home

Advantages of bellows over U-shaped compensators. Design of heat networks of an industrial enterprise

In heat networks, stuffing box, U-shaped and bellows (wavy) expansion joints are widely used. The compensators must have sufficient compensating capacity to absorb the thermal expansion of the pipeline section between the fixed supports, while the maximum stresses in the radial compensators should not exceed the allowable ones (usually 110 MPa).

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

(81)

where
- average coefficient of linear expansion of steel,

(for typical calculations, you can take
),

- estimated temperature difference, determined by the formula

(82)

where - design temperature of the coolant, o C;

- estimated outdoor air temperature for heating design, o C;

L - distance between fixed supports, m (see Appendix No. 17).

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

Reaction of the stuffing box compensator- friction force in stuffing box packing is determined by the formula

where - operating pressure of the coolant, MPa;

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

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

- coefficient of friction of the packing against the metal, is taken equal to 0.15.

When selecting compensators, their compensating capacity and technical parameters can be determined according to the application.

Axial reaction of bellows expansion jointsis made up of two terms:

(84)

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

(85)

here l - temperature elongation of the pipeline section, m;

 - wave stiffness, N/m, taken according to the compensator passport;

n is the number of waves (lenses).

- axial reaction from internal pressure, determined by the formula

(86)

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

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

- excess pressure of the coolant, Pa.

When calculating self-compensation the main task is to determine the maximum stressat the base of the short arm of the turn angle of the track, which is determined for the turn angles of 90 ° along formula

(87)

for angles greater than 90 o, i.e. 90+, according to the formula

(88)

where l - elongation of the short arm, m;

l is the length of the short arm, m;

E - the modulus of longitudinal elasticity, equal to the average for steel 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 arm.

When calculating angles for self-compensation, the value of the maximum stress  should not exceed [] = 80 MPa.

When arranging fixed supports at the angles of rotation used for self-compensation, it must be taken into account that the sum of the lengths of the angle arms between the supports should not exceed 60% of the maximum distance for straight sections. It should also be taken into account that the maximum angle of rotation used for self-compensation should not exceed 130°.

The program is designed to quickly assess the compensating capacity of individual sections of the pipeline route, check the wall thickness, and calculate the distances between the supports. Pipelines of above-ground, channel and channelless (in the ground) laying are calculated.

Start right now

Getting started with the program is very easy.

To work in the system, you need to register using the address of your Email. After confirming the address, you will be able to log in with it.

Your data is stored on the server and is available to you at any time. The exchange with the server is carried out using a secure protocol.

Calculations are made on the server, the speed of their execution does not depend on the performance of your device.

Settlement core

The core of the START software package is used for calculations.

The calculation core is updated simultaneously with the release of new START versions.

With StartExpress you can define:

compensating ability of L-, Z-shaped and U-shaped expansion joints when laying pipelines above ground and in underground channels;
compensating ability of L-, Z-shaped and U-shaped compensators for channelless laying of pipelines in the ground;
wall thickness or pressure limit for pipes according to the selected regulatory document;
distances between intermediate supports of the pipeline from the conditions of strength and rigidity;

The calculation of L-, Z-shaped turns and U-shaped expansion joints when laying pipelines above the ground and in underground channels is carried out for sections located between two fixed (dead) supports. With a known distance between the fixed supports, the required reach for the U-shaped compensator, Z-shaped turn and the short arm for the L-shaped turn are determined based on the allowable compensation stresses. This relieves designers of the need to use outdated nomograms for L-, Z- and U-shaped sections.

The calculation of L-shaped, Z-shaped turns and U-shaped compensators for channelless laying of pipelines in the ground allows you to determine the allowable distance between fixed supports from a given reach for a U-shaped compensator or Z-shaped turn and the length of the short arm of the L-shaped turn, then is the length of the section of the pipeline pinched in the ground, which can be compensated for a given temperature difference. U-shaped expansion joints and L-, Z-shaped turns with arbitrary angles are considered. For the same pipeline sections, you can perform a verification calculation - for given dimensions, determine stresses, displacements and loads on fixed supports.

