An example of hydraulic calculation of a low pressure gas pipeline. Hydraulic calculation of gas pipelines

I. Varieties of network calculations:

1) Optimization and feasibility calculations solve the problem of choosing the main parameters included in the design task, in particular: choosing the optimal direction and conditions for laying the pipeline, determining the most effective technological scheme transportation and pipeline parameters, determination of an 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 modes of operation, and others

3) Hydraulic calculations provide for the determination of the pressure and velocity of the medium moving through the pipeline in various sections of the pipeline, as well as the head loss of the moving stream

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 losses from pipelines and their thermal resistances

5) Mechanical calculations involve an assessment of the strength, stability, and deformation of the pipeline, structures, installations and equipment under the influence of temperature, pressure and other loads and the choice of parameter values ​​that ensure reliable operation under specified conditions

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

7) The calculation of the properties of the transported medium provides for the determination of physical, chemical, thermodynamic and other characteristics necessary for the design of pipelines and forecasting of its operating modes

II. Purpose of hydraulic calculation

A direct task in the design of gas pipelines is to determine the inner diameter of pipes when passing required amount gas at allowable pressure losses for specific conditions.

The inverse problem is the determination of pressure losses at a given flow rate, pipeline diameter and pressure.

III. Equations that are the basis for the derivation of hydraulic calculation formulas

For most gas pipeline calculation problems, the 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's equation in differential form, which determines the pressure loss to overcome resistance:

Where is the coefficient of friction, d is the inner diameter

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

3) Continuity equation:

Where M is the mass flow, Q 0 is the 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, we substitute , and since ≈Р 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 of change in speed and direction of movement

According to 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 calculation according to
SP 42-101-2003

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

a) For medium and high pressure:

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

Р to - absolute pressure at the end of the gas pipeline, MPa;

P 0 \u003d 0.101325 MPa;

Coefficient of hydraulic friction;

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

d - internal diameter of the gas pipeline, cm;

Gas density at normal conditions, kg / m 3;

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

b) For low pressure:

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

Р to - excess pressure at the end of the gas pipeline, Pa

c) In pipelines liquid phase LPG:

V - average speed 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. The mode of gas movement through the gas pipeline, characterized by the Reynolds number:

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

The condition of 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 to 0.01 cm for new steel, 0.1 cm for used steel, and 0.0007 cm for polyethylene, regardless of the operating time

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

a) for laminar gas flow Re ≤ 2000:

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

c) at 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:

For 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 of SP 42-101-2003 depending on the category of the network (by pressure) and the material of the gas pipeline

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

ΔP beats - specific pressure losses (Pa / m - for low pressure networks, MPa / m - for medium and high pressure networks)

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 next smaller one is for polyethylene.

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

where g is the free fall acceleration, 9.81 m/s 2 ;

h is the difference between the absolute marks 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 - the sum of the coefficients of local resistances of the gas pipeline section

The pressure drop in local resistances (elbows, tees, 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 the gas pressure loss due to local resistances in the amount of:

On gas pipelines from inputs to the building:

up to riser - 25% line losses

on risers - 20% line losses

On the interior wiring:

with a wiring length of 1 - 2 m - 450% of line losses

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

with a wiring length of 5 - 7 m - 120% of line losses

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

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

7. The calculation of ring networks of gas pipelines should be carried out with the linkage of gas pressures at the nodal points of the design rings. The problem of pressure loss in the ring is allowed up to 10%. When performing a hydraulic calculation of above-ground and internal gas pipelines, taking into account the degree of noise generated by gas movement, it is necessary to take gas movement speeds of 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, allow you to save on pipelines, because they have a minimum length)

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

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

Questions for self-examination

11. Varieties of network calculations

12. Objectives 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. Accounting for local resistance in the hydraulic calculation of gas pipelines

16. Permissible discrepancies and gas velocities in networks

17. Classification of networks by configuration.

B2L10 SGRGP

Lecture 10

To facilitate calculations based on formulas (VI. 19) - (VI.22), tables and nomograms have been developed. According to them, with sufficient accuracy for practical purposes, they determine: for a given flow rate and pressure loss - the required diameter of the gas pipeline; according to the given diameter and losses - the capacity of the gas pipeline; for a given diameter and flow - pressure loss; according to known local resistances - equivalent lengths. Each table and nomogram is compiled for a 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 an outer diameter d„, wall thickness s and inner diameter d. Each diameter corresponds to the 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 \u003d 0.73 kg / m 3, v \u003d 14.3 * 10 "* m 2 / s, 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, and the denominator is the nvivalent length, u.

A- natural woof, p - 0.73 kg / m *, v \u003d 14.3'Yu - * m * / sec; b - propane gas phase, р?= 2 Kf/m *, v "= 3.7* 10~* m"/sec.

Example 17. Through a pipe (GOST 3262-62) d H X s= 26.8 x 2.8mm long I= 12 m natural gas is supplied at low pressure with p \u003d 0.73 kg / m 9 in the amount V\u003d 4 m 3 / h. A plug cock is installed on the gas pipeline and two 90° bends are installed. Determine the pressure loss in the pipeline.

Solution.Г1о tab. VJ.2 we find that at the expense V\u003d 4 m 9 / h specific friction losses Ar - 0.703 kg / m 2 per 1 m, and the equivalent length? Ek p = = 0.52 m. 108 we find the coefficients of local resistance: For a plug valve = 2.0 and for a 90 ° bend? 2 = 0.3. Estimated length of the gas pipeline according to the formula (VI.29) / calculated = 12 + (2.0 + 2-0.3) X 0.52 = = 13.5 m. The desired total pressure loss Dr sum - 13.5-0.703 = \u003d 9.52 kg / m 2.

Example 18. Through a low-pressure steel distribution pipeline assembled from pipes d H X s= 114 X 4 mm long I= 250 m natural gas is supplied with p \u003d 0.73 kg / m 9 in the amount V- 200 m 3 / h. The geodetic mark 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 losses due to friction in the gas pipeline d H Xs = 114 X X 4 mm A R - 0.35 kg / m 2 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 \u003d 1.1 1act \u003d 1.1 * 250 \u003d 275 m. The total pressure loss due to friction and in local resistances Lr SuI \u003d 0.35-275 \u003d 96 kg / m 2.

The transported gas is lighter than air, so a hydrostatic head is created in the gas pipeline. By formula (VI.24) Ar g ~ 18 (1,293 - 0,73)

* = "10 kg / m 2. Then the required pressure losses in the pipeline 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 long 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° bend. Determine the pressure loss in the pipeline.

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

V = 1.2 m 3 /h specific friction losses Ar\u003d 0.75 kg / m 2 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 coefficients of local resistance: for a plug cock?, = 2.0, for a bent branch 90 s ? 2 = 0.3.

