The formula for gas flow from pressure and pipe diameter. How to calculate pipe capacity for different systems - examples and rules

Laying a pipeline is not very difficult, but rather troublesome. One of the most difficult problems this is the calculation bandwidth pipes, which directly affects the efficiency and performance of the structure. In this article, we will talk about how the throughput of a pipe is calculated.

Throughput is one of the most important indicators of any pipe. Despite this, this indicator is rarely indicated in the marking of the pipe, and there is little sense in this, because the throughput depends not only on the dimensions of the product, but also on the design of the pipeline. That is why this indicator has to be calculated independently.

Methods for calculating the throughput of the pipeline

1. External diameter. This indicator is expressed in the distance from one side of the outer wall to the other side. In calculations, this parameter has the designation Day. The outside diameter of the pipes is always shown on the label.
2. Nominal diameter. This value is defined as the diameter of the internal section, which is rounded to whole numbers. When calculating, the value of the conditional passage is displayed as Du.

Calculation of pipe patency can be carried out according to one of the methods, which must be chosen depending on the specific conditions for laying the pipeline:

1. Physical calculations. In this case, the pipe capacity formula is used, which allows taking into account each design indicator. The choice of formula is influenced by the type and purpose of the pipeline - for example, for sewer systems has its own set of formulas, as for other types of structures.
2. Tabular Calculations. Pick up optimal value patency can be using a table with approximate values, which is most often used for arranging wiring in an apartment. The values ​​indicated in the table are rather blurry, but this does not prevent them from being used in calculations. The only drawback of the tabular method is that it calculates the capacity of the pipe depending on the diameter, but does not take into account changes in the latter due to deposits, so for lines prone to build-up, this calculation will not be the best choice. To get accurate results, you can use the Shevelev table, which takes into account almost all factors affecting pipes. Such a table is great for the installation of highways on separate land plots.
3. Calculation using programs. Many companies specializing in laying pipelines use computer programs in their activities that allow them to accurately calculate not only the throughput of pipes, but also a host of other indicators. For independent calculations, you can use online calculators, which, although they have a slightly larger error, are available at free mode. good option a large shareware program is "TAScope", and in the domestic space the most popular is "Hydrosystem", which also takes into account the nuances of installing pipelines depending on the region.

Calculation of the throughput capacity of gas pipelines

The design of a gas pipeline requires a sufficiently high accuracy - the gas has a very large ratio compression, due to which leaks are possible even through microcracks, not to mention serious breaks. That is why the correct calculation of the throughput of the pipe through which the gas will be transported is very important.

If we are talking about gas transportation, then the throughput of pipelines, depending on the diameter, will be calculated according to the following formula:

• Qmax = 0.67 DN2 * p,

Where p is the value of the working pressure in the pipeline, to which 0.10 MPa is added;

Du - the value of the conditional passage of the pipe.

The above formula for calculating the throughput of a pipe by diameter allows you to create a system that will work in a domestic environment.

In industrial construction and when performing professional calculations, a different type of formula is used:

• Qmax \u003d 196.386 Du2 * p / z * T,

Where z is the compression ratio of the transported medium;

T is the temperature of the transported gas (K).

To avoid problems, when calculating the pipeline, professionals also have to take into account the climatic conditions in the region where it will pass. If a outside diameter pipe will be less than the gas pressure in the system, then the pipeline is very likely to be damaged during operation, resulting in the loss of the transported substance and an increased risk of explosion in the weakened pipe section.

If necessary, you can determine the patency gas pipe using a table that describes the relationship between the most common pipe diameters and the working pressure level in them. By and large, the tables have the same drawback that the throughput of the pipeline calculated by the diameter has, namely, the inability to take into account the impact of external factors.

Calculation of the capacity of sewer pipes

When designing a sewer system, it is imperative to calculate the throughput of the pipeline, which directly depends on its type (sewer systems are pressure and non-pressure). Hydraulic laws are used to carry out calculations. The calculations themselves can be carried out both using formulas and using the corresponding tables.

For the hydraulic calculation of the sewer system, the following indicators are required:

• Pipe diameter - Du;
• The average speed of movement of substances - v;
• The value of the hydraulic slope - I;
• Degree of filling – h/DN.

As a rule, only the last two parameters are calculated during calculations - the rest after that can be determined without any problems. The amount of hydraulic slope is usually equal to the slope of the ground, which will allow the flow of water to move at the speed necessary for the system to self-clean.

The speed and maximum filling level of domestic sewage are determined by the table, which can be written as follows:

1. 150-250 mm - h / DN is 0.6, and the speed is 0.7 m / s.
2. Diameter 300-400 mm - h / DN is 0.7, speed - 0.8 m / s.
3. Diameter 450-500 mm - h / DN is 0.75, speed - 0.9 m / s.
4. Diameter 600-800 mm - h / DN is 0.75, speed - 1 m / s.
5. Diameter 900+ mm - h / DN is 0.8, speed - 1.15 m / s.

For a product with a small cross section, there are normative indicators for the minimum slope of the pipeline:

• With a diameter of 150 mm, the slope should not be less than 0.008 mm;
• With a diameter of 200 mm, the slope should not be less than 0.007 mm.

The following formula is used to calculate the volume of wastewater:

• q = a*v,

Where a is the free area of ​​the flow;

v is the speed of effluent transportation.

