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

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

Methods for calculating the throughput of the pipeline

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

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

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

Calculation of the throughput capacity of gas pipelines

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

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

• Qmax = 0.67 DN2 * p,

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

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

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

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

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

Where z is the compression ratio of the transported medium;

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

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

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

Calculation of the capacity of sewer pipes

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

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

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

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

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

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

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

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

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

• q = a*v,

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

v is the speed of effluent transportation.

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

• v=C√R*i,

where R is the value of the hydraulic radius,

C is the wetting coefficient;

i - the degree of slope of the structure.

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

• i=v2/C2*R.

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

• С=(1/n)*R1/6,

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

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

For other situations, a simple formula is used:

• R=A/P

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

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

Tabular calculation of sewer pipes

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

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

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

Calculation of the capacity of the water supply

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

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

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

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

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

The main parameters taken into account in these tables are:

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

Conclusion

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

Water flow parameters:

1. The value of the pipe diameter, which also determines the further throughput.
2. The size of the pipe walls, which will then determine the internal pressure in the system.

The only thing that does not affect consumption is the length of communications.

If the diameter is known, the calculation can be carried out according to the following data:

1. Structural material for pipe construction.
2. Technology affecting the pipeline assembly process.

Characteristics affect the pressure inside the water supply system and determine the flow of water.

If you are looking for an answer to the question of how to determine the flow of water, then you must learn two calculation formulas that determine the parameters of use.

1. The formula for daily calculation is Q=ΣQ×N/100. Where ΣQ is the annual daily water use per 1 inhabitant, and N is the number of inhabitants in the building.
2. The formula for calculating per hour is q=Q×K/24. Where Q is the daily calculation, and K is the ratio according to SNiP, uneven consumption (1.1-1.3).

These simple calculations can help determine the expense, which will show the needs and requirements of this house. There are tables that can be used in calculating the liquid.

Reference data in the calculation of water

When using tables, you should calculate all the taps, bathtubs and water heaters in the house. Table SNiP 2.04.02-84.

Standard consumption rates:

• 60 liters - 1 person.
• 160 liters - for 1 person, if the house has better plumbing.
• 230 liters - for 1 person, in a house where high-quality plumbing and a bathroom are installed.
• 350 liters - for 1 person with running water, built-in appliances, bathroom, toilet.

Why calculate water according to SNiP?

How to determine the water flow for each day is not the most requested information among ordinary residents of the house, but pipeline installers need this information even less. And for the most part, they need to know what the diameter of the connection is, and what pressure it maintains in the system.

But in order to determine these indicators, you need to know how much water is needed in the pipeline.

The formula to help determine the pipe diameter and fluid flow rate:

The standard liquid velocity in a headless system is 0.7 m/s and 1.9 m/s. And the speed from an external source, such as a boiler, is determined by the source passport. When the diameter is known, the flow rate in communications is determined.

Water head loss calculation

The loss of water flow is calculated taking into account the pressure drop using one formula:

In the formula, L - denotes the length of the connection, and λ - friction loss, ρ - malleability.

The friction index varies from the following values:

• the level of roughness of the coating;
• obstacle in the equipment at the locking points;
• fluid flow rate;
• pipeline length.

Ease of calculation

Knowing the pressure loss, the velocity of the liquid in the pipes and the volume of water needed, how to determine the flow of water and the size of the pipeline becomes much clearer. But in order to get rid of long calculations, you can use a special table.

Where D is the diameter of the pipe, q is the consumption of water, and V is the speed of the water, i is the course. To determine the values, they must be found in the table and connected in a straight line. Also determine the flow rate and diameter, while taking into account the slope and speed. Therefore, the easiest way to calculate is to use tables and graphs.

Method for calculating the Shevelev table theoretical hydraulics SNiP 2.04.02-84

Initial data

Pipe material: New steel without an internal protective coating or with a bitumen protective coating New cast iron without an internal protective coating or with a bitumen protective coating Non-new steel and cast iron without an internal protective coating or with a bitumen protective coating spin-applied plastic or polymer-cement coating Steel and cast iron, with an internal spray-applied cement-sand coating Steel and cast-iron, with an internal spin-applied cement-sand coating Made of polymeric materials (plastic) Glass

