement of the compensator, depending on the nature of the pipeline, installation conditions and the prevention of stress conditions.

The peak expansion values ​​of the pipeline depend on the minimum and maximum temperatures of its operation. For example, the minimum operating temperature of the pipeline is Tmin = 0°C and the maximum Tmax = 100°C. Those. temperature difference At = 100°C. With a pipeline length L equal to 90 m, the maximum value of its extension to the pipeline AL will be 100 mm. Let’s imagine that for installation on such a pipeline, compensators with an offset of ±50 mm are used, i.e. with a total offset of 100 mm. Let’s also imagine that the ambient temperature at the installation stage Ty is 20°C. The nature of the compensator's operation under such conditions will be as follows:

• at 0°C - the compensator will be stretched by 50 mm
• at 100°C - the compensator will be compressed by 50 mm
• at 50°C - the compensator will be in a free state
• at 20°C - the compensator will be stretched by 30 mm

Consequently, preliminary stretching by 30 mm during installation (T y = 20°C) will ensure its effective operation. When the temperature rises from 20°C to 50°C during commissioning of the pipeline, the compensator will return to the free (unstressed) state. When the pipeline temperature increases from 50°C to 100°C, the displacement of the compensator from the relatively free state towards compression will be the calculated 50 mm.

Definitionvaluespreliminarysprains

Let us take the pipeline length to be 33 meters, maximum/minimum operating temperature+150°С /-20°С respectively. With such a temperature difference, the coefficient of linear expansion a will be 0.012 mm/m*°C.

The maximum extension of the pipeline can be calculated as follows:

ΔL = α*L*Δ t = 0.012 x 33 x 170 = 67 mm

Meaning pre-stretch PS is determined by the formula:

PS = (ΔL/2) - ΔL(Ty-Tmin): (Tmax-Tmin)

Thus, during the installation of the compensator, it must be installed with a pre-stretch PS equal to 18 mm.

In Fig. Figure 1 shows the distance required for installing the compensator in the pipeline line, defined as the sum of the values ​​of the compensator length lq in the free state and pre-stretch PS.

In Fig. 2 shows that during installation, on one side the compensator is fixed with a flange or welded.

Calculation of the pre-stretching of the compensator during installation is necessary for maximum use of the compensating capacity of the bellows compensator for its intended purpose.

Compensating capacity of compensator

First, let's define what compensating ability is. As a rule, the compensating ability is expressed in negative (-) and positive (+) values ​​in its marking. For example, KSR 200-16-80, where 80 is the value of the maximum compensating ability. It means that the CSR compensator has c.s. 80mm (i.e. +/-40) +40mm in tension and -40mm in compression.

The maximum expansion (constriction) values ​​of pipelines depend on the highest and lowest temperature values working environment.

Let us present a method for installing a bellows expansion joint in a cold state, determining the installation length of the bellows expansion joint in order to use its compensating ability to the maximum:

							∆.(E mouth - T min)
							T max - T min

Determination of the total length of the extended expansion joint:

L=L 0 +H [mm], where:

Δ - total pipeline expansion [mm]
L 0- free length of compensator [mm]
L- installation length of the compensator (length of the stretched compensator) [mm]
T max- maximum operating temperature [°C]
T min- minimum operating temperature [°C]
T mouth- installation temperature [°C]

The axial compensator must be installed in a cold state, the direction of movement installed in this cold state. The amount of pre-stretch depends on the installation temperature.

The minimum operating temperature of the pipeline is 0 o C, and the maximum is 100 o C. Thus, the difference is 100 o C. Let's take the length of the heating main 90 m. Calculating the maximum elongation of pipes, we obtain ∆L=100mm, i.e. a suitable compensator would be a KSO with a compensating capacity of +/-50mm.

Now let’s determine the nature of the compensator’s operation at an installation temperature of 20 o C:

• at 0 o C the CSO is stretched by 50 mm;
• at 100 o C the CSO is compressed by 50 mm;
• at 20 o C the CSO is stretched by 30 mm;
• at 50 o C no forces act on the CSO.