The rate of transport of a substance can be determined using the following formula:

• v=C√R*i,

where R is the value of the hydraulic radius,

C is the wetting coefficient;

i - the degree of slope of the structure.

From the previous formula, the following can be deduced, which will allow you to determine the value of the hydraulic slope:

• i=v2/C2*R.

To calculate the wetting coefficient, a formula of the following form is used:

• С=(1/n)*R1/6,

Where n is a coefficient that takes into account the degree of roughness, which varies from 0.012 to 0.015 (depending on the pipe material).

The R value is usually equated to the usual radius, but this is only relevant if the pipe is completely filled.

For other situations, a simple formula is used:

• R=A/P

Where A is the cross-sectional area of ​​the water flow,

P is the length of the inner part of the pipe that is in direct contact with the liquid.

Tabular calculation of sewer pipes

It is also possible to determine the patency of the pipes of the sewer system using tables, and the calculations will directly depend on the type of system:

1. Non-pressure sewerage. To calculate non-pressure sewer systems, tables are used that contain all required indicators. Knowing the diameter of the pipes to be installed, you can select all other parameters depending on it and substitute them into the formula (read also: ""). In addition, the table indicates the volume of liquid passing through the pipe, which always coincides with the pipeline's permeability. If necessary, you can use the Lukin tables, which indicate the throughput of all pipes with a diameter in the range from 50 to 2000 mm.
2. Pressure sewer. Determine throughput in this type systems through tables are somewhat simpler - it is enough to know the maximum degree of filling of the pipeline and the average speed of liquid transportation. See also: "".

Bandwidth table polypropylene pipes allows you to find out all the parameters necessary for arranging the system.

Calculation of the capacity of the water supply

Water pipes in private construction are used most often. In any case, the water supply system has a serious load, so the calculation of the throughput of the pipeline is mandatory, because it allows you to create the maximum comfortable conditions operation of the future structure.

To determine the patency water pipes you can use their diameter (read also: ""). Of course, this indicator is not the basis for calculating the patency, but its influence cannot be ruled out. The increase in the inner diameter of the pipe is directly proportional to its permeability - that is, a thick pipe almost does not impede the movement of water and is less susceptible to the accumulation of various deposits.

However, there are other indicators that also need to be taken into account. For example, a very important factor is the coefficient of fluid friction about inner part pipes (different materials have their own values). It is also worth considering the length of the entire pipeline and the pressure difference at the beginning of the system and at the outlet. An important parameter is the number of different adapters present in the design of the water supply system.

The throughput of polypropylene water pipes can be calculated depending on several parameters using the tabular method. One of them is a calculation in which the main indicator is the temperature of the water. As the temperature rises, the liquid expands in the system, so friction increases. To determine the patency of the pipeline, you need to use the appropriate table. There is also a table that allows you to determine the patency in the pipes depending on the water pressure.

The most accurate calculation of water according to the throughput of the pipe is made possible by the Shevelev tables. In addition to accuracy and a large number standard values, in these tables there are formulas that allow you to calculate any system. This material fully describes all situations related to hydraulic calculations, therefore, most professionals in this field most often use the Shevelev tables.

The main parameters taken into account in these tables are:

• External and internal diameters;
• Pipeline wall thickness;
• The period of operation of the system;
• The total length of the highway;
• Functional purpose of the system.

Conclusion

Pipe capacity calculation can be done in different ways. Choice best way calculation depends on a large number of factors - from the size of the pipes to the purpose and type of system. In each case, there are more and less accurate calculation options, so both a professional specializing in laying pipelines and an owner who decides to independently lay a highway at home will be able to find the right one.

This characteristic depends on several factors. First of all, this is the diameter of the pipe, as well as the type of liquid, and other indicators.

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

When calculating any systems based on the circulation of fluid through pipes, it becomes necessary exact definition pipe capacity. This is a metric value that characterizes the amount of fluid flowing through pipes in a certain period of time. This indicator is directly related to the material from which the pipes are made.

If we take, for example, plastic pipes, then they differ in almost the same throughput throughout the entire period of operation. Plastic, unlike metal, is not prone to corrosion, so a gradual increase in deposits is not observed in it.

As for metal pipes, their throughput decreases year after year. Due to the appearance of rust, material detachment occurs inside the pipes. This leads to surface roughness and the formation of even more deposits. This process occurs especially quickly in pipes with hot water.

The following is a table of approximate values ​​\u200b\u200bwhich was created to facilitate the determination of the throughput of pipes for intra-apartment wiring. This table does not take into account the reduction in throughput due to the appearance of sediment buildup inside the pipe.

Pipe capacity table for liquids, gas, steam.

Most often, ordinary water is used as a coolant. The rate of decrease in throughput in pipes depends on its quality. The higher the quality of the coolant, the longer the pipeline made of any material (steel, cast iron, copper or plastic) will last.

Calculation of pipe throughput.

For accurate and professional calculations, you must use the following indicators:

• The material from which pipes and other elements of the system are made;
• Pipeline length
• Number of water consumption points (for water supply system)

The most popular calculation methods:

1. Formula. A rather complicated formula, which is understandable only to professionals, takes into account several values ​​at once. The main parameters that are taken into account are the material of the pipes (surface roughness) and their slope.