Estimated consumption

l/s m3/h

Outside diameter mm

Wall thickness mm

Pipeline length m

Average water temperature °C

Eq. roughness inside. pipe surfaces: Heavily rusted or heavily deposited Steel or cast iron old rusted Steel galv. after several years Steel after several years Cast iron new Galvanized steel new Welded steel new Seamless steel new Drawn from brass, lead, copper Glass

Sum of sets of local resistances

Payment

Dependence of pressure loss on pipe diameter

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When calculating a water supply or heating system, you are faced with the task of selecting the diameter of the pipeline. To solve such a problem, you need to make a hydraulic calculation of your system, and for an even simpler solution, you can use hydraulic calculation online which we will now do.
Operating procedure:
1. Select the appropriate calculation method (calculation according to Shevelev tables, theoretical hydraulics or according to SNiP 2.04.02-84)
2. Select piping material
3. Set the estimated water flow in the pipeline
4. Set the outer diameter and wall thickness of the pipeline
5. Set the piping length
6. Set the average water temperature
The result of the calculation will be the graph and the following hydraulic calculation values.
The graph consists of two values ​​(1 - water head loss, 2 - water speed). The optimum pipe diameter values ​​will be written in green below the graph.

Those. you must set the diameter so that the point on the graph is exactly above your green values ​​for the pipeline diameter, because only at such values ​​will the water velocity and head loss be optimal.

The pressure loss in the pipeline shows the pressure loss in a given section of the pipeline. The higher the losses, the more work will have to be done to deliver water to the right place.
The hydraulic resistance characteristic shows how effectively the pipe diameter is selected depending on the pressure loss.
For reference:
- if you need to find out the velocity of liquid/air/gas in a pipeline of various sections, use

35001 0 27

Pipe capacity: simple about the complex

How does the throughput of a pipe vary with diameter? What factors, besides the cross section, affect this parameter? Finally, how to calculate, albeit approximately, the permeability of a water supply system with a known diameter? In the article I will try to give the most simple and accessible answers to these questions.

Our task is to learn how to calculate the optimal cross-section of water pipes.

Why is it needed

Hydraulic calculation allows you to get the optimal minimum the diameter of the pipeline.

On the one hand, there is always a catastrophic shortage of money during construction and repair, and the price of a linear meter of pipes grows non-linearly with an increase in diameter. On the other hand, an underestimated section of the water supply will lead to an excessive drop in pressure at the end devices due to its hydraulic resistance.

With a flow rate at the intermediate device, the pressure drop at the end device will lead to the fact that the water temperature with the cold water and hot water taps open will change dramatically. As a result, you will either be doused with ice water or scalded with boiling water.

Restrictions

I will deliberately limit the scope of the tasks under consideration to the plumbing of a small private house. There are two reasons:

1. Gases and liquids of different viscosities behave completely differently when transported through a pipeline. Consideration of the behavior of natural and liquefied gas, oil and other media would increase the volume of this material several times and would take us far from my specialty - plumbing;
2. In the case of a large building with numerous plumbing fixtures, for the hydraulic calculation of the water supply system, it will be necessary to calculate the probability of using several water points at the same time. In a small house, the calculation is performed for peak demand by all available appliances, which greatly simplifies the task.

Factors

Hydraulic calculation of a water supply system is a search for one of two quantities:

• Calculation of the throughput of a pipe with a known cross section;
• Calculation of the optimal diameter with a known planned flow rate.

In real conditions (when designing a water supply system), the second task is much more often necessary.

Household logic suggests that the maximum flow of water through a pipeline is determined by its diameter and inlet pressure. Alas, the reality is much more complicated. The fact is that the pipe has hydraulic resistance: Simply put, the flow slows down due to friction against the walls. Moreover, the material and condition of the walls predictably affect the degree of braking.

Here is a complete list of factors that affect the performance of a water pipe:

• Pressure at the beginning of the water supply (read - pressure in the route);
• bias pipes (change in its height above the conditional ground level at the beginning and end);

• Material walls. Polypropylene and polyethylene have much less roughness than steel and cast iron;
• Age pipes. Over time, steel becomes overgrown with rust and lime deposits, which not only increase the roughness, but also reduce the internal clearance of the pipeline;

This does not apply to glass, plastic, copper, galvanized and metal-polymer pipes. They are in like new condition even after 50 years of operation. An exception is the silting of the water supply with a large amount of suspensions and the absence of filters at the inlet.

• Quantity and Angle turns;
• Diameter changes plumbing;
• Presence or absence welds, soldering beads and connecting fittings;

• Shut-off valves. Even full bore ball valves offer some resistance to flow.