Therefore, if you pre-stretch the KSO compensator with a compensating capacity of +/-50 mm at an installation temperature of 20 o C, then it will show maximum efficiency on a pipeline section 90 m long. If the temperature of the working environment increases to 50 o C, the compensator will assume a non-stressed state. When the pipeline temperature reaches 100 o C, the compensator bellows will be stretched by 50 mm (maximum operating condition).

1.1. Products may be used in construction areas with a design external temperature for designing heating systems of at least minus 40°C. The seismicity of construction areas is no more than nine points on the Richter scale.

1.2. The products can be used when the chloride content in the supply water is no more than 250 mg/kg.

1.3. The products must be installed on straight sections of pipelines limited by fixed supports. Only one product is allowed to be placed between fixed supports.

Deviation from straightness in plan and profile is allowed with mandatory installation at least two guide supports in the same places in front of each compensating device.

1.4. The method of connection to the pipeline is welding.

1.5. For any method of laying pipelines, except underground channelless, the installation of compensating devices should, as a rule, be provided at one of the fixed supports.

1.6. On ductless underground heating networks, the product should be placed in the middle of the pipeline section, limited by fixed supports.

1.7. Before and after the compensating device, it is necessary to install guide supports to prevent the pipelines from moving in the radial direction.

When laying a pipeline without a channel, installation of guide supports is not required.

Examples of layouts for the bellows compensating device, guides and fixed supports are shown in the figure:

6.8. On sections of pipelines with bellows compensating devices, the use of suspended supports is not allowed.

6.9. When choosing fixed supports, the following factors should be taken into account:

Expansion force of the compensator;

Compensator stiffness force;

Friction in guides and sliding supports;

The magnitude of the centrifugal force that occurs when the pipeline is bent.

Calculation of loads on end and intermediate fixed supports at in various ways The installation of bellows compensating devices is carried out at the design stage of the heating network and is given in specialized literature.

6.10. The maximum distance between the fixed supports of the pipeline is determined by the formula:

where 0.9 is the safety factor, taking into account calculation inaccuracies and errors

installation details;

Compensating capacity of compensator, mm

a is the average linear expansion coefficient of pipe steel at

heating from 0°С to t°С, mm/m°С;

t - design temperature of network water in the supply pipeline, °C;

t RO - design outdoor temperature for system design

heating, taken equal to average temperature air most

after a cold five-day meeting on the chapter of SNiP “Construction climatology”

and geophysics", °C.

1.8. The products do not require maintenance during operation and belong to the class of non-repairable products; they do not require the construction of special chambers, or, when installed above ground, maintenance platforms.

Installation instructions.

2.1. Installation of products is carried out in accordance with the pipeline design completed by the design organization.

2.2. Before installation, products must be checked for compliance with their technical characteristics design of the heating network, as well as for the absence of mechanical damage.

2.3. When moving compensating devices during installation, measures must be taken to protect the product from shocks, shocks and to prevent contamination or flooding groundwater its internal cavity.

2.4. When executing welding work The ends of the insulation of the compensating device should be protected with tin split screens 0.8...1 mm thick to prevent its fire.

Installation of products is permitted at air temperatures not lower than minus 30°C.

2.5. Before welding the product to the pipeline, deviations of the connections of the product to the pipeline are checked, which should not exceed the following values: pipe alignment tolerance - 2 mm;

tolerance for parallelism of the ends of the connecting pipes and connected pipes is 3 mm.

The maximum welding gap between the pipe and the pipeline is 2 mm.

2.6. The product should be installed on heat pipelines so that the direction of the arrow (if any) on the body of the compensating device coincides with the direction of movement of the coolant.

2.7. The products are mounted on the pipeline with pre-stretching.

The length of the compensator during installation Lmont., mm is determined by the formula:

L builds.- construction length of the compensator as delivered, mm;

Compensating capacity of the compensator, mm;

A- coefficient of linear expansion of pipe steel, approx.

measured 0.012 mm/m °C;

t name. - lowest air temperature during operation, °C;

L- length of the compensator section between the fixed supports,

on which the compensator is mounted, m.