2. Table. This is an easier way by which anyone can determine the throughput of the pipeline. An example is the engineering table of F. Shevelev, by which you can find out the throughput based on the pipe material.

3. computer program. One of these programs can be easily found and downloaded on the Internet. It is designed specifically to determine the throughput for pipes of any circuit. In order to find out the value, it is necessary to enter the initial data into the program, such as material, pipe length, coolant quality, etc.

It should be said that last way, although it is the most accurate, is not suitable for simple calculations household systems. It is quite complex and requires knowledge of the values ​​of a variety of indicators. To calculate a simple system in a private house, it is better to use tables.

An example of calculating the throughput of the pipeline.

Pipeline length - important indicator when calculating throughput The length of the backbone has a significant impact on throughput performance. How greater distance water passes through, the less pressure it creates in the pipes, which means that the flow rate decreases.

Here are some examples. Based on tables developed by engineers for these purposes.

Pipe capacity:

• 0.182 t/h at 15 mm diameter
• 0.65 t/h with pipe diameter 25 mm
• 4 t/h at 50 mm diameter

As can be seen from the examples above, a larger diameter increases the flow rate. If the diameter is increased by 2 times, then the throughput will also increase. This dependence must be taken into account when installing any liquid system, whether it be water supply, sewerage or heat supply. Especially it concerns heating systems, since in most cases they are closed, and the heat supply in the building depends on the uniform circulation of the liquid.

Today, gas is the cheapest and most accessible type of fuel. This is especially noticeable when compared with electricity. Therefore, in recent times owners of country houses are interested in how to calculate the diameter of the gas pipeline and what to look for during installation.

After all, the paths leading to the house of explosive fuel should be laid with extreme caution and comply with all standards.

The main reason is cheapness and convenience. The difficult economic situation in the country is forcing the owners of private houses to look for the most affordable option building heating. Therefore, it is not at all surprising that over time, the owners of cottages come to the conclusion that it is necessary to gasify the building.

Yes, of course, you can heat your home with electricity. But such a solution is quite expensive, especially if you need to heat several hundred square meters.

Yes, and the vagaries of nature in the form strong wind or a hurricane can break the cables and you will have to sit for who knows how long without heating, food and hot water.

Modern gas pipelines are laid using durable and high quality pipes and details. Therefore, natural disasters are unlikely to harm such a structure.

Another alternative to gas is the old and proven way - to warm yourself with a fireplace or stove. The main disadvantage of this solution is that storing firewood or coal will lead to dirt.

In addition, additional square meters for their storage. Therefore, blue fuel will hold a leading position for more than one year.

The main types of gas pipelines

There are three types of highways. The first is a gas pipeline low pressure. For such a system, the maximum allowable pressure is 5 kPa. Most often this type is laid in small settlements. It is also used for gas supply medical institutions, residential buildings, children's and public buildings.

For the second variety - the medium pressure line - the fuel flow can be supplied with a force of up to 0.3 MPa. The scope of this type is limited to providing gas to quarterly and regional regulatory stations.

As for the high pressure line, it is designed to supply fuel to large industrial enterprises. For owners of private houses, such a decision is irrelevant. Indeed, gas is supplied to the cottage using a pipe, the pressure in which does not exceed 5 kPa.

Laying the highway is a complex and time-consuming process. To protect yourself and your home from gas leakage, you must use high-quality fittings and follow the recommendations of specialists

Norms and standards for laying pipes

Gas is supplied to residential buildings through inputs coming from distributing fuel stations. They are usually installed on ground floor and further laid on the stairwells.

The pipe that is connected to the residential building must be manufactured by the seamless method, and its wall thickness is at least 3.5 mm.

When connecting the main to a private house, it must be located at least 15 cm from the water supply pipes and the heating network. In the case of telephone or electric cables this value increases to half a meter.

The gas pipeline is predominantly made of steel. Therefore, to prevent corrosion of the pipe, it is covered with a special insulating material. Due to this, the structure does not come into contact with wet ground.

Laying a gas pipeline in any living room is strictly prohibited. It should be placed in a separate well-ventilated area

Mounting methods and their features

Gas pipeline can be laid various methods. It is underground, ground or underwater installation. In buildings, the laying of the network can be carried out hidden or open.

Each variety has its own advantages and disadvantages. Therefore, before giving preference to any of the varieties, it is necessary to understand in detail all its features.

Advantages and disadvantages of the underground method

More recently, when installing a gas pipeline, the underground method was mainly used. In this case, the pipes are laid in pre-dug trenches. Moreover, their depth must exactly correspond to the value specified in the project.

Today, this solution is used less and less. The drop in demand is due to the high cost of this kind of gasket. In addition, digging holes where pipes will be laid will take quite a lot of time.

Currently, engineers prefer trenchless method. Its peculiarity lies in the use of equipment that can perform horizontal directional drilling.

Thanks to this, the cost of laying is reduced threefold, and the time required to organize the highway is reduced by at least two times.

Horizontal directional drilling avoids the dismantling of the roadbed. In addition, the well will be able to go around any obstacle without any problems, for example, an already laid pipeline.

The underground method with the help of HDD equipment eliminates the need to restore green spaces. Therefore, such a solution can be called as harmless as possible for environment.

Installation by this method is the drilling of a pilot well, which is further expanded to the required dimensions. Further, the walls are strengthened with a special solution.

