For safe and trouble-free operation of gas supply it must be designed and calculated. It is important to perfectly match the pipes for all types of pressure lines, ensuring a stable supply of gas to the instruments.
To make the selection of pipes, fittings and equipment as accurate as possible, produce hydraulic calculation of the pipeline. How to make it? Admit it, you are not well versed in this matter, let's understand.
We suggest to get acquainted with the scrupulously selected and thoroughly processed information on the options for the production of hydraulic calculation for gas pipeline systems. The use of the data presented by us will ensure supply of blue fuel to the instruments with the required pressure parameters. Carefully verified data is based on regulatory documents.
The article is very thoroughly described the principles and schemes for the production of calculations. An example of performing calculations. Graphic applications and video instructions were used as a useful informative supplement.
The content of the article:
Specificity of hydraulic calculation
- Pipelines requiring settlement
- Hydraulic resistance and its role
- Calculation Rules
- PC Calculation Option
- The effect of pipe material on the calculation
Calculation of consumption in a limited area
- Definition of data using the program
- Calculation using formulas
- Calculations using nomograms
- Calculation Example
- Conclusions and useful video on the topic
Specificity of hydraulic calculation
Any hydraulic calculation performed is the determination of the parameters of a future gas pipeline. This procedure is mandatory, as well as one of the most important stages of preparation for construction. It depends on the correctness of calculation whether the pipeline will function optimally.
In the implementation of each hydraulic calculation is the definition:
- necessary pipe diameterthat will ensure efficient and stable transportation of the right amount of gas;
- whether pressure losses will be acceptable when moving the required volume of blue fuel in pipes of a given diameter.
Pressure losses occur because hydraulic resistance exists in any gas pipeline. If it is incorrectly calculated, it can lead to the fact that consumers do 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 make specific indicators in the columns.
|Beginning of the plot||End of plot||Estimated consumption m³ / h||Pipeline length||Internal diameter, cm||Initial pressure, Pa||Final pressure, Pa||Pressure drop, Pa|
Such an operation is a state-standardized procedure that is carried out according to the formulas, the requirements set out in SP 42-101–2003.
Calculations are required to carry out the developer. The basis is the data of technical specifications of the pipeline, which can be obtained in your city gas store.
Pipelines requiring settlement
The state requires that hydraulic calculations are 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, the gas pressure should not exceed 3 kPa, at household enterprises (non-production) this indicator is higher and reaches 5 kPa.
The second type of pipelines is designed to supply networks, with various, low, medium pressure through gas control points, as well as supplying gas to individual consumers.
It can be industrial, agricultural, various utilities, and even detached, or attached to industrial, buildings. But in the latter two cases there will be significant pressure limitations.
The specialists listed above are conventionally divided into the following categories:
- house, intra shopthat is, transporting blue fuel inside a building and delivering it to individual units, appliances;
- subscriber branchesused to supply gas from a distribution network to all existing customers;
- distributionused for supplying gas to certain territories, for example, cities, their individual regions, industrial enterprises. Their configuration is different and depends on the characteristics of the layout. The pressure inside the network can be any provided - low, medium, high.
In addition, the hydraulic calculation is performed for gas networks with different numbers of pressure levels, of which there are many varieties.
So, to meet the needs can be used two-stage networks working with gas transported at low, high pressure or low, medium. And also found the use of three-stage and various multistage networks. That is, it all depends on the availability of consumers.
Hydraulic resistance is the main reason for the need to perform this type of calculation. Moreover, it depends on the pipe material
Despite the wide variety of gas pipeline options, hydraulic calculation is similar in any of the cases. As for manufacturing, structural elements with similar materials are used, and the same processes take place inside the pipes.
Hydraulic resistance and its role
As mentioned above, the basis for the calculation is the presence of hydraulic resistance in each pipeline.
It acts on the entire structure of the pipeline, as well as on its individual parts, nodes - tees, places of significant reduction in the diameter of pipes, valves, and various valves. This results in a loss of pressure by the transported gas.
Hydraulic resistance is always the sum of:
- linear resistance, that is, acting along the entire length of the structure;
- local resistance acting on each component of the structure, where there is a change in the speed of gas transportation.