The estimated length of the gas pipeline according to the formula (VI.29) 1 paS h \u003d 10 + 0.41 (2.0 + + 0.3) \u003d 10.94 11 m. The desired total pressure loss Dr sum \u003d 11 X

X 0.75 \u003d 8.25 kg / m 2.

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 2.5 kgf / cm 2.

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

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 / cm 2. Overpressure at the end of the pipeline R,-\u003d 2.22 kgf / cm 8,

Gas consumption is characterized by great unevenness by months of the year, days, weeks and hours of the day.

The mode of operation of the gas supply system of buildings depends on many factors: in residential buildings - on the number and type of installed gas appliances, the degree of improvement of buildings, climatic conditions, time of year, the number of people living in buildings; in municipal, public and industrial buildings, in addition to the above factors - on the nature of the work technological equipment and technological processes, the mode of operation of shops and the enterprise as a whole.

Gas supply systems rely on the supply of the maximum estimated hourly gas flow, which is determined by the annual gas demand.

The maximum hourly gas consumption for household and industrial needs under normal conditions (pressure 0.1 MPa at 0°C) is determined by the formula

where - annual gas consumption, m 3 / year; − coefficient of transition from annual gas consumption to maximum hourly (coefficient of hourly maximum gas consumption).

For residential and public buildings, the estimated hourly gas consumption is determined taking into account the total number of gas appliances of the same type n, the number of their types or groups of the same type m, the nominal gas consumption of one gas appliance - according to the passport or technical specification, m 3 / h, and the coefficient of simultaneous operation of devices , according to the formula

To calculate gas pipelines, a hydraulic calculation is performed from the conditions of uninterrupted gas supply during the hours of maximum gas consumption.

The calculation of gas network pipelines is reduced to the selection of pipe diameters according to the estimated flow rates and gas pressure losses.

Preliminary determination of the diameters of individual calculated sections of gas pipelines is carried out according to the formula

where is the hourly gas consumption, m 3, under normal initial conditions of gas pressure and temperature (0.1 MPa and 0 ° С); − absolute gas pressure in the design section of the gas pipeline, MPa; is the speed of gas movement, m/s.

Next, the gas pressure drop is determined along the length of the gas pipeline and in local resistances: at bends, at joints, at fittings, fittings, etc. Taking into account the additional hydrostatic head of the gas, this pressure drop is compared with the allowable one. If the pressure drop exceeds the allowable value, then the diameters are recalculated in separate calculated sections in the direction of their increase.

The gas pressure drop along the length of the low-pressure gas pipeline is determined depending on the gas movement mode, which is characterized by the Reynolds number:

For the laminar regime of gas flow at Re ≤ 2000, the gas pressure drop due to friction along the length:

for turbulent regime with Re > 4000

where is the pressure drop, Pa; - gas consumption, m 3 / h, under normal conditions (pressure 0.1 MPa and temperature 0 ° C); d is the internal diameter of the gas pipeline, cm; - coefficient of kinematic viscosity of the gas, m 2 /s, under normal initial conditions of the state of the gas; is the density of the gas, kg/m 3 , also under normal initial conditions, the states of the gas; - equivalent absolute roughness of pipes: for steel pipes = 0.01, polyethylene pipes = 0.005; - the estimated length of a gas pipeline section of the same diameter, see.

For internal and external gas pipelines, the calculated length is determined taking into account the reduced length, which depends on the equivalent length of the pipe, taking into account local resistances:

where is the estimated length of the gas pipeline, m; - the actual length of the gas pipeline, m; − reduced length of the gas pipeline, m, equal to:

is the equivalent length at which the gas pressure drop due to friction is equal to the pressure drop in local resistances at = 1; ∑ζ is the sum of the coefficients of local resistances on the estimated section of the gas pipeline with a length of .

The equivalent length is determined by the formulas:

for laminar gas flow

for turbulent gas flow

For residential buildings in low-pressure gas pipelines, local gas pressure losses are determined as part of the losses along the length, i.e. linear losses, %:

from input to riser…………………………………………………………… 25

on risers………………………………………………………………………20

on intra-apartment wiring, depending on the length,%:

up to 2 m………………450 up to 7 m…………………120

» 4 m………………300 » 12 m…………………50

The permissible value of pressure losses is taken:

in internal and yard gas pipelines……………60 daPa (60 mm)

in street and intra-quarter gas pipelines…….120 daPa (120 mm)

Thus, the total allowable pressure loss in low-pressure distribution networks (from hydraulic fracturing to the most distant gas consumer) is 180 daPa.

When hydraulically calculating the gas pipeline network of a building, it is necessary to take into account the natural hydrostatic head of the gas, which occurs due to the fact that the density of the gas is less than the density of air, and as a result, the gas rises up the gas pipeline.

Hydrostatic head, Pa, is determined by the formula

where is the gas rise height, i.e. the difference between the geodetic marks of the initial and

final section of the gas pipeline, m;

And - the density of air and gas, kg / m 3, under normal initial conditions

gas conditions (pressure 0.1 MPa and temperature 0°C).

As a result of the hydraulic calculation, it is necessary to check the condition for ensuring the supply of gas to consumers, i.e. so that the gas pressure at the inlet is not less than the required pressure, taking into account the hydrostatic head:

The required pressure is:

where is the required gas pressure at the dictating gas appliance, Pa or daPa; − hydrostatic head, Pa;

∑ - the sum of pressure losses along the length and in local resistances in the network from the input to the dictating gas appliance, Pa.

If the inequality is not met, then the pipe diameters should be increased in order to reduce the overall pressure loss.

For normal operation of household gas appliances, the nominal gas pressure of 2 (200 mm) or 1.3 kPa (130 mm) is always indicated, therefore, after hydraulic fracturing, the gas pressure is set in the gas network, respectively, 3 (300 mm) or 2 kPa (200 mm).

Thus, when calculating gas networks in buildings, the following conditions must be taken into account:

1. Available gas pressure is created at the inlet equal to the current (actual) pressure plus additional natural gas pressure (hydrostatic head), i.e.

2. The available pressure must always be not less than the required one:

3. The required pressure is the sum of losses along the length and in local resistances and the nominal pressure for gas appliances without natural hydrostatic head.

4. The calculation of the gas network should be performed correctly so that the sum of the allowable pressure losses in gas networks would not be less than the actual losses:

The permissible value of pressure losses in gas networks is given

in table. 25.1.

Hydraulic modes of operation of distributed gas pipelines should be taken from the conditions of creation (with Δ P max.adm.) a system that ensures the stability of the operation of all hydraulic fracturing, burners within the permissible limits of gas pressure.

The calculation of gas pipelines is reduced to determining the required diameters and checking the given pressure drops. In practical calculations of gas networks, nomograms are widely used, built in coordinates and calculated flow Q r.h., for standard diameters.