To protect the pipeline from underground water flows and excessive mechanical stress, it is placed in a protective case. The final step is to pull the pipes through the well.

External organization of the gas pipeline

The external method is used most often. In this case, the gas pipeline, as a rule, stretches through the yard of the cottage. In this case, the structure must be protected from unauthorized persons. For this purpose, the pipes are located at a considerable height.

Particular attention should be paid to fixation. Fastenings must be as strong and reliable as possible to minimize the risk of falling and, as a result, damage to the gas pipe.

Only experienced and qualified specialists should be engaged in the assembly of the structure. The installation must be carried out in accordance with building regulations and technical documentation

Ground and overground laying

Compared to the underground installation method, the ground installation will cost almost half as much. But in this case, you need to pay Special attention protection of the structure from environmental influences and mechanical damage.

For example, the pipe must be insulated so that atmospheric precipitation does not fall on it and temperature changes are not noticeable. Moreover, the type of protection is selected depending on the climatic conditions of the region.

To prevent unauthorized connection to the highway, you need to take care of security. Indeed, due to the fact that the pipe lies on special supports on the ground, third parties can easily access it. Therefore, unlike underground laying, such a solution is less reliable.

The onshore gas pipeline will become ideal solution for well-protected private houses and cottages. Especially if it is impossible to lay pipes underground due to a rather dense network of utilities

What is the best way to install a gas pipeline?

It is necessary to give preference to one or another solution depending on the climate of the region where the work will be carried out, building density and soil characteristics. Accordingly, there is simply no single answer.

To determine which installation method is best to choose, consider the following recommendations:

1. When the soil on the site is characterized by rather high corrosive properties, then the most right decision the gas pipeline will be installed by the ground method.
2. If the pipeline is laid across the road, then the combined option is economically viable. That is, in the area of ​​\u200b\u200bthe auto-canvas, the pipe should be located underground, and on the territory of the cottage - on the surface.
3. In the case of laying the pipeline through neighboring sections, it is recommended to choose the ground (open) method.
4. When at the site where the installation is planned, there are high voltage lines transmission lines, then a hidden installation of the main line would be a reasonable solution.

The laying method directly affects the material from which the pipeline should be made. The question related to which reinforcement to use in a particular case will be discussed further.

What documents will be needed?

Before proceeding directly to the installation, you will have to start collecting the necessary papers. To do this as soon as possible, you must immediately prepare a passport, as well as documentation that confirms the ownership of the site and the house located on it.

The next step is to submit an application to the relevant service. It expresses a desire to gasify the house. Employees will issue a form that lists all the technical conditions.

issued gas service the document is filled in by the specialist involved in the drafting of the project. Choose a qualified designer. After all, the result of work and the safety of residents depend on his competence.

According to the project, the gas network is being installed. Sometimes pipes are laid through the sections of neighbors. In this case, you must ask them for written permission to carry out such work.

In addition to the papers listed above, you will also need to obtain the following documents:

• the act of commissioning gas-powered equipment;
• agreement on the preparation of technical documentation and work;
• permission to supply natural gas and pay for this service;
• document on the installation of equipment and gasification of the house.

A chimney inspection will also be required. After that, the experts will issue the appropriate act. The last document - permission to gasify a private house - is issued by a local architectural and planning company.

How to calculate the diameter of a gas pipeline?

When drawing up a project, special attention is paid to the diameter of the pipe. The designer will do this using complex formulas or a program.

In order not to bother your head with various formulas, good choice will use one of specialized programs. The benefit of such software on the Internet is full.

Using the calculators is as easy as shelling pears - you just need to fill in the fields with the relevant information.

To determine the optimal diameter gas pipeline you can use the table. To obtain the required value, you only need to select the required amount of fuel consumption

Selection of pipes and fasteners

Since the pipeline with blue fuel is an object of increased danger, all fittings used must have the necessary quality certificates. Otherwise, the commission conducting the final check will not allow the house with such pipes to be gasified.

The nuances of choosing a material

Pipe material is selected depending on the pipeline laying method. Products made of polyethylene and steel are in the greatest demand. The main advantage of the latter variety is its versatility.

After all, steel pipes can be used for both underground and outdoor installations. But such a solution will cost more.

Polymer piping can only be used for concealed installation. This is due to the fact that under the influence of the sun the material decomposes and quickly loses its properties.

As for fasteners, for installation you will need corners, couplings, tees, crosses, plugs and adapters. As a rule, they are made of cast iron, steel or polyethylene.

Also, do not hesitate to install the counter. After all, it will significantly reduce costs.

Advantages of polyethylene pipes

First of all, such fittings do not rust over time. Therefore, it allows you to save on maintenance and repair of the pipeline. Thanks to a special production technology, polyethylene products have an absolutely smooth inner surface. As a result, the fuel flow rate is not slowed down in any way.

One of the main advantages of polymer pipes is their safety. No stray currents will appear in them, due to which gas can explode. So in the case of underground laying, there is no need to use a special expensive case.

If we compare the weight steel pipe and polymer, the latter type is as much as 7 times lighter. This property makes it possible to significantly reduce the cost of construction, because it is not necessary to involve equipment with an increased carrying capacity.

A polyethylene pipeline, subject to all standards, will last at least half a century. And over time it performance characteristics won't get worse in any way.