The listed parameters constantly and significantly affect the performance of each pipeline. Therefore, as a result of an incorrect calculation, there will be additional and significant financial losses due to the fact that the project will have to be redone.
It was stated above that the procedure for any hydraulic calculation is regulated by the profile rulebook with the number 42-101–2003.
The document testifies that the main way of performing the calculation is to use a computer with this special programs to calculate the planned pressure loss between sections of the future gas pipeline or the required pipe diameter
Any hydraulic calculation is performed after the creation of a design scheme, including 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 impractical, then other methods allowed by the Code of Practice can be applied.
- calculation by the formulas given in the joint venture is the most complicated method of calculation;
- the calculation of the so-called nomograms is a simpler option than using formulas, because any calculations it is not necessary to produce, because the necessary data is indicated in a special table and is given in the Code, and they just need pick up.
Any of the calculation methods leads to the same results. And therefore, the newly built gas pipeline will be able to provide timely, uninterrupted supply of the planned amount of fuel even during the hours of its maximum use.
PC Calculation Option
Performing calculus using a computer is the least time consuming - all that is required of a person is to insert the necessary data into the corresponding columns.
Therefore, the hydraulic calculation is done in a few minutes, and this operation will 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 conditions:
- gas density;
- kinetic viscosity coefficient;
- gas temperature in your region.
The necessary technical conditions are obtained in the gas outlet of the settlement in which 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.
Using special programs is the simplest method of hydraulic calculation, eliminating the search and study of formulas for carrying out calculations
Next, the developer needs to know the gas flow rate 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 there are often used cooking plates, various heating boilers, and their passports always have the necessary numbers.
In addition, you need to know the number of burners for each plate that will be connected to the pipe.
At the next stage of collecting the necessary data, information is collected on the pressure drop at the installation sites. any equipment - it can be a meter, a valve, a slam shut, a thermal shut-off valve, a filter, etc. items.
In this case, the required numbers are easy to find - 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 should be indicated at the maximum gas consumption.
From a special table attached to the passport of products, you can find information about pressure loss when connecting devices to the network.
In the next step, it is recommended to find out what the pressure of the blue fuel will be at the tie-in point. Such information may contain the technical conditions of its Gorgaz, a previously drawn scheme of the future gas pipeline.
If the network consists of several sections, they must be numbered and indicate the actual length. In addition, for each, you should register all variable indicators separately - this is the total consumption of any device that will be used, pressure drop, other values.
Without fail, a simultaneity factor is required. It takes into account the possibility of joint operation of all gas consumers connected to the network. For example, all heating equipment located in an apartment building or a private house.
Such data is used by a program that performs a hydraulic calculation to determine the maximum load on any section or in the entire gas pipeline.
For each individual apartment or house, this coefficient should not be calculated, since its values are known and are shown in the attached table below:
A table with coefficients of simultaneity, the data from which are used for any type of calculations. Simply select the column corresponding to a specific household appliance, and take the desired number.
If at any object it is planned to use more than two heating boilers, furnaces, and capacitive water heaters, then the simultaneity indicator will always be equal to 0.85. As it will be necessary to specify in the appropriate column used for calculation, the program.
The following should indicate pipe diameter, and roughness coefficients will be needed, which will be used in the construction of the pipeline. These values are standard and can be easily found in the Code of Practice.
The effect of pipe material on the calculation
For the construction of gas pipelines can be used pipes made only of certain materials: steel, polyethylene. In some cases, copper products are used. Soon will be massively used metal structures.
Each pipe has a roughness, which leads to linear resistance, which affects the process of moving gas. Moreover, this indicator is significantly higher in steel products than in plastic
Today, the necessary information can be obtained only for steel and polyethylene pipes. As a result, design and hydraulic calculation can be performed only taking into account their characteristics, which is required by the profile Code of Practice. The document also contains the necessary data for the calculation.
The roughness coefficient is always equal 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 specified in the Code. Therefore, they should not be used for the construction of a new gas pipeline, as the experts of the Gorgas Company may require amendments. And this again is an additional cost.