There are currently two types of elements available to the user:

Straight sections of the pipeline. Verification calculation and selection of wall thickness, calculation of span length.
Pipe expansion joints of various configurations (G, Z, U-shaped) and location (vertical and horizontal ground laying, underground channel laying, underground in the ground). Verification calculation and selection of compensator parameters.

Regulatory documents in accordance with which the calculation is made:

RD 10-249-98: Pipelines for steam and hot water
GOST 55596-2013: Heat networks
CJJ/T 81-2013 - Heating networks (PRC standard)
SNIP 2-05.06-85: Main pipelines
SP 36.13330.2012: Main pipelines
GOST 32388-2013: Process pipelines

User interface

Responsive design automatically takes into account the current screen size and orientation.

The app is optimized to work on various devices- from desktop to smartphone.

Always at hand, always the latest version

To work, it is enough to have an Internet connection.

Your data and calculation results are stored on the server and you can access them wherever you are.

New versions are released for all types of devices at the same time.

High calculation speed

The calculation speed does not depend on the performance of your device.

All calculations are performed on servers equipped with the most latest version kernel START.

The number of processors used for calculations changes dynamically depending on the load.

To date, the use of U-type expansion joints or any other is carried out if the substance passing through the pipeline is characterized by a temperature of 200 degrees Celsius or higher, as well as high pressure.

General description of compensators

Metal expansion joints are devices that are designed to compensate or balance the influence of various factors on the operation of pipeline systems. In other words, the main purpose of this product is to ensure that the pipe is not damaged when substances are transported through it. Such networks, which provide transportation of the working environment, are almost constantly exposed to such negative influences, as thermal expansion and pressure, vibration, and subsidence of the foundation.

It is in order to eliminate these defects that it is necessary to install flexible elements, which have come to be called compensators. The U-shaped type is just one of many types that are used for this purpose.

What are U-shaped elements

It should be noted right away that the U-shaped type of parts is the simplest option that helps to solve the compensation problem. This category of devices has the widest range of applications in terms of temperature and pressure indicators. For the manufacture of U-shaped expansion joints, either one long pipe is used, which is bent in the right places, or they resort to welding several bent, sharply bent or welded bends. It is worth noting here that some of the pipelines must be periodically disassembled for cleaning. For such cases, expansion joints of this type are manufactured with connecting ends on flanges.

Since the U-type compensator is the simplest design, it has a number of certain disadvantages. These include a large consumption of pipes to create an element, large dimensions, the need to install additional supports, as well as the presence of welded joints.

Compensator requirements and cost

If we consider the installation of U-type expansion joints from the point of view of material resources, then their installation in systems with a large diameter will be the most disadvantageous. The consumption of pipes and material resources for the creation of a compensator will be too high. Here you can compare this equipment with Action and the parameters of these elements are approximately the same, but the cost of installation for the U-shaped is about twice as much. The main reason for this cost Money in that you need a lot of materials for construction, as well as the installation of additional supports.

In order for the U-shaped compensator to be able to completely neutralize the pressure on the pipeline, no matter where it comes from, it is necessary to mount such devices at one point with a difference of 15-30 degrees. These parameters are suitable only if the temperature of the working substance inside the network does not exceed 180 degrees Celsius and does not fall below 0. Only in this case and with this installation, the device will be able to compensate for the stress on the pipeline from soil movements from any point.

Installation Calculations

The calculation of the U-shaped compensator is to find out which minimum dimensions the device is enough to compensate for the pressure on the pipeline. In order to carry out the calculation, certain programs are used, but this operation can be performed even through online applications. The main thing here is to follow certain recommendations.

The maximum stress that is recommended for the back of the compensator is in the range from 80 to 110 MPa.
There is also such an indicator as the departure of the compensator to the outer diameter. This parameter is recommended to be taken within H/Dn=(10 - 40). With such values, it must be taken into account that 10Dn will correspond to a pipeline with an indicator of 350DN, and 40Dn - a pipeline with parameters of 15DN.
Also, when calculating the U-shaped compensator, it is necessary to take into account the width of the device to its reach. Optimal values L/H=(1 - 1.5) are considered. However, the introduction of other numerical parameters is also allowed here.
If during the calculation it turns out that for a given pipeline it is necessary to create an expansion joint of this type that is too large, then it is recommended to choose a different type of device.