Pipes made of polyethylene, due to their flexibility, have earned the respect of specialists. Due to this, installation by horizontal directional drilling will not cause any difficulties or problems.

This solution is especially relevant when the well has an uneven shape or any obstacles were found during its creation.

When should you stop using polymer?

In some cases, polyethylene products will be a poor choice. The limiting conditions include the situation when the soil temperature in winter time year can fall below -15 degrees.

Plastic pipelines should be abandoned in regions where there is a risk of an earthquake with a magnitude of more than 7 on the Richter scale

Usage polymer reinforcement also prohibited in the following situations:

• the pipeline will supply liquefied hydrocarbons;
• was chosen open way installation;
• if the gas pipeline passes over any obstacles ( Railway or highway).

After all the necessary products have been purchased, and the documents have been collected, you can deal with the features of laying a highway with blue fuel.

The procedure for laying a gas pipeline

Despite the fact that the installation of pipes should be carried out exclusively by professionals with the necessary qualifications, each owner of a private house should familiarize himself in detail with the procedure for carrying out the work. This will avoid trouble and the appearance of unplanned financial expenses.

Installation of the riser and preparation of the premises

If a private house is gasified in order to organize heating, then you need to take care of the arrangement of the premises. The room with all the equipment should be separate and fairly well ventilated. After all natural gas not only explosive, but also toxic to the human body.

The boiler room must have a window. This will provide the opportunity to ventilate the room at any time, which will avoid fuel vapor poisoning.

As for the dimensions, the ceiling height in the room should be at least 2.2 m. For a kitchen where a stove with two burners will be installed, an area of ​​​​8 m 2 will be enough, and for a four-burner model - 15 m 2.

If equipment with a capacity of more than 30 kW is used to heat the house, then the boiler room should be moved outside the house and be a separate building.

Gas is supplied to the cottage using a special inlet, which is a hole above the foundation. It is equipped with a special case through which the pipe passes. One end is connected to the riser, and the other is part of internal system gas supply.

The riser is mounted exactly vertically and the structure must be at least 15 cm away from the wall. The reinforcement can be fixed using special hooks.

Subtleties of laying pipes

During the installation of the pipeline in the wall, all its parts must be passed through the sleeves. In this case, the entire structure must be covered with oil paint.

The free space present between the pipe and the sleeve is filled with tarred tow and bitumen.

It is necessary to ensure that during the installation of the pipeline, as few threaded and welded connections as possible are used. This approach will make the whole structure as reliable as possible. Accordingly, for this it is necessary to select pipes of maximum length

Each of the nodes is assembled at the bottom, and at a height only fasteners of pre-preparatory components are carried out. If the diameter of the pipes does not exceed 4 cm, then they can be fixed with clamps or hooks. For all others, it is recommended to use brackets or hangers.

Welding, assembly and acceptance rules

All components of the pipeline are interconnected by welding. In this case, the seam must be of high quality and reliable. To achieve this, you must first level the end of the pipe and strip about 1 cm on each side of it.

As for assembly threaded connections, then you need to use a special technique for this. First, the joint is processed with whitewash. The next step is to wind long-staple flax or a special tape. Only then can the threaded connection be tightened.

As soon as the masters finish the work, a commission should come to the house and check the quality of the installation. Moreover, without fail, the owner is given a detailed briefing on the rules for using the gas pipeline. Employees will also tell you how to properly use equipment that consumes blue fuel.

Conclusions and useful video on the topic

All about gasification of a private house:

The main stages of installation:

Laying a gas pipeline to a private house is a laborious and responsible process. After all, the safety of residents directly depends on the quality of the work. Therefore, it is better to entrust the execution of calculations and the installation itself to highly qualified and experienced employees.

B.K. Kovalev, Deputy Director for R&D

Recently, more and more often we have to deal with examples when placing orders for industrial gas equipment conducted by managers who do not have sufficient experience and technical knowledge in relation to the subject of procurement. Sometimes the result is not a completely correct application or a fundamentally incorrect selection of ordered equipment. One of the most common mistakes is the choice of nominal sections of the inlet and outlet pipelines of a gas distribution station, oriented only to the nominal values ​​of gas pressure in the pipeline without taking into account the gas flow rate. The purpose of this article is to issue recommendations for determining the throughput of GDS pipelines, which allow, when choosing the size of a gas distribution station, to carry out a preliminary assessment of its performance for specific values ​​of operating pressures and nominal diameters of inlet and outlet pipelines.

When choosing the required standard sizes of GDS equipment, one of the main criteria is performance, which largely depends on the capacity of the inlet and outlet pipelines.

The capacity of pipelines of a gas distribution station is calculated taking into account the requirements normative documents limiting the maximum allowable gas flow rate in the pipeline to 25m/s. In turn, the gas flow rate depends mainly on the pressure of the gas and the cross-sectional area of ​​the pipeline, as well as on the compressibility of the gas and its temperature.