Any calculation of pipeline capacity will be very approximate. Willy-nilly, we will have to use average coefficients that are typical for conditions close to ours.

Law of Torricelli

Evangelista Torricelli, who lived in the early 17th century, is known as a student of Galileo Galilei and the author of the very concept of atmospheric pressure. He also owns a formula describing the flow rate of water pouring out of a vessel through an opening of known dimensions.

For the Torricelli formula to work, it is necessary:

1. So that we know the pressure of the water (the height of the water column above the hole);

One atmosphere under the earth's gravity is capable of lifting a column of water by 10 meters. Therefore, pressure in atmospheres is converted into head by simply multiplying by 10.

1. For the hole to be significantly smaller than the diameter of the vessel, thus eliminating the loss of pressure due to friction against the walls.

In practice, Torricelli's formula allows you to calculate the flow of water through a pipe with an internal section of known dimensions at a known instantaneous head during flow. Simply put: to use the formula, you need to install a pressure gauge in front of the tap or calculate the pressure drop on the water supply at a known pressure in the line.

The formula itself looks like this: v^2=2gh. In it:

• v is the flow velocity at the outlet of the orifice, in meters per second;
• g is the acceleration of fall (for our planet it is equal to 9.78 m/s^2);
• h - head (height of the water column above the hole).

How will this help us in our task? And the fact that fluid flow through an orifice(the same throughput) is equal to S*v, where S is the cross-sectional area of ​​the orifice and v is the flow velocity from the above formula.

Captain Evidence suggests: knowing the cross-sectional area, it is easy to determine the inner radius of the pipe. As you know, the area of ​​a circle is calculated as π*r^2, where π is rounded to 3.14159265.

In this case, Torricelli's formula will look like v^2=2*9.78*20=391.2. The square root of 391.2 is rounded to 20. This means that water will pour out of the hole at a speed of 20 m / s.

We calculate the diameter of the hole through which the stream flows. Converting the diameter to SI units (meters), we get 3.14159265*0.01^2=0.0003141593. And now we calculate the water flow: 20 * 0.0003141593 \u003d 0.006283186, or 6.2 liters per second.

Back to reality

Dear reader, I would venture to suggest that you do not have a pressure gauge installed in front of the mixer. It is obvious that some additional data are needed for a more accurate hydraulic calculation.

Usually, the calculation problem is solved from the opposite: with known water flow through plumbing fixtures, the length of the water pipe and its material, a diameter is selected that ensures the pressure drop to acceptable values. The limiting factor is the flow rate.

Reference data

The flow rate for internal water pipes is considered to be 0.7 - 1.5 m / s. Exceeding the latter value leads to the appearance of hydraulic noise (primarily at bends and fittings).

Water consumption rates for plumbing fixtures are easy to find in the regulatory documentation. In particular, they are given by the appendix to SNiP 2.04.01-85. To save the reader from lengthy searches, I will give this table here.

The table shows data for mixers with aerators. Their absence equalizes the flow through the sink, washbasin and shower faucets with the flow through the faucet when taking a bath.

Let me remind you that if you want to calculate the water supply of a private house with your own hands, sum up the water consumption for all installed appliances. If this instruction is not followed, surprises will await you, such as a sharp drop in the temperature in the shower when you open the hot water tap on.

If there is a fire water supply in the building, 2.5 l / s for each hydrant is added to the planned flow. For fire water supply, the flow velocity is limited to 3 m/s: in case of fire, hydraulic noise is the last thing that will unnerve the residents.

When calculating the pressure, it is usually assumed that on the device extreme from the input it must be at least 5 meters, which corresponds to a pressure of 0.5 kgf / cm2. Some plumbing fixtures (flowing water heaters, filling valves of automatic washing machines, etc.) simply do not work if the pressure in the water supply is below 0.3 atmospheres. In addition, it is necessary to take into account the hydraulic losses on the device itself.

In the photo - instantaneous water heater Atmor Basic. It includes heating only at a pressure of 0.3 kgf/cm2 and above.

Flow rate, diameter, speed

Let me remind you that they are linked to each other by two formulas:

1. Q=SV. The water flow in cubic meters per second is equal to the cross-sectional area in square meters multiplied by the flow rate in meters per second;
2. S = r ^2. The cross-sectional area is calculated as the product of the number "pi" and the square of the radius.

