Calculation of water consumption is carried out before the construction of pipelines and is integral part hydrodynamic calculations. During the construction of highways and industrial pipelines These calculations are made using special programs. When building a domestic pipeline with your own hands, you can carry out the calculation yourself, but it is worth considering that the result obtained will not be as accurate as possible. Read on to learn how to calculate the water consumption parameter.

Factors affecting throughput

The main factor used to calculate the pipeline system is throughput. This indicator is influenced by many different parameters, the most significant of which are:

pressure in the existing pipeline (in the main network, if the pipeline under construction will be connected to an external source). The calculation method taking into account pressure is more complex, but also more accurate, since an indicator such as throughput, that is, the ability to pass a certain amount of water in a certain unit of time, depends on pressure;
total pipeline length. The larger this parameter, the greater the amount of losses that appears during its use and, accordingly, to avoid a pressure drop it is necessary to use pipes of larger diameter. Therefore, this factor is also taken into account by specialists;
the material from which the pipes are made. If for a construction or other highway they are used metal pipes, then the uneven internal surface and the possibility of gradual clogging with sediment contained in the water will lead to a decrease in bandwidth and, accordingly, a slight increase in diameter. Using plastic pipes(PVC), polypropylene pipes and so the possibility of clogging with deposits is practically excluded. Moreover, the inner surface of plastic pipes is smoother;

pipe section. Based on the internal cross-section of the pipe, you can independently make a preliminary calculation.

There are other factors that are taken into account by experts. But for this article they are not significant.

Method for calculating diameter depending on pipe cross-section

If when calculating a pipeline it is necessary to take into account all of the listed factors, it is recommended to carry out calculations using special programs. If it is enough to build a system preliminary calculations, then they are carried out in the following sequence:

preliminary determination of the amount of water consumption by all family members;
count optimal size diameter

How to calculate water consumption in a house

Determine yourself the amount of cold or hot water in the house there are several methods:

according to the meter reading. If meters are installed when entering the pipeline into the house, then determining the water consumption per day per person is not a problem. Moreover, with observation over several days, fairly accurate parameters can be obtained;

By established standards, by certain specialists. The standard water consumption per person is established for individual species premises with the presence/absence of certain conditions;

according to the formula.

To determine the total amount of water consumed in the room, it is necessary to make a calculation for each plumbing unit (bathtub, shower stall, faucet, etc.) separately. Calculation formula:

Qs = 5 x q0 x P, Where

Qs is an indicator that determines the amount of flow;

q0 — established norm;

P is a coefficient that takes into account the possibility of using several types of plumbing fixtures simultaneously.

The q0 indicator is determined depending on the type of plumbing equipment according to the following table:

Probability P is determined by the following formula:

P = L x N1 / q0 x 3600 x N2, Where

L—peak water flow for 1 hour;

N1 - number of people using plumbing fixtures;

q0 - established standards for a separate plumbing unit;

N2 - number of installed plumbing fixtures.

It is unacceptable to determine water flow without taking into account probability, since the simultaneous use of plumbing fixtures leads to an increase in flow power.

We will calculate the water for specific example. It is necessary to determine water consumption according to the following parameters:

5 people live in the house;
6 units of plumbing equipment are installed: bath, toilet, kitchen sink, washing machine and Dishwasher, installed in the kitchen, shower;
peak water flow for 1 hour in accordance with SNiP is set equal to 5.6 l/s.

Determine the probability size:

P = 5.6 x 4 / 0.25 x 3600 x 6 = 0.00415

We determine the water consumption for the bath, kitchen and toilet room:

Qs (baths) = 4 x 0.25 x 0.00518 = 0.00415 (l/s)

Qs (kitchens) = 4 x 0.12 x 0.00518 = 0.002 (l/s)

Qs (toilet) = 4 x 0.4 x 0.00518 = 0.00664 (l/s)

Calculation of the optimal section

To determine the cross section, the following formula is used:

Q = (πd²/4)xW, Where

Q is the calculated amount of water consumed;

d – required diameter;

W is the speed of water movement in the system.

By simple mathematical operations it can be deduced that

d = √(4Q/πW)

The W indicator can be obtained from the table:

The indicators presented in the table are used for approximate calculations. To obtain more accurate parameters, a complex mathematical formula is used.

Let's determine the diameter of the pipes for the bath, kitchen and toilet according to the parameters presented in the example under consideration:

d (for bathroom) = √(4 x 0.00415 / (3.14 x 3)) = 0.042 (m)

d (for kitchen) = √(4 x 0.002 / (3.14 x 3)) = 0.03 (m)

d (for toilet) = √(4 x 0.00664 / (3.14 x 3)) = 0.053 (m)

To determine the cross-section of pipes, the largest calculated indicator is taken. Taking into account the small reserve in in this example It is possible to carry out water supply wiring with pipes with a cross-section of 55 mm.

How to make calculations using a special semi-professional program, watch the video.

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Pipe throughput: simple about complex things

How does the capacity of a pipe change depending on the diameter? What factors other than cross-section influence this parameter? Finally, how to calculate, even approximately, the permeability of a water pipeline with a known diameter? In this article I will try to give the most simple and accessible answers to these questions.

Our task is to learn to count optimal cross section water pipes.

Why is this necessary?

Hydraulic calculation allows you to obtain optimal minimum water pipe diameter value.

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

When the flow rate is 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 sharply. As a result, you will either be doused ice water, or scald with boiling water.

Restrictions

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

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;
In the case of a large building with numerous plumbing fixtures, for the hydraulic calculation of the water supply it will be necessary to calculate the probability of simultaneous use of several water points. IN small house the calculation is performed for peak consumption by all available devices, which greatly simplifies the task.

Factors

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

Calculation of pipe capacity for a known cross-section;
Calculation optimal diameter at a known planned flow rate.

In real conditions (when designing a water supply system), it is much more common to perform the second task.

Everyday logic dictates that the maximum water flow 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 is slowed down by friction against the walls. Moreover, the material and condition of the walls predictably influence the degree of braking.

