Hydraulic calculation of gas pipelines. Hydraulic calculation of gas pipelines Plotting a graph of the city’s annual gas consumption

When designing pipelines, the choice of pipe sizes is carried out on the basis of a hydraulic calculation that determines the internal diameter of the pipes to pass the required amount of gas with acceptable pressure losses or, conversely, the pressure loss when transporting the required amount of gas through log houses of a given diameter.

Resistance to gas movement in pipelines is composed of linear friction resistances and local resistances: friction resistances “work” along the entire length of pipelines, and local ones are created only at points of change in the speed and direction of gas movement (corners, tees, etc.). Detailed hydraulic calculations of gas pipelines are carried out according to the formulas given in SP 42-101–2003, which take into account both the mode of gas movement and the hydraulic resistance coefficients of gas pipelines. A shortened version is provided here.

To calculate the internal diameter of the gas pipeline, use the formula:

Dp = (626Аρ 0 Q 0 /ΔP beat) 1/m1 (5.1)

Where dp is the estimated diameter, cm; A, m, m1 - coefficients depending on the network category (pressure) and gas pipeline material; Q 0 - calculated gas flow, m 3 / h, under normal conditions; ΔРsp - specific pressure loss (Pa/m for low pressure networks)

ΔP beat = ΔP add /1.1L (5.2)

Here ΔР add - permissible pressure loss (Pa); L - distance to the most distant point, m. Coefficients A, m, m1 are determined from the table below.

The internal diameter of the gas pipeline is taken from the standard range of internal diameters of pipelines: the nearest larger one is for steel gas pipelines and the nearest smaller one is for polyethylene ones.

The calculated total gas pressure loss in low-pressure gas pipelines (from the gas supply source to the most remote device) is accepted to be no more than 1.80 kPa (including in distribution gas pipelines - 1.20 kPa), in gas inlet pipelines and internal gas pipelines - 0.60 kPa.

To calculate the pressure drop, it is necessary to determine such parameters as the Reynolds number, which depends on the nature of the gas movement, and the coefficient of hydraulic friction λ. The Reynolds number is a dimensionless ratio that reflects the mode in which a liquid or gas moves: laminar or turbulent.

The transition from laminar to turbulent regime occurs upon reaching the so-called critical Reynolds number R eкp. At Re< Re кp течение происходит в ламинарном режиме, при Re >Re kp - turbulence may occur. The critical value of the Reynolds number depends on the specific type of flow.

The Reynolds number as a criterion for the transition from laminar to turbulent flow and back works relatively well for pressure flows. When transitioning to free-flow flows, the transition zone between laminar and turbulent regimes increases, and the use of the Reynolds number as a criterion is not always valid.

The Reynolds number is the ratio of the inertial forces acting in the flow to the viscous forces. Also, the Reynolds number can be considered as the ratio of the kinetic energy of a fluid to the energy loss over a characteristic length.
The Reynolds number in relation to hydrocarbon gases is determined by the following relationship:

Re = Q/9πdπν (5.3)

Where Q is gas flow, m 3 / h, under normal conditions; d - internal diameter of the gas pipeline, cm; π - number pi; ν is the coefficient of kinematic viscosity of gas under normal conditions, m 2 /s (see Table 2.3).
The diameter of the gas pipeline d must meet the condition:

(n/d)< 23 (5.4)

Where n is the equivalent absolute roughness of the inner surface of the pipe wall, taken equal to:

For new steel ones - 0.01 cm;
- for used steel ones - 0.1 cm;
- for polyethylene, regardless of operating time - 0.0007 cm.

The coefficient of hydraulic friction λ is determined depending on the mode of gas movement through the gas pipeline, characterized by the Reynolds number. For laminar gas flow (Re ≤ 2000):

λ = 64/Re (5.5)

For critical gas movement mode (Re = 2000–4000):

λ = 0.0025 Re 0.333 (5.6)

If the Reynolds number value exceeds 4000 (Re > 4000), the following situations are possible. For a hydraulically smooth wall at a ratio of 4000< Re < 100000:

λ = 0.3164/25 Re 0.25 (5.7)

For Re > 100000:

λ = 1/(1.82logRe – 1.64) 2 (5.8)

For rough walls at Re > 4000:

λ = 0.11[(n/d) + (68/Re)] 0.25 (5.9)

After determining the above parameters, the pressure drop for low pressure networks is calculated using the formula

P n – P k = 626.1λQ 2 ρ 0 l/d 5 (5.10)

Where P n is the absolute pressure at the beginning of the gas pipeline, Pa; P k - absolute pressure at the end of the gas pipeline, Pa; λ - coefficient of hydraulic friction; l is the estimated length of a gas pipeline of constant diameter, m; d - internal diameter of the gas pipeline, cm; ρ 0 - gas density under normal conditions, kg/m 3 ; Q - gas consumption, m 3 / h, under normal conditions;

Gas consumption in sections of low-pressure external gas distribution pipelines that have gas travel costs should be determined as the sum of transit and 0.5 gas travel costs in a given section. The pressure drop in local resistances (elbows, tees, shut-off valves, etc.) is taken into account by increasing the actual length of the gas pipeline by 5–10%.

For external above-ground and internal gas pipelines, the estimated length of gas pipelines is determined by the formula:

L = l 1 + (d/100λ)Σξ (5.11)

Where l 1 is the actual length of the gas pipeline, m; Σξ - the sum of the local resistance coefficients of the gas pipeline section; d - internal diameter of the gas pipeline, cm; λ is the coefficient of hydraulic friction, determined depending on the flow regime and the hydraulic smoothness of the walls of the gas pipeline.

Local hydraulic resistance in gas pipelines and the resulting pressure losses occur when the direction of gas movement changes, as well as in places where flows separate and merge. Sources of local resistance are transitions from one size of gas pipeline to another, elbows, bends, tees, crosses, compensators, shut-off, control and safety valves, condensate collectors, hydraulic valves and other devices leading to compression, expansion and bending of gas flows. The pressure drop in the local resistances listed above can be taken into account by increasing the design length of the gas pipeline by 5–10%. Estimated length of external overhead and internal gas pipelines

L = l 1 + Σξl e (5.12)

Where l 1 is the actual length of the gas pipeline, m; Σξ - the sum of the local resistance coefficients of a gas pipeline section of length l 1, l e - the conventional equivalent length of a straight section of a gas pipeline, m, the pressure loss on which is equal to the pressure loss in local resistance with the value of the coefficient ξ = 1.

Equivalent length of a gas pipeline depending on the mode of gas movement in the gas pipeline:
- for laminar movement mode

L e = 5.5 10 -6 Q/v (5.13)

For critical gas flow conditions

L e = 12.15d 1.333 v 0.333 /Q 0.333 (5.14)

For the entire region of turbulent gas movement

L e = d/ (5.15)

When calculating internal low-pressure gas pipelines for residential buildings, permissible gas pressure losses due to local resistances, % of linear losses:
- on gas pipelines from the entrances to the building to the riser - 25;
- on risers - 20;
- on intra-apartment wiring - 450 (with a wiring length of 1–2 m), 300 (3–4 m), 120 (5–7 m) and 50 (8–12 m),

Approximate values of the coefficient ξ for the most common types of local resistances are given in Table. 5.2.
The pressure drop in the pipelines of the liquid phase of LPG is determined by the formula:

H = 50λV 2 ρ/d (5.12)

Where λ is the coefficient of hydraulic friction (determined by formula 5.7); V - average speed of movement of liquefied gases, m/s.

Taking into account the anti-cavitation reserve, the average speeds of movement of the liquid phase are accepted:
- in suction pipelines - no more than 1.2 m/s;
- in pressure pipelines - no more than 3 m/s.

When calculating low pressure gas pipelines, the hydrostatic head Hg, daPa, is taken into account, determined by the formula

H g = ±lgh(ρ a – ρ 0) (5.13)

Where g is the acceleration of gravity, 9.81 m/s 2 ; h is the difference in absolute elevations of the initial and final sections of the gas pipeline, m; ρ a - air density, kg/m 3, at a temperature of 0°C and a pressure of 0.10132 MPa; ρ 0 - gas density under normal conditions kg/m 3.

When performing hydraulic calculations of overhead and internal gas pipelines, taking into account the degree of noise created by gas movement, gas movement speeds should be taken as no more than 7 m/s for low-pressure gas pipelines, 15 m/s for medium-pressure gas pipelines, 25 m/s for high-pressure gas pipelines .

Table 5.2. Local resistance coefficients ξ for turbulent gas movement (Re > 3500)

Type of local resistance	Meaning	Type of local resistance	Meaning
Bends:		Condensate collectors	0,5–2,0
bent smooth	0,20–0,15	Hydraulic valves	1,5–3,0
welded segmental	0,25–0,20	Sudden expansion of pipelines	0,60–0,25
Plug valve	3,0–2,0	Sudden narrowing of pipelines	0,4
Valves:		Smooth expansion of pipelines (diffusers)	0,25–0,80
parallel	0,25–0,50	Smooth narrowing of pipelines (confusers)	0,25–0,30
with symmetrical narrowing of the wall	1,30–1,50	Tees
Compensators:		merge threads	1,7
wavy	1,7–2,3	thread separation	1,0
lyre-shaped	1,7–2,4
U-shaped	2,1–2,7

For safe and trouble-free operation of the gas supply, it must be designed and calculated. It is important to perfectly select pipes for mains of all types of pressure, ensuring a stable supply of gas to the devices.

To ensure that the selection of pipes, fittings and equipment is as accurate as possible, a hydraulic calculation of the pipeline is performed. How to make it? Admit it, you are not too knowledgeable about this issue, let's figure it out.

We offer you to familiarize yourself with carefully selected and thoroughly processed information about options for producing hydraulic calculations for gas pipeline systems. Using the data we present will ensure that the devices are supplied with blue fuel with the required pressure parameters. Carefully verified data is based on the regulations of regulatory documentation.

The article describes in great detail the principles and schemes for performing calculations. An example of performing calculations is given. Graphic 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, as well as one of the most important stages of preparation for construction. Whether the gas pipeline will function optimally depends on the correctness of the calculation.

When performing each hydraulic calculation, the following is determined:

necessary, which will ensure efficient and stable transportation of the required amount of gas;
Will the pressure loss be acceptable when moving the required volume of blue fuel in pipes of a given diameter?

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

This table is the result of a hydraulic calculation carried out taking into account the given values. To perform calculations, you will need to enter specific indicators in the columns.

Beginning of the section	End of the section	Estimated flow m³/h	Gas pipeline length	Inner diameter, cm	Initial pressure, Pa	Final pressure, Pa	Pressure drop, Pa
1	2	31,34	120	9,74	2000,00	1979,33	20,67
2	3	31,34	150	9,74	1979,33	1953,48	25,84
3	4	31,34	180	7,96	1953,48	1872,52	80,96
4	5	29,46	90	7,96	1872,52	1836,2	36,32
5	6	19,68	120	8,2	1836,2	1815,45	20,75
6	7	5,8	100	8,2	1815,45	1813,95	1,5

4	8	9,14	140	5	1872,52	1806,38	66,14

6	9	4,13	70	5	1815,45	1809,83	5,62

Such an operation is a state-standardized procedure that is performed in accordance with the formulas and requirements set out in SP 42-101–2003.