Restrictions on calculations

If the calculations are not experienced specialist, it is better to familiarize yourself with some limitations that must not be exceeded when calculating or entering data into the program. For a U-shaped pipe compensator, the following restrictions apply:

The working medium can be either water or steam.
The pipeline itself must be made only of steel pipe.
The maximum temperature indicator for the working environment is 200 degrees Celsius.
The maximum pressure observed in the network must not exceed 1.6 MPa (16 bar).
The compensator can only be installed on horizontal type pipeline.
The dimensions of the U-shaped compensator should be symmetrical, and its shoulders should be the same.
The pipeline network should not experience additional loads (wind or any other).

Installing devices

Firstly, it is not recommended to place fixed supports further than 10DN from the compensator itself. This is due to the fact that the transmission of the pinching moment of the support will greatly reduce the flexibility of the structure.

Secondly, it is highly recommended to split sections from fixed support to a U-shaped compensator of the same length, throughout the network. It is also important to note here that the displacement of the fixture installation site from the center of the pipeline to one of its edges will increase the elastic deformation force, as well as the stress by about 20-40% of those values that can be obtained if the structure is mounted in the middle.

Thirdly, in order to further increase the compensating ability, U-shaped expansion joints are stretched. At the time of installation, the structure will experience a bending load, and when heated, it will assume an unstressed state. When the temperature reaches the maximum value, then the device will come back to the voltage. Based on this, a stretching method was proposed. The preliminary work is to stretch the compensator by an amount that will be equal to half thermal elongation pipeline.

Design pros and cons

If we talk in general about this design, then we can say with confidence that it has such positive qualities like ease of production, high ability compensation, no need for maintenance, the forces that are transmitted to the supports are negligible. However, among the obvious shortcomings, the following stand out: high consumption of material and a large number of the space occupied by the structure, high rate hydraulic resistance.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

Calculation of U-shaped compensators

Ph.D. S.B. Gorunovich,

hands design group of Ust-Ilimskaya CHPP

To compensate for thermal expansions, U-shaped expansion joints are most widely used in heating networks and power plants. Despite its many shortcomings, among which are: relatively large dimensions (the need for compensatory niches in heating networks with a channel gasket), significant hydraulic losses (compared to stuffing box and bellows); U-shaped expansion joints have a number of advantages.

Of the advantages, one can first of all single out simplicity and reliability. In addition, this type of compensators is the most well studied and described in educational and methodological and reference literature. Despite this, often young engineers who do not have specialized programs, the calculation of compensators causes difficulties. This is primarily due to a rather complex theory, the presence of a large number of correction factors and, unfortunately, the presence of typos and inaccuracies in some sources.

Below is a detailed analysis of the procedure for calculating the U-shaped compensator for two main sources, the purpose of which was to identify possible typos and inaccuracies, as well as to compare the results.

The typical calculation of compensators (Fig. 1, a)), proposed by most authors, suggests a procedure based on the use of the Castiliano theorem:

where: U- potential energy of deformation of the compensator, E- modulus of elasticity of the pipe material, J- axial moment of inertia of the section of the compensator (pipe),

where: s- outlet wall thickness,

D n- outer diameter of the outlet;

M- bending moment in the compensator section. Here (from the equilibrium condition, Fig. 1 a)):

M=P yx-P xy+M 0 ; (2)

L- full length of the compensator, J x- axial moment of inertia of the compensator, J xy- centrifugal moment of inertia of the compensator, S x- static moment of the compensator.

To simplify the solution, the coordinate axes are transferred to the elastic center of gravity (new axes Xs, Ys), then:

S x= 0, J xy = 0.