The nomogram is built on the basis of the formula for the entire region of the turbulent regime.

Where k e And d in cm

The calculation procedure can be as follows:

1. The initial pressure is determined by the operating mode of the gas distribution station or hydraulic fracturing, and the final pressure is determined by the passport characteristics of consumer gas appliances.

2. Choose the most remote points of branched gas pipelines and determine the total length l about. them in selected areas. Each direction is calculated separately.

3. In gas supply systems, the rule of constant pressure drop per unit length of the gas pipeline. Local resistances in the gas pipeline are taken into account by an increase in the total estimated length by 5-10%, (km).

4. Determine the estimated gas flow rates for each section of the gas pipeline Q p . i ..

5. By magnitude A Wed And Q p . i . according to the nomogram, the diameters of the sections are selected, rounding them up according to GOST, i.e. in the direction of lower pressure differences in the area.

6. For the selected standard diameters, according to GOST, the actual values ​​\u200b\u200bare found A d then clarify R to according to the formula

7. Determine the pressure, starting from the beginning of the gas pipeline, because the initial pressure of the GDS or hydraulic fracturing is known. If the pressure R k.d. significantly more than the specified value (more than 10%), then the diameters of the end sections are reduced

main direction.

8. after determining the pressure in this main direction, a hydraulic calculation of gas pipelines-outlets is carried out according to the same method, starting from the second point. In this case, the pressure at the sampling point is taken as the initial pressure.

Problem 9.2.2. Carry out a hydraulic calculation of an extensive high-pressure network, such as a "tree" according to two options: a, b (Fig. 9.4).

A) Q6= 700 m 3 / h; R 6= 0.3 MPa;

Q7= 900 m 3 / h; R 7= 0.33 MPa;

Q4= 1200 m 3 / h; R 4= 0.4 MPa;

Q2= 1700 m 3 / h; R 2= 0.5 MPa;

R GRS= 1 MPa;

l GDS-1= 4 km; l 1-2= 7 km;

l 1-3= 6 km; l 3-4= 8 km;

l 3-5= 10 km; l 5-6= 3 km; l 5-7= 7 km;

b) Q8= 1500 m 3 / h; R 8= 0.3 MPa; Q10= 2000 m 3 / h; R 10= 0.4 MPa; Q 13

2100 m 3 / h; R 13= 0.45 MPa; Q14= 2300 m 3 / h; R 14= 0.6 MPa; R GRS= 0.8 MPa; l GDS-11= =5km; l 11-12=7 km; l 12-14 =l 12-13=8 km; l 11-9=20 km; l 9-8=4 km; l 9-10=6 km;

Rice. 9.5. Nomogram of high and medium pressure gas pipelines.

9.2.3. Calculation of high and medium pressure gas pipelines

Example 9.2.1. Determine the gas flow rate in a gas pipeline 5 km long and 500 mm in diameter. Excess pressure at the beginning and at the end of the gas pipeline, respectively, is equal to p 1\u003d 3 10 5 N / m 3 and p 2\u003d 1 ∙ 10 5 N / m 3. Gas constant 500 (N∙m)/(kg∙K). Gas temperature 5 ° C. Hydraulic resistance coefficient λ =0.02. Gas density 0.7 kg/m 3 .

Solution

Absolute gas temperature

T= 273+5=278 K.

The coefficient of deviation of the value of real gases from the value of ideal gases is taken equal to unity ( z=1).

The mass flow will be

.

Volumetric gas flow

.

Hourly gas consumption

Example 9.2.2. Determine the pressure drop in a horizontal gas pipeline 10 km long, 300 mm in diameter, at a gas flow rate of 500,000 m 3 / day. Gas density 0.7 kg/m3, gas constant R=500 (N∙m)/(kg∙K). Hydraulic resistance coefficient λ =0.015. Coefficient Z=1. The temperature of the gas in the gas pipeline is 7 o C. The absolute pressure at the end of the gas pipeline is p 2\u003d 6 10 5 Pa.

Solution

Let us express the second mass flow rate of gas in terms of volumetric

Determine the difference in the square of pressure

Pressure drop

Example 9.2.3.z= 500 m T= 280 K p 2=5∙10 5 Pa (absolute pressure), R=500 (N∙m)/(kg∙K). Gas pipeline stopped ( M 0=0).

Solution

Determine the value of the coefficient b

Example 9.2.4. Determine the pressure of the gas column in the inclined gas pipeline if Δ z= 280 m, absolute pressure at the starting point of the gas pipeline p 2\u003d 3 10 5 Pa, R=490 (N∙m)/(kg∙K), T=280 K. The gas pipeline is stopped ( M=0).

Solution

Determine the coefficient b

Determine the pressure of the gas column

or R 1 -R 2 is 2% of the pressure at the beginning of the gas pipeline R 1 .

Example 9.2.5. Determine the mass and volume flow rate of methane gas in a gas pipeline 10 km long, with an internal diameter of 0.3 m. The positive difference in the elevations of the gas pipeline is 500 m. The overpressure at the beginning of the gas pipeline is p 1 = 15 kgf / cm 2, at the end of the gas pipeline R 2 \u003d 14 kgf / cm 2. Gas temperature 5 ° C, density ρ \u003d 0.7 kg / m 3, gas constant R=500(N∙m)/(kg∙K).

Solution

Determine the coefficient b

Reduced pressure and temperature

The compressibility coefficient according to the graphs is set equal to 0.95.

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

HYDRAULIC CALCULATION OF GAS PIPELINES

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

If it is impossible or inappropriate to perform the calculation on an electronic computer (lack of an appropriate program, separate small sections of gas pipelines, etc.), it is allowed to make a hydraulic calculation according to the formulas below or nomograms drawn up according to these formulas.

2. Estimated pressure losses in high and medium pressure gas pipelines should be taken within the pressure limits adopted for the gas pipeline.

Estimated pressure losses in low-pressure distribution gas pipelines should be taken no more than 180 daPa (mm water column), incl. in street and intra-quarter gas pipelines - 120, yard and internal gas pipelines - 60 daPa (mm of water column).

3. The values ​​​​of the calculated pressure loss of gas 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 specifications accepted for installation gas burners, safety automation devices and automatic control of the technological regime of thermal units.

4. Hydraulic calculation of medium and high pressure gas pipelines in the entire area of ​​turbulent gas flow 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 is the estimated length of a gas pipeline of constant diameter, m;

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

Q is the gas flow rate under normal conditions (at a temperature of 0°C and a pressure of 0.10132 MPa), m3/h;

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

ro is the density of the gas at a temperature of 0°C and a pressure of 0.10132 MPa, kg/m3.