The developer is required to carry out the calculations. The data is taken as a basis technical specifications pipelines, which can be obtained from 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 when gas moves are always the same.

These gas pipelines include the following types:

low pressure;
medium, high pressure.

The first ones are intended for transporting fuel to residential buildings, all kinds of public buildings, and household enterprises. Moreover, in private, apartment buildings, and cottages, the gas pressure should not exceed 3 kPa; in household (non-industrial) enterprises this figure is higher and reaches 5 kPa.

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

These can be industrial, agricultural, various public utility enterprises, and even free-standing or attached to industrial buildings. But in the last two cases there will be significant pressure restrictions.

Experts conditionally divide the types of gas pipelines listed above into the following categories:

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

In addition, hydraulic calculations are performed for gas networks with different numbers of pressure stages, of which there are many varieties.

Thus, to meet the needs, two-stage networks can be used, operating with gas transported at low, high pressure or low, medium pressure. Three-stage and various multi-stage networks have also found application. That is, everything depends only on the availability of consumers.

Despite the wide variety of gas pipeline options, the hydraulic calculations are 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 affects the entire pipeline structure, as well as its individual parts, assemblies - tees, places of significant reduction in pipe diameter, shut-off valves, and various valves. This leads to 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 the gas transportation speed changes.

The listed parameters constantly and significantly influence the performance characteristics of each gas pipeline. Therefore, as a result of incorrect calculations, additional and significant financial losses will occur due to the fact that the project will have to be redone.

Rules for performing calculations

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

The document indicates 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 creating a calculation diagram that includes the main indicators. Moreover, the user enters known data into the appropriate columns

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

Which include:

calculation using the formulas given in the SP is the most complex method of calculation;
calculation using so-called nomograms is a simpler option than using formulas, because you don’t have to make any calculations, because the necessary data is indicated in a special table and given in the Code of Rules, and you just need to select them.

Any of the calculation methods leads to the same results. Therefore, the newly built 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 computing option

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

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

To perform it correctly, 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 locality 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.

Each pipe has a roughness, which leads to linear resistance, which affects the process of gas movement. Moreover, this figure is significantly 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 calculations can only be carried out taking into account their characteristics, which is required by the relevant Code of Practice. The document also contains the data necessary 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 ones steel structures- 0.01 cm.

For any other types of pipes this indicator is not indicated in the Code of Practice. Therefore, they should not be used for the construction of a new gas pipeline, since Gorgaz specialists may require adjustments to be made. And these are again additional costs.

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 using the program

Knowing the initial indicators, having access to the simultaneity table and technical data sheets of stoves and boilers, you can begin the calculation.

To do this, perform the following steps (the example is given for a low-pressure intra-house gas pipeline):

The number of boilers is multiplied by the productivity of each of them.
The resulting value is multiplied by the simultaneity coefficient specified using a special table for this type of consumer.
The number of stoves intended for cooking is multiplied by the productivity of each of them.
The value obtained after the previous operation is multiplied by the simultaneity coefficient taken from a special table.
The resulting amounts for boilers and stoves are summed up.

Similar manipulations are carried out for all sections of the gas pipeline. The obtained data is entered into the appropriate columns of the program with which the calculations are performed. The 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 carry out a number of intermediate operations in order to use the obtained values for the final calculation.

You will also have to devote quite a lot of time to understand many concepts and issues that a person does not encounter when using a special program. The validity of the above can be verified by familiarizing yourself with the formulas to be used.

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

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

Calculations using nomograms

Any special nomogram is a table that shows a number of values, by studying which you can obtain the desired indicators without performing calculations. In the case of hydraulic calculations - the diameter of the pipe and the thickness of its walls.

Nomograms for calculation are a simple way to obtain the necessary information. 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 internal walls. Therefore, you don’t have to worry about the correctness of the information.

Calculation example

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

These are listed in the paragraph on computer hydraulic calculations above. These are gas temperature, kinetic viscosity coefficient, and density.

In this case, calculations are carried out for boilers and stoves; therefore, it is necessary to specify the exact number of burners, which can be 2 or 4. Accuracy is important, because the program will automatically select the simultaneity coefficient.

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

It is worth paying attention to the numbering of sections - they are not invented independently, but are taken from a previously drawn up diagram, where similar numbers are indicated.

Next, the actual length of the gas pipeline and the so-called calculated length, which is longer, are written down. 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 prevent insufficient gas pressure among consumers. The program performs the calculations independently.

The total consumption in cubic meters, for which a separate column is provided, at each site is calculated in advance. If the building is multi-apartment, then you need to indicate the number of housing, starting from maximum value, as can be seen in the corresponding column.

It is mandatory to enter into the table all elements of the gas pipeline, during the passage of which pressure is lost. The example shows a thermal shut-off valve, a shut-off valve and a meter. The value of the loss in each case was taken from the product passport.

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

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

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

Conclusions and useful video on the topic

This video makes it possible to understand where hydraulic calculations begin and where designers get the necessary data:

The following video shows an example of one type of computer calculation:

To perform a hydraulic calculation using a computer, as the profile Code of Rules allows, it is enough to spend a little time familiarizing yourself with the program and collecting the necessary data.

But all this has no practical significance, since drawing up a project is a much more extensive procedure and includes many other issues. In view of this, most citizens will have to seek help from specialists.

Do you have any questions, find any shortcomings, or can you add valuable information to our material? Leave your comments, ask questions, share your experience in the block below.

To facilitate calculations based on formulas (VI. 19) - (VI.22), tables and nomograms have been developed. From them, with sufficient accuracy for practical purposes, they determine: based on a given flow rate and pressure loss, the required diameter of the gas pipeline; for a given diameter and losses - the throughput of the gas pipeline; for a given diameter and flow rate - pressure loss; according to known local resistances - equivalent lengths. Each table and nomogram is compiled for gas with a certain density and viscosity and separately for low or medium and high pressure. To calculate low-pressure gas pipelines, tables are most often used, the structure of which is well illustrated in Table. VI.2. The range of pipes in them is characterized by the outer diameter d„, wall thickness s and inner diameter d. Each diameter corresponds to specific pressure loss D R and equivalent length Z 3KB, depending on a certain gas flow V. Nomograms (Fig. VI.3 - VI.7) are the graphic equivalent of the data given in the tables.

Table VI.2

Pressure loss Ar and equivalent lengths in for natural gas (p = 0.73 kg/m 3, v = 14.3 * 10 "* m 2 / sec, steel water and gas pipes according to GOST 3262-62)

d H X« (d), mm
21.3X2.8 (15,7)	26.8X2.8 (21,2)	33.5X3.2 (27,1)	42.3X3.2 (35,9)	48.0X3.5 (41,0)

Note. The numerator shows the pressure loss, kgf/m* per 1 u, the denominator is the invivalent length, and.

A- natural woof, p - 0.73 kg/m*, v = 14.3‘Yu - * m*/sec; b - propane gas, p?= 2 Kf/m *, v "= 3.7* 10~* m"/sec.

Example 17. Through a pipe (GOST 3262-62) dH X s= 26.8 X 2.8 mm long I = 12 m natural gas of low pressure with p = 0.73 kg/m 9 is supplied in quantity V= 4 m 3 / h. A plug valve is installed on the gas pipeline and two 90° bent elbows are installed. Determine pressure loss in the gas pipeline.

Solution. G1o table VJ.2 we find that at flow V= 4 m 9 /h specific friction losses Ar - 0.703 kg/m2 per 1 m, and the equivalent length? Ek p = = 0.52 m. According to pas data. 108 we find the coefficients of local resistance: For a plug valve = 2.0 and for a bent elbow 90°? 2 = 0.3. Calculated length of the gas pipeline according to formula (VI.29) / calculated = 12 + (2.0 + 2-0.3) X 0.52 = = 13.5 m. Required total pressure loss Dr sum - 13.5-0.703 = = 9.52 kg/m2.

Example 18. Along a low-pressure steel gas distribution pipeline assembled from pipes dH X s= 114 X 4 mm, long I = 250 m natural gas is supplied with p = 0.73 kg/m 9 in quantity V- 200 m 3 /h. The geodetic elevation of the end gas pipeline is 18 m higher than the initial one. Determine the pressure loss in the gas pipeline.

Solution. According to the nomogram in Fig. VI.3 we find that at a flow rate V = = 200 m 3 / h, the specific pressure loss due to friction in the gas pipeline d H Xs = 114 X X 4 mm A R - 0.35 kg/m2 per 1 m. To take into account pressure losses in local resistances, we increase the actual length of the gas pipeline by 10%, T.V. I race Ch = 1.1 1fact = 1.1 *250 = 275 m. Total pressure loss due to friction and local resistance Lr SuI = 0.35-275 = 96 kg/m 2.

The transported gas is lighter than air, therefore hydrostatic pressure is created in the gas pipeline. According to formula (VI.24) Ar g ~ 18 (1,293 - 0,73)

*=“10 kg/m2. Then the required pressure loss in the gas pipeline is Ap* aKX = 96 - - 10 = 86 kgf/cm 2.

Example 19. Through a low-pressure steel gas pipeline d H X s = = 21.3-2.8 mm and length I = 10 m propane is supplied in quantity V== 1.2’m 8 /h. A plug valve is installed on the gas pipeline and there is one 90° bent elbow. Determine pressure loss in the gas pipeline.

Solution. According to the nomogram in Fig. VI.4 we find that at gas flow

V= 1.2 m 3 /h specific friction losses Ar= 0.75 kg/m2 per 1 m. According to the nomogram in Fig. VI.5, b for these conditions, the equivalent length of the gas pipeline /ekp = 0.41 m. According to the data on p. 108 local resistance coefficients: for a plug valve?, = 2.0, for a bent bend 90 s ? 2 = 0.3.

Calculated length of the gas pipeline according to formula (VI.29) 1 raS h = 10 + 0.41 (2.0 + + 0.3) = 10.94 11 m. The required total pressure loss Dr sum = 11 X

X 0.75 = 8.25 kg/m2.

Example 20. Through a steel gas pipeline Dy= 200 mm, 1600 m long, natural gas with a density p = 0.73 kg/m 3 is supplied in an amount of 5000 m 8 /h. Determine the excess pressure at the end of the gas pipeline if at the beginning of the gas pipeline it is equal to 2.5 kgf/cm 2.