Where can I get the values ​​for the radius of the inner section?

• For steel pipes, it is, with a minimum error, equal to half of the control(conditional pass, which is marked pipe rolling);
• For polymer, metal-polymer, etc. the inner diameter is equal to the difference between the outer one, with which the pipes are marked, and twice the wall thickness (it is also usually present in the marking). The radius, respectively, is half the inner diameter.

1. The inner diameter is 50-3 * 2 = 44 mm, or 0.044 meters;
2. The radius will be 0.044/2=0.022 meters;
3. The area of ​​​​the internal section will be equal to 3.1415 * 0.022 ^ 2 \u003d 0.001520486 m2;
4. At a flow rate of 1.5 meters per second, the flow rate will be 1.5 * 0.001520486 = 0.002280729 m3 / s, or 2.3 liters per second.

head loss

How to calculate how much pressure is lost on a water supply system with known parameters?

The simplest formula for calculating the pressure drop is H = iL(1+K). What do the variables in it mean?

• H is the cherished pressure drop in meters;
• i - hydraulic slope of the water pipe meter;
• L is the length of the water supply in meters;
• K- coefficient, which makes it possible to simplify the calculation of the pressure drop on the stop valves and . It is tied to the purpose of the water supply network.

Where can I get the values ​​of these variables? Well, except for the length of the pipe - no one has canceled the roulette yet.

The coefficient K is taken equal to:

With a hydraulic slope, the picture is much more complicated. The resistance offered by a pipe to flow depends on:

• Internal section;
• Wall roughness;
• Flow rates.

A list of 1000i values ​​(hydraulic slope per 1000 meters of water supply) can be found in Shevelev's tables, which, in fact, are used for hydraulic calculation. The tables are too large for an article as they give 1000i values ​​for all possible diameters, flow rates and life corrected materials.

Here is a small fragment of the Shevelev table for a 25 mm plastic pipe.

The author of the tables gives the values ​​of the pressure drop not for the internal section, but for the standard sizes that mark the pipes, adjusted for the wall thickness. However, the tables were published in 1973, when the corresponding market segment had not yet formed.
When calculating, keep in mind that for metal-plastic it is better to take values ​​corresponding to a pipe one step smaller.

Let's use this table to calculate the pressure drop on a polypropylene pipe with a diameter of 25 mm and a length of 45 meters. Let's agree that we are designing a water supply system for household purposes.

1. With a flow velocity as close as possible to 1.5 m/s (1.38 m/s), the value of 1000i will be equal to 142.8 meters;
2. The hydraulic slope of one meter of pipe will be equal to 142.8 / 1000 \u003d 0.1428 meters;
3. The correction factor for domestic water pipes is 0.3;
4. The formula as a whole will take the form H=0.1428*45(1+0.3)=8.3538 meters. This means that at the end of the water supply at a water flow rate of 0.45 l / s (the value from the left column of the table), the pressure will drop by 0.84 kgf / cm2 and at 3 atmospheres at the inlet it will be quite acceptable 2.16 kgf / cm2.

This value can be used to determine consumption according to the Torricelli formula. The calculation method with an example is given in the corresponding section of the article.

In addition, in order to calculate the maximum flow through a water supply system with known characteristics, one can select in the “flow rate” column of the complete Shevelev table such a value at which the pressure at the end of the pipe does not fall below 0.5 atmospheres.

Conclusion

Dear reader, if the above instructions, despite the extreme simplification, still seemed tedious to you, just use one of the many online calculators. As always, more information can be found in the video in this article. I will be grateful for your additions, corrections and comments. Good luck, comrades!

July 31, 2016

If you want to express gratitude, add a clarification or objection, ask the author something - add a comment or say thanks!

Why do we need such calculations

When drawing up a plan for the construction of a large cottage with several bathrooms, a private hotel, the organization of a fire system, it is very important to have more or less accurate information about the transport capabilities of the existing pipe, taking into account its diameter and pressure in the system. It's all about pressure fluctuations during the peak of water consumption: such phenomena seriously affect the quality of the services provided.

In addition, if the water supply system is not equipped with water meters, then when paying for utility services, the so-called. "Permeability of the pipe". In this case, the question of the tariffs applied in this case quite logically emerges.

At the same time, it is important to understand that the second option does not apply to private premises (apartments and cottages), where, in the absence of meters, sanitary standards are taken into account when calculating payment: usually this is up to 360 l / day per person.