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

6. When performing a hydraulic calculation of gas pipelines according to 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 be preliminarily determined by the formula:

where: t – gas temperature, °C;

P_m is the average gas pressure (absolute) in the design section of the gas pipeline, MPa;

V - gas velocity m / s (it is assumed not more than 7 m / s for low pressure gas pipelines, 15 m / s - medium and 25 m / s - for high pressure gas pipelines);

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

The obtained value of the diameter of the gas pipeline should be taken as the initial value when performing the hydraulic calculation 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 institutes VNIPIGazdobycha and GiproNIIGaz 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.

According to formula (2), we first find the diameter of the gas pipeline. It will make:

We accept the nearest larger diameter according to the nomogram, it is 110 mm (di = 90 mm). Then, according to the nomogram (Fig. 1), we determine the pressure loss. To do this, draw a straight line through the point of the given flow rate on the Q scale and the point of the obtained diameter on the d_i scale until it intersects with the I axis. The resulting point on the I axis is connected to the point of the given length on the l axis and the straight line continues until it intersects with the axis. Since the scale l 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 a 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

Determine the value of P_2 by the formula:

The obtained negative result means that pipes with a diameter of 110 mm will not provide the 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

A positive result means that the project requires a pipe with a diameter of 160 mm.

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

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

where: H – pressure drop, Pa;

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

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

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

where: h is the difference between the absolute marks of the initial and final sections of the gas pipeline, m;

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

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

10. Hydraulic calculation of ring networks of gas pipelines should be performed with the linkage of gas pressures at the nodal points of the calculated rings with the maximum use of the allowable loss of gas pressure. The problem of pressure loss in the ring is allowed up to 10%.

When performing a hydraulic calculation of above-ground and internal gas pipelines, taking into account the degree of noise generated by gas movement, gas movement speeds should be taken not more than 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. Given the complexity and laboriousness of calculating the diameters of low-pressure gas pipelines, especially ring networks, it is recommended that this calculation be carried out on a computer or using known nomograms to determine pressure losses in low-pressure gas pipelines. A nomogram for determining pressure losses in low-pressure gas pipelines for natural gas with ro = 0.73 kg/m3 and theta = 14.3 106 m2/s is shown in fig. 2.

Due to the fact that these 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

The gas pipeline is a structural system, the main purpose of which is the transportation of gas. The pipeline helps to carry out the movement of blue fuel to the final destination, that is, to the consumer. In order to make it easier to do this, the gas enters the pipeline at a certain pressure. For reliable and correct operation the entire structure of the gas pipeline and its adjacent branches, a hydraulic calculation of the gas pipeline is required.

Why is it necessary to calculate the gas pipeline

1. The calculation of the gas pipeline is necessary to identify possible resistance in the gas pipe.
2. Correct calculations make it possible to qualitatively and reliably select the necessary equipment for a gas structural system.
3. After the calculation, you can best choose the correct pipe diameter. As a result, the gas pipeline will be able to carry out 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 desired points gas pipeline system.
4. Gas pipelines will work in an optimal mode.
5. With proper calculation, the design should not have excessive and excessive indicators when installing the system.
6. If the calculation is done correctly, the developer can save money. All work will be performed according to the scheme, only necessary materials and equipment.

1. A network of gas pipelines is located within the city limits. At the end of each pipeline through which gas must flow, special gas distribution systems are installed, they are also called gas distribution stations.
2. When gas is delivered to such a station, the pressure is redistributed, or rather, the pressure of the gas decreases.
3. Then the gas goes to the regulatory point, and from it to the network with a higher pressure.
4. Pipeline with highest pressure connected to underground storage.
5. To regulate the daily consumption of fuel, special stations are installed. They are called gas stations.
6. Gas pipes, in which gas with high and medium pressure flows, serve as a kind of replenishment of gas pipelines with low gas pressure. In order to control this, there are adjustment points.
7. 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 the gas pipes are already installed, then with the help of calculations it is possible to find out the pressure loss during the movement of fuel 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 on turns, at points of change in gas velocity, when the diameter of a particular pipe changes. Even more often there is resistance during friction, it occurs regardless of the turns and speed of the gas, its place of distribution is the entire length of the gas pipeline.

The gas main has the ability to conduct gas, both to industrial enterprises and organizations, and to municipal consumer sectors.

With the help of calculations, the points where low pressure fuel is needed 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 the pipeline

1. Tentatively, it is necessary to know the number of inhabitants (consumers) in the settlement area where low-pressure gas will be supplied.
2. The entire volume of gas per year is taken into account, which will be used for various needs.
3. 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.
4. The location of gas distribution points is established, their number is counted.

Calculate the pressure drop of the gas pipeline section. In this case, these areas include distribution points. As well as intra-house pipeline, branches of subscribers. Then the total pressure drops of the entire gas pipeline are taken into account.

1. The area of ​​all individual pipes is calculated.
2. The population density of consumers in a given area is established.
3. Calculation of the gas flow rate is performed based on the indication of the area of ​​each individual pipe.
4. Computational work is carried out on the following indicators:

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

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

Hydraulic calculation with average fuel pressure in the gas pipeline

When calculating a gas pipeline with an average pressure, the indication of the initial gas pressure is initially taken into account. Such a 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 allowable values ​​\u200b\u200bat peak load on the gas pipeline.

The calculation applies the principle of pressure change, taking into account the unit length of the measured pipeline.

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

1. At the initial stage, it becomes possible to calculate the pressure loss. Losses that occur in the main section of the gas pipeline are taken into account.
2. Then the calculation of the gas flow rate for this section of the pipe is performed. Based on the obtained average pressure loss and fuel consumption calculations, it is determined what thickness of the pipeline is required, and the required pipe dimensions are determined.
3. All possible pipe sizes are taken into account. Then, according to 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 losses in the pipe sections will have a constant value.

Hydraulic calculation with high fuel pressure through the gas pipeline

It is necessary to execute the computational program of hydraulic calculation on the basis of a high onslaught of concentrated gas. Several versions of the gas pipe are selected, they must meet all the requirements of the received project:

1. Determined minimum diameter pipes, which can be taken as part of the project for the normal functioning of the entire system.
2. It takes into account the conditions under which the operation of the gas pipeline will take place.
3. A special specification is being specified.

1. The area in the area where the gas pipeline will pass is being studied. The plan of the area is thoroughly considered in order to avoid any errors in the project during further work.
2. The project diagram is displayed. Her main condition is that she pass through the ring. The diagram must clearly show the various branches to the consumption stations. When drawing up a diagram, they make the minimum length of the pipe path. This is necessary in order for the entire gas pipeline to operate as efficiently as possible.
3. In the diagram shown, measurements are made of sections of the gas pipeline. Then the calculation program is executed, and, of course, the scale is taken into account.
4. The readings obtained are changed, the estimated length of each pipe section shown in the diagram is slightly increased, by about ten percent.
5. Computational work is being done to determine what the total fuel consumption will be. This takes into account the gas consumption in each section of the pipeline, then it is summed up.
6. The final stage in the calculation of a pipeline with a high gas pressure will be the determination of the internal size of the pipe.

