High and medium pressure. High and medium pressure Hydraulic calculation of a low pressure gas pipeline design example

Gas control points are designed to reduce the gas pressure and maintain it at a given level, regardless of the flow rate. For cities with a population of 50 to 250 thousand people, a two-stage gas supply system is recommended.

With a known estimated consumption of gaseous fuel, the city district determines the number of hydraulic fracturing jobs based on the optimal performance

(= 1500..2000m 3 / h) according to the formula:

After determining the number of hydraulic fracturing, their location is outlined on the general plan of the city district, installing them in the center of the gasified area on the territory of the blocks.

3.2 Hydraulic calculation of main gas pipelines of high and medium pressure (GVD and GDS)

On the general plan of the district of the city, it is planned to lay high and medium pressure gas pipelines. Looping gas pipelines is most expedient in areas with multi-storey buildings. Gas pipelines are routed in such a way that the length of the branches from the ring gas pipeline to consumers is minimal (no more than 200 m to increase the reliability of gas networks). All industrial enterprises, boiler houses and hydraulic fracturing stations are connected to the high and medium pressure gas pipeline.

Hydraulic calculation is performed for two emergency and normal gas consumption modes.

The initial pressure is taken on assignment, it is equal to 450 kPa. (At the exit from the GDS). In most cases, before fracturing, it is sufficient to have an absolute gas pressure of about 200 ... 250 kPa.

On the design diagram of high or medium pressure gas pipelines, the numbers of the sections, the distance between the sections in meters, the estimated gas consumption, the name of industrial enterprises and their costs, quarter or district boiler houses are applied.

First, a normal mode is outlined on the design scheme of the HPM or HPM, when the gas flow moves along the half rings. The confluence point of the naza flows is in the middle of the gas pipeline length at the closing section.

To equalize the loads along the half-rings, we distribute gas consumption to boiler houses No. 1 and No. 2. To do this, we determine the gas consumption along the half-rings of the main gas pipeline and, taking into account the load on the hydraulic fracturing, industrial enterprises, etc., except for boiler houses, and find the absolute discrepancy according to the formula:

where V 1 is the total load on the first half-ring, m 3 / h;

V 2 - total load on the second half-ring, m 3 / h;

V 1 = V grp1 + V pp3 = 1400.02 + 3300 = 4700.02m 3 / h;

V 2 = V pp2 + V grp2 = 2800 + 1422.5 = 4222.5 m 3 / h;

∆V = V 1 -V 2 = 4700.02-4222.5 = 477.5 m 3 / h;

Gas consumption for boiler room No. 1 is:

V cat2 = (V cat -∆V) / 2, m 3 / h;

V cat1 = (V cat -∆V) / 2 = (12340.4-477.5) / 2 = 5931.4m 3 / h

Gas consumption for boiler room No. 2 is:

V cat2 = V cat -V cat1 = 12340.4-5931.4 = 6409 m3 / h

Determination of emergency gas consumption:

V av = 0.59 * Σ (V i * K about), m 3 / h

V av = 0.59 * Σ (V i * K about), = 0.59 * ((1422.5 + 1400.02) * 0.8 + (3300 +2800) * 0.9 + (5931.4 + 6409) * 0.7) = 9894 , 5 m 3 / h,

Where K about = 0.8, K about = 0.7, K about = 0.9 are the coefficients of gas supply in emergency situations for hydraulic fracturing, industrial enterprises and heating-production boilers.

The root-mean-square loss of gas pressure along the ring is equal to:

A av = (Pн 2 - Рк 2) / Σl р = (450 2 -250 2) / 8184 = 17.106 kPa 2 / m

where P n, P to - the initial and final gas pressure;

l p = 1.1 * l f = 1.1 * 7440 = 8184 m - the estimated length of the ring gas pipeline,

where l f is the actual length of the ring gas pipeline.

According to the nomogram for hydraulic calculation of high or medium pressure gas pipelines. According to V calc and A cf, we determine the preliminary diameters of the annular gas pipeline. It is desirable to have one diameter around the ring, maximum two.

The first emergency mode is when the head section of the gas pipeline is disconnected to the left of the gas supply source (GDS), the second emergency mode is when the section of the gas pipeline to the right of the GDS is disconnected.

The diameters of the gas pipeline are pre-selected according to the nomogram for the hydraulic calculation of high or medium pressure. Then, depending on the calculated gas flow rate for the sections and the diameter, we determine the actual square-law loss of gas pressure in the sections of the gas pipeline. The pressure at the end consumer must not be lower than the minimum permissible limit (P to +50), k Pa abs.

The final pressure is determined by the formula, kPa abs.

According to V AB and A cf, we determine the preliminary diameter of the annular gas pipeline 325x8.0

Table 3 - Hydraulic calculation of a high and medium pressure gas pipeline

Section length, m

Gas consumption, Vр, m3 / h

Gas pipeline diameter

Root mean square loss of gas pressure, A, kPa / m

Gas pressure at the site, Pa

1 emergency mode (GRS-1-2-3 ...)

Check: 404≥250 + 50 2 emergency mode (GRS-1-7-6 ...)

Checking: 400≥250 + 50

Normal mode 1
Normal mode 2

Check: 430≥250 + 50

Discrepancy: (430-428) / 430 * 100 = 0.46%

Calculation of gas pipeline branches normal. mode

Calculation of branches of the gas pipeline 1 avar.
Calculation of branches of the gas pipeline 2 avar.

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 low pressure networks;

· Calculation of dead-end networks of low pressure.

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

· The design diagram of the gas pipeline with the indication on it the numbers and lengths of the sections;

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

· Permissible gas pressure drops in the network.