Calculation of consumption in a limited area
If the gas pipeline consists of separate sections, the calculation of the total flow at each of them will have to be carried out separately. But it is not difficult, since already known figures will be required for calculations.
Definition of data using the program
Knowing the initial indicators, having access to the table of simultaneity and to the technical passports of stoves and boilers, you can proceed to the calculation.
To do this, the following actions are performed (an example is given for a low-pressure in-house gas pipeline):
- The number of boilers is multiplied by the performance of each one.
- The resulting value is multiplied by the coefficient of simultaneity for this type of consumers that was refined using a special table.
- The number of cooking plates is multiplied by the performance of each one.
- The value obtained after the previous operation is multiplied by the coefficient of simultaneity, taken from a special table.
- The amounts received for boilers and stoves are summarized.
Such manipulations are carried out for all sections of the pipeline. The obtained data is entered into the corresponding columns of the program, with which the calculus is performed. Electronics does everything else itself.
Calculation using formulas
This type of hydraulic calculation is similar to that 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.
You will also have to spend a lot of time to understand many concepts, questions that a person does not meet when using a special program. In the fairness of the foregoing, you can be sure of, having read the formulas to be used.
The calculation with the help of formulas is complicated, therefore it is not accessible to everyone. The picture shows the formula 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 gas pipelines of low, medium and, of course, high pressure. And this should be remembered, as the error is fraught, and always, with impressive financial costs.
Calculations using nomograms
Any special nomogram is a table where a number of values are indicated, after studying which you can get the necessary 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 an easy way to get the information you need. It is enough to refer to the lines that meet the specified network characteristics.
There are separate nomograms for polyethylene and steel products. When calculating them, standard data were used, for example, the roughness of the inner walls. Therefore, the correctness of the information can not worry.
An example of a hydraulic calculation using the program for low-pressure gas pipelines is given. In the proposed table, all the data that the designer must enter on his own is highlighted in yellow.
They are listed in the paragraph on computerized hydraulic calculation above. This is the gas temperature, the 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 coefficient of simultaneity.
The columns in the picture are highlighted in yellow in which the designer himself must enter the indicators. Below is the formula for calculating the flow on the site
It is worth paying attention to the numbering of the plots - it is not invented independently, but taken from the previously drawn scheme, where similar figures are indicated.
Next, the actual length of the pipeline and the so-called estimated length, which is longer, is 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 eliminate insufficient gas pressure at consumers. The program performs the calculation independently.
The total consumption in cubic meters, for which a separate column is provided, is calculated in advance at each site. If a multi-family house, then you need to specify the number of housing, and starting with the maximum value, as can be seen in the corresponding column.
It is mandatory to include all elements of the pipeline in the table, with the passage of which pressure is lost. In the example, the valve is thermosetting, shut-off and counter. The value of loss in each case was taken in the passport of the product.
With the help of one program, you can do calculations for all types of gas pipelines. In the picture calculus for the network of medium pressure
The internal diameter of the pipe is indicated according to the technical task, if the Gorgas has any requirements, or from a previously drawn scheme. In this case, in most sections it is registered at a size of 5 cm, since most of the gas pipeline goes along the facade, and the local city gas station requires that the diameter be not less.
If it is even superficial to become familiar with the example of performing hydraulic calculations, it is easy to see that, in addition to the values entered by the person, there are a large number of others. This is all the result of the program, since after entering the numbers in the concrete columns highlighted in yellow, the calculation work is completed for the person.
That is, the calculation itself takes place rather quickly, after which the received data can be sent for approval to the city gas department.
Conclusions and useful video on the topic
This video makes it possible to understand how the hydraulic calculation begins, from where designers take the necessary data:
The following video shows an example of one of the types of computer calculation:
Then you can see an example of calculation using a computer program:
To perform a hydraulic calculation using a computer, as the profile code of rules allows, it is enough to spend a little time getting to know the program and collecting the necessary data.
But all this has no practical significance, since the drafting of a project is a much more extensive procedure and involves many other issues. Therefore, the majority of citizens will have to seek help from specialists.
Have any questions, found shortcomings, or can you supplement our material with valuable information? Leave your comments, ask questions, share your experience in the block below.