From (1) we obtain the elastic repulse force P x:

The displacement can be interpreted as the compensating ability of the compensator:

where: b t- coefficient of linear thermal expansion, (1.2x10 -5 1 / deg for carbon steels);

t n- initial temperature (average temperature of the coldest five-day period over the past 20 years);

t to- final temperature ( Maximum temperature coolant);

L uch- the length of the compensated section.

Analyzing formula (3), we can conclude that the greatest difficulty is the determination of the moment of inertia J xs, especially since it is first necessary to determine the center of gravity of the compensator (with y s). The author reasonably suggests using an approximate, graphic method definitions J xs, while taking into account the coefficient of rigidity (Karman) k:

The first integral is determined with respect to the axis y, second relative to the axis y s(Fig. 1). The axis of the compensator is drawn on millimeter paper to scale. All curved shaft compensator L split into many sections Ds i. Distance from the center of the segment to the axis y i measured with a ruler.

The stiffness coefficient (Karmana) is designed to reflect the experimentally proven effect of local flattening cross section bends during bending, which increases their compensating ability. AT normative document the Karman coefficient is determined by empirical formulas different from those given in , . Stiffness factor k used to determine the reduced length L prd arc element, which is always greater than its actual length l G. In the source, the Karman coefficient for bent bends:

where: l - bend characteristic.

Here: R- bend radius.

where: b- retraction angle (in degrees).

For welded and short-curved stamped bends, the source suggests using other dependencies to determine k:

where: h- characteristics of the bend for welded and stamped bends.

Here: R e is the equivalent radius of the welded elbow.

For branches from three and four sectors b = 15 deg, for a rectangular two-sector branch it is proposed to take b = 11 deg.

It should be noted that in , coefficient k ? 1.

Regulatory document RD 10-400-01 provides for the following procedure for determining the coefficient of flexibility To R* :

where To R- coefficient of flexibility without taking into account the constraint of deformation of the ends of the bent section of the pipeline; o - coefficient taking into account the constraint of deformation at the ends of the curved section.

In this case, if, then the flexibility coefficient is taken equal to 1.0.

Value To p is determined by the formula:

Here P- excess internal pressure, MPa; E t- modulus of elasticity of the material at operating temperature, MPa.

It can be proved that the coefficient of flexibility To R* will be greater than one, therefore, when determining the reduced length of the tap according to (7), it is necessary to take its reciprocal value.

For comparison, let's determine the flexibility of some standard taps according to OST 34-42-699-85, at overpressure R=2.2 MPa and module E t\u003d 2x 10 5 MPa. The results are summarized in the table below (Table No. 1).

Analyzing the obtained results, we can conclude that the procedure for determining the flexibility coefficient according to RD 10-400-01 gives a more "rigorous" result (less bend flexibility), while additionally taking into account overpressure in the pipeline and the modulus of elasticity of the material.

The moment of inertia of the U-shaped compensator (Fig. 1 b)) relative to the new axis y sJ xs define as follows:

where: L etc- reduced length of the axis of the compensator,

y s- coordinate of the center of gravity of the compensator:

Maximum bending moment M Max(valid at the top of the compensator):

where H- offset of the compensator, according to Fig. 1 b):

H=(m + 2)R.

The maximum stress in the section of the pipe wall is determined by the formula:

where: m 1 - correction factor (factor of safety), taking into account the increase in stresses on the bent sections.

For bent bends, (17)

For welded bends. (eighteen)

W- moment of resistance of the branch section:

Permissible stress (160 MPa for compensators made of steels 10G 2S, St 3sp; 120 MPa for steels 10, 20, St 2sp).

I would like to immediately note that the safety factor (correction) is quite high and grows with an increase in the diameter of the pipeline. For example, for a 90° elbow - 159x6 OST 34-42-699-85 m 1 ? 2.6; for bend 90° - 630x12 OST 34-42-699-85 m 1 = 4,125.

Fig.2. Design scheme compensator according to RD 10-400-01.

In the governing document, the calculation of the section with a U-shaped compensator, see Fig. 2, is carried out according to the iterative procedure:

Here the distances from the axis of the compensator to the fixed supports are set. L 1 and L 2 back AT and the departure is determined N. In the process of iterations in both equations, one should achieve that it becomes equal; from a pair of values, the largest is taken = l 2. Then the desired offset of the compensator is determined H:

The equations represent geometric components, see Fig. 2:

Components of elastic repulse forces, 1/m2:

Moments of inertia about the central axes x, y.