The design diagram of the gas pipeline is drawn up in a simplified form according to the plan of the gasified area. All sections of gas pipelines are straightened, as it were, and their full lengths with all bends and bends are indicated. The points of location of gas consumers on the plate are determined by the locations of the corresponding 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 based on the conditions of maximum gas consumption.

The calculation of such networks consists of three stages:

· Calculation in emergency modes;

· Calculation for normal flow distribution;

· Calculation of branches from the ring gas pipeline.

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

The high-pressure gas pipeline has an excess gas pressure at the initial point of 0 P H = 0.6 MPa. Final gas pressure R 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 gas pressure, so the calculated P N = 0.7 MPa and P K = 0.25 MPa. Section lengths converted to kilometers.

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

A CP = (P 2 n - P 2 k) / 1.1 е l i

where е l i- the sum of the lengths of all sections in the calculated direction, km.

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

Further, using the mean A Wed and the estimated gas consumption in the corresponding section, according to the nomogram in Fig. 11.2 we determine the diameter of the gas pipeline and along it, using the same nomogram, we specify the value A for the selected standard pipe diameter. Then, according to the specified value A and the calculated length, we determine the exact value of the difference R 2 n - R 2 k Location on. All calculations are tabulated.

12.1.1 Calculation in emergency modes.

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

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

Gas consumption at the sites is determined by the formula:

V P = 0.59 S (K OB i V i)(m 3 / h),

where K OB i- coefficient of supply for various gas consumers;

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

For simplicity, the coefficient of supply is taken equal to 0.8 for all gas consumers.

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

l Р = 1.1 l G(km),

The average specific difference in the squares of the pressures in the first emergency mode will be:

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

е l i = 6.06(km),

Refused site 1
Account no.	d Y mm	l R km	V P m 3 / h	R 2 n-R 2 k l P	R 2 n-R 2 k, MPa 2
		0,077	10053,831	0,045	0,003465
		1,848	9849,4501	0,04	0,07392
		0,407	9809,2192	0,04	0,01628
		0,726	9796,579	0,04	0,02904
		0,077	9787,3632	0,19	0,01463
		0,473	9785,6909	0,19	0,08987
		0,253	9745,46	0,18	0,04554
		0,044	2566,8403	0,1	0,0044
		0,121	2554,2002	0,1	0,0121
		0,22	1665,1787	0,053	0,01166
		0,121	1663,5064	0,053	0,006413
		0,176	1459,1257	0,045	0,00792
		0,154	1449,9099	0,045	0,00693
		0,913	1437,2697	0,045	0,041085
		0,451	903,3339	0,045	0,020295
		0,154	901,6616	0,2	0,0308
		0,363	12,64016	0,031	0,011253
		ål P = 6.578			å (P 2 n-P 2 k) = 0.425601

P K= Ö (0.7 2 - 0.425601) - 0.1 = 0.1537696 Error: 1,5 % <5 %

We proceed to the calculation in the second emergency mode.

Refused plot 18
Account no.	d Y mm	l R km	V P m 3 / h	R 2 n-R 2 k l P	R 2 n-R 2 k, MPa 2
		0,22	10053,831	0,045	0,0099
		0,231	10041,191	0,045	0,010395
		0,154	9152,1692	0,038	0,005852
		0,451	9150,4969	0,038	0,017138
		0,913	8616,5611	0,1	0,0913
		0,154	8603,9209	0,1	0,0154
		0,176	8594,7051	0,1	0,0176
		0,121	8390,3244	0,1	0,0121
		0,22	8388,6521	0,1	0,022
		0,121	7499,6307	0,085	0,010285
		0,044	7486,9905	0,085	0,00374
		0,253	308,37082	0,085	0,021505
		0,473	268,1399	0,06	0,02838
		0,077	266,4676	0,06	0,00462
		0,726	257,2518	0,06	0,04356
		0,407	244,61169	0,06	0,02442
		1,903	204,38072	0,045	0,085635
		ål P = 6.644			å (P 2 n-P 2 k) = 0.42383

P K= Ö (0.7 2 - 0.42383) - 0.1 = 0.1572353 Error: 2,9 % <5 %

Hence it follows that the calculation is done correctly.

This completes the calculation in the second emergency mode.

Knowing the pressure loss at each section, we determine the absolute pressure at each point in both emergency modes:

P i = Ö P 2 H - S (P 2 H - P 2 K) i,

where S (P 2 H - P 2 K)- the sum of the difference between the squares of the pressures in the sections preceding the point of pressure determination.

All calculations for determining the pressures at various points of the ring can be summarized in a table.

Point number on the ring	Refused site 1	Denied plot 19
	Gas pressure, MPa	Gas pressure, MPa
	0,7	0,7
	0,2537696	0,6928925
	0,2750491	0,6853503
	0,3262698
	0,3560154	0,6683674
	0,409673	0,5961669
	0,418055	0,5831081
	0,4274131	0,567816
	0,4348505	0,5570592
	0,4480569	0,5369497
	0,4613621	0,5272855
	0,4661062	0,523727
	0,5126353	0,5027773
	0,593856	0,473714
	0,6060487	0,4688123
	0,6295514	0,4197916
	0,6423512	0,3896216
	0,6975206	0,2572353

The gas pressure at the points of connection to the consumer ring must be known to determine the diameters of the branches in the hydraulic calculation of the latter.

12.1.2 Calculation of branches.

In this calculation, the diameters of gas pipelines supplying gas from the ring gas pipeline to consumers V 1, V 2, ....., etc. are determined. For this, the calculation of pressure at points of change in flow rates 1, 2, 3, ... is used. .17 tabulated? ... Differential pressure at the point of connection of the branch gas pipeline to the ring gas pipeline and the specified final pressure at the consumer.