Solution. According to the nomogram in Fig. VI.7 we find that with gas consumption

V- 5000 m 3 /h for gas pipeline Dy= 200 mm (p - pl)IL= 1.17. Hence the absolute pressure at the end of the gas pipeline

kgf/cm2. Excessive pressure at the end of the gas pipeline R,-= 2.22 kgf/cm 8,

I. Types of network calculations:

1) Optimization and technical and economic calculations solve the problem of selecting the main parameters included in the design task, in particular: choosing the optimal direction and conditions for laying the pipeline, determining the most efficient technological transportation scheme and pipeline parameters, determining the appropriate level of redundancy in system elements, and others

2) Technological calculations include the choice of technology and technological scheme of transportation, justification of the technological structure of the pipeline, determination of the composition and type of equipment used, its operating modes, and others

3) Hydraulic calculations involve determining the pressure and speed of the medium moving through the pipeline in various sections of the pipeline, as well as the pressure loss of the moving flow

4) Thermal calculations include determining the temperature of the transported product, assessing the temperature of the walls of pipelines and equipment, as well as heat loss by pipelines and their thermal resistances

5) Mechanical calculations involve assessing the strength, stability, and deformation of pipelines, structures, installations and equipment under the influence of temperature, pressure and other loads and selecting parameter values that ensure reliable operation under given conditions

6) Calculation of external influences on the transportation process includes determination of ambient temperature, wind, snow and other mechanical loads, assessment of seismicity and others

7) Calculation of the properties of the transported medium involves the determination of physical, chemical, thermodynamic and other characteristics necessary for the design of pipelines and prediction of its operating modes

II. Purpose of hydraulic calculation

The direct task when designing gas pipelines is to determine the internal diameter of the pipes when passing the required amount of gas at pressure losses acceptable for specific conditions.

The inverse problem is to determine the pressure loss at a given flow rate, gas pipeline diameter and pressure.

III. Equations that are the basis for deriving hydraulic calculation formulas

For most problems of calculating gas pipelines, gas movement can be considered isothermal; the pipe temperature is assumed to be equal to the ground temperature. Therefore, the determining parameters will be: gas pressure p, its density ρ and speed ω. To determine them, we need a system of 3 equations:

1) Darcy equation in differential form, which determines the pressure loss to overcome resistance:

Where is the friction coefficient, d is the internal diameter

2) Equation of state to take into account changes in density due to changes in pressure:

3) Continuity equation:

Where M is mass flow, Q 0 is volume flow reduced to normal conditions

Solving the system, we obtain the basic equation for calculating high and medium pressure gas pipelines:

To calculate urban gas pipelines T≈T 0, therefore:

To calculate low pressure, let’s substitute , and since ≈P 0, the formula will take the form:

IV. The main components of gas movement resistance

· Linear friction resistance along the entire length of the gas pipeline

· Local resistance in places where speeds and direction of movement change

Based on the ratio of local losses and pressure losses along the length of the network, there are:

Short – local losses commensurate with losses along the length

Long - local losses are negligible in relation to the loss along the length (5-10%)

V. Basic formulas for hydraulic calculations according to
SP 42-101-2003

1. The pressure drop in a section of the gas network can be determined using the formulas:

a) For medium and high pressure:

P n - absolute pressure at the beginning of the gas pipeline, MPa;

P k - absolute pressure at the end of the gas pipeline, MPa;

P 0 = 0.101325 MPa;

Coefficient of hydraulic friction;

l is the estimated length of a gas pipeline of constant diameter, m;

d - internal diameter of the gas pipeline, cm;

Gas density under normal conditions, kg/m 3 ;

Q 0 - gas flow, m 3 / h, under normal conditions;

b) For low pressure:

P n - excess pressure at the beginning of the gas pipeline, Pa;

P k - excess pressure at the end of the gas pipeline, Pa

c) In pipelines of the liquid phase of LPG:

V – average speed of movement of liquefied gases, m/s: in suction pipelines – no more than 1.2 m/s; in pressure pipelines – no more than 3 m/s

2. Mode of gas movement through a gas pipeline, characterized by the Reynolds number:

where ν is the coefficient of kinematic viscosity of gas under normal conditions, 1.4 10 -6 m 2 /s

Condition for hydraulic smoothness of the inner wall of the gas pipeline:

n is the equivalent absolute roughness of the inner surface of the pipe wall, taken equal for new steel - 0.01 cm, for used steel - 0.1 cm, for polyethylene, regardless of the time of operation - 0.0007 cm/

3. The coefficient of hydraulic friction λ is determined depending on the value of Re:

a) for laminar gas movement Re ≤ 2000:

b) for the critical mode of gas movement 2000≤ Re ≤ 4000:

c) for Re > 4000 - depending on the fulfillment of the condition of hydraulic smoothness of the inner wall of the gas pipeline:

For a hydraulically smooth wall:

· at 4000< Re < 100000:

· at Re > 100000:

For rough walls:

4. Preliminary selection of diameters of network sections

, Where

· d p - design diameter [cm]

· A, B, m, m1 - coefficients determined according to tables 6 and 7 SP 42-101-2003 depending on the network category (pressure) and gas pipeline material

· - design gas consumption, m 3 /h, under normal conditions;

· ΔPsp - specific pressure loss (Pa/m - for low pressure networks, MPa/m - for medium and high pressure networks)

5. When calculating low-pressure gas pipelines, the hydrostatic head Hg, daPa, is taken into account, determined by the formula:

where g is the acceleration of gravity, 9.81 m/s 2 ;

h is the difference in absolute elevations of the initial and final sections of the gas pipeline, m;

ρ a - air density, kg/m 3, at a temperature of 0°C and pressure
0.10132 MPa;

ρ 0 - gas density under normal conditions, kg/m 3

6. Local resistances:

For external above-ground and internal gas pipelines, the estimated length of gas pipelines is determined by the formula:

where l 1 is the actual length of the gas pipeline, m;

Σξ – sum of local resistance coefficients of the gas pipeline section

The pressure drop in local resistances (elbows, tees, shut-off valves, etc.) can be taken into account by increasing the actual length of the gas pipeline by 5 - 10%

When calculating internal low-pressure gas pipelines for residential buildings, it is allowed to determine gas pressure losses due to local resistance in the amount of:

On gas pipelines from inputs into the building:

· to the riser – 25% of linear losses

· on risers – 20% linear losses

On internal wiring:

· with a wiring length of 1 - 2 m – 450% of linear losses

· with a wiring length of 3 - 4 m – 300% linear losses

· with a wiring length of 5 - 7 m – 120% linear losses

· with a wiring length of 8 - 12 m – 50% of linear losses

More detailed data on the value of ξ are given in the reference book by S.A. Rysin:

7. Calculation of ring networks of gas pipelines should be carried out by linking gas pressures at the nodal points of the calculation rings. The discrepancy between pressure loss in the ring is allowed up to 10%. When performing hydraulic calculations of overhead and internal gas pipelines, taking into account the degree of noise created by gas movement, gas movement speeds should be taken as no more than 7 m/s for low-pressure gas pipelines, 15 m/s for medium-pressure gas pipelines, 25 m/s for high-pressure gas pipelines .

VI. According to the network configuration there are:

1) Simple: pipelines with a constant diameter and no branches

2) Complex: having at least one branch

a) Dead-end (usually low-pressure networks, they allow you to save on pipelines because they have a minimum length)

b) Ring networks (usually high- and medium-pressure networks, have the possibility of redundancy, i.e., continued supply of gas to facilities in the event of an accident in one of the sections by redistributing flows)

c) Mixed (combine the capabilities of stub and ring networks, usually obtained from stub networks by looping them - adding a jumper between strategically important points)

Self-test questions

11. Types of network calculations

12. Purposes of hydraulic calculation

13. The concept of resistance to gas movement

14. Determination of the main constants and variables included in the hydraulic calculation formulas

15. Taking into account local resistance in the hydraulic calculation of gas pipelines

16. Acceptable residuals and gas velocities in networks

17. Classification of networks by configuration.

B2L10 SGRGP

Lecture 10

DESIGN AND CONSTRUCTION OF GAS PIPELINES FROM POLYETHYLENE PIPES WITH A DIAMETER OF UP TO 300 MM - SP 42-101-96 (2017) Current in 2017

HYDRAULIC CALCULATION OF GAS PIPELINES

1. Hydraulic calculations of gas pipelines should be performed, as a rule, on electronic computers using the optimal distribution of calculated pressure losses between sections of the network.

If it is impossible or impractical to perform calculations on an electronic computer (lack of an appropriate program, certain small sections of gas pipelines, etc.), hydraulic calculations can be performed using the formulas given below or nomograms compiled using these formulas.

2. The calculated pressure losses in high and medium pressure gas pipelines should be taken within the pressure limits accepted for the gas pipeline.

The calculated pressure loss in low-pressure gas distribution pipelines should be taken to be no more than 180 daPa (mm water column), incl. in street and intra-block gas pipelines - 120, in yard and internal gas pipelines - 60 daPa (mm water column).

3. The values of the calculated gas pressure loss when designing gas pipelines of all pressures for industrial, agricultural and municipal enterprises are taken depending on the gas pressure at the connection point, taking into account the technical characteristics accepted for installation, gas burners, automatic safety devices and automatic control of the technological regime of thermal units.

4. Hydraulic calculations of medium and high pressure gas pipelines throughout the entire area of turbulent gas movement should be made according to the formula:

where: P_1 – maximum gas pressure at the beginning of the gas pipeline, MPa;

Р_2 – the same, at the end of the gas pipeline, MPa;

l – design length of a gas pipeline of constant diameter, m;

theta – coefficient of kinematic viscosity of gas at a temperature of 0°C and a pressure of 0.10132 MPa, m2/s;

Q – gas consumption under normal conditions (at a temperature of 0°C and a pressure of 0.10132 MPa), m3/h;

n – equivalent absolute roughness of the inner surface of the pipe wall, taken for polyethylene pipes equal to 0.002 cm;

po – gas density at a temperature of 0°C and a pressure of 0.10132 MPa, kg/m3.

5. The pressure drop in local resistances (tees, shut-off valves, etc.) can be taken into account by increasing the design length of gas pipelines by 5-10%.

6. When performing hydraulic calculations of gas pipelines using the formulas given in this section, as well as using various methods and programs for electronic computers compiled on the basis of these formulas, the diameter of the gas pipeline should first be determined using the formula:

where: t – gas temperature, °C;

P_m – average gas pressure (absolute) at the design section of the gas pipeline, MPa;

V – gas speed m/s (accepted to be no more than 7 m/s for low-pressure gas pipelines, 15 m/s for medium pressure and 25 m/s for high-pressure gas pipelines);

d_i, Q – the designations are the same as in formula (1).

The obtained value of the gas pipeline diameter should be taken as the initial value when performing hydraulic calculations of gas pipelines.

7. To simplify calculations for determining pressure losses in polyethylene gas pipelines of medium and high pressure, it is recommended to use the one shown in Fig. 1 nomogram developed by the VNIPIGazdobycha and GiproNIIGaz institutes for pipes with a diameter of 63 to 226 mm inclusive.

Calculation example. It is required to design a gas pipeline with a length of 4500 m, a maximum flow rate of 1500 m3/h and a pressure at the connection point of 0.6 MPa.

Using formula (2), we first find the diameter of the gas pipeline. It will be:

We accept the nearest larger diameter according to the nomogram; it is 110 mm (di=90 mm). Then, using the nomogram (Fig. 1), we determine the pressure loss. To do this, draw a straight line through the point of a given flow rate on the Q scale and the point of the resulting diameter on the d_i scale until it intersects with the I axis. The resulting point on the I axis is connected to a point of a given length on the l axis and the straight line continues until it intersects with the axis. Since the l scale determines the length of the gas pipeline from 10 to 100 m, for the example under consideration we reduce the length of the gas pipeline by 100 times (from 9500 to 95 m) and the corresponding increase in the resulting pressure drop is also 100 times. In our example, the value 106 will be:

0.55 100 = 55 kgf/cm2

We determine the value of P_2 using the formula:

A negative result means that pipes with a diameter of 110 mm will not provide transport of a given flow rate of 1500 m3/h.