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

During the period of settlement 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.

Depict a diagram of the entire in-house system. This makes it possible to identify any malfunctions in time, to clearly assemble.

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

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

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

Pressure losses that may occur along the gas delivery path are also taken into account. The design system should have the smallest possible pressure loss. In in-house gas systems, a decrease in pressure is a fairly common occurrence, so calculating this indicator is very important for effective work the entire highway.

In high-rise buildings, in addition to changes and pressure drops, hydrostatic head calculations are made. The phenomenon of hydrostatic head occurs due to the fact that air and gas have different densities, resulting in the formation of this species pressure in a low pressure gas pipeline system.

The size of the gas pipes is calculated. The optimal pipe diameter can provide the least pressure loss from the redistribution station to the point of gas delivery to the consumer. In this case, the calculation program should take into account that the pressure drop should not be higher than four hundred pascals. This pressure drop is also included in the distribution area and conversion point.

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 and its branches. The total indicator will not exceed the maximum allowable values, it will be less than seventy percent of the nominal pressure shown by the devices.

A gas pipeline is a structural system, the main purpose of which is to transport gas. The pipeline assists in the movement of natural gas to the consumer, that is, to the final destination. In order to do this more simply, the gas enters the pipeline at a certain pressure. For the correct and reliable operation of the entire structure of the gas pipeline, as well as its adjacent branches, there is a need for a hydraulic calculation of the gas pipeline.

What is the calculation of the gas pipeline

• 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 the 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.
• The operation of gas pipelines will be carried out in the optimal mode.
• With the correct calculation of the structure, there should be no excessive and unnecessary indicators when installing the system.
• If the calculation is carried out correctly, the developer has the opportunity to save financial resources. All necessary work will be carried out according to the agreed scheme, only necessary equipment and materials.

How does the gas pipeline 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 rather, the gas pressure is reduced.
• Further, the gas is sent to the regulatory point, and from it to the network with a higher pressure level.
• The pipeline with the highest pressure level is connected to the underground gas storage.
• In order to regulate the daily consumption of natural gas, special gas holder stations are being installed.
• Gas pipes, in which gas with medium and high pressure flows, serve as a kind of make-up for gas pipelines with low gas pressure. There are adjustment points to control this process.
• In order to determine what the pressure loss will be, as well as the exact flow 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 the installation of gas pipes has already been made, then with the help of calculations it is possible to find out the pressure loss during the period of 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 changing the diameter of the pipes, at the points of change in gas velocity, on bends. There is also often frictional drag that occurs regardless of whether turns are present and also what the gas flow rate is. The place of its distribution is the entire length of the gas pipeline.

The gas main allows gas to be carried both to utility consumer areas and to industrial organizations and enterprises.

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

Hydraulic calculation of pipelines with low gas pressure

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

Calculation of pressure drops of the section of the gas pipeline. In our case, these sections include distribution points and an in-house pipeline, branches of subscribers. After that, the total pressure drops throughout the entire gas pipeline are taken into account.

• All pipes are calculated separately.
• In this area, the density of the population of consumers is established.
• Calculation of natural gas consumption is carried out based on the indication of the area of ​​each individual pipe.
• Computational work is carried out on a number of the following indicators:
• equivalent data;
• The actual length of the entire section;
• Estimated data on the length of the gas pipeline section.

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

Hydraulic calculation of pipelines with medium gas pressure

When calculating gas pipelines with an average level of gas pressure, the indication of the initial gas pressure is taken into account first of all. This pressure can be determined by observing the fuel delivery from the main gas distribution point to the conversion region and the transition from a high pressure level to a medium distribution. The pressure in the structure must be such that at peak load on the gas pipeline, the indicators do not fall below the minimum allowable values.

The calculation uses the principle of pressure change, taking into account the unit length of the measured pipeline.

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

• At the initial stage, the pressure loss is calculated. The losses arising on the main section of the gas pipeline are taken into account.
• After that, the gas flow rate for this section of the pipe is calculated. According to the calculations of the fuel consumption and the resulting average pressure loss, it is determined what thickness of the pipeline is needed, and the required pipe sizes are also found out.
• All possible pipe sizes are taken into account. After that, the amount of losses for each size is calculated from the monogram.

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

Hydraulic calculation of pipelines with high gas pressure

The computational program of the hydraulic calculation should be performed on the basis of a high onslaught of concentrated gas. Several versions of the gas pipe are selected, which must meet all the requirements of the received project:

• The minimum diameter of the pipe is determined, which can be accepted within the framework of the project for the normal functioning of the entire system as a whole.
• The conditions under which the gas pipeline will be operated are taken into account.
• The special specification is being refined.

After that, a hydraulic calculation is carried out according to the following stages:

• The area where the gas pipeline will run is being specified. In order to avoid errors in the project during further work, the site plan is thoroughly considered.
• The project diagram is displayed. The main condition of this scheme is that it must pass through the ring. On the diagram, the different branches to the consumption stations must be clearly distinguishable. When drawing up a diagram, the length of the pipe path is made minimal. This is necessary in order to make the work of the entire gas pipeline as a whole as efficient as possible.
• In the diagram shown, measurements of sections of the gas pipeline are carried out. After that, the calculation program is executed, while, of course, the scale is taken into account.
• The resulting readings change slightly. The calculated length of each section of the pipe shown in the diagram is increased 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 on each section of the highway, after which it is summed up.
• The final stage in the calculation of a pipeline with a high level of gas pressure is to determine the internal size of the pipe.

Why do we need a hydraulic calculation of an intra-house gas pipeline

During the period of settlement work, the types of necessary gas elements are determined. The devices involved in the delivery and regulation of gas depict a diagram of the entire in-house system. This allows you to identify a variety of problems in time, as well as accurately carry out installation work.

There are certain points in the project where, according to the norms, 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 the number of living quarters are taken into account. In the kitchen, the presence of such elements as a chimney, an extractor hood is also taken into account. All this is necessary in order to produce a high-quality installation of instruments and pipelines for the delivery of natural gas.

Hydraulic calculation of the house gas system

In this case, just as in the calculation of 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 highway is calculated.

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

In high-rise buildings, in addition to pressure drops and changes, hydrostatic head calculations are made. Hydrostatic head occurs due to the fact that gas and air have different densities, as a result of which this type of pressure is formed in gas systems with a low gas pressure level.

Calculate the size of the gas pipes. 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 the fact that the pressure drop should not exceed four hundred pascals. Also, such a pressure drop is put into the conversion points and the distribution area.

When calculating the consumption of natural gas, one 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 allowable values, but will be less than seventy percent of the nominal pressure shown by the instruments.