Here full list Factors affecting the performance of a water pipe:

Pressure at the beginning of the water supply (read - pressure in the line);
Slope 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 roughness, but also reduce the internal clearance of the pipeline;

This does not apply to glass, plastic, copper, galvanized and metal-polymer pipes. Even after 50 years of operation they are in new condition. The exception is silting of the water supply when large quantities suspensions and the absence of filters at the inlet.

Quantity and angle turns;
Diameter changes water supply;
Presence or absence welds, burr from soldering and connecting fittings;

Shut-off valves. Even full bore Ball Valves provide a certain resistance to the flow.

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

Torricelli's Law

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

For the Torricelli formula to work, you must:

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

One atmosphere under Earth's gravity is capable of raising a water column by 10 meters. Therefore, pressure in atmospheres is converted into pressure simple multiplication on 10.

So that there is a hole significantly smaller than the diameter of the vessel, thus eliminating loss of pressure due to friction against the walls.

In practice, Torricelli's formula allows one to calculate the flow of water through a pipe with an internal cross-section of known dimensions at a known instantaneous pressure at the time of flow. Simply put: to use the formula, you need to install a pressure gauge in front of the tap or calculate the pressure drop in the water supply system 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 hole in meters per second;
g is the acceleration of the fall (for our planet it is equal to 9.78 m/s^2);
h is the pressure (the height of the water column above the hole).

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

Captain Obviousness suggests: knowing the cross-sectional area, it is not difficult to determine the internal radius of the pipe. As you know, the area of a circle is calculated as π*r^2, where π is taken to be rounded equal to 3.14159265.

In this case, Torricelli’s formula will look like v^2=2*9.78*20=391.2. Square root out of 391.2 is rounded equal 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 flow flows. Converting the diameter to SI units (meters), we get 3.14159265*0.01^2=0.0003141593. Now let’s calculate the water consumption: 20*0.0003141593=0.006283186, or 6.2 liters per second.

Back to reality

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

Usually calculation problem it is solved from the opposite: with known water flow through plumbing fixtures, the length of the water supply system 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 normal flow rate for internal water supply systems is considered to be 0.7 - 1.5 m/s. Exceeding the last value leads to the appearance of hydraulic noise (primarily at bends and fittings).

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

The table shows data for mixers with aerators. Their absence equalizes the flow through the mixers of the sink, washbasin and shower with the flow through the mixer when setting the bath.

Let me remind you that if you want to calculate the water supply of a private house with your own hands, add up the water consumption for all installed devices. If these instructions are not followed, you will be in for surprises like a sharp drop in the temperature in the shower when you turn on the hot water tap.

If the building has a fire water supply, 2.5 l/s is added to the planned flow rate for each hydrant. For fire water supply, the flow speed is limited to 3 m/s: In the event of a fire, hydraulic noise is the last thing that will irritate residents.

When calculating the pressure, it is usually assumed that at the device farthest from the input it should be at least 5 meters, which corresponds to a pressure of 0.5 kgf/cm2. Some plumbing fixtures (instantaneous water heaters, automatic filler valves) 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 hydraulic losses on the device itself.

On the picture - instantaneous water heater Atmor Basic. It turns on heating only at a pressure of 0.3 kgf/cm2 and above.

Flow, diameter, speed

Let me remind you that they are linked together by two formulas:

Q = SV. Water consumption in cubic meters per second equal to area sections in square meters, multiplied by the flow speed in meters per second;
S = π r^2. The cross-sectional area is calculated as the product of pi and the square of the radius.

Where can I get the radius values for the internal section?

U steel pipes with a minimum error it is equal to half the remote control(conditional bore used to mark rolled pipes);
For polymer, metal-polymer, etc. the internal diameter is equal to the difference between the external one, which is used to mark the pipes, and twice the wall thickness (it is also usually present in the marking). The radius, accordingly, is half internal diameter.

The internal diameter is 50-3*2=44 mm, or 0.044 meters;
The radius will be 0.044/2=0.022 meters;
The internal cross-sectional area will be equal to 3.1415*0.022^2=0.001520486 m2;
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.

Loss of pressure

How to calculate how much pressure is lost in a water pipeline 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 desired pressure drop in meters;
i — hydraulic slope of a water pipe meter;
L is the length of the water pipeline in meters;
K— coefficient, which makes it possible to simplify the calculation of pressure drop on shut-off 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 tape measure yet.

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 values for 1000i (hydraulic slope per 1000 meters of water supply) can be found in Shevelev’s tables, which, in fact, serve for hydraulic calculations. The tables are too large for an article because they provide 1000i values for all possible diameters, flow rates and materials, adjusted for service life.

Here is a small fragment of Shevelev’s table for plastic pipe size 25 mm.

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

Let's use this table to calculate the pressure drop by 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.

At a flow speed as close as possible to 1.5 m/s (1.38 m/s), the 1000i value will be equal to 142.8 meters;
The hydraulic slope of one meter of pipe will be equal to 142.8/1000=0.1428 meters;
The correction factor for domestic water supply systems is 0.3;
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 system, with 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 Torricelli formula. The calculation method with an example is given in the corresponding section of the article.

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

Conclusion

Dear reader, if the given instructions, despite being extremely simplified, still seem tedious to you, just use one of the many online calculators. As always, Additional information can be found in the video in this article. I would appreciate your additions, corrections and comments. Good luck, comrades!

July 31, 2016

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

Pipelines for the transport of various liquids are an integral part of units and installations in which work processes related to various fields of application are carried out. When selecting pipes and piping configuration great importance has the cost of both the pipes themselves and pipeline fittings. The final cost of pumping a medium through a pipeline is largely determined by the dimensions of the pipes (diameter and length). The calculation of these quantities is carried out using specially developed formulas specific to certain types operation.

A pipe is a hollow cylinder made of metal, wood or other material used for transporting liquid, gaseous and granular media. The transported medium can be water, natural gas, steam, oil products, etc. Pipes are used everywhere, from various industries to domestic use.