Strength parameter A, m:

[y sk ] - allowable compensation voltage,

Permissible compensation voltage [y sk ] for pipelines located in a horizontal plane is determined by the formula:

for pipelines located in a vertical plane according to the formula:

where: - rated allowable stress at operating temperature (for steel 10G 2S - 165 MPa at 100 °? t? 200 °, for steel 20 - 140 MPa at 100 °? t? 200 °).

D- inner diameter,

It should be noted that the authors could not avoid typos and inaccuracies. If we use the flexibility factor To R* (9) in the formulas for determining the reduced length l etc(25), coordinates of the central axes and moments of inertia (26), (27), (29), (30), then an underestimated (incorrect) result will be obtained, since the coefficient of flexibility To R* according to (9) is greater than one and should be multiplied by the length of the bent bends. The given length of bent bends is always greater than their actual length (according to (7)), only then will they acquire additional flexibility and compensatory ability.

Therefore, in order to correct the procedure for determining the geometric characteristics according to (25) and (30), it is necessary to use the inverse value To R*:

To R*=1/K R*.

In the design scheme of Fig. 2, the compensator supports are fixed ("crosses" usually denote fixed supports (GOST 21.205-93)). This can move the "calculator" to count the distances L 1 , L 2 from fixed supports, that is, take into account the length of the entire expansion section. In practice, the lateral movements of the sliding, (movable) supports of an adjacent pipeline section are often limited; from these movable, but limited in transverse movement of supports, and distances should be counted L 1 , L 2 . If the transverse movements of the pipeline along the entire length from the fixed to the fixed support are not limited, there is a danger of the sections of the pipeline closest to the compensator coming off the supports. To illustrate this fact, Fig. 3 shows the results of the calculation for temperature compensation site main pipeline Du 800 made of steel 17G 2S, length 200 m, temperature difference from - 46 ° C to 180 ° C in the MSC Nastran program. The maximum transverse movement of the central point of the compensator is 1.645 m. An additional risk of falling off the pipeline supports is also possible water hammer. So the decision about the lengths L 1 , L 2 should be taken with caution.

Fig.3. Compensation stress calculation results for the section of the pipeline DN 800 with a U-shaped compensator using the MSC/Nastran software package (MPa).

The origin of the first equation in (20) is not entirely clear. Moreover, in terms of dimension, it is not correct. After all, in brackets under the sign of the modulus, the values \u200b\u200bare added R X and P y(l 4 +…) .

The correctness of the second equation in (20) can be proved as follows:

in order to, it is necessary that:

This is true if we put

For a special case L 1 =L 2 , R y=0 , using (3), (4), (15), (19), one can arrive at (36). It is important to note that in the notation in y=y s.

For practical calculations, I would use the second equation in (20) in a more familiar and convenient form:

where A 1 \u003d A [y ck].

In the particular case when L 1 =L 2 , R y=0 (symmetrical compensator):

The obvious advantages of the technique in comparison with is its great versatility. The compensator in Fig. 2 can be asymmetrical; normativity allows to carry out calculations of compensators not only for heating networks, but also for critical high-pressure pipelines, which are in the register of RosTechNadzor.

Let's spend comparative analysis results of calculation of U-shaped compensators according to methods , . Let's set the following initial data:

a) for all compensators: material - Steel 20; P=2.0 MPa; E t\u003d 2x 10 5 MPa; t?200°; loading - preliminary stretching; bent bends according to OST 34-42-699-85; compensators are located horizontally, from pipes with fur. processing;

b) calculation scheme with geometric designations according to Fig. 4;

Fig.4. Calculation scheme for comparative analysis.

c) we will summarize the standard sizes of compensators in table No. 2 together with the results of calculations.