We repeat the calculation for the next larger diameter, i.e. 160 mm. In this case, P2 will be:

= 5.3 kgf/cm2 = 0.53 MPa

The positive result obtained means that the project needs to lay a pipe with a diameter of 160 mm.

Rice. 1. Nomogram for determining pressure loss in polyethylene gas pipelines of medium and high pressure

8. The pressure drop in low-pressure gas pipelines should be determined using the formula:

where: Н – pressure drop, Pa;

n, d, theta, Q, rho, l – the designations are the same as in formula (1).

Note: for aggregated calculations, the second term indicated in parentheses in formula (3) can be neglected.

9. When calculating low-pressure gas pipelines, the hydrostatic head Hg, mm water column, should be taken into account, determined by the formula:

where: h – difference in absolute elevations of the initial and final sections of the gas pipeline, m;

po_a – air density, kg/m3, at a temperature of 0°C and a pressure of 0.10132 MPa;

ro_o – the designation is the same as in formula (1).

10. Hydraulic calculations of ring gas pipeline networks should be performed by linking gas pressures at the nodal points of the calculation rings with maximum use of the permissible gas pressure loss. The discrepancy between pressure losses in the ring is allowed up to 10%.

When performing hydraulic calculations of above-ground and internal gas pipelines, taking into account the degree of noise created by the movement of gas, gas movement speeds should be taken within 7 m/s for low-pressure gas pipelines, 15 m/s for medium-pressure gas pipelines, 26 m/s for gas pipelines high pressure.

11. Considering the complexity and labor intensity of calculating the diameters of low-pressure gas pipelines, especially ring networks, it is recommended to carry out this calculation on a computer or using known nomograms for determining pressure losses in low-pressure gas pipelines. A nomogram for determining pressure losses in low-pressure gas pipelines for natural gas with rho = 0.73 kg/m3 and theta = 14.3 106 m2/s is shown in Fig. 2.

Due to the fact that the indicated nomograms were compiled for the calculation of steel gas pipelines, the obtained diameter values, due to the lower coefficient, the roughness of polyethylene pipes, should be reduced by 5-10%.

Rice. 2. Nomogram for determining pressure losses in low-pressure steel gas pipelines

A gas pipeline is a structural system whose main purpose is gas transportation. The pipeline helps to carry out the movement of blue fuel to the final point, that is, to the consumer. To make this easier, gas enters the pipeline under a certain pressure. For reliable and correct operation of the entire gas pipeline structure and its adjacent branches, a hydraulic calculation of the gas pipeline is required.

Why is a gas pipeline calculation necessary?

Calculation of the gas pipeline is necessary to identify possible resistance in the gas pipe.
Correct calculations make it possible to qualitatively and reliably select the necessary equipment for a gas structural system.
After the calculation has been made, you can best select the correct pipe diameter. As a result, the gas pipeline will be able to provide a stable and efficient supply of blue fuel. Gas will be supplied at the design pressure, it will be quickly and efficiently delivered to all the necessary points of the gas pipeline system.
Gas lines will operate optimally.
With proper calculation, the design should not contain unnecessary or excessive indicators when installing the system.
If the calculation is done correctly, the developer can save financially. All work will be carried out according to the plan, only the necessary materials and equipment will be purchased.

The network is located within the city limits gas pipes wires At the end of each pipeline through which gas must flow, special gas distribution systems are installed, also called gas distribution stations.
When gas is delivered to such a station, a redistribution of pressure occurs, or rather, the gas pressure decreases.
Then the gas flows to the regulatory point, and from there to a network with higher pressure.
The highest pressure pipeline is connected to the underground storage facility.
To regulate daily fuel consumption, special stations are installed. They are called gas tank stations.
Gas pipes, in which gas flows at high and medium pressure, serve as a kind of replenishment of gas pipelines with low gas pressure. In order to control this, there are adjustment points.
To determine the pressure loss, as well as the exact flow of the entire required volume of blue fuel to the final destination, the optimal pipe diameter is calculated. Calculations are made by hydraulic calculation.

If gas pipes are already installed, then using calculations you can find out the pressure loss during the movement of fuel through the pipes. The dimensions of the existing pipes are also immediately indicated. Pressure losses occur due to resistance.

There is local resistance that occurs at turns, at points of change in gas velocity, and when the diameter of a particular pipe changes. More often than not, friction resistance occurs; it occurs regardless of turns and gas speed; its distribution point is the entire length of the gas line.

The gas pipeline has the ability to carry gas both to industrial enterprises and organizations, and to municipal consumer areas.

Using calculations, the points where low pressure fuel needs to be supplied are determined. Such points most often include residential buildings, commercial premises and public buildings, small utility consumers, some small boiler houses.

Hydraulic calculation with low gas pressure through a pipeline

It is approximately necessary to know the number of residents (consumers) in the design area where low-pressure gas will be supplied.
The entire volume of gas per year is taken into account, which will be used for various needs.
The value of fuel consumption by consumers for a certain time is determined by calculations; in this case, a reading of one hour is taken.
The location of gas distribution points is determined and their number is calculated.

The pressure drops of the gas pipeline section are calculated. In this case, such areas include distribution points. As well as the intra-house pipeline, subscriber branches. Then the total pressure drops of the entire gas pipeline are taken into account.

The area of all individual pipes is calculated.
The population density of consumers in a given area is determined.
The gas flow rate is calculated based on the area of each individual pipe.
Computational work is carried out according to the following indicators:

calculated data on the length of the gas pipeline section;
actual data on the length of the entire section;
equivalent data.

For each section of the gas pipeline, it is necessary to calculate the specific travel and node costs.

Hydraulic calculation with average fuel pressure in the gas pipeline

When calculating a gas pipeline with medium pressure, the initial gas pressure reading is initially taken into account. This pressure can be determined by observing the fuel supply from the main gas distribution point to the conversion area and the transition from high pressure to medium distribution. The pressure in the structure must be such that the indicators do not fall below the minimum permissible values during peak load on the gas pipeline.

The calculations apply the principle of pressure variation, taking into account the unit length of the measured pipeline.

To perform the most accurate calculation, calculations are performed in several stages:

At the initial stage, it becomes possible to calculate the pressure loss. The losses that occur in the main section of the gas pipeline are taken into account.
Then the gas flow rate for a given section of pipe is calculated. Based on the obtained average pressure loss values and fuel consumption calculations, it is established what the required pipeline thickness is and the required pipe sizes are determined.
All possible pipe sizes are taken into account. Then, using the nomogram, the amount of losses for each of them is calculated.

If the hydraulic calculation of a pipeline with an average gas pressure is correct, then the pressure loss on the pipe sections will have a constant value.

Hydraulic calculation with high fuel pressure through a gas pipeline

It is necessary to carry out a hydraulic calculation program based on the high pressure of concentrated gas. Several versions of the gas pipe are selected; they must meet all the requirements of the resulting project:

The minimum pipe diameter that can be accepted within the project for the normal functioning of the entire system is determined.
The conditions under which the gas pipeline will be operated are taken into account.
Specific specifications are specified.

The area in the area where the gas pipeline will pass is being studied. The site plan is thoroughly reviewed to avoid any errors in the project during further work.
The project diagram is shown. Its main condition is that it goes around the ring. The diagram must clearly show the various branches to the consumption stations. When drawing up a diagram, make the minimum length of the pipe path. This is necessary to ensure that the entire gas pipeline operates as efficiently as possible.
In the diagram shown, sections of the gas main are measured. Then the calculation program is executed, taking into account the scale, of course.
The obtained readings are changed, the estimated length of each pipe section shown in the diagram is slightly increased, by about ten percent.
Computational work is carried out to determine what the total fuel consumption will be. In this case, the gas consumption at each section of the pipeline is taken into account, then it is summed up.
The final stage of calculating a pipeline with high gas pressure will be determining the internal size of the pipe.

Why is a hydraulic calculation of an intra-house gas pipeline necessary?

During the period of calculation work, the types of necessary gas elements are determined. Devices that are involved in the regulation and delivery of gas.

There are certain points in the project where gas elements will be placed in accordance with the standards, which also take into account safety conditions.

Shows a diagram of the entire intra-house system. This makes it possible to identify any problems in time and carry out installation accurately.

In terms of fuel supply, the number of living spaces, bathroom and kitchen is taken into account. In the kitchen, the presence of such components as a hood and chimney is taken into account. All this is necessary in order to properly install devices and pipelines for the delivery of blue fuel.

In this case, as in the calculation of a high-pressure gas pipeline, the concentrated volume of gas is taken into account.

The diameter of the section of the intra-house main is calculated according to the consumed amount of blue fuel.

Pressure losses that may occur along the gas delivery route are also taken into account. The design system should have the lowest possible pressure losses. In intra-house gas systems, a decrease in pressure is a fairly common occurrence, so calculating this indicator is very important for the efficient operation of the entire pipeline.

In high-rise buildings, in addition to pressure changes and differences, hydrostatic head is calculated. The phenomenon of hydrostatic pressure occurs because air and gas have different densities, resulting in this type of pressure in a low pressure gas pipeline system.

Calculations are made of the size of gas pipes. The optimal pipe diameter can ensure the lowest pressure loss from the redistribution station to the point of gas delivery to the consumer. In this case, the calculation program must take into account that the pressure drop should not exceed four hundred pascals. This pressure drop is also included in the distribution area and conversion points.

When calculating gas consumption, it is taken into account that the consumption of blue fuel is uneven.

The final stage of the calculation is the sum of all pressure drops; it takes into account the total loss coefficient on the main line and its branches. The total indicator will not exceed the maximum permissible values; it will be less than seventy percent of the nominal pressure indicated by the instruments.

A gas pipeline is a structural system whose main purpose is to transport gas. The pipeline assists in moving natural gas to the consumer, that is, to the final destination. To make this easier, gas enters the pipeline at a certain pressure. For the correct and reliable operation of the entire gas pipeline structure, as well as its adjacent branches, there is a need for a hydraulic calculation of the gas pipeline.

Why do you need a gas pipeline calculation?

The gas line must be calculated in order to identify possible resistance in the gas pipe.
Correct calculations allow you to reliably and efficiently select the necessary equipment for a gas structural system.
After the calculation has been made, it is possible to select the most effective pipe diameter. This will result in an efficient and stable flow of natural gas through the pipeline.
Gas pipelines will operate in optimal mode.
With correct design calculations, there should be no excessive or unnecessary indicators when installing the system.
If the calculation is carried out correctly, the developer has the opportunity to save money. All necessary work will be carried out according to the agreed scheme, and only necessary equipment and materials.

How does the gas main system work?

