The formula for calculating water by the throughput of the pipe. How to calculate water consumption based on pipe cross-section
A water supply system is a collection of pipelines and devices that provide an uninterrupted supply of water to various sanitary appliances and other devices for the operation of which it is required. In its turn calculation of water supply is a set of measures, as a result of which the maximum second, hourly and daily water consumption is initially determined. Moreover, not only the total fluid consumption is calculated, but also the consumption of cold and hot water separately. The rest of the parameters described in SNiP 2.04.01-85 * "Internal water supply and sewerage of buildings", as well as the diameter of the pipeline, are already dependent on the indicators of water consumption. For example, one of such parameters is the counter nominal bore diameter.
This article presents example of calculating water supply for internal water supply for a private 2-storey building. As a result of this calculation, the total second water consumption and the diameters of pipelines for plumbing fixtures located in the bathroom, toilet and kitchen were found. It also defines the minimum cross-section for the entrance pipe to the house. That is, we mean a pipe that originates at the source of water supply and ends at the point where it branches to consumers.
As for the other parameters given in the mentioned normative document, practice shows that it is not necessary to calculate them for a private house.
Example of calculating water supply
Initial data
The number of people living in the house is 4 people.
The house has the following sanitary fittings.
Bathroom:
Bathroom with mixer - 1 pc.
San. node:
Toilet bowl with flush cistern - 1 pc.
Kitchen:
Washbasin with mixer - 1 pc.
Calculation
The formula for the maximum second water consumption:
q c \u003d 5 q 0 tot α, l / s,
Where: q 0 tot - the total flow rate of one consumed device, determined in accordance with clause 3.2. We accept by adj. 2 for a bathroom - 0.25 l / s, san. node - 0.1 l / s, kitchen - 0.12 l / s.
α - coefficient determined according to App. 4 depending on the probability P and the number of plumbing fixtures N.
Determination of the likelihood of action of sanitary appliances:
P \u003d (U q hr, u tot) / (q 0 tot N 3600) \u003d (4 10.5) / (0.25 3 3600) \u003d 0.0155,
Where: U \u003d 4 people - the number of water consumers.
q hr, u tot \u003d 10.5 l is the total rate of water consumption in liters, by the consumer in the hour of the highest water consumption. We accept according to the adj. 3 for a residential building of an apartment type with water supply, sewerage and baths with gas water heaters.
N \u003d 3 pcs. - the number of plumbing fixtures.
Determination of water consumption for a bathroom:
α \u003d 0.2035 - we take according to the table. 2 app. 4 depending on NP \u003d 1 · 0.0155 \u003d 0.0155.
q s \u003d 5 0.25 0.2035 \u003d 0.254 l / s.
Determination of water consumption for dignity. node:
α \u003d 0.2035 - exactly the same as in the previous case, since the number of devices is the same.
q s \u003d 5 0.1 0.2035 \u003d 0.102 l / s.
Determination of water consumption for the kitchen:
α \u003d 0.2035 - as in the previous case.
q s \u003d 5 0.12 0.2035 \u003d 0.122 l / s.
Determination of the total water consumption for a private house:
α \u003d 0.267 - since NP \u003d 3 0.0155 \u003d 0.0465.
q s \u003d 5 0.25 0.267 \u003d 0.334 l / s.
The formula for determining the diameter of the water supply system in the calculated area:
d \u003d √ ((4 q s) / (π V)) m,
Where: d is the inner diameter of the pipeline in the calculated section, m.
V - water flow rate, m / s. We accept it equal to 2.5 m / s in accordance with clause 7.6, which says that the speed of the liquid in the internal water supply system cannot exceed 3 m / s.
q c - liquid flow rate at the site, m 3 / s.
Determination of the internal section of a bathroom pipe:
d \u003d √ ((4 0, 000254)/ (3.14 2.5)) \u003d 0.0114 m \u003d 11.4 mm.
Determination of the inner section of the pipe for dignity. node:
d \u003d √ ((4 0, 000102)/ (3.14 2.5)) \u003d 0.0072 m \u003d 7.2 mm.
Determination of the internal section of the pipe for the kitchen:
d \u003d √ ((4 0, 000122)/ (3.14 2.5)) \u003d 0.0079 m \u003d 7.9 mm.
Determination of the internal section of the entrance pipe to the house:
d \u003d √ ((4 0, 000334)/ (3.14 2.5)) \u003d 0.0131 m \u003d 13.1 mm.