The installation length of the compensating device is determined by the installation organization.

The pipeline sections before and after the compensating device must be mounted and secured in fixed supports so that the distance between the ends of the pipes at the installation site of the product corresponds to the installation length L installation. at ambient temperature at the moment of fixing the pipeline in the second fixed support; the ambient temperature and the distance between the ends of the fixed pipes must be recorded in the act;

The compensating device is welded to one of the sections of the pipeline;

A universal mounting fixture, with the help of which the compensator of the product is stretched to the junction with the pipeline, and the joint is welded;

The mounting fixture is removed from the product.

When stretching the compensator, it is necessary to ensure equal movements of the connecting pipes relative to the ends of the product.

If it is impossible to install the product in the middle of a straight section of a heat pipe between fixed supports, it is allowed to install it anywhere in a straight section of a heat pipe. To do this, when stretching the compensator, it is necessary to ensure that the connecting pipes move relative to the ends of the compensating device in inverse proportion to the lengths of the heat pipe sections between the product and the fixed supports.

2.9. The connection of the product indicator conductors with the general signaling system must be made after completion of welding work before insulating the joints of the connecting pipes with the heat pipe. The indicator conductors should not touch the metal of the pipes anywhere.

	bellows compensating device
	end fixed support

The amount of displacement (compensating capacity) of compensators is usually expressed as a combination of positive and negative numerical values ​​(±). A negative (-) value indicates the permissible compression of the compensator, a positive (+) value indicates its permissible stretch. The sum of the absolute values ​​of these values ​​represents the total displacement of the compensator. In most cases, compensators work in compression, compensating for the thermal expansion of pipelines, less often (refrigerated media and cryogenic products) - in tension.

Preliminary stretching during installation is necessary for the rational use of the full displacement of the compensator, depending on the nature of the pipeline, installation conditions and the prevention of stress conditions.

The peak expansion values ​​of the pipeline depend on the minimum and maximum temperatures of its operation. For example, the minimum operating temperature of the pipeline is Tmin = 0°C and the maximum Tmax = 100°C. Those. temperature difference At = 100°C. With a pipeline length L equal to 90 m, the maximum value of its extension to the pipeline AL will be 100 mm. Let’s imagine that for installation on such a pipeline, compensators with an offset of ±50 mm are used, i.e. with a total offset of 100 mm. Also, imagine that the ambient temperature at the stage of their installation T y is 20°C. The nature of the compensator's operation under such conditions will be as follows:

• at 0°C - the compensator will be stretched by 50 mm
• at 100°C - the compensator will be compressed by 50 mm
• at 50°C - the compensator will be in a free state
• at 20°C - the compensator will be stretched by 30 mm

Consequently, preliminary stretching by 30 mm during installation (T y = 20°C) will ensure its effective operation. When the temperature rises from 20°C to 50°C during commissioning of the pipeline, the compensator will return to the free (unstressed) state. When the pipeline temperature increases from 50°C to 100°C, the displacement of the compensator from the relatively free state towards compression will be the calculated 50 mm.

Definitionvaluespreliminarysprains

Let’s assume the pipeline length is 33 meters, the maximum/minimum operating temperature is +150°C /-20°C, respectively. With such a temperature difference, the coefficient of linear expansion a will be 0.012 mm/m*°C.

The maximum extension of the pipeline can be calculated as follows:

ΔL = αxLxΔ t = 0.012 x 33 x 170 = 67 mm

The pre-stretch value PS is determined by the formula:

PS = (ΔL/2) - ΔL (Ty-Tmin): (Tmax-Tmin)

Thus, during the installation of the compensator, it must be installed with a pre-stretch PS equal to 18 mm.

In Fig. Figure 1 shows the distance required for installing the compensator in the pipeline line, defined as the sum of the values ​​of the compensator length lq in the free state and pre-stretch PS.

In Fig. 2 shows that during installation, on one side the compensator is fixed with a flange or welded.