Elbows and pipes of the compensator, D n H s, mm	Size, see fig.4	Pre-stretch, m	Maximum stress, MPa	Permissible stress, MPa
					according to	according to	according to	according to

findings

compensator heat pipe voltage

Analyzing the results of calculations for two different methods: reference - and normative - , it can be concluded that despite the fact that both methods are based on the same theory, the difference in results is very significant. The selected standard sizes of compensators "pass with a margin" if they are calculated according to and do not pass according to the allowable stresses, if they are calculated according to . The most significant influence on the result is produced by the correction factor m 1 , which increases the voltage calculated by the formula by 2 or more times. For example, for a compensator in the last line of Table No. 2 (from pipe 530Ch12) the coefficient m 1 ? 4,2.

The result is also influenced by the value of the allowable stress, which is significantly lower for steel 20.

In general, despite the greater simplicity, which is associated with the presence of a smaller number of coefficients and formulas, the methodology turns out to be much more rigorous, especially in terms of large diameter pipelines.

For practical purposes, when calculating U-shaped expansion joints for heating networks, I would recommend a "mixed" tactic. The coefficient of flexibility (Karman) and the allowable stress should be determined according to the standard, i.e.: k=1/To R* and further according to formulas (9) h (11); [y sk ] - according to formulas (34), (35) taking into account RD 10-249-88. The "body" of the methodology should be used according to , but without taking into account the correction factor m 1 , i.e.:

where M Max determined by (15) h (12).

The possible asymmetry of the compensator, which is taken into account in can be neglected, because in practice, when laying heating networks, movable supports are installed quite often, the asymmetry is random and does not have a significant effect on the result.

Distance b it is possible to count not from the nearest adjacent sliding supports, but to make a decision on limiting lateral movements already on the second or third sliding support, if measured from the axis of the compensator.

Using this "tactic" the calculator "kills two birds with one stone": a) strictly follows the regulatory documentation, since the "body" of the methodology is special case. The proof is given above; b) simplifies the calculation.

To this we can add an important savings factor: after all, in order to select a compensator from a 530Ch12 pipe, see table. No. 2, according to the reference book, the calculator will need to increase its dimensions by at least 2 times, but according to the current standard, this compensator can also be reduced by one and a half times.

Literature

1. Elizarov D.P. Thermal power plants of power plants. - M.: Energoizdat, 1982.

2. Water heating network: Reference manual for design / I.V. Belyaikina, V.P. Vitaliev, N.K. Gromov et al., ed. N.K. Gromova, E.P. Shubin. - M.: Energoatomizdat, 1988.

3. Sokolov E.Ya. Heat supply and heat networks. - M.: Energoizdat, 1982.

4. Norms for calculating the strength of pipelines of heating networks (RD 10-400-01).

5. Norms for calculating the strength of stationary boilers and pipelines of steam and hot water (RD 10-249-98).

Hosted on Allbest.ru

...

The principle of operation of the U-shaped compensator

According to its design, the U-shaped compensator is considered the simplest, since it consists of a minimum set of elements. It was this minimalism that made it possible to provide a wide range specifications(temperature, pressure). The compensator is made in one of two ways.

A single pipe bends in the right places with a certain bending radius, forming a U-shaped structure.
The compensator consists of 7 elements, including three straight bends and 4 rotary corners, which are welded into a single structure.

Due to the fact that this compensator has to be serviced frequently, because sediments in the form of dirt or other dense structures often accumulate in the U-shaped elbow, its connecting pipes are equipped with flanges or threaded couplings. This allows you to mount and dismantle the device without the use of special tools.

U-shaped compensators are provided for both steel pipes, and for polyethylene pipes. The design is not without flaws. So, for example, the installation of a U-shaped compensator in the heating system requires spending additional material in the form of pipes, corners, sgons. For heating networks, everything is complicated by the installation of additional supports.

Installation requirements and installation cost of U-shaped devices

Despite the relative simplicity of the device, the installation of a U-shaped compensator is not always lower in cost, compared, for example, with the cost of a bellows compensator. Now we are talking about pipelines of large diameter. In this case, the cost of additional elements and their installation exceed the cost of the bellows device, and if we take into account the need to build supports, then the difference in price will be very noticeable.