Output:to supply water to a bath with a mixer, a pipe with an internal diameter of at least 11.4 mm is required, a toilet bowl in a dignity. node - 7.2 mm, sink in the kitchen - 7.9 mm. As for the inlet diameter of the water supply system to the house (for supplying 3 devices), it must be at least 13.1 mm.
Pipelines for the transport of various liquids are an integral part of plants and plants in which work processes related to various fields of application are carried out. When choosing pipes and the configuration of the pipeline, the cost of both the pipes themselves and the pipeline fittings is of great importance. The final cost of pumping the medium through the pipeline is largely determined by the size of the pipes (diameter and length). The calculation of these values \u200b\u200bis carried out using specially developed formulas specific to certain types of operation.
A pipe is a hollow cylinder made of metal, wood or other material used to transport liquid, gaseous and bulk media. The transported medium can be water, natural gas, steam, oil products, etc. Pipes are used in a wide range of industries, from various industries to domestic applications.
A wide variety of materials can be used to make pipes, such as steel, cast iron, copper, cement, plastic such as ABS plastic, PVC, chlorinated polyvinyl chloride, polybutene, polyethylene, etc.
The main dimensions of a pipe are its diameter (outer, inner, etc.) and wall thickness, which are measured in millimeters or inches. Also used is such a value as the nominal diameter or nominal bore - the nominal value of the internal diameter of the pipe, also measured in millimeters (indicated by DN) or inches (indicated by DN). The nominal diameters are standardized and are the main criterion for the selection of pipes and fittings.
Correspondence of nominal sizes 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 perimeter-to-area ratio, and when applied to a pipe, this means that, with equal throughput, the material consumption for round pipes will be minimal in comparison with pipes of other shapes. This also implies the lowest possible costs for insulation and protective coating;
- A circular cross-section is most advantageous for moving a liquid or gaseous medium from a hydrodynamic point of view. Also, due to the smallest possible internal area of \u200b\u200bthe pipe per unit of its length, minimization of friction between the transported medium and the pipe is achieved.
- The round shape is the 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 the purpose and field of application. So the 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, with a small diameter have a 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, which lists data on thickness, pipe size, route, etc. Raw materials, intermediate products and / or finished products go through production stages, moving between different devices and installations, which are connected using pipelines and fittings. Correct calculation, selection and installation of the piping system is necessary for reliable implementation of the entire process, ensuring safe pumping of media, as well as for sealing the system and preventing leaks of the pumped substance into the atmosphere.
There is no single formula or rule that can be used to select piping for every possible application and operating environment. In each individual area of \u200b\u200bpipeline application, there are a number of factors that need to be considered and can have a significant impact on the requirements for the pipeline. For example, when dealing with sludge, a large pipeline will not only increase the cost of the installation, but also create operational difficulties.
Typically, pipes are selected after optimizing material and operating costs. The larger the pipeline diameter, i.e. the higher the initial investment, the lower the pressure drop will be and, accordingly, the lower the operating costs. Conversely, the small size of the pipeline will reduce the primary costs of the pipes and pipe fittings themselves, but an increase in speed will entail an increase in losses, which will lead to the need to spend additional energy for pumping the medium. The speed limits fixed for various applications are based on optimal design conditions. Piping sizes are calculated using these codes for the application.
Piping design
When designing pipelines, the following basic design parameters are taken as a basis:
- required performance;
- entry point and exit point of the pipeline;
- composition of the medium, including viscosity and specific gravity;
- topographic conditions of the pipeline route;
- maximum allowable working 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 piping design is ensured by adhering to proper design codes. Personnel training is also a key factor in ensuring the long service life of the pipeline and its tightness and reliability. Permanent or periodic monitoring of the pipeline operation can be carried out by monitoring, accounting, control, regulation and automation systems, personal control devices in production, and safety devices.
Additional pipeline coverage
A corrosion-resistant coating is applied to the outside of most pipes to prevent the corrosive effects of environmental corrosion. In the case of pumping corrosive media, a protective coating can be applied to the inner surface of the pipes. Before commissioning, all new pipes intended for the transport of hazardous liquids are tested 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 be very different from liquid to liquid. One of the important indicators is the viscosity of the medium, characterized by such a parameter as the coefficient of viscosity. Irish engineer-physicist Osborne Reynolds conducted a series of experiments in 1880, according to 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 \u003d (v L ρ) / μ
where:
ρ is the density of the liquid;
v is the flow rate;
L is the characteristic length of the flow element;
μ is the dynamic coefficient of viscosity.