Within the city there is a network of gas pipelines. At the end of each pipeline through which gas will be supplied, special gas distribution systems are installed, which are also called gas distribution stations.
After the gas is delivered to such a station, the pressure is redistributed, or more precisely, the gas pressure is reduced.
Next, the gas is sent to a regulatory point, and from there to a network with a higher pressure level.
The pipeline with the highest pressure level is connected to the underground gas storage facility.
In order to regulate the daily consumption of natural gas, special gas tank stations are being installed.
Gas pipes, in which gas flows at medium and high pressure, serve as a kind of recharge for gas pipelines with low gas pressure. To control this process, there are adjustment points.
In order to determine what the pressure loss will be, as well as the exact supply of the entire required volume of natural gas to the final destination, the optimal pipe diameter is calculated. These calculations are made by hydraulic calculation.

If gas pipes have already been installed, then using calculations it is possible to find out the pressure loss during the movement of natural gas through the pipes. The dimensions of the existing pipes are also immediately indicated. Pressure loss occurs due to resistance.

There is local resistance that occurs when the diameter of the pipes changes, at points of change in gas speed, and at turns. There is also often frictional drag that occurs regardless of whether cornering is present or what the gas flow rate is. The place of its distribution is the entire length of the gas main.

The gas pipeline allows gas to be supplied both to municipal consumer areas and to industrial organizations and enterprises.

Using calculations, the points at which low-pressure gas needs to be supplied are determined. Most often, such points include individual small boiler houses, small utility consumers, public buildings and commercial premises, and residential buildings.

Hydraulic calculation of pipelines with low gas pressure

You should know approximately the number of consumers (residents) in the design area to which low-pressure gas will be supplied.
The entire volume of gas per year that will be used for various needs is accounted for.
Through calculations, the value of gas consumption by consumers is determined for a specific period of time, in this case it is one hour.
The location and number of gas distribution points are established.

The pressure drops of the gas pipeline section are calculated. In our case, these areas include distribution points and in-house pipelines, and subscriber branches. After this, the total pressure drops throughout the entire gas pipeline are taken into account.

All pipes are calculated separately.
The population density of consumers is established in this area.
The natural gas consumption is calculated based on the area of each individual pipe.
Computational work is being carried out on a number of the following indicators:
Equivalent data;
Actual data on the length of the entire section;
Calculated data for the length of the gas pipeline section.

For each section of the gas pipeline, it is necessary to calculate the specific node and travel costs.

Hydraulic calculation of pipelines with average gas pressure

When calculating gas pipelines with an average level of gas pressure, the first thing to take into account is the indication of the initial gas pressure. This pressure can be determined by observing the fuel supply from the main gas distribution point to the conversion area and transition from high level pressure to the average distribution. The pressure in the structure must be such that during peak load on the gas pipeline the indicators do not fall below the minimum permissible values.

The calculations use the principle of pressure variation, taking into account the unit length of the measured pipeline.

In order to make the calculation as accurately as possible, calculations are carried out in several stages:

At the initial stage, pressure loss is calculated. Losses occurring in the main section of the gas pipeline are taken into account.
After this, the gas flow rate for a given section of pipe is calculated. According to calculations of fuel consumption and the obtained average pressure loss values, it is established what thickness of the pipeline is required, and the required pipe sizes are also determined.
All possible pipe sizes are taken into account. After this, the amount of loss for each size is calculated from the monogram.

If the hydraulic calculation of a pipeline with average gas pressure is carried out correctly, then the pressure loss on the pipe sections will have a constant value.

Hydraulic calculation of pipelines with high gas pressure

The hydraulic calculation program should be carried out based on the high pressure of the concentrated gas. Several versions of the gas pipe are selected, which must meet all the requirements of the resulting project:

The minimum pipe diameter that can be adopted within the project for the normal functioning of the entire system as a whole is determined.
The conditions in which the gas pipeline will be operated are taken into account.
The specific specification is being clarified.

After this, hydraulic calculations are made at the following stages:

The area where the gas pipeline will pass is being clarified. In order to avoid errors in the project when carrying out further work, the site plan is thoroughly reviewed.
The project diagram is shown. The main condition of this scheme is that it must pass along the ring. The diagram must clearly distinguish different branches to consumption stations. When drawing up a diagram, the length of the pipe path is kept to a minimum. This is necessary in order to make the operation of the entire gas pipeline as efficient as possible.
In the diagram shown, sections of the gas main are measured. After this, the calculation program is executed, and, of course, the scale is taken into account.
The resulting readings change slightly. The estimated length of each pipe section shown in the diagram increases by approximately ten percent.
In order to determine the total fuel consumption, computational work is performed. At the same time, gas consumption is taken into account at each section of the pipeline, after which it is summed up.
The final stage of calculating a pipeline with a high level of gas pressure is to determine the internal size of the pipe.

Why do you need a hydraulic calculation of an in-house gas pipeline?

During the period of calculation work, the types of required gas elements are determined. The devices involved in the delivery and regulation of gas depict a diagram of the entire intra-house system. This allows you to identify various problems in a timely manner, as well as accurately carry out installation work.

There are certain points in the project where, according to the standards, gas elements will be placed. Also, according to these standards, safety conditions are taken into account.

In terms of fuel supply, the kitchen room, bathroom and number of living spaces are taken into account. In the kitchen, the presence of elements such as a chimney and hood are also taken into account. All this is necessary in order to carry out high-quality installation of instruments and pipelines for the delivery of natural gas.

Hydraulic calculation of the intra-house gas system

In this case, just as when calculating a gas pipeline with a high level of gas pressure, the concentrated volume of gas is taken into account.

According to the consumed amount of natural gas, the diameter of the section of the intra-house pipeline is calculated.

Pressure losses that may occur during the delivery of blue fuel are also taken into account. The design system must have the minimum possible pressure loss. In intra-house gas systems, a decrease in pressure is a fairly common occurrence, so calculating this indicator is very important to ensure that the operation of the entire gas pipeline is as efficient as possible.

In high-rise buildings, in addition to pressure differences and changes, hydrostatic head is calculated. Hydrostatic pressure occurs due to the fact that gas and air have different densities, resulting in the formation of this type of pressure in gas systems with a low level of gas pressure.

The dimensions of gas pipes are calculated. An optimally selected pipe diameter is able to ensure a minimum level of pressure loss from the redistribution station to the point of delivery of natural gas to the consumer. In this case, the calculation program must take into account that the pressure drop should not exceed four hundred pascals. Also, such a pressure difference is included in the conversion points and distribution area.

When calculating natural gas consumption, you should take into account the fact that gas consumption is uneven.

The final stage of the calculation is the sum of all pressure drops, which takes into account the total loss coefficient on the main line itself, as well as its branches. The total indicator will not exceed the maximum permissible values, but will be less than seventy percent of the nominal pressure indicated by the instruments.

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Calculation of the capacity of a low pressure gas pipeline

Calculation of the capacity of a low pressure gas pipeline. Hydraulic calculation of gas pipelines DESIGN AND CONSTRUCTION OF GAS PIPELINES FROM POLYETHYLENE PIPES WITH DIAMETER UP TO 300 MM - SP 42-101-96

Calculation of gas supply systems for the city area

Download: Calculation of gas supply systems for a city area

1. Initial data
2. Introduction
3. Determination of population size
4. Determination of annual heat consumption
4.1. Determination of annual heat consumption for gas consumption in apartments
4.2. Determination of annual heat consumption for gas consumption at enterprises
4.3. Determination of annual heat consumption for gas consumption at enterprises
4.4. Determination of annual heat consumption for gas consumption in healthcare institutions
4.5. Determination of annual heat consumption for gas consumption at bakeries
4.6. Determination of annual heat consumption for heating, ventilation,
4.7. Determination of annual heat consumption when consuming gas for trade needs
4.8. Drawing up a final table of gas consumption in the city
5. Determination of annual and hourly gas consumption by various city consumers
6. Plotting a graph of the city’s annual gas consumption
7. Selection and justification of the gas supply system
8. Determination of the optimal number of gas distribution stations and hydraulic fracturing units
8.1. Determination of the number of GDS
8.2. Determining the optimal number of hydraulic fracturing
9. Typical schemes GRP and GRU
9.1. Gas control points
9.2. Gas control units
10. Selection of equipment for gas control points and installations
10.1. Selecting a pressure regulator
10.2. Selection of safety shut-off valve
10.3. Safety relief valve selection
10.4. Filter selection
10.5. Choice shut-off valves
11. Structural elements of gas pipelines
11.1. Pipes
11.2. Gas pipeline details
12. Hydraulic calculations of gas pipelines
12.1. Hydraulic calculation of high and medium pressure ring networks
12.1.1. Calculation in emergency modes.
12.1.2. Branch calculation
12.1.3. Calculation for normal flow distribution
12.2. Hydraulic calculation of low pressure gas networks
12.3. Hydraulic calculation of low-pressure dead-end gas pipelines
13. Bibliography

1. Initial data

1. City area plan: Option 4.

2. Construction area: Novgorod.

3. Population density: 270 people/ha.

4. Gas supply coverage (%):

– cafes and restaurants (4). 50

– baths and laundries (2). 100

– bakeries (2). 50

– medical institutions (2). 50

– kindergartens (1). 100

– boiler rooms (1). 100

5. Proportion of population (%) using:

– cafes and restaurants. 10

6. Heat consumption for an industrial enterprise: 250 10 6 MJ/year.

7. Initial gas pressure in the ring gas pipeline: 0.6 MPa.

8. Final gas pressure in the ring gas pipeline: 0.15 MPa.

9. Initial gas pressure in the low pressure network: 5 kPa.

10. Permissible pressure drop in the low pressure network: 1200 Pa.

2. Introduction

The purpose of supplying cities and towns with natural gas is to:

· improvement of living conditions of the population;

· replacement of more expensive solid fuel or electricity in thermal processes with industrial enterprises, thermal power plants, at public utility enterprises, in medical institutions, public catering establishments, etc.;

·improving the environmental situation in cities and towns, since natural gas, when burned, practically does not emit harmful gases into the atmosphere.

Natural gas is supplied to cities and towns through gas pipelines starting from gas production sites (gas fields) and ending at gas distribution stations (GDS) located near cities and towns.

To supply gas to all consumers in the cities, a gas distribution network is being built, gas control points or installations (GRP and GRU) are being equipped, control points and other equipment necessary for the operation of gas pipelines are being built.

In cities and towns, gas pipelines are laid only underground.

On the territory of industrial enterprises and thermal power plants, gas pipelines are laid above the ground on separate supports, along overpasses, as well as along the walls and roofs of industrial buildings.

The laying of gas pipelines is carried out in accordance with the requirements of SNiP.

Natural gas is used by the population for combustion in household gas appliances: stoves, water gas heaters, heating boilers

At public utility enterprises, gas is used to produce hot water and steam, bake bread, cook food in canteens and restaurants, and heat premises.

In medical institutions, natural gas is used for sanitary treatment, preparing hot water, and for cooking.

In industrial enterprises, gas is burned primarily in boilers and industrial furnaces. It is also used in technological processes for heat treatment of products manufactured by the enterprise.

In agriculture, natural gas is used to prepare animal feed, to heat agricultural buildings, and in production workshops.