To determine the initial pressure from table 2.3 for the same point, select the lowest absolute gas pressure. Next, the specific difference between the squares of the pressures on the site is determined:

A = (P 2 H - P 2 K) / 1.1 l G i, (MPa 2 / km),

According to the nomogram in Fig. 11.2 from we determine the diameter of the gas pipeline.

All calculations for determining the diameters of the branches are summarized in the table:

A 19 = 0.0145;

A 20 = 0.1085;

A 21 = 0.4997;

A 22 = 0.3649;

A 23 = 2.3944;

A 24 = 0.8501;

A 25 = 1.5606;

A 26 = 1.1505;

A 27 = 0.8376;

A 28 = 0.9114;

A 29 = 2.3447;

A 30 = 2.4715;

A 31 = 0.8657;

A 32 = 1.7872;

A 33 = 1.2924;

A 34 = 1.3528;

A 35 = 0.0664;

Branch number.	Initial pressure, MPa	Final pressure, MPa	Section length, Km	Gas consumption, m 3 / h	Nominal diameter, mm
	0,2538	0,25	0,12	26,78
	0,275	0,25	0,11	1883,52
	0,3263	0,25	0,08	3,543
	0,356	0,25	0,16	1131,22
	0,4097	0,25	0,04	26,78
	0,418	0,25	0,12	19,525
	0,4274	0,25	0,07	433,01
	0,4348	0,25	0,1	3,543
	0,448	0,25	0,15	1883,52
	0,4614	0,25	0,15	26,78
	0,4661	0,25	0,06	15208,94
	0,5028	0,25	0,07	85,235
	0,4737	0,25	0,17	3,543
	0,4688	0,25	0,08	19,525
	0,4198	0,25	0,08	26,78
	0,3896	0,25	0,06	85,235
	0,2572	0,25	0,05	433,01

12.1.3 Calculation with normal flow distribution.

Normal flow distribution assumes the movement of gas from the feed to the ring in both directions.

The vanishing point of both gas streams should be somewhere on the ring. This point is determined from the following conditions - gas flow rates in both directions of the ring should be approximately the same.

Calculations for normal flow distribution are recommended to be summarized in a table.

Table 6.

N About the site.	Consumption on the site, m 3 / h	Gas pipeline diameter, mm	Section length, km	Р 2 Н -Р 2 К / l, MPa 2 / km	Р 2 Н -Р 2 К, MPa 2	Р 2 Н -Р 2 К / V УЧ, 10 -6
	-10650,2445		0,2	0,052	0,0104	0,976
	-10623,4645		0,21	0,052	0,01092	1,026
	-8739,9445		0,14	0,034	0,00476	0,545
	-8736,4015		0,41	0,034	0,01394	1,596
	-7605,1815		0,83	0,085	0,07055	9,277
	-7578,4015		0,14	0,085	0,0119	1,57
	-7558,8765		0,16	0,085	0,0136	1,799
	-7125,8665		0,11	0,075	0,00825	1,158
	-7122,3235		0,2	0,075	0,015	2,106
	-5238,8035		0,11	0,039	0,00429	0,819
	-5212,0235		0,04	0,039	0,00156	0,299
	+9996,9165		0,23	0,122	0,02806	2,807
	+10082,1515		0,43	0,122	0,05246	5,203
	+10085,6945		0,07	0,122	0,00854	0,847
	+10105,2195		0,66	0,045	0,0297	2,939
	+10131,9995		0,37	0,045	0,01665	1,643
	+10217,2345		1,68	0,045	0,0756	7,399
	+10650,2445		0,07	0,05	0,0035	0,329
					S = 0.37968	S = 42.34 10 -6
					+0,04934

* The signs "+" and "-" mean the conditional division of gas flows into positive (clockwise direction) and negative (counterclockwise movement).

To determine the error, it is necessary to sum up all the numbers in column 6 in absolute value and evaluate the difference between positive and negative numbers in the same column using the formula below

The error is: 0.04934 100 / 0.5 0.37968 = 25,99 %

The diameters of the gas pipeline sections in this mode are selected from the table of calculations in emergency modes. For each section, the largest of the two diameters is taken. In this case, the dimensions of the diameters on the head sections of the ring will be the largest. Further, the sizes of diameters will decrease monotonically in the direction of the point of flow descent.

To determine the specific difference in the squares of the pressures on the site, use the nomogram in Fig. 11.2. ... They are determined by the known diameter and flow rate and entered in column 5 of the table. Knowing the calculated lengths of the sections, the differences in the squares of the pressures in the sections are calculated and entered into column 6 of the table.

The criterion for the correctness of the calculation is the equality of the sums of positive and negative values ​​of P2 n - P2 k. If there is no equality, then the difference between these values ​​should not exceed 10% of half the absolute value of the sum of the numbers in column 6 of the table. In our example, this difference is 25.99%, which is too much.

Therefore, the calculation must be repeated.

DV = å (P 2 n - P 2 k) 10 6 / 2 å (Р 2 n - Р 2 к) / Vi.

DV = 0,04934 10 6 / 2 42,34 = 582,66 "600(m 3 / h),

The sum in the denominator of this formula is taken from column 7 of table 6.

We will increase all positive flow rates by 600 m 3 / h, and we will also reduce all negative flow rates by 600 m 2 / h. Let's repeat the calculation with new values ​​of flow rates in the sections

Table 7.