If the compensator is made by bending a straight pipe, it must be taken into account that the radius of this bend must be equal to eight radii of the pipe itself. If there are seams, the structure is made so that these seams fall on straight sections. When forming steeply curved bends, of course, one has to deviate from these rules.

Pros and cons of the U-shaped design

It is advisable to apply given type expansion joints when installing pipelines of small diameters. It should be noted here that the size range of bellows expansion joints is somewhat wider. The U-bend copes well with vibrations, but its manufacture requires a large amount of material, which significantly increases the cost of the device.

Comparison of the characteristics of bellows and U-shaped expansion joints allows us to identify the main advantages and disadvantages of each type of device. For example, a U-shaped compensator needs to be periodically serviced and cleaned from deposits. Bellows expansion joints do not suffer from such shortcomings.

Another point that I would like to note concerns the compensating ability of the two types of devices. If we consider only absolute values, then in this regard clear advantage not visible from either side. However, to increase the maximum displacement in the U-shaped compensator, you will have to increase the size of the knee. For a bellows compensator, it is enough to use a two-section corrugation, which practically does not affect the dimensions.

I would like to add to the treasury of positive properties such a quality as the lack of control during operation. But in a densely populated area, there is not always free space for arranging a pipeline with a U-shaped compensator. The elbow can only be mounted on horizontal sections, while the bellows expansion joint is installed on any straight section.

Finally, another advantage of the bellows expansion joint is that it does not increase the resistance to the flow of liquid and gas. The U-bend greatly reduces the flow rate. When using this type of device in a home heating system, you will have to install circulation pump, since due to natural convection, the liquid may not circulate, encountering an obstacle on the way.

Calculations for compensators

The absence of GOST standards for U-shaped devices sometimes significantly complicates the task of project planning, so a preliminary calculation of the U-shaped compensator is necessary. First of all, it is necessary to build on the needs of the project. The dimensions of the pipeline, its diameter, maximum pressure and the magnitude of the expected displacement are taken into account.

This means that it is almost impossible to purchase a ready-made compensator. For each specific case, it must be made individually. This is another disadvantage compared to bellows devices.

When calculating the parameters, the following restrictions and conditions should be taken into account:

steel is used as the material for the pipeline;
compensators are designed for both water and gaseous media;
the maximum carrier pressure does not exceed 1.6 atmospheres;
the compensator must have the correct shape in the form of the letter "P";
mounted only on horizontal sections;
no effect of wind.

It should be understood that the given parameters are considered ideal. In real conditions, it is possible to observe only a couple of points. When it comes to the temperature of the environment, it is necessary to take its value to the maximum, and take the ambient temperature to the minimum.

Mounting the compensator

During the construction of the highway, certain rules should be used, which also apply to the arrangement of U-shaped expansion joints. It is installed so that the flight is directed to the right side. The parties determine when looking at the pipeline from the source to the receiver. If there is no space required for the compensator on the right, then the flight is made to the left, however, the return line will have to be led from right side, and this leads to changes in the project.

Before the direct commissioning of the heating main, a mandatory preliminary stretching of the compensator is required. Filled pipes experience excessive pressure, so if this procedure is not done, the metal will soon begin to collapse.

The tension is made with special jacks, and after starting they are removed, and the knee takes its previous position. The amount of tension is indicated by the passport data provided for each device. When installing supports, it is necessary to calculate their location, they must be located so that deformations lead only to axial displacement of the pipe on the support.

What else to read

Compliments in Estonian Russian-Estonian phrasebook: how to explain yourself in an unfamiliar country. Popular phrases and expressions for travelers....

Help Beltelecom on settlements Belarusian mobile operator "Beltelecom", under which it offers services for providing Internet access....

Exactly a month has passed since the disappearance of the schoolboy in Pushcha Alyaksandr Lukashenka's abilities could be useful in solving the disappearance of 10-year-old Maxim Markhaliuk, a resident of...

Advantages of bellows over U-shaped compensators. Design of heat networks of an industrial enterprise

Start right now