When designing gas networks of cities and towns, the following issues have to be addressed:

·identify all gas consumers in the gasified territory;

· determine gas consumption for each consumer;

· determine the location of gas distribution pipelines;

· determine the diameters of all gas pipelines;

· select equipment for all hydraulic fracturing and main control units and determine their locations;

· select all shut-off valves (valves, taps, valves);

· determine the installation location of control tubes and electrodes to monitor the condition of gas pipelines during their operation;

· develop methods for laying gas pipelines at their intersection with other communications (roads, heating mains, rivers, ravines, etc.);

· determine the estimated cost of construction of gas pipelines and all structures on them;

· analyze measures for the safe operation of gas pipelines.

The scope of issues to be solved from the above list is determined by the assignment for a course or diploma project.

The initial data for designing gas supply networks are:

· composition and characteristics of natural gas or gas deposits;

climatic characteristics of the construction area;

· development plan for a city or town;

· information on the coverage of gas supply to the population;

· characteristics of heat supply sources for the population and industrial enterprises;

· data on the output of industrial enterprises and the rate of heat consumption per unit of this product;

· city population or population density per hectare;

· a list of all gas consumers for the period of gasification and prospects for the development of a city or town for the next 25 years;

· list and type of gas-using equipment at industrial and municipal enterprises;

· number of storeys in residential areas.

3.Determination of population

Gas consumption for municipal and heating needs of a city or town depends on the number of residents. If the number of inhabitants is not known exactly, then it can be approximately determined as follows.

Based on population density per hectare of gasified territory.

Where F P– area of the district in hectares, obtained as a result of measurements according to the development plan;

m– population density, people/ha.

4. Determination of annual heat consumption

Gas consumption for various needs depends on the heat consumption required, for example, for cooking, washing clothes, baking bread, producing a particular product at an industrial enterprise, etc.

It is very difficult to accurately calculate gas consumption for household needs, since gas consumption depends on a number of factors that cannot be accurately taken into account. Therefore, gas consumption is determined by average heat consumption rates obtained on the basis of statistical data. Typically, these standards are determined per person, or per breakfast or lunch, or per ton of linen, or per unit of output by an industrial enterprise. Heat consumption is measured in MJ or kJ.

Heat consumption standards according to SNiP for household and utility needs are given in Table 3.1..

4.1 Determination of annual heat consumption for gas consumption in apartments

The calculation formula for determining the annual heat consumption (MJ/year) for gas consumption in apartments is written as

Here Y K– degree of gas supply coverage of the city (determined by the task);

N– number of inhabitants;

Z 1 – the proportion of people living in apartments with centralized hot water supply (determined by calculation);

Z 2 – the proportion of people living in apartments with hot water supply from gas water heaters (determined by calculation);

Z 3 – the proportion of people living in apartments without a centralized hot water supply and without gas water heaters (determined by calculation);

gK1, gK2, gK3– norms of heat consumption (Table 3.1) per person per year in apartments with the corresponding Z.

For the population using gas Z 1 + Z 2 + Z 3 = 1.

Q K = 1 48180 (2800 0,372 + 8000 0,274 + 4600 0,354) = 232256,508 (MJ/year).

4.2 Determination of annual heat consumption for gas consumption at consumer service enterprises

The heat consumption for these consumers takes into account the gas consumption for washing clothes in laundries, for washing people in bathhouses, for sanitary treatment in disinfection chambers. Very often in cities and towns, laundries and baths are combined into one enterprise. Therefore, the heat consumption for them must also be combined.

Heat consumption in baths is determined by the formula

Where ZB– proportion of the city’s population using baths (set);

YB– the share of city baths using gas as fuel (set);

gB– rate of heat consumption for washing one person;

All g are accepted according to Table 3.1 from.

The formula includes the frequency of visiting baths, equal to once a week.

Heat consumption for washing clothes in laundries is determined by the formula:

Here ZP– share of the city population using laundries (set);

YP– share of laundries in the city. using gas as fuel (set);

gP– rate of heat consumption per 1 ton of dry laundry (table).

The formula includes the average rate of receipt of laundry in laundries, equal to 100 tons per 1000 inhabitants.

All g are accepted according to Table 3.1 from.

QP = 100 (0,2 1 48180) / 1000 18800 = 18115680 (MJ/year),

4.3 Determination of annual heat consumption for gas consumption in public catering establishments

Heat consumption in catering establishments takes into account gas consumption for cooking in canteens, cafes and restaurants.

It is believed that the same amount of heat is used to prepare breakfast and dinner. The heat consumption for preparing lunch is greater than for preparing breakfast or dinner. If a catering establishment operates all day, then heat consumption should be for breakfast, dinner, and lunch. If the enterprise operates half a day, then the heat consumption is made up of the heat consumption for preparing breakfast and lunch, or lunch and dinner.

Heat consumption in public catering establishments is determined by the formula:

Here ZP.OP– share of the city population using public catering establishments (set);

Y P.OP– the share of public catering establishments in the city that use gas as fuel (set);

It is believed that of the people who constantly use canteens, cafes and restaurants, each person visits them 360 times a year.

All g are accepted according to Table 3.1 from.

4.4 Determination of annual heat consumption for gas consumption in healthcare institutions

When using gas in hospitals and sanatoriums, it should be taken into account that their total capacity should be 12 beds per 1000 residents of a city or town. Heat consumption in healthcare institutions is necessary for preparing food for patients, for sanitizing linen, instruments, and premises.

It is determined by the formula:

Here YZD – degree of gas supply coverage of city healthcare institutions (set);

gZD– annual rate of heat consumption in medical institutions;

Where gP , gG– norms of heat consumption for cooking and preparing hot water in medical institutions.

All g are accepted according to Table 3.1 from.

4.5. Determination of annual heat consumption for gas consumption in bakeries and bakeries

When baking bread and confectionery, which constitute the main product of these gas consumers, the difference in heat consumption for different types of products should be taken into account. The rate of bread baking per day per 1000 inhabitants is assumed to be 0.6 ¸ 0.8 tons. This standard includes baking both black and white bread, as well as baking confectionery. It is very difficult to determine exactly how much of which type of product residents consume. Therefore, the general norm of 0.6 ¸ 0.8 tons per 1000 inhabitants can be roughly divided in half, assuming that bakeries and bakeries bake black and white bread equally. Baked confectionery products can be accounted for separately, for example, at the rate of 0.1 tons per 1000 inhabitants per day.

When calculating gas consumption, the gas supply coverage of bakeries and bakeries should be taken into account. The total heat consumption (MJ/year) for bread factories and bakeries is determined by the formula:

Where YHZ– share of gas supply coverage of bread factories and bakeries (set);

gCH– rate of heat consumption for baking 1 ton of black bread

gBH– rate of heat consumption for baking 1 ton of white bread

gCI– the rate of heat consumption for baking 1 ton of confectionery products.

All g are accepted according to Table 3.1 from.

QHZ= 0,5 48180 365 / 1000=34775721,75 (MJ/year).

4.6 Determination of annual heat consumption for heating, ventilation, hot water supply of residential and public buildings

The annual heat consumption (MJ/year) for heating and ventilation of residential and public buildings is calculated using the formula:

tVN, tSR.O, tRO– temperatures, respectively, of the internal air of heated premises, the average external air for the heating period, the calculated external temperature for a given construction area according to [2], O C.

K, K 1– coefficients taking into account heat consumption for heating and ventilation of public buildings (in the absence of specific data, they take K = 0.25 And K 1 = 0,4 );

Z– average number of hours of operation of the ventilation system of public buildings during the day ( Z= 16 );

nABOUT– duration of the heating period in days;

F– total area of heated buildings, m2;

gOB– an aggregated indicator of the maximum hourly heat consumption for heating residential buildings according to Table 3.2 from , MJ/h. m 2;

Using the data from Table 2.1 we calculate F:

F= 3200 48,875 + 4200 66,351565 = 435076,5 (m2),

The annual heat consumption (MJ/year) for centralized hot water supply from boiler houses and thermal power plants is determined by the formula:

Where gGW– the aggregated indicator of the average hourly heat consumption for hot water supply is determined according to Table 3.3 (MJ/person h.);

NGW– the number of city residents using hot water supply from boiler houses or thermal power plants, people;

b– coefficient taking into account the reduction in hot water consumption in the summer ( b=0.8);

tHZ, tHL– temperature of tap water in the heating and summer periods, °С (in the absence of data, take tHL= 15, tHZ= 5 ).

4.7 Determination of annual heat consumption when consuming gas for the needs of trade, consumer services enterprises, schools and universities

In schools and universities in the city, gas can be used for laboratory work. For these purposes, the average heat consumption per student is assumed to be 50 MJ/(person year):

Where N– number of residents, (persons),

coefficient 0,3 – share of the population school age and younger

4.8 Drawing up a final table of gas consumption in the city

Final table of gas consumption in the city.

Annual heat consumption,

Annual gas consumption,

Hours of use max. Loads, m, hour/year

Hourly gas consumption

Heating and ventilation

5. Determination of annual and hourly gas consumption by various city consumers

The annual gas consumption in m 3 /year for any consumer in a city or region is determined by the formula:

QiYEAR– annual heat consumption of the corresponding gas consumer (taken from column 3 of Table 1);

Q N R– lower calorific value (MJ/m 3), determined by the chemical composition of the gas (in the absence of data, it is taken equal to 34 MJ/m 3).

The results of calculations of annual gas costs for all consumers in the city are entered into Table 1 in Column 4.

Gas consumption in the city by various consumers depends on many factors. Each consumer has its own characteristics and consumes gas in its own way. There is a certain unevenness in gas consumption between them. Taking into account the unevenness of gas consumption is carried out by introducing an hourly maximum coefficient, which is inversely proportional to the period during which the annual gas resource is consumed at its maximum consumption

Where m– number of hours of maximum load use per year, h/year

By using Km The hourly gas consumption is determined for each consumer in the city (m 3 / h)

Coefficient values m are given in table 4.1.

The number of hours of maximum use for heating boiler houses is determined by the formula:

6. Plotting a graph of the city’s annual gas consumption

Annual gas consumption schedules are fundamental both for planning gas production and for selecting and justifying measures to regulate uneven gas consumption. In addition, knowledge of annual gas consumption schedules has great importance for the operation of urban gas supply systems, as it allows you to correctly plan the demand for gas by month of the year, determine the required power of urban consumers - regulators, plan reconstruction and repair work on gas networks and their structures. Using gaps in gas consumption to shut down individual sections of the gas pipeline and gas control points for repairs, it is possible to carry out repairs without disrupting the gas supply to consumers [3].

Different gas consumers in the city take gas from gas pipelines in different ways. Heating boiler houses and thermal power plants have the greatest seasonal unevenness. The most stable consumers of gas are industrial enterprises. Residential consumers have a certain unevenness in gas consumption, but much less compared to heating boiler houses.

In general, the unevenness of gas consumption by individual consumers is determined by a number of factors: climatic conditions, the way of life of the population, the operating mode of an industrial enterprise, etc. It is impossible to take into account all the factors that influence the gas consumption regime in the city. Only the accumulation of a sufficient amount of statistical data on gas consumption by various consumers can give an objective description of the city in terms of gas consumption.