What determines the permeability of the pipe

What determines the flow of water in a round pipe? One gets the impression that the search for an answer should not cause difficulties: the larger the cross section of the pipe, the greater the volume of water it can pass in a certain time. At the same time, pressure is also remembered, because the higher the water column, the faster the water will be forced through the communication. However, practice shows that these are far from all the factors affecting water consumption.

In addition to them, the following points also have to be taken into account:

1. Pipe length. With an increase in its length, the water rubs against its walls more strongly, which leads to a slowdown in the flow. Indeed, at the very beginning of the system, water is only affected by pressure, but it is also important how quickly the next portions will have the opportunity to enter the communication. Braking inside the pipe often reaches large values.
2. Water consumption depends on the diameter to a much more complex extent than it seems at first glance. When the size of the pipe diameter is small, the walls resist the water flow by an order of magnitude more than in thicker systems. As a result, as the diameter of the pipe decreases, its benefit in terms of the ratio of the water flow rate to the indicator of the internal area in a section of a fixed length decreases. To put it simply, a thick plumbing system transports water much faster than a thin one.
3. Production material. Another important point that directly affects the speed of movement of water through the pipe. For example, smooth propylene promotes water sliding to a much greater extent than rough steel walls.
4. Service life. Over time, rust appears on steel water pipes. In addition, for steel, as well as for cast iron, it is typical to gradually accumulate lime deposits. The resistance to water flow of a pipe with deposits is much higher than that of new steel products: this difference sometimes reaches 200 times. In addition, the overgrowth of the pipe leads to a decrease in its diameter: even if we do not take into account the increased friction, its permeability clearly decreases. It is also important to note that products made of plastic and metal-plastic do not have such problems: even after decades of intensive use, their level of resistance to water flows remains at the original level.
5. The presence of turns, fittings, adapters, valves contributes to additional braking of water flows.

All of the above factors have to be taken into account, because we are not talking about some small errors, but about a serious difference several times over. As a conclusion, it can be said that a simple determination of the pipe diameter from the water flow is hardly possible.

New possibility of water consumption calculations

If the use of water is carried out by means of a tap, this greatly simplifies the task. The main thing in this case is that the dimensions of the hole for the outpouring of water are much smaller than the diameter of the water pipe. In this case, the formula for calculating water over the cross section of the Torricelli pipe v ^ 2 \u003d 2gh is applicable, where v is the speed of flow through a small hole, g is the acceleration of free fall, and h is the height of the water column above the tap (a hole having a cross section s, per unit time passes water volume s*v). It is important to remember that the term "section" is used not to denote the diameter, but its area. To calculate it, use the formula pi * r ^ 2.

If the column of water has a height of 10 meters and the hole has a diameter of 0.01 m, the water flow through the pipe at a pressure of one atmosphere is calculated as follows: v^2=2*9.78*10=195.6. After taking the square root, v=13.98570698963767. After rounding to get a simpler speed figure, the result is 14m/s. The cross section of the hole, having a diameter of 0.01 m, is calculated as follows: 3.14159265*0.01^2=0.000314159265 m2. As a result, it turns out that the maximum water flow through the pipe corresponds to 0.000314159265 * 14 = 0.00439822971 m3 / s (slightly less than 4.5 liters of water / second). As you can see, in this case, the calculation of water over the cross section of the pipe is quite simple. Also freely available are special tables indicating the water consumption for the most popular plumbing products, with a minimum value for the diameter of the water pipe.

As you can already understand, there is no universal simple way to calculate the diameter of the pipeline depending on the water flow. However, you can still deduce certain indicators for yourself. This is especially true in cases where the system is equipped with plastic or metal-plastic pipes, and water is consumed by taps with a small outlet cross section. In some cases, this calculation method is applicable to steel systems, but we are talking primarily about new water pipes that have not had time to become covered with internal deposits on the walls.

Water flow rate by pipe diameter: determination of the pipeline diameter depending on the flow rate, calculation by section, formula for the maximum flow rate at pressure in a round pipe

Water flow rate by pipe diameter: determination of the pipeline diameter depending on the flow rate, calculation by section, formula for the maximum flow rate at pressure in a round pipe

Water flow through a pipe: is a simple calculation possible?

Is it possible to calculate the flow of water by the diameter of the pipe in any simple way? Or is the only way - to contact specialists, having previously shown a detailed map of all water pipes in the area?