N About the Plot.	Consumption on the site, m 3 / h	Gas pipeline diameter, mm	Section length, km	Р 2 Н -Р 2 К / l, MPa 2 / km	Р 2 Н -Р 2 К, MPa 2	Р 2 Н -Р 2 К / V УЧ, 10 -6
	-11250,2445		0,2	0,06	0,012	0,976
	-11223,4645		0,21	0,06	0,0126	1,026
	- 9339,9445		0,14	0,037	0,00518	0,545
	-9336,4015		0,41	0,037	0,01517	1,596
	-8205,1815		0,83	0,1	0,083	9,277
	-8178,4015		0,14	0,1	0,014	1,57
	-8158,8765		0,16	0,1	0,016	1,799
	-7125,8665		0,11	0,085	0,00935	1,158
	-7725,3235		0,2	0,085	0,017	2,106
	-5838,8035		0,11	0,048	0,00528	0,819
	-5812,0235		0,04	0,048	0,00192	0,299
	+9396,9165		0,23	0,117	0,02691	2,807
	+9482,1515		0,43	0,117	0,05031	5,203
	+9485,6945		0,07	0,117	0,00819	0,847
	+9505,2195		0,66	0,038	0,02508	2,939
	+9531,9995		0,37	0,038	0,01406	1,643
	+9617,2345		1,68	0,038	0,06384	7,399
	+10050,2445		0,07	0,045	0,00315	0,329
					S = 0.38304	S = 43.5 10 -6
					+0,00004

The error is: 0.00004 100 / 0.5 0.38304 = 0,02 %,

After the introduction of the circular flow rate, the error decreased to 0.02%, which is acceptable.

This completes the hydraulic calculation of the high-pressure gas pipeline.

12.2. Hydraulic calculation of low pressure multi-ring gas networks.

Hydraulic calculation of low pressure gas pipelines (up to 5 kPa) is reduced to solving the transport problem with its subsequent optimization.

Initial data for the calculation:

1. Total gas consumption through the hydraulic fracturing, feeding the low pressure network:

V 0 = 1883.52(m 3 / h).

2. Design scheme: fig. 3.

3. Estimated pressure drop in the network:

DP = 1200(Pa).

The task of the hydraulic calculation of a low-pressure network is to determine the diameters of all its sections while observing a given DP... The minimum pipe diameter in the network must be equal to 50 mm.

Gas travel costs in the sections are determined by the formula:

V PUT = l PR i V 0 / Sl PR i

where l OL i- reduced length of the section, m

l OL i = l R K E K Z

l Р - estimated length of the section ( l Р = 1.1 l Г), m;

l G- the geometrical length of the section according to the plan of the gasification area, m;

K E- coefficient of number of storeys, taking into account the presence of buildings of different storeys;

K Z- the building factor, taking into account the density of residential buildings along the gas pipeline route.

The calculation of gas travel costs is summarized in Table 8.

Lot number	Geometric Length, m	Estimated length, m	Coeff. Floors	Coeff. Buildings	Reduced length, m	Travel flow rate, m 3 / h
0-1
1-2						48,29538
2-3						96,59077
1-4						144,8862
4-5						144,8862
2-6						144,8862
3-7						144,8862
5-6						193,1815
6-7						96,59077
7-8						96,59077
6-9						96,59077
4-10						144,8862
3-12						144,8862
10-14						96,59077
10-11						96,59077
12-13						96,59077
12-14						96,59077
					Sl OL = 5940

Determine the nodal gas consumption:

V KNOT i = 0.5 S V RATE i, (m 3 / h),

where S V ROUTE i - the amount of gas travel costs in the sections adjacent to the node, (m 3 / h),

V KNOT 1= 96,59077 (m 3 / h),

V NODE 2 = 144.8862(m 3 / h),

V NODE 3 = 193.1815(m 3 / h),

V KNOT 4 = 217.3292(m 3 / h),

V NODE 5 = 169.0338(m 3 / h),

V KNOT 6 = 265.6246(m 3 / h),

V KNOT 7 = 169.0338(m 3 / h),

V NODE 8 = 48.0338(m 3 / h),

V KNOT 9 = 48.29538(m 3 / h),

V KNOT 10 = 169.0338(m 3 / h),

V KNOT 11 = 48.29538(m 3 / h),

V NOD 12 = 169.0338(m 3 / h),

V KNOT 13 = 48.29538(m 3 / h),

V KNOT 14 = 96.59077(m 3 / h),

Determine the estimated gas consumption at the sites.

When calculating the estimated gas flow rate, the first Kirchhoff rule for networks is used, which can be formulated as follows: the algebraic sum of all gas flows in the node is zero.

The minimum value of the estimated gas consumption in the section should be equal to half of the track. To ensure the efficiency of the system, it is necessary to highlight the main directions along which most of the gas is transported.

These areas will be:

In these directions, it is possible to distinguish sections along which transit gas flows go. These are the plots:

1-2; 2-6; 2-3; 3-12; 1-4; 4-10.

Here, the estimated flow rate is determined by the Kirchhoff rule.

In areas where there are no transit gas flows:

V P = 0.5 V PUT(m 3 / h),

V Р 0-1 = 1786,929 (m 3 / h)

V P 1-2 = 1134,942 (m 3 / h)

V P 2-3 = 531,2492 (m 3 / h)

V Р 1-4 = 555,3969 (m 3 / h)

V P 4-5 = 72,44308 (m 3 / h)

V Р 2-6 = 458,8062 (m 3 / h)

V Р 3-7 = 72,44308 (m 3 / h)

V P 5-6 = 96,59077 (m 3 / h)

V Р 6-7 = 48,29538 (m 3 / h)

V P 7-8 = 48,29538 (m 3 / h)

V Р 6-9 = 48,29538 (m 3 / h)

V P 4-10 = 265,6246 (m 3 / h)

V P 3-12 = 265,6246 (m 3 / h)

V P 10-14 = 48,29538 (m 3 / h)

V P 10-11 = 48,29538 (m 3 / h)

V P 12-13 = 48,29538 (m 3 / h)

V P 12-14 = 48,29538 (m 3 / h)

Determine the diameters of the sections:

To do this, using a given differential pressure DP, calculate the average initial specific pressure loss in the main directions:

A = DP / S l P i(Pa / m)

where S l Р i - the sum of the calculated lengths of the sections included in this main direction.