For the manufacture of pipes the most different materials, such as steel, cast iron, copper, cement, plastic such as ABS plastic, polyvinyl chloride, chlorinated polyvinyl chloride, polybutene, polyethylene, etc.

The main dimensional indicators of a pipe are its diameter (external, internal, etc.) and wall thickness, which are measured in millimeters or inches. A value such as nominal diameter or nominal bore is also used - the nominal value of the internal diameter of the pipe, also measured in millimeters (denoted by DN) or inches (denoted by DN). The values of nominal diameters are standardized and are the main criterion when selecting pipes and connecting fittings.

Correspondence of nominal diameter values in mm and inches:

A pipe with a circular cross-section is preferred over other geometric sections for a number of reasons:

A circle has a minimum ratio of perimeter to area, and when applied to a pipe, this means that with equal throughput, the material consumption of the pipes is round shape will be minimal compared to pipes of other shapes. This also implies the minimum possible costs for insulation and protective covering;
Round cross section most advantageous for moving a liquid or gaseous medium from a hydrodynamic point of view. Also, due to the minimum possible internal area of the pipe per unit of its length, friction between the moving medium and the pipe is minimized.
The round shape is most resistant to internal and external pressures;
The process of making round pipes is quite simple and easy to implement.

Pipes can vary greatly in diameter and configuration depending on their purpose and application. Thus, main pipelines for moving water or oil products can reach almost half a meter in diameter with a fairly simple configuration, and heating coils, which are also pipes, have a small diameter complex shape with many turns.

It is impossible to imagine any industry without a pipeline network. The calculation of any such network includes the selection of pipe material, drawing up a specification that lists data on the thickness, size of pipes, route, etc. Raw materials, intermediate products and/or finished products pass through production stages by moving between various apparatuses and installations, which are connected by pipes and fittings. Correct calculation, selection and installation of the pipeline system is necessary for the reliable implementation of the entire process, ensuring safe pumping media, as well as to seal the system and prevent leakage of the pumped substance into the atmosphere.

There is no single formula or rules that could be used to select a pipeline for any possible application and work environment. In each individual application of pipelines there are a number of factors that require consideration and can have a significant impact on the requirements for the pipeline. So, for example, when working with sludge, the pipeline big size will not only increase the installation cost, but also create operational difficulties.

Typically, pipes are selected after optimizing material and operating costs. The larger the diameter of the pipeline, that is, the higher the initial investment, the lower the pressure drop and, accordingly, the lower the operating costs. Conversely, the small size of the pipeline will reduce the primary costs of the pipes themselves and pipe fittings, but an increase in speed will entail an increase in losses, which will lead to the need to spend additional energy on pumping the medium. Speed limits fixed for various applications are based on optimal design conditions. The size of pipelines is calculated using these standards taking into account the areas of application.

Pipeline design

When designing pipelines, the following basic design parameters are taken as a basis:

required performance;
entry and exit points of the pipeline;
composition of the medium, including viscosity and specific gravity;
topographic conditions of the pipeline route;
maximum permissible operating pressure;
hydraulic calculation;
pipeline diameter, wall thickness, tensile yield strength of the wall material;
number of pumping stations, distance between them and power consumption.

Pipeline reliability

Reliability in pipeline design is ensured by adherence to proper design standards. Also, staff training is a key factor in ensuring long term pipeline service and its tightness and reliability. Continuous or periodic monitoring of pipeline operation can be carried out by monitoring, accounting, control, regulation and automation systems, personal production monitoring devices, and safety devices.

Additional pipeline coating

A corrosion-resistant coating is applied to the outside of most pipes to prevent the damaging effects of corrosion from the external environment. In the case of pumping corrosive media, a protective coating can also be applied to the inner surface of the pipes. Before being put into service, all new pipes intended to transport hazardous liquids are checked for defects and leaks.

Basic principles for calculating flow in a pipeline

The nature of the flow of the medium in the pipeline and when flowing around obstacles can vary greatly from liquid to liquid. One of important indicators is the viscosity of the medium, characterized by such a parameter as the viscosity coefficient. Irish engineer-physicist Osborne Reynolds conducted a series of experiments in 1880, based on the results of which he was able to derive a dimensionless quantity characterizing the nature of the flow of a viscous fluid, called the Reynolds criterion and denoted Re.

Re = (v·L·ρ)/μ

Where:
ρ—liquid density;
v—flow velocity;
L is the characteristic length of the flow element;
μ - dynamic viscosity coefficient.

That is, the Reynolds criterion characterizes the ratio of inertial forces to viscous friction forces in a fluid flow. A change in the value of this criterion reflects a change in the ratio of these types of forces, which, in turn, affects the nature of the fluid flow. In this regard, it is customary to distinguish three flow modes depending on the value of the Reynolds criterion. At Re<2300 наблюдается так называемый ламинарный поток, при котором жидкость движется тонкими слоями, почти не смешивающимися друг с другом, при этом наблюдается постепенное увеличение скорости потока по направлению от стенок трубы к ее центру. Дальнейшее увеличение числа Рейнольдса приводит к дестабилизации такой структуры потока, и значениям 23004000, a stable regime is already observed, characterized by a random change in the speed and direction of the flow at each individual point, which in total equalizes the flow rates throughout the entire volume. This regime is called turbulent. The Reynolds number depends on the pressure set by the pump, the viscosity of the medium at operating temperature, as well as the size and cross-sectional shape of the pipe through which the flow passes.

Flow velocity profile
laminar mode	transitional regime	turbulent regime

Character of the current
laminar mode	transitional regime	turbulent regime

The Reynolds criterion is a similarity criterion for the flow of a viscous fluid. That is, with its help it is possible to simulate a real process in a reduced size, convenient for study. This is extremely important, since it is often extremely difficult, and sometimes even impossible, to study the nature of fluid flows in real devices due to their large size.