The city's annual gas consumption schedule is constructed taking into account the average statistical data on gas consumption by month of the year for various categories of consumers. The total gas consumption throughout the year is broken down by month. Gas consumption for each month in total gas consumption is determined based on the following calculation

Where qi– share of a given month in total annual gas consumption, %.

Table 5.1 provides data for determining monthly gas costs for various categories of consumers.

The share of annual gas consumption in each month of the heating and ventilation load is determined by the formula

nM– number of heating days in a month.

Gas consumption for hot water supply in each month can be considered uniform. This gas flow determines the minimum load of the boiler room in the summer.

The monthly gas costs determined by the formula are depicted on the graph of the city’s annual gas consumption in the form of ordinates, constant for a given month. After constructing all ordinates for each month for all categories of consumers, the total annual consumption is plotted by month. This is done by summing the ordinates of all consumers within each month.

7. Selection and justification of the gas supply system

Gas supply systems are a complex set of structures. The choice of a city's gas supply system is influenced by a number of factors. This is, first of all: the size of the territory being gasified, the features of its layout, population density, the number and nature of gas consumers, the presence of natural and artificial obstacles to the laying of gas pipelines (rivers, dams, ravines, railways, underground structures, etc.). When designing gas supply systems are developing a number of options and making their technical and economic comparison. The most advantageous option is used for construction.

Depending on the maximum gas pressure, city gas pipelines are divided into the following groups:

· high pressure category 1 with pressure from 0.6 to 1.2 MPa;

· average pressure from 5 kPa to 0.3 MPa;

· low pressure up to 5 kPa;

High and medium pressure gas pipelines serve to supply medium and low pressure urban distribution networks. They carry the bulk of gas to all consumers in the city. These gas pipelines are the main arteries supplying the city with gas. They are made in the form of rings, semi-rings or rays. Gas is supplied to high and medium pressure gas pipelines from gas distribution stations (GDS).

Modern systems of urban gas networks have a hierarchical construction system, which is linked to the above classification of gas pipelines by pressure. The upper level consists of high-pressure gas pipelines of the first and second categories, the lower level consists of low-pressure gas pipelines. The gas pressure gradually decreases when moving from a high level to a lower one. This is done using pressure regulators installed on the hydraulic fracturing unit.

According to the number of pressure stages used in urban gas networks, they are divided into:

· two-stage, consisting of high or medium pressure and low pressure networks;

· three-stage, including high, medium and low pressure gas pipelines;

· multi-stage, in which gas is supplied through gas pipelines of high (1 and 2 categories) pressure, medium and low pressure.

The choice of a gas supply system in a city depends on the nature of gas consumers who need gas of appropriate pressure, as well as on the length and load of gas pipelines. The more diverse gas consumers are and the greater the length and load of gas pipelines, the more complex the gas supply system will be.

In most cases, for cities with a population of up to 500 thousand people, a two-stage system is the most economically feasible. For large cities with a population of more than 1,000,000 people and the presence of large industrial enterprises, a three or multi-stage system is preferable.

8. Determination of the optimal number of gas distribution stations and hydraulic fracturing units

8.1 Determination of the number of GDS

Gas distribution stations are at the head of gas supply systems. Through them, the ring gas pipelines of high or medium pressure are fed. Gas is supplied to the GDS from main gas pipelines at a pressure of 6 ¸ 7 MPa. At the gas distribution station, the gas pressure decreases to high or medium. In addition, gas at the gas distribution station acquires a specific odor. It will be odorized. Here the gas is also subjected to additional purification from mechanical impurities and dries.

Choosing the optimal number of gas distribution stations for a city is one of the most important issues. With an increase in the number of gas distribution stations, the loads and range of action of city highways decrease, which leads to a decrease in their diameters and a reduction in metal costs. However, an increase in the number of gas distribution stations increases the costs of their construction and the construction of main gas pipelines supplying gas to gas distribution stations increases operating costs due to the maintenance of GDS service personnel.

When determining the number of GDS, you can focus on the following:

· for small cities and towns with a population of up to 100 ¸ 120 thousand people, the most rational are systems with one gas distribution system;

· for cities with a population of 200 ¸ 300 thousand people, the most rational are systems with two and three gas distribution stations;

· for cities with a population of more than 300 thousand people, systems with three gas distribution stations are the most economical.

GDSs are usually located outside the city limits. If there is more than one GDS, then they are located on different sides of the city. GDS are usually connected by two strings of gas pipelines, which provides more high reliability gas supply to the city. Very large gas consumers (CHPs, industrial enterprises, metallurgical plants, etc.) are supplied directly from the gas distribution system.

8.2 Determination of the optimal number of hydraulic fracturing

Gas control points are at the head of low-pressure gas distribution networks that supply gas to residential buildings. The optimal number of hydraulic fracturing is determined from the relation

Where V hour– hourly gas consumption for residential buildings, m 3 /h;

V OPT – optimal gas flow through the hydraulic fracturing, m 3 /h.

For determining V OPT, it is necessary to first determine the optimal radius of hydraulic fracturing, which should be within 400 ¸ 800 meters. This radius is determined by the formula:

R OPT = 249 (DP 0.081 / j 0.245 (m e) 0.143) (m),

Where DP – calculated pressure drop in low pressure networks (1000 ¸ 1200 Pa);

j– coefficient of density of low-pressure networks, 1/m;

m– population density in the area of GRP operation, people/ha;

e– specific hourly gas consumption per person, m 3 / person h, which is set or calculated if the number of residents (N) consuming gas is known and the amount of gas (V) consumed by them per hour is known

e=V/N(m 3 /person h)

The optimal gas flow through the hydraulic fracturing is determined from the relationship:

The resulting optimal number of hydraulic fracturing units is used in the design of low-pressure gas networks. Network gas distribution stations are usually located in the center of the gasified territory so that all gas consumers are located from the gas station at approximately the same distances. The maximum distance of hydraulic fracturing from the projected main gas pipelines of high or medium pressure should be 50 ¸ 100 meters.

j= 0,0075 + 0,003 270 / 100 = 0,0156 (1m),

e = 2627,33 / 48180 = 0,0545 (m 3 / person.h),

ROPT = 249 1000 0,081 / = 822 (m),

Let's correct it V TO HOUR in accordance with the obtained number of hydraulic fracturing:

9. Typical hydraulic fracturing and gas distribution systems

Gas control points (GRP) are located in separate buildings made of brick or reinforced concrete blocks. The placement of hydraulic fracturing in populated areas is regulated by SNiP. At industrial enterprises, hydraulic fracturing stations are located at the sites where gas pipelines enter their territory.

The GRP building has 4 separate rooms (Fig. 8.1):

· main room 2, where all gas control equipment is located;

· room 3 for instrumentation;

· room 4 for heating equipment with a gas boiler;

· room 1 for inlet and outlet gas pipelines and manual regulation of gas pressure.

In a typical hydraulic fracturing system shown in Fig. 8.1, the following nodes can be distinguished:

· gas input/output unit with bypass 7 for manual regulation of gas pressure after hydraulic fracturing;

· mechanical gas purification unit with filter 1;

· gas pressure control unit with regulator 2 and safety shut-off valve 3;

· gas flow measurement unit with diaphragm 6 or gas meter.

The instrumentation room contains recording pressure gauges that measure gas pressure before and after hydraulic fracturing, a gas flow meter, and a differential pressure gauge that measures the pressure drop across the filter. In the main hydraulic fracturing room, indicating pressure gauges are installed that measure gas pressure before and after hydraulic fracturing; expansion thermometers that measure the gas temperature at the gas inlet into the hydraulic fracturing unit and after the gas flow measurement unit.

An axonometric diagram of hydraulic fracturing gas pipelines is shown in Fig. 8.2. On the diagram in conventional images in accordance with GOST 21.609-83, pipelines, shut-off valves, regulators (2), safety shut-off valves (3), filter (1), hydraulic valve (5), spark plugs for releasing gas into the atmosphere (10,9,8) are shown. diaphragm (6) and bypass (7).

The gas pipeline from the city network of medium or high pressure approaches the hydraulic fracturing underground. Having passed the foundation, the gas pipeline rises into the room (1). Gas is removed from the hydraulic fracturing system in the same way. Insulating flanges (11) are installed on the gas pipeline at the gas inlet and outlet to the hydraulic fracturing unit.

High- or medium-pressure gas is purified from mechanical impurities in the filter (1) in the hydraulic fracturing unit. After the filter, the gas is directed to the control line. Here the gas pressure is reduced to the required level and maintained constant using the regulator (2). The safety shut-off valve (3) closes the control line in cases where the gas pressure after the regulator increases or decreases beyond the permissible limits. The upper valve response limit is 120% of the pressure maintained by the pressure regulator. The lower valve setting limit for low pressure gas pipelines is 300 – 3000 Pa; for medium pressure gas pipelines – 0.003 – 0.03 MPa.

The safety relief valve (PSV) (4) protects the gas network after hydraulic fracturing from a short-term increase in pressure within 110% of the pressure value maintained by the pressure regulator. When the PSC is triggered, excess gas is released into the atmosphere through the safety gas pipeline (9).

In the hydraulic fracturing room it is necessary to maintain a positive air temperature of at least 10 °C. For this purpose, the gas distribution center is equipped with a local heating system or connected to the heating system of one of the nearest buildings.

To ventilate the hydraulic fracturing unit, a deflector is installed on the roof, providing three times air exchange in the main fracturing room. The entrance door to the main fracking room in its lower part must have slots for air passage.

Illumination of the gas distribution center is most often performed externally by installing directional light sources on the windows of the gas distribution center. It is possible to provide explosion-proof lighting for hydraulic fracturing. In any case, switching on the hydraulic fracturing lighting must be done from outside.

Lightning protection and a grounding circuit are installed near the GRP building.

9.2 Gas control units.

Gas control units (GRU) are no different from hydraulic fracturing units in their tasks and operating principle. Their main difference from the GRU is that the GRU can be placed directly in the premises where gas is used, or somewhere nearby, providing free access to the GRU. There are no separate buildings being built for the GRU. The GRU is surrounded by a protective net and warning posters are hung near it. GRUs, as a rule, are constructed in production shops, in boiler houses, and at residential gas consumers. GRU can be carried out in metal cabinets, which are mounted on the external walls of industrial buildings. The rules for the placement of GRU are regulated by SNiP.

In Fig. 8.3 shows an axonometric diagram of a typical GRU. The following notations are used here:

1. filter for mechanical gas purification;

2. steel valves;

3. safety shut-off valve;

4. pressure regulator;

7. safety relief valve;

8. gas flow meter;

9. recording pressure gauges;

10. indicating pressure gauges;

11. differential pressure gauge on the filter;

12. expansion thermometers;

15. steel valves;

16. three-way valves;

17. plug valves on impulse lines;

18.19. plug taps.

In terms of ventilation and lighting, the room where the GRU is located is subject to the same requirements as for the GRU.

10. Selection of equipment for gas control points and installations

The selection of hydraulic fracturing and gas distribution equipment begins with determining the type of gas pressure regulator. After selecting a pressure regulator, the types of safety shut-off and safety relief valves are determined. Next, a filter for gas purification is selected, and then shut-off valves and instrumentation.