According to the value of A and the estimated gas consumption at each section, according to the nomogram in Fig. 11.4, the diameters of the gas pipeline are determined. The actual value of the specific pressure loss in the section is determined by choosing the standard value of the nominal diameter according to the same nomogram. The actual value of the specific loss in the section is multiplied by the calculated length of the section and, thus, the pressure loss in this section is calculated. The total pressure loss in all sections of the main direction should not exceed the specified DP.

All calculations for determining the diameters of the low-pressure gas pipeline sections are summarized in a table.

Plot number	Calculated consumption, m 3 / h	Calculation length, m	Average pressure loss, Pa / m	Diameter Nominal, mm	Valid. specific pressure loss, Pa / m	Pressure loss in the section, Pa	Pressure At the end of the section, Pa
0-1	1786,92		1,33	325 ´ 8	1,1	24,2	4975,8
1-2	1134,94		1,33	273 ´ 7			4865,8
2-3	531,25		1,33	219 ´ 6	0,7		4711,8
3-7	72,44		1,33	108 ´ 4	0,9		4414,8
7-8	48,29		1,33	88.5 ´ 4	1,38	303,6	4111,2
2-6	458,81		1,33	219 ´ 6	0,47	155,1	4710,7
6-7	48,29		1,33	88.5 ´ 4	1,38	303,6	4407,1
Residual at node 7: (4414.8-4407.1) / 4414.8 100% = 0.17%
3-12	265,62		1,33	159 ´ 4	1,1		4348,8
12-14	48,29		1,33	88.5 ´ 4	1,3		4062,8
1-4	555,4		1,33	219 ´ 6	0,75	247,5	4728,3
4-10	265,62		1,33	159 ´ 4	1,1		4365,3
10-14	48,29		1,33	88.5 ´ 4	1,38	303,6	4061,7
Residual at node 14: (4062.8-4061.7) / 4062.8 100% = 0.03%
5-6	96,59		1,33	114 ´ 4	1,2		4182,7
4-5	72,44		1,76	89 ´ 3	1,8		4117,8
Residual at node 5: (4182.7-4117.8) / 4182.7 100% = 1.55%
6-9	48,29		1,76	88.5 ´ 4	1,38	303,6	4407,1
10-11	48,29		1,33	88.5 ´ 4	1,38	303,6	4061,7
12-13	48,29		1,33	88.5 ´ 4	1,38	303,6	4045,2

The first criterion for the correctness of the calculation is the pressure discrepancy at the nodal points, which should not be more than 10%. The pressure at the nodal points is determined by subtracting the pressure losses in the sections from the initial pressure from the hydraulic fracturing when the gas flow moves to the considered node along the shortest distance. The pressure difference is formed due to the different directions of the gas approach to the node.

The second criterion is the assessment of pressure losses from hydraulic fracturing to the most distant consumers. This loss should not be more than the calculated pressure drop equal to 1200 Pa and differ from it by no more than 10%.

The conditions for the correctness of the calculation are met and this is where the calculation of low-pressure multi-ring networks ends.

12.3 Hydraulic calculation of low pressure dead-end gas pipelines.

Low-pressure dead-end gas pipelines are laid inside residential buildings, inside production workshops and across the territory of small rural-type settlements.

The power source for such gas pipelines is low pressure hydraulic fracturing.

Hydraulic calculation of dead-end gas pipelines is carried out according to the nomogram in Fig. 11.4. The peculiarity of the calculation here is that when determining the pressure loss in the vertical sections, it is necessary to take into account the additional excess pressure due to the difference in the density of gas and air, that is

DР Д = ± h (r В - r Г) g,

where h -

r B, r G -

g

For natural gas, which is lighter than air, when it moves up the gas pipeline, the value DP will be negative, and positive when moving down.

Local resistances can be taken into account by introducing allowances for friction

l Р = l Г * (1 + a / 100), (m),

where a- percentage mark-up.

on risers - 20%;

with a length of 1-2 m - 450%,

with a length of 3-4 m - 200%,

with a length of 5-7 m. - 120%,

with a length of 8-12 m - 50%.

Pressure drop DP in dead-end low-pressure gas pipelines it is determined by the initial pressure after hydraulic fracturing or GRU, which is 4-5 kPa, and the pressure required for the operation of gas burners or gas appliances. Pressure drop DP, according to the recommendations of table 11.10. we take equal 350 Pa.

1. We create a design diagram of the gas pipeline: fig. 4.

2. We assign the main direction.

3. Determine the calculated gas consumption for each section of the main direction according to the formula,

V P = V HOUR TO OD, (m 3 / h),

where is the maximum hourly gas consumption of the corresponding consumer, m 3 / h,

V HOUR = 1,17 (m 3 / h),

CODE- coefficient of simultaneity, taking into account the likelihood of simultaneous operation of all consumers.

4. Determine the estimated length of the sections of the main direction ( l Р i) according to the formula,

l Р = l Г (1 + a / 100), (m),

where a- percentage mark-up.

on gas pipelines from the entrance to the building to the riser - 25%;

on risers - 20%;

on the inside of the apartment wiring:

with a length of 1-2 m - 450%,

with a length of 3-4 m - 200%,

with a length of 5-7 m. - 120%,

with a length of 8-12 m - 50%.