Pipeline calculation. Calculation of pipeline diameter

If the pipeline is not thermally insulated, that is, heat exchange is possible between the fluid being moved and the environment, then the nature of the flow in it can change even at a constant speed (flow). This is possible if the pumped medium at the inlet has a sufficiently high temperature and flows in turbulent mode. Along the length of the pipe, the temperature of the transported medium will drop due to heat losses to the environment, which may lead to a change in the flow regime to laminar or transitional. The temperature at which a regime change occurs is called the critical temperature. The value of liquid viscosity directly depends on temperature, therefore, for such cases, a parameter such as critical viscosity is used, corresponding to the point of change of flow regime at the critical value of the Reynolds criterion:

v cr = (v D)/Re cr = (4 Q)/(π D Re cr)

Where:
ν cr - critical kinematic viscosity;
Re cr - critical value of the Reynolds criterion;
D - pipe diameter;
v - flow speed;
Q - consumption.

Another important factor is the friction that occurs between the pipe walls and the moving flow. In this case, the friction coefficient largely depends on the roughness of the pipe walls. The relationship between the coefficient of friction, the Reynolds criterion and roughness is established by the Moody diagram, which allows one to determine one of the parameters knowing the other two.

The Colebrook-White formula is also used to calculate the friction coefficient of turbulent flow. Based on this formula, it is possible to construct graphs from which the friction coefficient is determined.

(√λ ) -1 = -2 log(2.51/(Re √λ ) + k/(3.71 d))

Where:
k - pipe roughness coefficient;
λ - friction coefficient.

There are also other formulas for approximate calculation of friction losses during pressure flow of liquid in pipes. One of the most commonly used equations in this case is the Darcy-Weisbach equation. It is based on empirical data and is mainly used in system modeling. Friction losses are a function of fluid velocity and pipe resistance to fluid movement, expressed through the value of the pipeline wall roughness.

∆H = λ L/d v²/(2 g)

Where:
ΔH - pressure loss;
λ - friction coefficient;
L is the length of the pipe section;
d - pipe diameter;
v - flow speed;
g is the acceleration of free fall.

Pressure loss due to friction for water is calculated using the Hazen-Williams formula.

∆H = 11.23 L 1/C 1.85 Q 1.85 /D 4.87

Where:
ΔH - pressure loss;
L is the length of the pipe section;
C is the Heisen-Williams roughness coefficient;
Q - flow rate;
D - pipe diameter.

Pressure

The operating pressure of a pipeline is the highest excess pressure that ensures the specified operating mode of the pipeline. The decision on pipeline size and number of pumping stations is usually made based on pipe operating pressure, pump capacity and costs. The maximum and minimum pipeline pressure, as well as the properties of the working medium, determine the distance between pumping stations and the required power.

Nominal pressure PN is a nominal value corresponding to the maximum pressure of the working medium at 20 °C, at which long-term operation of a pipeline with the given dimensions is possible.

As the temperature increases, the load capacity of the pipe decreases, as does the permissible excess pressure as a result. The pe,zul value shows the maximum pressure (gp) in the piping system as the operating temperature increases.

Permissible excess pressure chart:

Calculation of pressure drop in a pipeline

The pressure drop in the pipeline is calculated using the formula:

∆p = λ L/d ρ/2 v²

Where:
Δp - pressure drop across the pipe section;
L is the length of the pipe section;
λ - friction coefficient;
d - pipe diameter;
ρ - density of the pumped medium;
v - flow speed.

Transported working media

Most often, pipes are used to transport water, but they can also be used to move sludge, suspensions, steam, etc. In the oil industry, pipelines are used to transport a wide range of hydrocarbons and their mixtures, which differ greatly in chemical and physical properties. Crude oil can be transported over greater distances from onshore fields or offshore oil rigs to terminals, intermediate points and refineries.

Pipelines also transmit:

petroleum products such as gasoline, aviation fuel, kerosene, diesel fuel, fuel oil, etc.;
petrochemical raw materials: benzene, styrene, propylene, etc.;
aromatic hydrocarbons: xylene, toluene, cumene, etc.;
liquefied petroleum fuels such as liquefied natural gas, liquefied petroleum gas, propane (gases at standard temperature and pressure but liquefied using pressure);
carbon dioxide, liquid ammonia (transported as liquids under pressure);
bitumen and viscous fuels are too viscous to be transported by pipeline, so distillate fractions of oil are used to dilute these raw materials and obtain a mixture that can be transported by pipeline;
hydrogen (short distances).

Quality of the transported medium

The physical properties and parameters of the transported media largely determine the design and operating parameters of the pipeline. Specific gravity, compressibility, temperature, viscosity, pour point and vapor pressure are the main parameters of the working environment that must be taken into account.

The specific gravity of a liquid is its weight per unit volume. Many gases are transported through pipelines under increased pressure, and when a certain pressure is reached, some gases can even be liquefied. Therefore, the degree of compression of the medium is a critical parameter for designing pipelines and determining throughput.

Temperature has an indirect and direct effect on pipeline performance. This is expressed in the fact that the liquid increases in volume after increasing temperature, provided that the pressure remains constant. Lower temperatures can also have an impact on both performance and overall system efficiency. Typically, when the temperature of a fluid decreases, this is accompanied by an increase in its viscosity, which creates additional frictional resistance on the inner wall of the pipe, requiring more energy to pump the same amount of fluid. Very viscous media are sensitive to changes in operating temperatures. Viscosity is the resistance of a medium to flow and is measured in centistokes cSt. Viscosity determines not only the choice of pump, but also the distance between pumping stations.

As soon as the fluid temperature drops below the pour point, the operation of the pipeline becomes impossible and several options are taken to restore its operation:

heating the medium or insulating pipes to maintain the operating temperature of the medium above its fluid point;
change in the chemical composition of the medium before entering the pipeline;
dilution of the transported medium with water.

Types of main pipes

Main pipes are made welded or seamless. Seamless steel pipes are produced without longitudinal welds in steel sections that are heat treated to achieve the desired size and properties. Welded pipe is produced using several manufacturing processes. The two types differ from each other in the number of longitudinal seams in the pipe and the type of welding equipment used. Welded steel pipe is the most commonly used type in petrochemical applications.