The throughput of the pipeline can be calculated from the classical formula for the velocity of gas in a gas pipeline (Design Guide main gas pipelines edited by A.K. Dertsakyan, 1977):

where W- speed of gas movement in the gas pipeline, m/s;
Q- gas flow through a given section (at 20 ° C and 760 mm Hg), m 3 / h;
z- compressibility factor (for an ideal gas z = 1);
T = (273 + t °C)- gas temperature, °K;
D- internal diameter of the pipeline, cm;
p\u003d (Prab + 1.033) - absolute gas pressure, kgf / cm 2 (atm);
In the SI system (1 kgf / cm 2 \u003d 0.098 MPa; 1 mm \u003d 0.1 cm), this formula will take the following form:

where D is the inner diameter of the pipeline, mm;
p = (Pwork + 0.1012) - absolute gas pressure, MPa.
It follows that the capacity of the pipeline Qmax, corresponding to the maximum gas flow rate w = 25m/s, is determined by the formula:

For preliminary calculations we can take z = 1; T \u003d 20? C \u003d 293? K and, with a sufficient degree of reliability, carry out calculations using a simplified formula:

The values ​​of the throughput capacity of pipelines with the most common conditional diameters in GDS at various values gas pressures are given in table 1.

Note: for a preliminary assessment of the throughput of pipelines, the inner diameters of the pipes are taken equal to their conventional values ​​(DN 50; 80; 100; 150; 200; 300; 400; 500).

Examples of using the table:

1. Determine the capacity of the GDS with DNin=100mm, DNout=150mm, with PNin=2.5 - 5.5 MPa and PNout=1.2 MPa.

From table 1 we find that the capacity of the outlet pipeline DN=150mm at PN=1.2 MPa will be 19595 m 3 / h, at the same time the inlet pipeline DN=100 mm at PN=5.5 MPa will be able to pass 37520 m 3 / h , and at PN=2.5 MPa - only 17420 m 3 /h. Thus, this GDS with PNin=2.5 - 5.5 MPa and PNout=1.2 MPa will be able to pass from 17420 to 19595 m 3 /h as much as possible. Note: more exact values Qmax can be obtained from formula (3).

2. Determine the diameter of the outlet pipeline of the GDS, with a capacity of 5000 m 3 / h at Pin=3.5 MPa for outlet pressures Pout1=1.2 MPa and Pout2=0.3 MPa.

From table 1 we find that a throughput of 5000m 3 /hour at Pout=1.2 MPa will be provided by a pipeline DN=80mm, and at Pout=0.3 MPa - only DN=150mm. At the same time, it is enough to have a pipeline DN=50mm at the GDS inlet.

For safe and trouble-free operation of gas supply, it must be designed and calculated. It is important to perfectly select pipes for lines of all types of pressure, ensuring a stable supply of gas to the devices. In order for the selection of pipes, fittings and equipment to be as accurate as possible, a hydraulic calculation of the pipeline is carried out. How to make it? Admit it, you are not too knowledgeable in this matter, let's figure it out.

We suggest that you familiarize yourself with the scrupulously selected and thoroughly processed information on the options for the production of hydraulic calculations for gas pipeline systems. Using the data presented by us will ensure the supply of blue fuel with the required pressure parameters to the devices. Carefully verified data is based on the regulation of regulatory documentation.

The author of the article talks in detail about the principles and schemes for performing calculations. Gives an example of performing calculations. Graphical applications and video instructions are used as a useful informative addition.

Any hydraulic calculation performed is a determination of the parameters of the future gas pipeline. This procedure is mandatory and also one of the milestones preparation for construction. Whether the gas pipeline will operate in the optimal mode depends on the correctness of the calculation.

When performing each hydraulic calculation, the following is determined:

• the required pipe diameter, which will ensure efficient and stable transportation the right amount gas;
• whether pressure losses will be acceptable when moving the required volume of blue fuel in pipes of a given diameter.

Pressure losses occur due to the fact that in any gas pipeline there is hydraulic resistance. If calculated incorrectly, it can lead to the fact that consumers will not have enough gas for normal operation in all modes or at the moments of its maximum consumption.

This table is the result of a hydraulic calculation based on the given values. To perform calculations, you will need to enter specific indicators in the columns

Such an operation is a procedure standardized by the state, which is performed in accordance with the formulas and requirements set forth in SP 42-101-2003.

Calculations must be carried out by the builder. Data is taken as a basis specifications pipelines, which can be obtained in your city gas.

Gas pipelines requiring calculations

The state requires that hydraulic calculations be performed for all types of pipelines related to the gas supply system. Since the processes occurring during the movement of gas are always the same.

These pipelines include the following types:

• low pressure;
• medium, high pressure.

The first are designed to transport fuel to residential facilities, all kinds of public buildings, household enterprises. Moreover, in private apartment buildings, cottages, gas pressure should not exceed 3 kPa, at household enterprises (non-industrial) this figure is higher and reaches 5 kPa.

The second type of pipelines is designed to supply networks, and all kinds of low, medium pressure through gas control points, as well as supplying gas to individual consumers.

These can be industrial, agricultural, various utilities, and even detached or attached to industrial buildings. But in the last two cases there will be significant pressure limitations.

The types of gas pipelines listed above are conventionally divided by specialists into the following categories:

• intra-house, intrashop, that is, transporting blue fuel inside a building and delivering it to individual units, devices;
• subscriber branches used to supply gas from some distribution network to all available consumers;
• distribution used to supply gas to certain territories, for example, cities, their individual districts, industrial enterprises. Their configuration is different and depends on the features of the layout. The pressure inside the network can be any provided - low, medium, high.

In addition, hydraulic calculation is performed for gas networks with a different number of pressure stages, of which there are many varieties.