10.1 Selecting a pressure regulator

The pressure regulator must ensure that the required amount of gas passes through the hydraulic fracturing system and maintain a constant pressure regardless of the flow rate.

The design equation for determining the capacity of the pressure regulator is selected depending on the nature of the gas flow through the regulator.

At subcritical outflow, when the gas velocity when passing through the regulator valve does not exceed the speed of sound, the design equation is written in the form

At supercritical pressure, when the gas speed in the pressure regulator valve exceeds the speed of sound, the design equation takes the form:

KV– pressure regulator capacity coefficient;

e– coefficient taking into account the inaccuracy of the original model for the equations;

DP – pressure drop in the control line, MPa:

Where P 1– absolute gas pressure before hydraulic fracturing or gas distribution unit, MPa;

P2– absolute gas pressure after hydraulic fracturing or gas injection, MPa;

DP– gas pressure loss in the control line, usually equal to 0.007 MPa ;

rABOUT = 0, 73 -gas density at normal pressure, kg/m 3 ;

T– the absolute temperature of the gas is equal to 283 TO;

Z– coefficient taking into account the deviation of gas properties from the properties of an ideal gas (at P1 £ 1.2 MPa Z = 1 ).

Estimated consumption VR should be greater than the optimal gas flow through the hydraulic fracturing by 15.20%, that is:

The mode of gas flow through the regulator valve can be determined by the relationship

If R 2 / R 1³ 0,5 , then the gas flow will be subcritical and therefore equation one should be applied.

Because R 2 / R 1 3/h gas consumption. The second type of filters is designed to pass high gas flows. The number after FG means the filter capacity in thousands of cubic meters per hour.

To select a filter, it is necessary to determine the gas pressure drop across it at the calculated gas flow through the hydraulic fracturing or gas distribution unit.

For filters, this pressure drop is determined by the formula:

Where DR GR– rated value of the gas pressure drop across the filter, Pa;

VGR– passport value of the filter throughput, m 3 /h;

r ABOUT– gas density under normal conditions, kg/m3;

P 1– absolute gas pressure in front of the filter, MPa;

VR– calculated gas flow through the hydraulic fracturing or gas distribution unit, m 3 /h.

Let's take the filter as the initial one FY 7 – 50 – 6

DP = 0,1 10000 (2260,224 / 7000) 2 0,73 / 0,25 = 304,43 (Pa),

The difference for the hydraulic fracturing filter does not exceed the permissible value of 10,000 Pa, therefore

filter selected FY 7 – 50 – 6.

10.5 Selection of shut-off valves

Shut-off valves (gate valves, valves, plug valves) used in hydraulic fracturing and gas distribution units must be designed for a gas environment. The main criteria when choosing shut-off valves are the nominal diameter D U and the operating pressure P U.

Gate valves are used with both retractable and non-retractable spindles. The former are preferable for above-ground installation, the latter for underground installation.

Valves are used in cases where increased pressure loss can be neglected, for example, on impulse lines.

Plug valves have significantly lower hydraulic resistance than valves. They are distinguished by the tightening of the conical plug into tension and stuffing box types, and according to the method of connecting to pipes - into coupling and flange types.

The materials for the manufacture of shut-off valves are: carbon steel, alloy steel, gray and ductile iron, brass and bronze.

Shut-off valves made of gray cast iron are used at a gas operating pressure of no more than 0.6 MPa. Steel, brass and bronze at pressures up to 1.6 MPa. The operating temperature for cast iron and bronze fittings must be no lower than -35 C, for steel – no less than -40 C.

At the gas inlet to the hydraulic fracturing system, steel fittings or fittings made of ductile cast iron should be used. At the outlet of the hydraulic fracturing unit at low pressure, gray cast iron fittings can be used. It is cheaper than steel.

The nominal diameter of the valves in the hydraulic fracturing unit must correspond to the diameter of the gas pipelines at the gas inlet and outlet. It is recommended to select the nominal diameter of valves and taps on the impulse lines of the hydraulic fracturing or gas distribution unit equal to 20 mm or 15 mm.

11. Structural elements of gas pipelines

The following structural elements are used on gas pipelines:

7. supports and brackets for external gas pipelines;

8.systems for protecting underground gas pipelines from corrosion;

9.control points for measuring the potential of gas pipelines relative to the ground and determining gas leaks.

Pipes make up the bulk of gas pipelines; they transport gas to consumers. All pipe connections on gas pipelines are made only by welding. Flange connections are allowed only where shut-off and control valves are installed.

For the construction of gas supply systems, straight-seam, spiral-welded and seamless steel pipes should be used, made from well-weldable steels containing no more than 0.25% carbon, 0.056% sulfur and 0.046% phosphorus. For gas pipelines, for example, carbon steel of ordinary quality, calm, group B GOST 14637-89 and GOST 16523-89 is used, not lower than the second category of grades Art. 2, Art. 3, as well as Art. 4 with a carbon content of no more than 0.25%.

A – standardization (guarantee) of mechanical properties;

B – standardization (guarantee) of the chemical composition;

B – standardization (guarantee) of chemical composition and mechanical properties;

G – standardization (guarantee) of the chemical composition and mechanical properties of heat-treated samples;

D – without standardized indicators of chemical composition and mechanical properties.

– at a design temperature of outside air up to – 40 °C – group B;

– at a temperature of – 40 °C and below – groups B and D.

When choosing pipes for the construction of gas pipelines, you should, as a rule, use pipes made of cheaper carbon steel in accordance with GOST 380-88 or GOST 1050-88.

11.2 Gas pipeline details

Gas pipeline parts include: bends, transitions, tees, plugs.

Bends are installed in places where gas pipelines turn at angles of 90°, 60° or 45°.

Transitions are installed in places where the diameters of gas pipelines change. In the drawings and diagrams they are depicted as follows

Tees are used to close and seal the end parts of dead-end sections of gas pipelines. They are used at points of connection to gas pipelines of consumers.

Plugs are used to close and seal the end parts of dead-end sections of gas pipelines. The plugs are a circle of the appropriate diameter, made of steel of the same grades as the gas pipeline. The designation of gas pipeline parts is given in Appendix 4.

12. Hydraulic calculation of gas pipelines

The main task of hydraulic calculations is to determine the diameters of gas pipelines. From the point of view of methods, hydraulic calculations of gas pipelines can be divided into the following types:

· calculation of high and medium pressure ring networks;

· calculation of dead-end networks of high and medium pressure;

· calculation of multi-ring low-pressure networks;

· calculation of low-pressure dead-end networks.

To carry out hydraulic calculations, you must have the following initial data:

· design diagram of the gas pipeline indicating the numbers and lengths of the sections;

· hourly gas costs for all consumers connected to this network;

· permissible gas pressure differences in the network.

The design diagram of the gas pipeline is drawn up in a simplified form according to the plan of the gasified area. All sections of gas pipelines are, as it were, straightened and their full lengths with all bends and turns are indicated. The locations of gas consumers on the plank are determined by the locations of the corresponding gas distribution stations or gas distribution units.

12.1 Hydraulic calculation of high and medium pressure ring networks

The hydraulic operating mode of high and medium pressure gas pipelines is assigned based on the conditions of maximum gas consumption.

The calculation of such networks consists of three stages:

· calculation in emergency modes;

· calculation for normal flow distribution;

· calculation of branches from a ring gas pipeline.

The design diagram of the gas pipeline is shown in Fig. 2. The lengths of individual sections are indicated in meters. The numbers of settlement areas are indicated by numbers in circles. Gas consumption by individual consumers is designated by the letter V and has the dimension m 3 / h. The places where gas flow changes on the ring are indicated by the numbers 0, 1, 2, . , etc. The gas power supply (GDS) is connected to point 0.

The high-pressure gas pipeline has excess gas pressure at the starting point 0 Р Н =0.6 MPa. Final gas pressure R K = 0.15 MPa. This pressure must be maintained the same for all consumers connected to this ring, regardless of their location.

The calculations use absolute gas pressure, so the calculated Р Н =0.7 MPa and R K =0.25 MPa. The lengths of the sections are converted to kilometers.

To begin the calculation, we determine the average specific pressure difference squared:

Where å l i– the sum of the lengths of all sections in the calculated direction, km.

A multiplier of 1.1 means an artificial increase in the length of the gas pipeline to compensate for various local resistances (turns, valves, compensators, etc.).

Next, using the average ASR and the calculated gas consumption in the corresponding area, according to the nomogram in Fig. 11.2 we determine the diameter of the gas pipeline and, using the same nomogram, we specify the value A for the selected standard gas pipeline diameter. Then, according to the specified value A and estimated length, we determine the exact value of the difference R 2 n – R 2 k Location on. All calculations are tabulated.

12.1.1 Calculation in emergency modes

Emergency modes of operation of a gas pipeline occur when sections of the gas pipeline adjacent to supply point 0 fail. In our case, these are sections 1 and 18. Power supply to consumers in emergency modes must be carried out via a dead-end network with the condition that gas pressure must be maintained at the last consumer R K = 0.25 MPa.

The calculation results are summarized in table. 2 and 3.

Gas consumption in areas is determined by the formula:

Where TO OBi– coefficient of supply of various gas consumers;

V i– hourly gas consumption of the corresponding consumer, m 3 / h.

For simplicity, the supply coefficient is assumed to be 0.8 for all gas consumers.

The estimated length of the gas pipeline sections is determined by the equation:

The average specific pressure square difference in the first emergency mode will be:

A SR = (0,7 2 – 0,25 2) / 1,1 6,06 = 0,064 (MPa 2/km),

Calculation of gas supply systems for the city area

This work is from the Construction section, work Calculation of gas supply systems for a city area on the website abstract plus

All about car tuning

Hydraulic calculation of gas pipelines. Hydraulic calculation of gas pipelines Plotting a graph of the city’s annual gas consumption

Gas pipelines requiring calculations

Hydraulic resistance and its role

Rules for performing calculations

PC computing option

Calculation of flow in a limited area

Defining data using the program

Calculation using formulas

Calculations using nomograms

Calculation example

Conclusions and useful video on the topic

HYDRAULIC CALCULATION OF GAS PIPELINES

Why is a gas pipeline calculation necessary?

Why is a hydraulic calculation of an intra-house gas pipeline necessary?

Why do you need a gas pipeline calculation?

How does the gas main system work?

Hydraulic calculation of pipelines with low gas pressure

Hydraulic calculation of pipelines with average gas pressure

Hydraulic calculation of pipelines with high gas pressure

Why do you need a hydraulic calculation of an in-house gas pipeline?

Hydraulic calculation of the intra-house gas system

Calculation of gas supply systems for the city area

1. Initial data

3.Determination of population

4. Determination of annual heat consumption

5. Determination of annual and hourly gas consumption by various city consumers

6. Plotting a graph of the city’s annual gas consumption

7. Selection and justification of the gas supply system

8. Determination of the optimal number of gas distribution stations and hydraulic fracturing units

9. Typical hydraulic fracturing and gas distribution systems

10. Selection of equipment for gas control points and installations

11. Structural elements of gas pipelines

12. Hydraulic calculation of gas pipelines