After all, hydrodynamic calculations are extremely complex ...

Our task is to find out how much water this pipe can pass.

What is it for?

1. When self-calculation of plumbing systems.

If you plan to build a large house with several guest baths, a mini-hotel, think over a fire extinguishing system - it is advisable to know how much water a pipe of a given diameter can supply at a certain pressure.

After all, a significant drop in pressure at the peaks of water consumption is unlikely to please residents. And a weak trickle of water from a fire hose is likely to be useless.

1. In the absence of water meters, utilities usually bill "pipe pass" organizations.

Please note: the second scenario does not affect apartments and private houses. If there are no water meters, utilities charge for water according to sanitary standards. For modern comfortable houses, this is no more than 360 liters per person per day.

It must be admitted: the water meter greatly simplifies relations with utilities

Factors affecting the patency of the pipe

What affects the maximum water flow in a round pipe?

The obvious answer

Common sense dictates that the answer should be very simple. There is a water pipe. There is a hole in it. The larger it is, the more water passes through it per unit of time. Ah, sorry, more pressure.

Obviously, a column of water 10 centimeters will force less water through a centimeter hole than a water column with a height of a ten-story building.

So, from the internal section of the pipe and from the pressure in the water supply, right?

Is there really something else needed?

Correct answer

No. These factors affect consumption, but they are just the beginning of a long list. Calculating the flow of water by the diameter of the pipe and the pressure in it is the same as calculating the trajectory of a rocket flying to the Moon, based on the apparent position of our satellite.

If we do not take into account the rotation of the Earth, the movement of the Moon in its own orbit, the resistance of the atmosphere and the gravity of celestial bodies, it is unlikely that our spacecraft will get at least approximately to the desired point in space.

How much water will pour out of a pipe with a diameter x at a pressure in the track y is influenced not only by these two factors, but also by:

• Pipe length. The longer it is, the stronger the friction of water against the walls slows down the flow of water in it. Yes, only the pressure in it affects the water at the very end of the pipe, but the following volumes of water should take its place. And the water pipe slows them down, and how.

It is because of the loss of pressure in a long pipe that oil pipelines have pumping stations.

• The diameter of the pipe affects the flow of water is much more complicated than "common sense" suggests. For small diameter pipes, the wall resistance to flow is much greater than for thick pipes.

The reason is that the smaller the pipe, the less favorable the ratio of internal volume and surface area in it from the point of view of the water flow rate at a fixed length.

Simply put, it is easier for water to move through a thick pipe than through a thin one.

• The material of the walls is another important factor on which the speed of water movement depends.. While water glides over smooth polypropylene like the sirloin of a clumsy lady on a pavement in ice, rough steel creates much more resistance to flow.
• The age of the pipe also greatly affects the permeability of the pipe.. Steel water pipes rust, in addition, steel and cast iron become overgrown with lime deposits over the years of operation.

An overgrown pipe has a much greater resistance to flow (the resistance of a polished new steel pipe and a rusty one differ by 200 times!). Moreover, the sections inside the pipe, due to overgrowth, reduce their clearance; even under ideal conditions, much less water will pass through an overgrown pipe.

Do you think it makes sense to calculate the permeability by the diameter of the pipe at the flange?

Please note: the surface condition of plastic and metal-polymer pipes does not deteriorate over time. After 20 years, the pipe will have the same resistance to water flow as it did at the time of installation.

• Finally, any turn, diameter transition, various valves and fittings - all this also slows down the flow of water.

Ah, if the above factors could be neglected! However, we are not talking about deviations within the error, but about a difference at times.

All this leads us to a sad conclusion: a simple calculation of the flow of water through a pipe is impossible.

Beam of light in the dark realm

In the case of water flow through a faucet, however, the task can be greatly simplified. The main condition for a simple calculation: the hole through which the water flows must be negligible compared to the diameter of the water supply pipe.

Then Torricelli's law applies: v^2=2gh, where v is the velocity of the outflow from the small hole, g is the free fall acceleration, and h is the height of the water column above the hole. In this case, a volume of liquid s * v will pass through a hole with a cross section s per unit time.

The master left you a gift

Don't forget: the cross section of the hole is not the diameter, it's the area equal to pi*r^2.