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Calculation bandwidth 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 A DIAMETER OF 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 district

1. Initial data
2. Introduction
3. Determining the population
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 for gas consumption for trade needs
4.8. Compilation of the final table of gas consumption by the city
5. Determination of annual and hourly gas consumption by various consumers of the city
6. Construction of a graph of annual gas consumption by the city
7. Selection and justification of the gas supply system
8. Determination of the optimal number of HRS and hydraulic fracturing
8.1. Definitions of the number of HRS
8.2. Determination of the optimal number of hydraulic fracturing
9. Typical hydraulic fracturing and GRU schemes
9.1. Gas control points
9.2. Gas control plants
10. Selection of equipment for gas control points and installations
10.1. Selecting a pressure regulator
10.2. Choice of safety shut-off valve
10.3. Relief valve selection
10.4. Filter selection
10.5. Choice of valves
11. Structural elements of gas pipelines
11.1. Pipes
11.2. Details of gas pipelines
12. Hydraulic calculations of gas pipelines
12.1. Hydraulic calculation of ring networks of high and medium pressure
12.1.1. Calculation in emergency modes.
12.1.2. Branch calculation
12.1.3. Calculation with normal flow distribution
12.2. Hydraulic calculation of low pressure gas networks
12.3. Hydraulic calculation of low-pressure dead-end gas pipelines
13. Bibliographic list

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 the 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 differential pressure in the low pressure network: 1200 Pa.

2. Introduction

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

Improving the living conditions of the population;

replacement of more expensive solid fuel or electricity in thermal processes on industrial enterprises, thermal power plants, public utilities, medical institutions, enterprises Catering and so on.;

improvement of the environmental situation in cities and settlements, since natural gas practically does not emit harmful gases into the atmosphere during combustion.

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

In order 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.

On the territory of 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.

Gas pipelines are laid 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

Public utilities use gas to produce hot water and steam, bake bread, cook food in canteens and restaurants, and heat rooms.

In hospitals, natural gas is used for sanitation, hot water preparation, and food preparation.

At 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:

Determine all gas consumers in the gasified area;

determine the gas consumption for each consumer;

determine the location of distribution gas pipelines;

determine the diameters of all gas pipelines;

· select equipment for all hydraulic fracturing and GRU and determine their locations;

Pick up all the shut-off valves (gate valves, taps, valves);

determine the installation locations 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;

sort out activities for safe operation gas pipelines.

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

The initial data for the design of gas supply networks are:

· composition and characteristics of natural gas or gas field;

· climatic characteristics of the construction area;

a plan for the development of a city or settlement;

information on gas coverage of the population;

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

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

The population of the city or population density per hectare;

· a list of all gas consumers for the period of gasification and prospects for the development of the city or village 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 the population

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

By population density per hectare of gasified territory.

Where F P- the 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, manufacturing a particular product at an industrial enterprise, etc.

It is very difficult to make an accurate calculation of gas consumption for domestic needs, since gas consumption depends on a number of factors that cannot be accurately accounted for. Therefore, gas consumption is determined by the average heat consumption rates obtained on the basis of statistical data. Usually these norms are determined on the basis of either one person, or one breakfast or lunch, or one ton of linen, or per unit of output by an industrial enterprise. Heat consumption is measured in MJ or kJ.

The norms of heat consumption according to SNiP for household and communal needs are given in table 3.1 ..

4.1 Determination of the 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- the degree of gas supply coverage of the city (determined by the task);

N- the 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 from gas water heaters (determined by calculation);

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

gK1, gK2, gK3- heat consumption rates (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 the annual heat consumption for gas consumption at public service enterprises

The heat consumption for these consumers takes into account the gas consumption for washing clothes in laundries, for washing people in baths, for sanitizing 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.

The heat consumption in the baths is determined by the formula

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

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

gB- the rate of heat consumption for washing one person;

All g are taken according to Table 3.1 from .

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

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

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

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

gP- the rate of heat consumption per 1 ton of dry linen (table).

The formula takes into account the average rate of receipt of linen in laundries, equal to 100 tons per 1000 inhabitants.

All g are taken according to Table 3.1 from .

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

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

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

It is believed that the same amount of heat is spent on preparing breakfasts and dinners. The heat consumption for cooking lunch is greater than for preparing breakfast or dinner. If a catering establishment operates all day, then the heat consumption here 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 at catering establishments is determined by the formula:

Here ZP.OP- the proportion of the population of the city using public catering enterprises (set);

Y P.OP- the share of public catering enterprises of the city that use gas as a fuel (set);

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

All g are taken according to Table 3.1 from .

4.4 Determination of the annual heat consumption for gas consumption in healthcare facilities

With gas consumption in hospitals and sanatoriums, it should be taken into account that their total capacity should be 12 beds per 1000 inhabitants of a city or village. Heat consumption in healthcare facilities is necessary for preparing food for the sick, for sanitizing linen, tools, and premises.

It is determined by the formula:

Here YZD – the degree of coverage of gas supply to health care institutions of the city (set);

gZD- the 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 taken according to Table 3.1 from .

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

When baking bread and confectionery, constituting the main product of these gas consumers, it is necessary to take into account the difference in heat consumption at different types products. The rate of bread baking per day per 1000 inhabitants is taken at the rate of 0.6 ¸ 0.8 tons. This norm 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 the inhabitants consume. Therefore, the total rate of 0.6 ¸ 0.8 tons per 1000 inhabitants can be conditionally divided in half, assuming that bakeries and bakeries bake black and white bread equally. Baking of confectionery products can be accounted for separately, for example, in the amount of 0.1 tons per 1000 inhabitants per day.

When calculating gas consumption, the coverage of gas supply to bakeries and bakeries should be taken into account. Total consumption heat (MJ / year) for bakeries and bakeries are determined by the formula:

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

gFH- the rate of heat consumption for baking 1 ton of black bread

gBH- the rate of heat consumption for baking 1 ton of white bread

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

All g are taken according to Table 3.1 from .

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

4.6 Determination of the 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 by the formula:

tVN, tSR.O, tRO- temperature, respectively, of the indoor air of the heated premises, the average outdoor air for the heating period, the calculated outdoor temperature for the given construction area according to [2], O С.

K, K 1- coefficients that take into account the 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- the 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 heated buildings, m 2;

gOV- 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 (m 2),

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

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

NGV- the number of city residents using hot water from boiler houses or CHPPs, 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 the annual heat consumption when consuming gas for the needs of trade, consumer services enterprises, schools and universities

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

Where N– number of inhabitants, (persons),

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

4.8 Compilation of the final table of gas consumption by the city

The final table of gas consumption by 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 consumers of the city

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

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

Q H 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 consumption for all consumers of the city are entered in table 1 in column 4.