5. We calculate the estimated length of the main direction in meters, summing up all the estimated lengths of its sections ( S l Р i).

6. Determine the specific pressure drop in the main direction

A = DP / S l P i, (Pa / m).

A = 8.1871345(Pa / m).

7. Using the diagram fig. 11.4. , we determine the diameters of the gas pipeline sections of the main direction and specify the specific pressure drop at each section in accordance with the selected standard diameter.

8. Determine the actual gas pressure drop at each section by multiplying the specific pressure drop by the calculated section length.

9. Let's summarize all the losses in individual sections of the main direction.

10. Determine the additional overpressure in the gas pipeline,

DР Д = ± h (r В - r Г) g,

DР D = 110.26538

where h - difference in geometric marks at the end and beginning of the gas pipeline, m;

r B, r G - density of air and gas under normal conditions, kg / m 3;

g- acceleration of gravity, m / s 2.

h = 20.7(m) ,

11. We calculate the algebraic sum of the pressure losses in the main line and additional overpressure and compare it with the permissible pressure loss in the gas pipeline DP.

The criterion for the correctness of the calculation will be the condition

(SDP i ± DP D + DP PRIB) £ DP,

where SDP i- the sum of pressure losses in all sections of the line, Pa;

DP D- additional overpressure in the gas pipeline, Pa;

DR PRIB- loss of gas pressure in the gas-using device, Pa;

DP- set pressure drop, Pa.

(SDP i ± DP D + DP PRIB) = 338.24462 The discrepancy is 3,36%.

Deviation (SDP i ± DP D + DP PRIB) from DP should be no more than 10%.

The calculation is done correctly.

All calculations for determining the diameters of the gas pipeline are summarized in the table.

N O plot	Gas consumption, m 3 / h	Coeff. one-time.	Payment. consumption, m 3 / h	Section length m	Nadb. for a month res.	Payment. length, m	CONV. dia. mm	Pressure loss Pa
								1 m	at uch-ke
10-15	1,17	0,65	1,17			13,2	21.3´2.8	2,2	29,04
9-10	0,34	0,45	1,521			3,6	21.3´2.8		14,4
8-9	3,51	0,35	1,5795			3,6	21.3´2.8	4,2	15,12
7-8	4,68	0,29	1,638			3,6	21.3´2.8	4,5	16,2
6-7	5,85	0,26	1,6965			8,75	21.3´2.8		43,75
1-6	11,7	0,255	3,042				21.3´2.8
0-1	17,55		4,47525				21.3´2.8
						S42.75			S388.51

Finally, we accept the following diameters of the gas pipeline in the sections of the main direction:

10-15: 21.3´2.8 mm

9-10: 21.3´2.8 mm

8-9: 21.3´2.8 mm

7-8: 21.3´2.8 mm

6-7: 21.3´2.8 mm

1-6: 21.3´2.8 mm

0-1: 21.3´2.8 mm

The other two risers carry the same load and are identical in design to the calculated one. Therefore, the diameters of the gas pipeline on these risers are assumed to be the same as for the calculated one.

The only exceptions will be sections of the supply gas pipeline 1-2, 6-11. Determine the diameters of gas pipelines in these areas:

1. The calculated lengths of the branches: 0-1-6-11-12-13-14, 0-1-2-3-4-5, respectively, will be LP 6-11 = 40.25, LP 1-2 = 41.5 (m).

2. Estimated gas consumption:

Section 1-2 V P= 1.6965 (m 3 / h)

Section 6-11 V P= 1.6965 (m 3 / h).

3.Average specific loss

The hydraulic operating modes of distributed gas pipelines should be taken from the conditions of creation (at Δ P max add.) a system that ensures the stability of the operation of all hydraulic fracturing and burners within the permissible limits of gas pressure.

Calculation of gas pipelines is reduced to determining the required diameters and checking the specified 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 based on the formula for the entire turbulent region.

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 the consumers' gas devices.

2. Select the most distant points of branched gas pipelines and determine the total length l vol. them in the selected main 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 calculated length by 5-10%, (km).

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

5. By values A Wed and Q p. i. the diameters of the sections are selected according to the nomogram, rounding them up in accordance with GOST, i.e. towards smaller pressure drops in the area.

6. For the selected standard diameters according to GOST, the actual values ​​are found A d, then clarify P to according to the formula

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

mainstream.

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

Task 9.2.2. Carry out a hydraulic calculation of a branched high-pressure network, type "tree" in two options: a, b (Fig. 9.4).

a) Q 6= 700 m 3 / h; R 6= 0.3 MPa;

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

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

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

R GRS= 1 MPa;

l GRS-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) Q 8= 1500 m 3 / h; R 8= 0.3 MPa; Q 10= 2000 m 3 / h; R 10= 0.4 MPa; Q 13

2100 m 3 / h; R 13= 0.45 MPa; Q 14= 2300 m 3 / h; R 14= 0.6 MPa; R GRS= 0.8 MPa; l GRS-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 consumption in a gas pipeline 5 km long and 500 mm in diameter. The excess pressure at the beginning and at the end of the gas pipeline, respectively, is p 1= 3 ∙ 10 5 N / m 3 and p 2= 1 ∙ 10 5 N / m 3. Gas constant 500 (N ∙ m) / (kg ∙ K). Gas temperature 5 о С. Coefficient of hydraulic resistance 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 to be equal to one ( z=1).

The mass flow will be

.

Volumetric gas flow

.