For a water column of 10 meters (which corresponds to an overpressure of one atmosphere) and a hole with a diameter of 0.01 meter, the calculation will be as follows:

We extract the square root and get v=13.98570698963767. For ease of calculation, we will round the value of the flow velocity to 14 m/s.

The cross section of a hole with a diameter of 0.01 m is 3.14159265*0.01^2=0.000314159265 m2.

Thus, the flow of water through our hole will be 0.000314159265 * 14 = 0.00439822971 m3 / s, or a little less than four and a half liters per second.

As you can see, in this variant the calculation is not very complicated.

In addition, in the appendix to the article you will find a table of water consumption by the most common plumbing fixtures, indicating the minimum diameter of the liner.

Conclusion

That's all in a nutshell. As you can see, we did not find a universal simple solution; however, we hope the article will be useful to you. Good luck!

How to calculate pipe throughput

Calculating capacity is one of the most difficult tasks in laying a pipeline. In this article, we will try to figure out exactly how this is done for different types of pipelines and pipe materials.

High capacity pipes

Throughput is an important parameter for any pipes, canals and other heirs of the Roman aqueduct. However, the throughput is not always indicated on the pipe packaging (or on the product itself). In addition, it also depends on the pipeline scheme how much liquid the pipe passes through the section. How to correctly calculate the throughput of pipelines?

Methods for calculating the throughput of pipelines

There are several methods for calculating this parameter, each of which is suitable for a particular case. Some notations that are important in determining the throughput of a pipe:

Outer diameter - the physical size of the pipe section from one edge of the outer wall to the other. In calculations, it is designated as Dn or Dn. This parameter is indicated in the marking.

Nominal diameter is the approximate value of the diameter of the internal section of the pipe, rounded up to a whole number. In calculations, it is designated as Du or Du.

Physical methods for calculating the throughput of pipes

Pipe throughput values ​​are determined by special formulas. For each type of product - for gas, water supply, sewerage - the methods of calculation are different.

Tabular calculation methods

There is a table of approximate values ​​\u200b\u200bcreated to facilitate the determination of the throughput of pipes for intra-apartment wiring. In most cases, high precision is not required, so the values ​​can be applied without complex calculations. But this table does not take into account the decrease in throughput due to the appearance of sedimentary growths inside the pipe, which is typical for old highways.

There is an exact capacity calculation table, called the Shevelev table, which takes into account the pipe material and many other factors. These tables are rarely used when laying water pipes around the apartment, but in a private house with several non-standard risers they can come in handy.

Calculation using programs

At the disposal of modern plumbing firms there are special computer programs for calculating the throughput of pipes, as well as many other similar parameters. In addition, online calculators have been developed that, although less accurate, are free and do not require installation on a PC. One of the stationary programs "TAScope" is a creation of Western engineers, which is shareware. Large companies use "Hydrosystem" - this is a domestic program that calculates pipes according to criteria that affect their operation in the regions of the Russian Federation. In addition to hydraulic calculation, it allows you to calculate other parameters of pipelines. The average price is 150,000 rubles.

How to calculate the throughput of a gas pipe

Gas is one of the most difficult materials to transport, in particular because it tends to compress and therefore can flow through the smallest gaps in pipes. Special requirements are imposed on the calculation of the throughput of gas pipes (as well as on the design of the gas system as a whole).

The formula for calculating the throughput of a gas pipe

The maximum capacity of gas pipelines is determined by the formula:

Qmax = 0.67 DN2 * p

where p is equal to the working pressure in the gas pipeline system + 0.10 MPa or the absolute pressure of the gas;

Du - conditional passage of the pipe.

There is a complex formula for calculating the throughput of a gas pipe. When carrying out preliminary calculations, as well as when calculating a domestic gas pipeline, it is usually not used.

Qmax = 196.386 Du2 * p/z*T

where z is the compressibility factor;

T is the temperature of the transported gas, K;

According to this formula, the direct dependence of the temperature of the transported medium on pressure is determined. The higher the T value, the more the gas expands and presses against the walls. Therefore, when calculating large highways, engineers take into account possible weather conditions in the area where the pipeline passes. If the nominal value of the DN pipe is less than the gas pressure generated at high temperatures in summer (for example, at + 38 ... + 45 degrees Celsius), then the line is likely to be damaged. This entails the leakage of valuable raw materials, and creates the possibility of an explosion of the pipe section.