So, to meet the needs, two-stage networks can be used, working with gas transported at low, high pressure or low, medium. And also three-stage and various multi-stage networks have found application. That is, it all depends on the availability of consumers.

Hydraulic resistance is the main reason that it is necessary to carry out this species calculation. Moreover, it also depends on the material of the pipe.

Despite the wide variety of gas pipeline options, the hydraulic calculation is similar in any case. Since structural elements from similar materials are used for manufacturing, and the same processes occur inside the pipes.

Hydraulic resistance and its role

As mentioned above, the basis for the calculation is the presence of hydraulic resistance in each gas pipeline.

It acts on the entire pipeline structure, as well as on its individual parts, nodes - tees, places of a significant reduction in the diameter of pipes, stop valves, various valves. This results in a loss of pressure in the transported gas.

Hydraulic resistance is always the sum of:

• linear resistance, that is, acting along the entire length of the structure;
• local resistances acting at each component part of the structure, where there is a change in the speed of gas transportation.

These parameters constantly and significantly affect the performance of each gas pipeline. Therefore, as a result of an incorrect calculation, additional and impressive financial losses will occur due to the fact that the project will have to be redone.

Calculation rules

It was mentioned above that the procedure for any hydraulic calculation is regulated by the profile Code of Rules with the number 42-101-2003.

The document shows that the main way to perform the calculation is to use a computer for this purpose with special programs that allow you to calculate the planned pressure loss between sections of the future gas pipeline or the required pipe diameter.

Any hydraulic calculation is performed after creation design scheme, which includes the main indicators. Moreover, the user enters known data into the corresponding columns

If there are no such programs or a person believes that their use is inappropriate, then other methods allowed by the Code of Rules can be used. Which include:

• calculation according to the formulas given in the joint venture is the most hard way calculation;
• calculation according to the so-called nomograms is an easier option than using formulas, because you don’t have to make any calculations, because the necessary data are indicated in a special table and are given in the Code of Rules, and they just need to be selected.

Any of the calculation methods leads to the same results. Therefore, the newly constructed gas pipeline will be able to ensure timely, uninterrupted supply of the planned amount of fuel even during the hours of its maximum use.

PC calculation option

Performing a calculus using a computer is the least laborious - all that is required of a person is to insert the necessary data into the appropriate columns.

Therefore, the hydraulic calculation is done in a few minutes, and this operation does not require a large stock of knowledge, which is necessary when using formulas.

For its correct implementation, it is necessary to take the following data from the technical specifications:

• gas density;
• coefficient of kinetic viscosity;
• gas temperature in your region.

The necessary technical conditions are obtained from the city gas department of the settlement where the gas pipeline will be built. Actually, the design of any pipeline begins with the receipt of this document, because it contains all the basic requirements for its design.

The use of special programs is the simplest method of hydraulic calculation, excluding the search and study of formulas for calculations.

Next, the developer needs to find out the gas consumption for each device that is planned to be connected to the gas pipeline. For example, if the fuel will be transported to a private house, then stoves for cooking, all kinds of heating boilers are most often used there, and the necessary numbers are always in their passports.

In addition, you will need to know the number of burners for each stove that will be connected to the pipe.

At the next stage of collecting the necessary data, information is selected on the pressure drop at the installation sites of any equipment - this can be a meter, a shut-off valve, a thermal shut-off valve, a filter, and other elements.

In this case, it is easy to find the necessary numbers - they are contained in a special table attached to the passport of each product. The designer should pay attention to the fact that the pressure drop at the maximum gas consumption should be indicated.

From a special table attached to the product passport, you can find out information about the pressure loss when connecting devices to the network

If the network will consist of several sections, then they must be numbered and indicate the actual length. In addition, for each, all variable indicators should be prescribed separately - this is the total flow rate of any device that will be used, the pressure drop, and other values.

A simultaneity factor is required. It takes into account the possibility of joint operation of all gas consumers connected to the network. For example, total heating equipment located in an apartment building or a private house.

This data is used by the hydraulic calculation program to determine maximum load in any section or in the entire pipeline.

For each individual apartment or house, the specified coefficient does not need to be calculated, since its values ​​are known and are indicated in the table below:

A table with simultaneity coefficients, the data from which is used in any type of calculation. It is enough to select the column corresponding to a particular household appliance, and take the desired number

If at some facility it is planned to use more than two heating boilers, furnaces, storage water heaters, then the simultaneity indicator will always be 0.85. Which will need to be indicated in the corresponding column used for the calculation of the program.

Next, you should specify the diameter of the pipes, and you will also need their roughness coefficients, which will be used in the construction of the pipeline. These values ​​are standard and can be easily found in the Rulebook.

Influence of pipe material on the calculation

For the construction of gas pipelines, you can use pipes made only from certain materials: steel, polyethylene. In some cases, copper products are used. Metal-plastic structures will soon be widely used.

Each pipe has roughness, which results in a linear resistance that affects the process of gas movement. Moreover, this figure is much higher for steel products than for plastic ones.

Today, the necessary information can only be obtained for steel and polyethylene pipes. As a result, design and hydraulic analysis can only be performed taking into account their characteristics, which is required by the profile Code of Practice. And also in the document the data necessary for calculation are specified.