Gas hourly 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 / m 3, gas constant R= 500 (N ∙ m) / (kg ∙ K). Hydraulic resistance coefficient λ = 0.015. Coefficient Z= 1. The gas temperature in the gas pipeline is 7 o C. The absolute pressure at the end of the gas pipeline is equal to p 2= 6 ∙ 10 5 Pa.

Solution

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

Determine the difference in the square of the pressures

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= 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 volumetric consumption of methane gas in a gas pipeline 10 km long, with an inner diameter of 0.3 m.The positive difference in the elevation of the gas pipeline is 500 m. The excess pressure at the beginning of the gas pipeline is p 1 = 15 kgf / cm 2, at the end of the gas pipeline R 2 = 14 kgf / cm 2. Gas temperature 5 о С, density ρ = 0.7kg / m 3, gas constant R= 500 (N ∙ m) / (kg ∙ K).

Solution

Determine the coefficient b

Reduced pressure and temperature

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

A gas pipeline is a structural system, the main purpose of which is gas transportation. 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 make the gas enters the pipeline under a certain pressure. For reliable and correct operation of the entire structure of the gas pipeline and its adjacent branches, a hydraulic calculation of the gas pipeline is required.

What is the calculation of the gas pipeline for?

1. The calculation of the gas pipeline is necessary to identify possible resistance in the gas pipe.
2. Correct calculations make it possible to select the necessary equipment for a gas construction system with high quality and reliability.
3. After the calculation, you can best select 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 the necessary points of the gas pipeline system.
4. Gas pipelines will operate at optimal conditions.
5. With the correct calculation, the design should not have excessive and excessive indicators when installing the system.
6. If the calculation is performed correctly, the developer can save financially. All work will be performed according to the scheme, only the necessary materials and equipment will be purchased.

How the gas line system works

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, pressure is redistributed, or rather, the gas pressure decreases.
3. Then the gas goes to the regulatory point, and from there to the network with a higher pressure.
4. The highest pressure pipeline is connected to the underground storage facility.
5. To regulate daily fuel consumption, special stations are installed. They are called gasholder stations.
6. Gas pipes, in which gas with high and medium pressure flows, serve as a kind of recharge for 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 supply of the entire required volume of blue fuel to the destination, the optimal pipe diameter is calculated. Calculations are made by hydraulic calculation.

If the gas pipes are already installed, then by means of calculations it is possible to find out the pressure loss during the period of movement of the fuel through the pipes. The dimensions of the existing pipes are also indicated immediately. Pressure losses are due to resistance.

There is a local resistance arising at bends, at the points of change in the gas velocity, when the diameter of one or another pipe changes. Even more often, there is frictional resistance, it occurs regardless of turns and gas speed, its distribution point is the entire length of the gas pipeline.

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

Calculations are used to determine the points where the low pressure fuel needs to be supplied. These points most often include residential buildings, commercial premises and public buildings, small communal consumers, some small boiler houses.

Hydraulic calculation with low gas pressure through the pipeline

1. It is roughly necessary to know the number of residents (consumers) in the estimated area where low pressure gas will be supplied.
2. The entire volume of gas for the year is taken into account, which will be used for all kinds of needs.
3. It is determined by calculating the value of fuel consumption by consumers for a certain time, in this case, an indication of one hour is taken.
4. The location of the gas distribution points is established, their number is calculated.

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

1. The area of ​​all pipes is calculated individually.
2. The density of the population of consumers in a given area is established.
3. The calculation of the gas consumption is carried out for the indication of the area of ​​each hotel pipe.
4. Computational work is carried out according to the following indicators:

• calculated data of the length of a section of the gas pipeline;
• actual data of the length 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. This pressure can be determined by observing the fuel supply from the main gas distribution point to the conversion area and the transition from high pressure to medium distribution. The pressure in the structure must be such that the indicators do not fall below the minimum permissible values ​​at the peak load on the gas pipeline.

In the calculations, the principle of pressure variation is applied, taking into account the unit of length of the measured pipeline.

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

1. At the initial stage, it becomes possible to calculate the pressure loss. The losses that occur in the main section of the gas pipeline are taken into account.
2. Then, the calculation of the gas flow rate for this section of the pipe is performed. According to the obtained average indicators of pressure losses and according to the calculations of fuel consumption, it is established what the required thickness of the pipeline is, and the required dimensions of the pipes are determined.
3. All possible pipe sizes are taken into account. Then, according to the nomogram, the value of losses is calculated for each of them.

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

Hydraulic calculation with high fuel pressure along the gas pipeline

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

1. The minimum pipe diameter is determined that can be accepted within the project for the normal functioning of the entire system.
2. The conditions under which the gas pipeline will operate is taken into account.
3. A special specification is being refined.

1. The terrain 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 mistakes in the project during further work.
2. A diagram of the project is shown. Its main condition is that it passes through the ring. The diagram must clearly show the various branches to the stations of consumption. When making 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 of sections of the gas pipeline are made. Then the calculation program is executed, and of course the scale is taken into account.
4. The readings obtained change, the estimated length of each pipe section shown in the diagram is slightly increased, by about ten percent.
5. Computational work is carried out in order to determine what the total fuel consumption will be. In this case, the gas consumption at each section of the pipeline is taken into account, then it is summed up.
6. The final stage in the design of a pipeline with a high gas pressure will be the determination of the internal size of the pipe.

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

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 the gas elements will be placed in accordance with the standards, according to which safety conditions are also taken into account.

Depict a diagram of the entire indoor system. This makes it possible to identify any malfunctions during the time, to make the installation clearly.

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 exhaust hood, a chimney is taken into account. All this is necessary in order to qualitatively install devices and a pipeline for the delivery of blue fuel.