Each length of pipe is welded together to form a pipeline. Also in main pipelines, depending on the application, pipes made of fiberglass, various plastics, asbestos cement, etc. are used.

To connect straight pipe sections, as well as to transition between pipeline sections of different diameters, specially manufactured connecting elements (elbows, bends, valves) are used.

elbow 90°	90° bend	transition branch	branching

elbow 180°	bend 30°	adapter fitting	tip

Special connections are used to install individual parts of pipelines and fittings.

welded	flanged	threaded	coupling

Temperature expansion of the pipeline

When a pipeline is under pressure, its entire internal surface is exposed to a uniformly distributed load, which causes longitudinal internal forces in the pipe and additional loads on the end supports. Temperature fluctuations also affect the pipeline, causing changes in pipe dimensions. Forces in a fixed pipeline during temperature fluctuations can exceed the permissible value and lead to excess stress, which is dangerous for the strength of the pipeline both in the pipe material and in the flange connections. Fluctuations in the temperature of the pumped medium also create temperature stress in the pipeline, which can be transmitted to fittings, a pumping station, etc. This can lead to depressurization of pipeline joints, failure of fittings or other elements.

Calculation of pipeline dimensions with temperature changes

Calculation of changes in the linear dimensions of the pipeline with temperature changes is carried out using the formula:

∆L = a·L·∆t

a - coefficient of thermal expansion, mm/(m°C) (see table below);
L - pipeline length (distance between fixed supports), m;
Δt - difference between max. and min. temperature of the pumped medium, °C.

Table of linear expansion of pipes made of various materials

The numbers given represent average values for the listed materials and for calculating a pipeline made of other materials, the data from this table should not be taken as a basis. When calculating the pipeline, it is recommended to use the linear elongation coefficient indicated by the pipe manufacturer in the accompanying technical specification or data sheet.

Thermal elongation of pipelines is eliminated both by the use of special compensation sections of the pipeline, and with the help of compensators, which can consist of elastic or moving parts.

Compensation sections consist of elastic straight parts of the pipeline, located perpendicular to each other and secured with bends. During thermal elongation, the increase in one part is compensated by the bending deformation of the other part on the plane or by the bending and torsion deformation in space. If the pipeline itself compensates for thermal expansion, then this is called self-compensation.

Compensation also occurs thanks to elastic bends. Part of the elongation is compensated by the elasticity of the bends, the other part is eliminated due to the elastic properties of the material of the area located behind the bend. Compensators are installed where it is not possible to use compensating sections or when the self-compensation of the pipeline is insufficient.

According to their design and operating principle, compensators are of four types: U-shaped, lens, wavy, stuffing box. In practice, flat expansion joints with an L-, Z- or U-shape are often used. In the case of spatial compensators, they usually represent 2 flat mutually perpendicular sections and have one common shoulder. Elastic expansion joints are made from pipes or elastic disks, or bellows.

Determining the optimal size of pipeline diameter

The optimal pipeline diameter can be found based on technical and economic calculations. The dimensions of the pipeline, including the size and functionality of the various components, as well as the conditions under which the pipeline must be operated, determine the transport capacity of the system. Larger pipe sizes are suitable for higher mass flows, provided that other components in the system are properly selected and sized for these conditions. Typically, the longer the section of main pipe between pumping stations, the greater the pressure drop in the pipeline is required. In addition, changes in the physical characteristics of the pumped medium (viscosity, etc.) can also have a great impact on the pressure in the line.

The optimum size is the smallest suitable pipe size for a particular application that is cost effective over the life of the system.

Formula for calculating pipe performance:

Q = (π d²)/4 v

Q is the flow rate of the pumped liquid;
d - pipeline diameter;
v - flow speed.

In practice, to calculate the optimal pipeline diameter, the values of the optimal velocities of the pumped medium are used, taken from reference materials compiled on the basis of experimental data:

Pumped medium		Range of optimal speeds in the pipeline, m/s
Liquids	Gravity movement:
	Viscous liquids	0,1 - 0,5
	Low viscosity liquids	0,5 - 1
	Pumping:
	Suction side	0,8 - 2
	Discharge side	1,5 - 3

Gases	Natural craving	2 - 4
	Low pressure	4 - 15
	Great pressure	15 - 25

Couples	Superheated steam	30 - 50
	Saturated steam under pressure:
	More than 105 Pa	15 - 25
	(1 - 0.5) 105 Pa	20 - 40
	(0.5 - 0.2) 105 Pa	40 - 60
	(0.2 - 0.05) 105 Pa	60 - 75

From here we get the formula for calculating the optimal pipe diameter:

d o = √((4 Q) / (π v o ))

Q is the specified flow rate of the pumped liquid;
d - optimal pipeline diameter;
v is the optimal flow rate.

At high flow rates, pipes of smaller diameter are usually used, which means reduced costs for the purchase of the pipeline, its maintenance and installation work (denoted by K 1). As the speed increases, pressure loss due to friction and local resistance increases, which leads to an increase in the cost of pumping liquid (denoted by K 2).

For large diameter pipelines, the costs K 1 will be higher, and the operating costs K 2 will be lower. If we add the values of K 1 and K 2, we obtain the total minimum costs K and the optimal pipeline diameter. Costs K 1 and K 2 in this case are given in the same time period.

Calculation (formula) of capital costs for a pipeline

K 1 = (m·C M ·K M)/n

m - pipeline mass, t;
C M - cost of 1 t, rub/t;
K M - coefficient that increases the cost of installation work, for example 1.8;
n - service life, years.

The indicated operating costs associated with energy consumption are:

K 2 = 24 N n day C E rub/year

N - power, kW;
n DN - number of working days per year;
S E - costs per kWh of energy, rub/kW * h.