Gas consumption in the city by different consumers depends on many factors. Each consumer has his own characteristics and consumes gas in his own way. Between them there is a certain unevenness in gas consumption. Accounting for uneven 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- the number of hours of use of the maximum load per year, h / year

By using km the hourly gas consumption is determined for each consumer of the city (m 3 / h)

Coefficient values m are given in table 4.1.

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

6. Construction of a graph of annual gas consumption by the city

Schedules of annual gas consumption are the basis both for planning gas production and for selecting and justifying measures to ensure the regulation of uneven gas consumption. In addition, knowledge annual schedules gas consumption has great importance for the operation of urban gas supply systems, as it allows you to correctly plan the demand for gas by months of the year, determine the required capacity of urban consumers - regulators, plan the reconstruction and repair work on gas networks and their facilities. Using dips in gas consumption to shut off individual sections of the gas pipeline and gas control points for repairs, it is possible to carry out it without disrupting the gas supply to consumers [З].

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

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

The annual schedule of gas consumption by the city is built, taking into account the average statistical data on gas consumption by months of the year for various categories of consumers. The total gas consumption during the year is broken down by months. The gas consumption for each month in the total gas consumption is determined based on the following calculation

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

Table 5.1 shows the data for determining the monthly gas consumption for various categories of consumers.

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

nM- the number of heating days in a month.

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

The monthly gas consumption determined by the formula is depicted on the graph of the annual gas consumption by the city in the form of ordinates that are constant for a given month. After constructing all the ordinates for each month for all categories of consumers, the construction of the total annual consumption by months is carried out. 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. A number of factors influence the choice of a city's gas supply system. First of all, these are: the size of the gasified territory, the features of its layout, population density, the number and nature of gas consumers, the presence of natural and artificial obstacles to laying gas pipelines (rivers, dams, ravines, railway tracks, underground structures, etc.). When designing a gas supply system, a number of options are developed and their technical and economic comparison is made. For construction, the most advantageous option is used.

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;

medium pressure from 5 kPa to 0.3 MPa;

low pressure up to 5 kPa;

High and medium pressure gas pipelines are used to supply urban distribution networks of medium and low pressure. Most of the gas goes through them 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, half rings or beams. 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 is made up of high-pressure gas pipelines of the first and second categories, the lower level is low-pressure gas pipelines. The pressure of the gas during the transition from a high level to a lower one gradually decreases. This is done with the help of pressure regulators installed on the hydraulic fracturing.

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

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

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

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

The choice of gas supply system in the city depends on the nature of gas consumers who need gas of the appropriate pressure, as well as on the length and load of gas pipelines. The more diverse gas consumers 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, the most economically viable is a two-stage system. 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 HRS and hydraulic fracturing

8.1 Determining the number of HRS

Gas distribution stations are at the head of gas supply systems. Through them there is a supply of ring gas pipelines of high or medium pressure. Gas is supplied to the GDS from main gas pipelines under pressure 6 ¸ 7 MPa. At the GDS, the gas pressure is reduced to high or medium. In addition, the gas acquires a specific smell at the GDS. He is being ostracized. Here, the gas is also subjected to additional purification from mechanical impurities and dries up.

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

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

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

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

· For cities with a population of more than 300 thousand people, systems with three GDS are the most economical.

GDS, as a rule, are located outside the city limits. If the number of GRS is more than one, then they are located on different sides of the city. Gas distribution stations are usually connected by two gas pipelines, which ensures a higher reliability of gas supply to the city. Very large gas consumers (thermal power plants, industrial enterprises, metallurgical plants, etc.) are fed directly from the GDS.

8.2 Determining 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 ratio

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

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

For determining V OPT it is necessary to first determine the optimal range of the 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– density coefficient of low pressure networks, 1/m;

m– population density in the area of ​​operation of the hydraulic fracturing, persons/ha;

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

e=V/N(m 3 / man. h)

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

The resulting optimal number of hydraulic fracturing is used in the design of low-pressure gas networks. Network fracs are usually located in the center of the gasified area so that all gas consumers are located at approximately the same distance from the frac. The maximum distance of the hydraulic fracturing from the designed 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 / man.h),

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

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

9. Typical hydraulic fracturing and GRU schemes

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

The hydraulic fracturing 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 pipeline and manual control of gas pressure.

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

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

· mechanical gas cleaning 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.

In the room for instrumentation there are self-recording pressure gauges that measure the gas pressure before and after hydraulic fracturing, a gas flow meter, a differential pressure gauge that measures the pressure drop across the filter. Indicative pressure gauges are installed in the main hydraulic fracturing room to measure gas pressure before and after hydraulic fracturing; expansion thermometers that measure the gas temperature at the gas inlet to the hydraulic fracturing and after the gas flow measurement unit.

The axonometric diagram of hydraulic fracturing gas pipelines is shown in fig. 8.2. The diagram in conditional images in accordance with GOST 21.609-83 shows pipelines, valves, regulators (2), safety shut-off valves (З), a filter (1), a hydraulic valve (5), candles for discharging gas into the atmosphere (10, 9.8), 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 to the room (1). Similarly, gas is removed from hydraulic fracturing. Insulating flanges (11) are installed at the gas inlet and outlet to the hydraulic fracturing on the gas pipeline.

Gas of high or medium pressure is cleaned from mechanical impurities in the filter (1) in the hydraulic fracturing. After the filter, the gas is directed to the control line. Here the gas pressure is reduced to the required value and maintained constant by means of the regulator (2). The safety shut-off valve (3) closes the control line in cases of increase and decrease in gas pressure after the regulator beyond the allowable limits. The upper actuation limit of the valve is 120% of the pressure maintained by the pressure regulator. The lower limit of the valve setting for low pressure gas pipelines is 300 - 3000 Pa; for gas pipelines of medium pressure - 0.003 - 0.03 MPa.

The safety relief valve (PSK) (4) protects the gas network after hydraulic fracturing from a short-term increase in pressure within 110% of the pressure 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, hydraulic fracturing is equipped local system heating or is connected to the heating system of one of the nearby buildings.

For hydraulic fracturing ventilation, a deflector is installed on the roof, which provides three-time air exchange in the main hydraulic fracturing room. The entrance door to the main hydraulic fracturing room in its lower part must have slots for air passage.

Hydraulic fracturing lighting is most often performed outdoors by installing directional light sources on the hydraulic fracturing windows. It is possible to carry out the lighting of hydraulic fracturing in an explosion-proof version. In any case, the lighting of the hydraulic fracturing should be switched on from the outside.

Lightning protection and a ground loop are installed near the hydraulic distribution plant building.

9.2 Gas control installations.

Gas control units (GRU) do not differ from hydraulic fracturing in their tasks and principle of operation. Their main difference from hydraulic fracturing is that the GRU can be placed directly in those premises where gas is used, or somewhere nearby, providing free access to the GRU. Separate buildings for the GRU are not being built. They surround the GRU with a protective net and hang warning posters near it. GRU, as a rule, are built in production shops, in boiler houses, at household gas consumers. GRU can be carried out in metal cabinets, which are fixed on the outer walls of industrial buildings. The rules for the placement of the GRU are regulated by SNiP.