Hydraulic calculation of the in-house gas system

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

The diameter of the section of the internal highway is calculated according to the consumed amount of blue fuel.

It also takes into account the pressure losses that can occur on the gas delivery route. The design system should have the lowest possible pressure loss. In domestic gas systems, a decrease in pressure is quite frequent, therefore it is very important to calculate this indicator for the efficient operation of the entire line.

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

Calculations are made of the size of the gas pipes. The optimal pipe diameter can provide the smallest 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 embedded in the distribution area and conversion points.

When calculating the 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 factor on the main line and its branches. The total indicator will not exceed the maximum permissible values, it will be less than seventy percent of the nominal pressure shown by the instruments.

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

To make the selection of pipes, fittings and equipment as accurate as possible, a hydraulic calculation of the pipeline is performed. How to do it? Admit it, you are not very well versed in this matter, let's figure it out.

We suggest that you familiarize yourself with the scrupulously selected and thoroughly processed information about the options for the production of hydraulic calculation for gas pipeline systems. The use of the data presented by us will ensure the supply of blue fuel to the devices with the required pressure parameters. The carefully checked data are based on the regulations of the regulatory documentation.

The article is extremely detailed about the principles and schemes of the production of computations. An example of performing calculations is given. Graphic applications and video instructions were used as a useful informative addition.

Any hydraulic calculation performed is a determination of the parameters of the future gas pipeline. This procedure is mandatory, as well as one of the most important stages of preparation for construction. It depends on the correctness of the calculation whether the gas pipeline will function optimally.

When performing each hydraulic calculation, a determination is made:

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

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

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

Beginning of the section	End of the section	Estimated flow rate m³ / h	Gas pipeline length	Inner diameter, cm	Initial pressure, Pa	Final pressure, Pa	Pressure drop, Pa
1	2	31,34	120	9,74	2000,00	1979,33	20,67
2	3	31,34	150	9,74	1979,33	1953,48	25,84
3	4	31,34	180	7,96	1953,48	1872,52	80,96
4	5	29,46	90	7,96	1872,52	1836,2	36,32
5	6	19,68	120	8,2	1836,2	1815,45	20,75
6	7	5,8	100	8,2	1815,45	1813,95	1,5
4	8	9,14	140	5	1872,52	1806,38	66,14
6	9	4,13	70	5	1815,45	1809,83	5,62

Such an operation is a state-standardized procedure that is performed according to the formulas, the requirements set out in SP 42-101-2003.

The developer is obliged to carry out the calculations. The data on the technical specifications of the pipeline, which can be obtained from your gas company, are taken as a basis.

Gas pipelines requiring calculations

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

These gas pipelines include the following types:

• low pressure;
• medium, high pressure.

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

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

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

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

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

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

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

Despite the wide variety of options for gas pipelines, the hydraulic calculation is similar in any of the cases. Since structural elements from similar materials are used for manufacturing, the same processes take place inside the pipes.

Hydraulic resistance and its role

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

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

Hydraulic resistance is always the sum:

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

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

Calculation rules

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

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

Any hydraulic calculation is performed after creating a calculation scheme that includes the main indicators. Moreover, the user enters known data in the corresponding columns.

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

Which include:

• calculation according to the formulas given in the joint venture is the most difficult method of calculation;
• calculation according to the so-called nomograms is an easier option than using formulas, because you do not have to make any calculations, because the necessary data are indicated in a special table and are given in the Code of Rules, and you just need to pick them up.

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

PC Computing Option

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

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

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

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

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

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

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

The roughness factor always equates to the following values:

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

For any other types of pipes, this indicator is not indicated in the Code of Rules. Therefore, it is not worth using them for the construction of a new gas pipeline, since Gorgaz specialists may require adjustments. And this, again, is an additional cost.

Calculation of flow in a limited area

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

Defining data using a program

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

To do this, the following actions are performed (an example is given for an in-house low-pressure gas pipeline):

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

Similar manipulations are carried out for all sections of the gas pipeline. The data obtained is entered into the corresponding columns of the program, with the help of which the calculations are performed. Electronics does the rest itself.

Calculation using formulas

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

And you will also have to devote a lot of time to understand many concepts, questions that a person does not meet when using a special program. You can verify the validity of the above by looking at the formulas to be used.

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

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

Calculations with nomograms

Any special nomogram is a table where a number of values ​​are indicated, having studied which you can get the necessary indicators without performing calculations. In the case of a hydraulic calculation, the diameter of the pipe and the thickness of its walls.

Calculation nomograms are an easy way to get the information you need. It is enough to refer to the lines corresponding to the given characteristics of the network

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

Calculation example

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

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

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

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

It is worth paying attention to the numbering of the plots - they do not come up with it independently, but are taken from a previously drawn up scheme, where similar numbers are indicated.

Next, the actual length of the gas pipeline is prescribed and the so-called calculated one, which is greater. This happens because in all areas where there is local resistance, it is necessary to increase the length by 5-10%. This is done in order to exclude insufficient gas pressure at consumers. The program calculates independently.

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

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

The inner diameter of the pipe is indicated in accordance with the terms of reference, if the gas company has any requirements, or from a previously drawn up diagram. In this case, in most sections, it is registered in the size of 5 cm, because most of the gas pipeline runs along the facade, and the local gas company requires that the diameter be no less.

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

That is, the calculation itself takes place quite quickly, after which, with the received data, you can send for approval to the gas department of your city.

Conclusions and useful video on the topic

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

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

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

But all this has no practical value, since drafting a project is a much more voluminous procedure and includes many other issues. In view of this, the majority of citizens will have to seek help from specialists.

Have questions, found bugs or can you supplement our material with valuable information? Leave your comments, ask questions, share your experience in the block below.