Formulas for determining pipeline dimensions

An example of general formulas for determining the size of pipes without taking into account possible additional impact factors such as erosion, suspended solids, etc.:

Name	The equation	Possible restrictions
Flow of liquid and gas under pressure
Loss of head due to friction Darcy-Weisbach	d = 12 [(0.0311 f L Q 2)/(h f)] 0.2	Q - volumetric flow, gal/min; d - internal diameter of the pipe; hf - loss of pressure due to friction; L - pipeline length, feet; f - friction coefficient; V - flow speed.
Equation of total fluid flow	d = 0.64 √(Q/V)	Q - volumetric flow, gal/min
Pump suction line size to limit frictional head loss	d = √(0.0744·Q)	Q - volumetric flow, gal/min
Total gas flow equation	d = 0.29 √((Q T)/(P V))	Q - volume flow, ft³/min T - temperature, K P - pressure lb/in² (abs); V - speed
Gravity flow
Manning's equation for calculating pipe diameter for maximum flow	d = 0.375	Q - volumetric flow; n - roughness coefficient; S - slope.
Froude number is the relationship between the force of inertia and the force of gravity	Fr = V / √[(d/12) g]	g - free fall acceleration; v - flow speed; L - pipe length or diameter.
Steam and evaporation
Equation for determining pipe diameter for steam	d = 1.75 √[(W v_g x) / V]	W - mass flow; Vg - specific volume of saturated steam; x - steam quality; V - speed.

Optimal flow rates for various piping systems

The optimal pipe size is selected based on the minimum cost of pumping the medium through the pipeline and the cost of the pipes. However, speed limits must also be taken into account. Sometimes, the size of the pipeline must match the requirements of the process. Also often the size of the pipeline is related to the pressure drop. In preliminary design calculations, where pressure losses are not taken into account, the size of the process pipeline is determined by the permissible speed.

If there are changes in the direction of flow in the pipeline, this leads to a significant increase in local pressures at the surface perpendicular to the direction of flow. This kind of increase is a function of fluid velocity, density, and initial pressure. Because velocity is inversely proportional to diameter, high-velocity fluids require special consideration when selecting piping size and configuration. The optimal pipe size, for example for sulfuric acid, limits the velocity of the medium to a value at which erosion of the walls in the pipe elbows is not allowed, thereby preventing damage to the pipe structure.

Gravity fluid flow

Calculating the size of a pipeline in the case of a gravity flow is quite complicated. The nature of the movement with this form of flow in the pipe can be single-phase (full pipe) and two-phase (partial filling). Two-phase flow is formed when liquid and gas are simultaneously present in the pipe.

Depending on the ratio of liquid and gas, as well as their velocities, the two-phase flow regime can vary from bubbly to dispersed.

bubble flow (horizontal)	projectile flow (horizontal)	wave flow	dispersed flow

The driving force for a liquid when moving by gravity is provided by the difference in the heights of the starting and ending points, and a prerequisite is that the starting point is located above the ending point. In other words, the difference in height determines the difference in the potential energy of the liquid in these positions. This parameter is also taken into account when selecting a pipeline. In addition, the magnitude of the driving force is influenced by the pressure values at the starting and ending points. An increase in pressure drop entails an increase in the fluid flow rate, which, in turn, makes it possible to select a pipeline of a smaller diameter, and vice versa.

If the end point is connected to a pressurized system, such as a distillation column, it is necessary to subtract the equivalent pressure from the existing height difference to estimate the actual effective differential pressure generated. Also, if the starting point of the pipeline is under vacuum, then its effect on the overall differential pressure must also be taken into account when selecting the pipeline. The final selection of pipes is carried out using differential pressure, taking into account all of the above factors, and is not based solely on the difference in height between the starting and ending points.

Hot liquid flow

Process plants typically face various challenges when handling hot or boiling media. The main reason is the evaporation of part of the hot liquid stream, that is, the phase transformation of the liquid into vapor inside the pipeline or equipment. A typical example is the phenomenon of cavitation of a centrifugal pump, accompanied by point boiling of a liquid with the subsequent formation of steam bubbles (steam cavitation) or the release of dissolved gases into bubbles (gas cavitation).

Larger piping is preferred due to the reduced flow rate compared to smaller piping at constant flow, resulting in a higher NPSH at the pump suction line. Also, the cause of cavitation due to loss of pressure can be points of sudden change in flow direction or reduction in the size of the pipeline. The resulting vapor-gas mixture creates an obstacle to the flow and can cause damage to the pipeline, which makes the phenomenon of cavitation extremely undesirable during pipeline operation.

Bypass pipeline for equipment/instruments

Equipment and devices, especially those that can create significant pressure drops, that is, heat exchangers, control valves, etc., are equipped with bypass pipelines (to allow the process not to be interrupted even during technical maintenance work). Such pipelines usually have 2 shut-off valves installed in the installation line and a flow control valve parallel to this installation.

During normal operation, the fluid flow, passing through the main components of the apparatus, experiences an additional pressure drop. Accordingly, the discharge pressure for it created by the connected equipment, such as a centrifugal pump, is calculated. The pump is selected based on the total pressure drop in the installation. During movement along the bypass pipeline, this additional pressure drop is absent, while the operating pump delivers the flow of the same force, according to its operating characteristics. To avoid differences in flow characteristics between the apparatus and the bypass line, it is recommended to use a smaller bypass line with a control valve to create a pressure equivalent to the main installation.

Sampling line

Typically, a small amount of liquid is sampled for analysis to determine its composition. Sampling can be done at any stage of the process to determine the composition of the raw material, intermediate product, finished product, or simply the transported substance, such as wastewater, coolant, etc. The size of the piping section from which sampling occurs typically depends on the type of fluid being analyzed and the location of the sampling point.

For example, for gases under high pressure conditions, small pipelines with valves are sufficient to collect the required number of samples. Increasing the diameter of the sampling line will reduce the proportion of media sampled for analysis, but such sampling becomes more difficult to control. However, a small sampling line is not well suited for the analysis of various suspensions in which solid particles can clog the flow path. Thus, the size of the sampling line for suspension analysis depends largely on the size of the solid particles and the characteristics of the medium. Similar conclusions apply to viscous liquids.