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. When 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 2300
| Flow velocity profile | ||
|---|---|---|
| laminar mode | transient regime | turbulent regime |
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| The nature of the flow | ||
| laminar mode | transient regime | turbulent regime |
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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 studying. 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.
Calculation of the pipeline. Calculation of the pipeline diameter
If the pipeline is not thermally insulated, that is, the exchange of heat between the transported and the environment is possible, then the nature of the flow in it can change even at a constant speed (flow rate). This is possible if the pumped medium at the inlet has a sufficiently high temperature and flows in a 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 entail a change in the flow regime to laminar or transitional. The temperature at which the change occurs is called the critical temperature. The value of the viscosity of the liquid directly depends on the temperature, therefore, for such cases, such a parameter is used as the critical viscosity corresponding to the point of change in the flow regime at the critical value of the Reynolds criterion:
v cr \u003d (v D) / Re cr \u003d (4 Q) / (π D Re cr)
where:
ν cr - critical kinematic viscosity;
Re cr is the critical value of the Reynolds criterion;
D is the pipe diameter;
v is the flow rate;
Q - consumption.
Another important factor is the friction that occurs between the pipe wall and the flowing stream. In this case, the coefficient of friction largely depends on the roughness of the pipe walls. The relationship between the coefficient of friction, Reynolds criterion and roughness is established by the Moody diagram, which allows you to determine one of the parameters, knowing the other two.
The Colebrook-White formula is also used to calculate the coefficient of friction of turbulent flow. Based on this formula, it is possible to build graphs by which the coefficient of friction is established.
(√λ) -1 \u003d -2log (2.51 / (Re √λ) + k / (3.71 d))
where:
k is the pipe roughness coefficient;
λ is the coefficient of friction.
There are also other formulas for the approximate calculation of friction losses during pressure flow of liquid in pipes. One of the most frequently used equations in this case is the Darcy-Weisbach equation. It is based on empirical data and is used primarily in system modeling. Friction loss is a function of the fluid velocity and the pipe's resistance to fluid movement, expressed in terms of the roughness value of the pipe walls.
∆H \u003d λ L / d v² / (2 g)
where:
ΔH - head loss;
λ is the coefficient of friction;
L is the length of the pipe section;
d - pipe diameter;
v is the flow rate;
g is the acceleration of gravity.
The pressure loss due to friction for water is calculated using the Hazen-Williams formula.
∆H \u003d 11.23 L 1 / C 1.85 Q 1.85 / D 4.87
where:
ΔH - head loss;
L is the length of the pipe section;
C is the Heisen-Williams roughness coefficient;
Q - consumption;
D is the pipe diameter.
Pressure
The operating pressure of the pipeline is the highest excess pressure that ensures the specified operating mode of the pipeline. The decision on the size of the pipeline and the number of pumping stations is usually made based on the operating pressure of the pipes, pump capacity and costs. The maximum and minimum pressure of the pipeline, as well as the properties of the working medium, determine the distance between the 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 a continuous operation of the pipeline with the given dimensions is possible.
As the temperature rises, the load capacity of the pipe decreases, as does the allowable overpressure as a result. The pe, zul value indicates the maximum pressure (g) in the piping system as the operating temperature rises.
Permissible overpressure graph:
Calculation of the pressure drop in the pipeline
The calculation of the pressure drop in the pipeline is made according to the formula:
∆p \u003d λ L / d ρ / 2 v²
where:
Δp is the pressure drop across the pipe section;
L is the length of the pipe section;
λ is the coefficient of friction;
d - pipe diameter;
ρ is the density of the pumped medium;
v is the flow rate.
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 pump a wide range of hydrocarbons and their mixtures, which differ greatly in chemical and physical properties. Crude oil can be transported further from onshore fields or offshore oil rigs to terminals, intermediate points and refineries.
Pipelines also transmit:
- refined 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 fuel oils 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 through pipelines, therefore, distillate fractions of oil are used to liquefy these raw materials and result in a mixture that can be transported through the pipeline;
- hydrogen (over 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 medium 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 elevated pressure, and when a certain pressure is reached, some gases may even undergo liquefaction. Therefore, the compression ratio of the medium is a critical parameter for the design of pipelines and for determining the throughput capacity.