Table of capacities of gas pipes depending on pressure

There is a table for calculating the throughput of a gas pipeline for commonly used diameters and nominal working pressure of pipes. Engineering calculations will be required to determine the characteristics of a gas pipeline of non-standard dimensions and pressure. Also, the pressure, speed of movement and volume of gas is affected by the temperature of the outside air.

The maximum velocity (W) of the gas in the table is 25 m/s and z (compressibility factor) is 1. The temperature (T) is 20 degrees Celsius or 293 Kelvin.

Capacity of the sewer pipe

The capacity of the sewer pipe is an important parameter that depends on the type of pipeline (pressure or non-pressure). The calculation formula is based on the laws of hydraulics. In addition to the laborious calculation, tables are used to determine the capacity of the sewer.

Hydraulic Calculation Formula

For the hydraulic calculation of sewerage, it is required to determine the unknowns:

1. pipeline diameter Du;
2. average flow velocity v;
3. hydraulic slope l;
4. degree of filling h / Du (in calculations, they are repelled from the hydraulic radius, which is associated with this value).

In practice, they are limited to calculating the value of l or h / d, since the remaining parameters are easy to calculate. The hydraulic slope in preliminary calculations is considered to be equal to the slope of the earth's surface, at which the movement of wastewater will not be lower than the self-cleaning speed. The speed values ​​as well as the maximum h/Dn values ​​for domestic networks can be found in Table 3.

In addition, there is a normalized value for the minimum slope for pipes with a small diameter: 150 mm

(i=0.008) and 200 (i=0.007) mm.

The formula for the volumetric flow rate of a liquid looks like this:

where a is the free area of ​​the flow,

v is the flow velocity, m/s.

The speed is calculated by the formula:

where R is the hydraulic radius;

C is the wetting coefficient;

From this we can derive the formula for the hydraulic slope:

According to it, this parameter is determined if calculation is necessary.

where n is the roughness factor, ranging from 0.012 to 0.015 depending on the pipe material.

The hydraulic radius is considered equal to the usual radius, but only when the pipe is completely filled. In other cases, use the formula:

where A is the area of ​​the transverse fluid flow,

P is the wetted perimeter, or the transverse length of the inner surface of the pipe that touches the liquid.

Capacity tables for non-pressure sewer pipes

The table takes into account all the parameters used to perform the hydraulic calculation. The data is selected according to the value of the pipe diameter and substituted into the formula. Here, the volumetric flow rate q of the liquid passing through the pipe section has already been calculated, which can be taken as the throughput of the pipeline.

In addition, there are more detailed Lukin tables containing ready-made throughput values ​​for pipes of different diameters from 50 to 2000 mm.

Capacity tables for pressurized sewer systems

In the capacity tables for sewer pressure pipes, the values ​​depend on the maximum degree of filling and the estimated average flow rate of the waste water.

Capacity of the water pipe

Water pipes in the house are used most often. And since they are subjected to a large load, the calculation of the throughput of the water main becomes an important condition for reliable operation.

Passability of the pipe depending on the diameter

Diameter is not the most important parameter when calculating pipe patency, but it also affects its value. The larger the inner diameter of the pipe, the higher the permeability, as well as the lower the chance of blockages and plugs. However, in addition to the diameter, it is necessary to take into account the coefficient of friction of water on the pipe walls (table value for each material), the length of the line and the difference in fluid pressure at the inlet and outlet. In addition, the number of bends and fittings in the pipeline will greatly affect the patency.

Table of pipe capacity by coolant temperature

The higher the temperature in the pipe, the lower its capacity, as the water expands and thus creates additional friction. For plumbing, this is not important, but in heating systems it is a key parameter.

There is a table for calculations of heat and coolant.

Pipe capacity table depending on the coolant pressure

There is a table describing the throughput of pipes depending on the pressure.

Pipe capacity table depending on diameter (according to Shevelev)

The tables of F.A. and A.F. Shevelev are one of the most accurate tabular methods for calculating the throughput of a water supply system. In addition, they contain all the necessary calculation formulas for each specific material. This is a voluminous informative material used by hydraulic engineers most often.

The tables take into account:

1. pipe diameters - internal and external;
2. wall thickness;
3. service life of the pipeline;
4. line length;
5. pipe assignment.

Pipe capacity depending on diameter, pressure: tables, calculation formulas, online calculator

Calculating capacity is one of the most difficult tasks in laying a pipeline. In this article, we will try to figure out exactly how this is done for different types of pipelines and pipe materials.