When selecting the size of the sampling pipeline, the following are usually taken into account:

characteristics of the liquid intended for sampling;
loss of the working environment during selection;
safety requirements during selection;
ease of operation;
location of the sampling point.

Coolant circulation

High speeds are preferred for circulating coolant lines. This is mainly due to the fact that the coolant in the cooling tower is exposed to sunlight, which creates the conditions for the formation of an algae layer. Part of this algae-containing volume enters the circulating coolant. At low flow rates, algae begins to grow in the piping and, after a while, makes it difficult for the coolant to circulate or pass into the heat exchanger. In this case, a high circulation rate is recommended to avoid the formation of algae blockages in the pipeline. Typically, the use of heavily circulating coolant is found in the chemical industry, which requires large piping sizes and lengths to supply power to various heat exchangers.

Tank overflow

Tanks are equipped with overflow pipes for the following reasons:

avoiding fluid loss (excess fluid goes into another reservoir rather than spilling out of the original reservoir);
preventing unwanted liquids from leaking outside the tank;
maintaining liquid levels in tanks.

In all of the above cases, the overflow pipes are designed to accommodate the maximum permissible fluid flow entering the tank, regardless of the fluid flow rate at the outlet. Other principles for selecting pipes are similar to the selection of pipelines for gravity liquids, that is, in accordance with the availability of available vertical height between the starting and ending points of the overflow pipeline.

The highest point of the overflow pipe, which is also its starting point, is located at the point of connection to the tank (tank overflow pipe) usually almost at the very top, and the lowest end point can be near the drain gutter almost at the ground. However, the overflow line may end at a higher elevation. In this case, the available differential pressure will be lower.

Sludge flow

In the case of mining, ore is usually mined from inaccessible areas. In such places, as a rule, there are no railway or road connections. For such situations, hydraulic transportation of media with solid particles is considered the most appropriate, including in the case of mining processing plants located at a sufficient distance. Slurry pipelines are used in various industrial applications to transport solids in crushed form along with liquids. Such pipelines have proven to be the most cost-effective compared to other methods of transporting solid media in large volumes. In addition, their advantages include sufficient safety due to the absence of several types of transportation and environmental friendliness.

Suspensions and mixtures of suspended solids in liquids are stored in a state of periodic stirring to maintain homogeneity. Otherwise, a separation process occurs in which suspended particles, depending on their physical properties, float to the surface of the liquid or settle to the bottom. Mixing is achieved through equipment such as a tank with a stirrer, while in pipelines, this is achieved by maintaining turbulent flow conditions.

Reducing the flow rate when transporting particles suspended in a liquid is not desirable, since the process of phase separation may begin in the flow. This can lead to clogging of the pipeline and changes in the concentration of the transported solids in the stream. Intensive mixing in the flow volume is facilitated by the turbulent flow regime.

On the other hand, excessive reduction in the size of the pipeline also often leads to blockage. Therefore, choosing the size of the pipeline is an important and responsible step that requires preliminary analysis and calculations. Each case must be considered individually as different slurries behave differently at different fluid velocities.

Pipeline repair

During the operation of the pipeline, various types of leaks may occur in it, requiring immediate elimination to maintain the operability of the system. Repair of the main pipeline can be carried out in several ways. This can range from replacing an entire segment of pipe or a small section that is leaking, or applying a patch to an existing pipe. But before choosing any repair method, it is necessary to conduct a thorough study of the cause of the leak. In some cases, it may be necessary not just to repair, but to change the route of the pipe to prevent repeated damage.

The first stage of repair work is to determine the location of the pipe section that requires intervention. Next, depending on the type of pipeline, a list of necessary equipment and measures required to eliminate the leak is determined, and the necessary documents and permits are also collected if the section of the pipe to be repaired is located on the territory of another owner. Since most pipes are located underground, it may be necessary to remove part of the pipe. Next, the pipeline coating is checked for general condition, after which part of the coating is removed to carry out repair work directly on the pipe. After repair, various inspection measures can be carried out: ultrasonic testing, color flaw detection, magnetic particle flaw detection, etc.

Although some repairs require a complete shutdown of the pipeline, often only a temporary interruption of work is sufficient to isolate the area being repaired or prepare a bypass route. However, in most cases, repair work is carried out when the pipeline is completely disconnected. Isolating a section of pipeline can be done using plugs or shut-off valves. Next, the necessary equipment is installed and repairs are carried out directly. Repair work is carried out on the damaged area, freed from the environment and without pressure. Upon completion of the repair, the plugs are opened and the integrity of the pipeline is restored.

This characteristic depends on several factors. First of all, this is the diameter of the pipe, as well as the type of liquid, and other indicators.

For hydraulic calculation of a pipeline, you can use the hydraulic pipeline calculation calculator.

When calculating any systems based on fluid circulation through pipes, there is a need to accurately determine pipe capacity. This is a metric value that characterizes the amount of liquid flowing through pipes over a certain period of time. This indicator is directly related to the material from which the pipes are made.

If we take, for example, plastic pipes, they differ in almost the same throughput throughout their entire service life. Plastic, unlike metal, is not prone to corrosion, so a gradual increase in deposits is not observed in it.

As for metal pipes, they throughput decreases year after year. Due to the appearance of rust, the material inside the pipes peels off. This leads to surface roughness and the formation of even more plaque. This process occurs especially quickly in hot water pipes.

The following is a table of approximate values, which was created to make it easier to determine the throughput of pipes in apartment wiring. This table does not take into account the reduction in throughput due to the appearance of sedimentary build-ups inside the pipe.

Table of pipe capacity for liquids, gas, water vapor.

Type of liquid	Speed (m/sec)
City water
Water pipeline
Central heating water
Pressure system water in pipeline line
Hydraulic fluid	up to 12m/sec
Oil pipeline line
Oil in the pressure system of the pipeline line
Steam in the heating system
Steam central piping system
Steam in a high temperature heating system
Air and gas in the central piping system

Most often, ordinary water is used as a coolant. The rate of decrease in throughput in pipes depends on its quality. The higher the quality of the coolant, the longer the pipeline made of any material (steel, cast iron, copper or plastic) will last.