On fig. 8.3 shows an axonometric diagram of a typical GRU. The following notation is adopted here:

1. filter for mechanical purification of gas;

2. steel gate valves;

3. safety shut-off valve;

4. pressure regulator;

7. safety relief valve;

8. gas flow meter;

9. self-recording manometers;

10. showing manometers;

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 valves.

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

10. Selection of equipment for gas control points and installations

The choice of hydraulic fracturing and GRU 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 is selected for gas purification, and then shut-off valves and instrumentation.

10.1 Selecting a pressure regulator

The pressure regulator must ensure the passage of the required amount of gas through the hydraulic fracturing and maintain its constant pressure, regardless of the flow rate.

The calculation equation for determining the capacity of the pressure regulator is selected depending on the nature of the outflow of gas through the regulatory body.

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

At over critical pressure, when the gas velocity in the pressure regulator valve exceeds the speed of sound, the calculation equation has the form:

KV is the throughput coefficient of the pressure regulator;

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

DP – differential pressure in the control line, MPa:

Where P1– absolute gas pressure before hydraulic fracturing or GRU, MPa;

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

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

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

T is the absolute gas temperature 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 15.20% more than the optimal gas flow rate through hydraulic fracturing, i.e.:

It is possible to determine the mode of gas outflow through the regulator valve by the ratio

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

Because R 2 / R 1 3 /h of gas consumption. The second type of filters is designed to pass high gas flow rates. The number after the FG indicates 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 estimated gas flow through the hydraulic fracturing or GRU.

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

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

VGR- passport value of the filter capacity, m 3 / h;

r ABOUT– gas density under normal conditions, kg/m 3 ;

R 1– absolute gas pressure before the filter, MPa;

VR- estimated gas flow through the hydraulic fracturing or GRU, m 3 / h.

For the initial take the filter FG 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 allowable value of 10000 Pa, therefore

filter selected FG 7 - 50 - 6.

10.5 Choice of shut-off valves

Shutoff valves (gate valves, valves, plug cocks) used in hydraulic fracturing and gas distribution units must be designed for a gaseous medium. The main criteria for the selection of valves are nominal diameter D U and executive pressure P U.

Gate valves are used with both rising and non-rising stems. The first is preferable for above-ground installation, the second - for underground.

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

Cork taps have significantly less hydraulic resistance than valves. They are distinguished by tightening the conical plug into tension and gland plugs, and by the method of connecting to pipes - into coupling and flange ones.

The material for the manufacture of valves are: carbon steel, alloy steel, gray and malleable cast iron, brass and bronze.

Shut-off valve made of gray cast iron it is used at a working gas pressure of not more than 0.6 MPa. Steel, brass and bronze at pressure up to 1.6 MPa. Working temperature for cast iron and bronze fittings it should be at least -35 C, for steel at least -40 C.

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

The nominal diameter of the valves in the hydraulic fracturing must correspond to the diameter of the gas pipelines at the inlet and outlet of the gas. It is recommended to choose the nominal diameter of valves and cocks on the hydraulic fracturing or GRU impulse lines 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 main part of gas pipelines, they transport gas to consumers. All pipe connections on gas pipelines are only welded. Flange connections are allowed only at the installation sites of shut-off and control valves.

For the construction of gas supply systems, steel longitudinal, spirally welded and seamless pipes should be used, made from well-welded 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 not more than 0.25%.

A - rationing (guarantee) mechanical properties;

B - rationing (guarantee) chemical composition;

B - regulation (guarantee) of the chemical composition and mechanical properties;

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

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

- at the design temperature of the outside air up to -40 ° C - group B;

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

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

11.2 Details of gas pipelines

The details of gas pipelines include: branches, transitions, tees, plugs.

Elbows 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 in places 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 parts of gas pipelines 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 ring networks of high and medium pressure;

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

calculation of multi-ring networks of low pressure;

calculation of dead-end low pressure networks.

To carry out hydraulic calculations, it is necessary to have the following initial data:

· calculation scheme of the gas pipeline with indication of the numbers and lengths of sections on it;

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

Permissible pressure drops of gas in the network.

The calculation scheme of the gas pipeline is compiled in a simplified form according to the plan of the gasified area. All sections of gas pipelines are straightened, as it were, and their full lengths are indicated with all bends and turns. The locations of gas consumers on the plate are determined by the locations of the respective hydraulic fracturing or GRU.

12.1 Hydraulic calculation of high and medium pressure ring networks

The hydraulic mode of operation of high and medium pressure gas pipelines is assigned from the conditions of maximum gas consumption.

The calculation of such networks consists of three stages:

Calculation in emergency modes;

Calculation with normal flow distribution;

calculation of branches from the ring gas pipeline.

The design scheme of the gas pipeline is shown in fig. 2. The lengths of the individual sections are given in meters. The numbers of the calculated sections are indicated by numbers in circles. Gas consumption by individual consumers is indicated by the letter V and has the dimension of m 3 / h. Places of gas flow change on the ring are marked with numbers 0, 1, 2, . , etc.. The gas supply source (GDS) is connected to point 0.

The high pressure gas pipeline has an excess gas pressure at the starting point 0 P H \u003d 0.6 MPa. Final gas pressure P K = 0.15 MPa. This pressure must be maintained for all consumers connected to this ring, the same regardless of their location.

The calculations use the absolute pressure of the gas, so the calculated P H \u003d 0.7 MPa and P K \u003d 0.25 MPa. Section lengths are converted to kilometers.

To start the calculation, we determine the average specific difference of squared pressures:

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

A factor 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 estimated gas flow in the corresponding section, according to the nomogram in Fig. 11.2 we determine the diameter of the gas pipeline and using it, using the same nomogram, we specify the value A for the selected standard 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 to Location on. All calculations are summarized in tables.

12.1.1 Calculation in emergency conditions

Emergency modes of operation of the gas pipeline occur when the sections of the gas pipeline adjacent to the supply point 0 fail. In our case, these are sections 1 and 18. Consumers in emergency modes should be powered through a dead-end network with the condition that gas pressure is maintained at the last consumer PK = 0.25 MPa.

The results of the calculations are summarized in Table. 2 and 3.

Gas consumption at the sites is determined by the formula:

Where K OBi- coefficient of provision of various gas consumers;

Vi- hourly gas consumption at the corresponding consumer, m 3 / h.

For simplicity, the security factor is taken equal to 0.8 for all gas consumers.

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

The average specific difference of pressure squares 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 section Construction, work Calculation of gas supply systems for a city district on the site abstract plus