The roughness factor is always equated to the following values:

• for all polyethylene pipes, regardless of whether they are new or not, - 0.007 cm;
• for already used steel products - 0.1 cm;
• for new steel structures- 0.01 cm.

For any other types of pipes, this indicator is not indicated in the Code of Rules. Therefore, they should not be used for the construction of a new gas pipeline, since Gorgaz specialists may require adjustments. Again, this is an additional cost.

Calculation of flow in a limited area

If the gas pipeline consists of separate sections, then the calculation of the total flow rate for each of them will have to be performed separately. But this is not difficult, since the calculations will require already known numbers.

Defining data with a program

Knowing the initial indicators, having access to the simultaneity table and to the technical data sheets of stoves and boilers, you can proceed to the calculation. To do this, the following actions are performed (an example is given for an intra-house gas pipeline of precisely low pressure):

1. The number of boilers is multiplied by the capacity of each of them.
2. The resulting value is multiplied by the coefficient of simultaneity specified using a special table for this type of consumer.
3. The number of stoves intended for cooking is multiplied by the performance of each of them.
4. The value obtained after the previous operation is multiplied by the simultaneity factor taken from a special table.
5. The amounts received for boilers and stoves are summed up.

Similar manipulations are carried out for all sections of the gas pipeline. The received data are entered into the corresponding columns of the program, with the help of which the calculations are performed. The electronics does everything else.

Calculation using formulas

This type of hydraulic calculation is similar to the one described above, that is, the same data will be required, but the procedure will be lengthy. Since everything will have to be done manually, in addition, the designer will need to perform a number of intermediate operations in order to use the obtained values ​​​​for the final calculation.

And you will also have to devote a lot of time to understand many concepts, issues that a person does not meet when using a special program. The validity of the above can be seen by reading the formulas to be used.

Calculation using formulas is complex, therefore not accessible to everyone. The picture shows the formulas for calculating the pressure drop in the network of high, medium and low pressure and the coefficient of hydraulic friction

In the application of formulas, as in the case of hydraulic calculation using a special program, there are features for high, medium and, of course, low pressure gas pipelines. And it is worth remembering this, since a mistake is fraught, and always, with impressive financial costs.

Calculations using nomograms

Any special nomogram is a table where a number of values ​​\u200b\u200bare indicated, by studying which you can get the desired indicators without performing calculations. In the case of hydraulic calculation - the diameter of the pipe and the thickness of its walls.

Nomograms for calculation are in a simple way obtaining the necessary information. It is enough to refer to the lines corresponding to the given characteristics of the network

There are separate nomograms for polyethylene and steel products. When calculating them, standard data were used, for example, the roughness of the inner walls. So you don't have to worry about the correctness of the information.

Calculation example

An example of performing a hydraulic calculation using a program for low-pressure gas pipelines is given. In the proposed table yellow all the data that the designer must enter himself are highlighted.

They are listed in the paragraph on computer hydraulic calculation above. These are gas temperature, coefficient of kinetic viscosity, density.

In this case, the calculation is carried out for boilers and stoves, in view of this, it is necessary to prescribe the exact number of burners, which can be 2 or 4. Accuracy is important, because the program will automatically select the simultaneity factor.

In the picture, columns are highlighted in yellow, in which the designer himself must enter the indicators. Below is the formula for calculating the flow rate on the site

It is worth paying attention to the numbering of the sections - they do not come up with it on their own, but take it from a previously drawn up scheme, where similar numbers are indicated.

Next, the actual length of the gas pipeline and the so-called calculated length, which is longer, are prescribed. This happens because in all areas where there is local resistance, it is necessary to increase the length by 5-10%. This is done in order to exclude insufficient gas pressure from consumers. The program performs the calculation itself.

Total consumption in cubic meters, for which a separate column is provided, is calculated in advance for each section. If the house is an apartment building, then you need to indicate the number of housing, and starting from the maximum value, as can be seen in the corresponding column.

Without fail, all elements of the gas pipeline are entered in the table, during the passage of which pressure is lost. The example shows a thermal shut-off valve, a cut-off valve and a meter. The value of the loss in each case was taken in the product passport.

Using one program, you can make calculations for all types of gas pipelines. In the picture, calculations for a medium pressure network

The inner diameter of the pipe is indicated according to the terms of reference, if Gorgas has any requirements, or from a previously drawn up diagram. In this case, in most areas it is prescribed in the amount of 5 cm, because most of the gas pipeline runs along the facade, and the local city gas company requires that the diameter be no less.

Even if you superficially familiarize yourself with the given example of performing a hydraulic calculation, it is easy to see that, in addition to the values ​​entered by a person, there is a large number of others. This is all the result of the program’s work, since after entering the numbers in specific columns highlighted in yellow, the calculation work for a person is completed.

That is, the calculation itself takes place quite quickly, after which the obtained data can be sent for approval to the gas department of your city.

Conclusions and useful video on the topic

This video makes it possible to understand where the hydraulic calculation begins, where designers get the necessary data from:

The following video shows an example of one of the types of computer calculation:

To perform a hydraulic calculation using a computer, as the profile Code of Practice allows, it is enough to spend a little time getting acquainted with the program and collecting the necessary data. But practical value all this does not have, since drafting a project is a much more voluminous procedure and includes many other issues. In view of this, most citizens will have to seek help from specialists.