Calculation of pipe capacity.

For accurate and professional calculations, you must use the following indicators:

The material from which pipes and other elements of the system are made;
Pipe length
Number of water consumption points (for water supply system)

The most popular calculation methods:

1. Formula. A rather complex formula, which is understandable only to professionals, takes into account several values at once. The main parameters that are taken into account are the material of the pipes (surface roughness) and their slope.

2. Table. This is a simpler way by which anyone can determine the throughput of a pipeline. An example is the engineering table of F. Shevelev, from which you can find out the throughput capacity based on the pipe material.

3. Computer program. One of these programs can be easily found and downloaded on the Internet. It is designed specifically to determine the throughput for pipes of any circuit. In order to find out the value, you need to enter initial data into the program, such as material, pipe length, coolant quality, etc.

It should be said that the latter method, although the most accurate, is not suitable for calculating simple household systems. It is quite complex and requires knowledge of the values of a wide variety of indicators. To calculate a simple system in a private house, it is better to use tables.

An example of calculating pipeline capacity.

Pipeline length is an important indicator when calculating throughput. The length of the pipeline has a significant impact on throughput indicators. The greater the distance water travels, the less pressure it creates in the pipes, which means the flow speed decreases.

Here are some examples. Based on tables developed by engineers for these purposes.

Pipe capacity:

0.182 t/h with a diameter of 15 mm
0.65 t/h with pipe diameter 25 mm
4 t/h with a diameter of 50 mm

As can be seen from the examples given, a larger diameter increases the flow rate. If the diameter is doubled, the throughput will also increase. This dependence must be taken into account when installing any liquid system, be it plumbing, drainage or heat supply. This is especially true for heating systems, since in most cases they are closed, and the heat supply in the building depends on the uniform circulation of the liquid.

Laying a pipeline is not very difficult, but quite troublesome. One of the most difficult problems in this case is calculating the pipe capacity, which directly affects the efficiency and performance of the structure. This article will discuss how pipe capacity is calculated.

Throughput is one of the most important indicators of any pipe. Despite this, this indicator is rarely indicated in pipe markings, and there is little point in this, because the throughput capacity 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 pipeline capacity

External diameter. This indicator is expressed in the distance from one side of the outer wall to the other side. In calculations, this parameter is designated Day. The outer diameter of the pipes is always indicated in the markings.
Nominal diameter. This value is defined as the diameter of the internal section, which is rounded to whole numbers. When calculating, the nominal diameter is displayed as Dn.

Calculation of pipe permeability can be carried out using one of the methods, which must be selected depending on the specific conditions of pipeline laying:

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 do other types of structures.
Spreadsheet calculations. You can select 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 quite vague, but this does not prevent them from being used in calculations. The only drawback of the tabular method is that it calculates the throughput of the pipe depending on the diameter, but does not take into account changes in the latter due to deposits, so for pipelines prone to build-up, such a calculation will not be the best choice. To get accurate results, you can use Shevelev’s table, which takes into account almost all factors affecting pipes. This table is perfect for installing highways on individual plots of land.
Calculation using programs. Many companies specializing in pipeline laying use computer programs in their activities that allow them to accurately calculate not only the pipe capacity, but also a host of other indicators. For independent calculations, you can use online calculators, which, although they have a slightly larger error, are available free of charge. 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 pipeline installation depending on the region.

Calculation of gas pipeline capacity

Designing a gas pipeline requires fairly high precision - gas has a very high compression ratio, due to which leaks are possible even through microcracks, not to mention serious ruptures. That is why correct calculation of the capacity of the pipe through which 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 using 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;

DN – the value of the nominal diameter of the pipe.

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

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

Qmax = 196.386 DN2 * p/z*T,

Where z is the compression ratio of the transported medium;

T – temperature of the transported gas (K).

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

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

Calculation of sewer pipe capacity

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

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

Pipe diameter – DN;
The average speed of movement of substances is v;
The magnitude of the hydraulic slope is I;
Filling degree – h/DN.

As a rule, when carrying out calculations, only the last two parameters are calculated - the rest can then be determined without any problems. The magnitude of the hydraulic slope is usually equal to the slope of the ground, which will ensure the movement of wastewater at the speed necessary for self-cleaning of the system.

The speed and maximum level of filling of domestic sewerage are determined from a table that can be written out as follows:

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

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

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.

To calculate the volume of wastewater, the following formula is used:

q = a*v,

Where a is the open cross-sectional area of the flow;

v – speed of wastewater transportation.

The speed 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 – wetting coefficient;

i is the degree of slope of the structure.

From the previous formula we can derive the following, which will allow us 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 material of the pipe).

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 in direct contact with the liquid.

Tabular calculation of sewer pipes

You can also determine the permeability of sewer system pipes using tables, and the calculations will directly depend on the type of system:

Gravity sewerage. To calculate free-flow sewer systems, tables are used that contain all the necessary indicators. Knowing the diameter of the pipes being 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 patency of the pipeline. 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.
Pressure sewer. Determining the throughput in this type of system using tables is somewhat simpler - it is enough to know the maximum degree of filling of the pipeline and the average speed of liquid transportation. Read also: "".

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

Calculation of water supply capacity

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

To determine the permeability of water pipes, you can use their diameter (read also: " "). Of course, this indicator is not the basis for calculating cross-country ability, but its influence cannot be excluded. The increase in the internal diameter of the pipe is directly proportional to its permeability - that is, a thick pipe almost does not interfere with 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 against 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 water temperature. As the temperature in the system increases, the fluid expands, causing friction to increase. To determine the permeability of the pipeline, you need to use the appropriate table. There is also a table that allows you to determine the permeability in the pipes depending on the water pressure.

The most accurate calculation of water based on pipe capacity can be made using 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, which is why 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;
System operation period;
Total length of the highway;
Functional purpose of the system.

Conclusion

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

What volume passes through the pipe. Independent calculation of pipe diameter based on water flow