Temperature indirectly and directly affects the performance of the pipeline. This is expressed in the fact that the liquid increases in volume after increasing temperature, provided that the pressure remains constant. A drop in temperature can also affect both performance and overall system efficiency. Usually, when the temperature of the liquid decreases, this is accompanied by an increase in its viscosity, which creates additional frictional resistance along the inner pipe wall, requiring more energy to pump the same amount of liquid. Highly viscous media are sensitive to fluctuations in operating temperatures. Viscosity is the resistance of a fluid 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 temperature of the medium falls below the pour point, the operation of the pipeline becomes impossible, and several options are taken to resume its operation:
- heating the medium or insulating pipes to maintain the operating temperature of the medium above its pour point;
- changing 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 made without longitudinal welds with heat treated steel lengths to achieve the desired size and properties. Welded pipe is manufactured using several manufacturing processes. These two types differ from each other in the number of longitudinal welds in the pipe and the type of welding equipment used. Steel welded 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 field of application, pipes made of fiberglass, various plastic, asbestos cement, etc. are used.
To connect straight pipe sections, as well as to transition between pipeline sections of different diameters, specially made connecting elements (elbows, bends, gates) are used.
| elbow 90 ° | bend 90 ° | transient branch | branching |
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| elbow 180 ° | bend 30 ° | adapter nipple | tip |
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For the installation of individual parts of pipelines and fittings, special connections are used.
| welded | flanged | threaded | clutch |
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Thermal expansion of the pipeline
When the pipeline is under pressure, its entire inner surface is subjected 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 excessive stress, dangerous for the strength of the pipeline, both in the pipe material and in flanged joints. Fluctuations in the temperature of the pumped medium also create a temperature stress in the pipeline, which can be transmitted to fittings, pumping stations, etc. This can lead to depressurization of pipeline joints, failure of fittings or other elements.
Calculation of pipeline dimensions with temperature changes
The calculation of the change in the linear dimensions of the pipeline with a change in temperature is carried out according to the formula:
∆L \u003d a L ∆t
a - coefficient of thermal elongation, mm / (m ° C) (see table below);
L - pipeline length (distance between fixed supports), m;
Δt is the difference between max. and min. temperature of the pumped-over medium, ° С.
Linear expansion table for pipes made of various materials
The numbers given are average values \u200b\u200bfor the listed materials and for calculating pipelines from 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 factor indicated by the manufacturer of the pipe in the accompanying technical specification or data sheet.
Thermal expansion of pipelines is eliminated both by using special compensation sections of the pipeline, and by using 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 fastened with bends. With thermal elongation, the increase in one part is compensated by the bending deformation of the other part on the plane or by the deformation of bending and torsion in space. If the pipeline itself compensates for thermal expansion, this is called self-compensation.
Compensation also takes place thanks to the elastic bends. A 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 section 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 the design and the principle of operation, there are four types of compensators: 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 expansion joints, they are usually 2 flat mutually perpendicular sections and have one common shoulder. Elastic expansion joints are made from pipes or elastic discs or bellows.
Determination of the optimal size of the pipe diameter
The optimum pipeline diameter can be found on the basis of technical and economic calculations. The dimensions of the pipeline, including the dimensions and functionality of the various components, and the conditions under which the pipeline must operate, determines the transport capacity of the system. Larger pipe sizes are suitable for higher mass flow rates, provided the other components in the system are properly sized and dimensioned. Typically, the longer the length of the main pipe between pumping stations, the greater the pressure drop in the pipeline is required. In addition, a change in the physical characteristics of the pumped medium (viscosity, etc.) can also have a large effect on the pressure in the line.
Optimal Size — The smallest suitable pipe size for a specific application, cost effective over the life of the system.
Formula for calculating pipe performance:
Q \u003d (π · d²) / 4 · v
Q is the flow rate of the pumped liquid;
d is the diameter of the pipeline;
v is the flow rate.
In practice, to calculate the optimal diameter of the pipeline, the values \u200b\u200bof the optimal velocities of the pumped medium are used, taken from reference materials compiled on the basis of experimental data:
| Pumped medium | Optimum speed range in the pipeline, m / s | |
|---|---|---|
| Liquids | Driving by gravity: | |
| Viscous liquids | 0,1 - 0,5 | |
| Low-viscosity liquids | 0,5 - 1 | |
| Transfer by pump: | ||
| Suction side | 0,8 - 2 | |
| Discharge side | 1,5 - 3 | |
| Gases | Natural cravings | 2 - 4 |
| Low pressure | 4 - 15 | |
| High 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 о \u003d √ ((4 Q) / (π v о))
Q is the specified flow rate of the pumped liquid;
d is the optimal diameter of the pipeline;
v is the optimal flow rate.
At high flow rates, pipes of a smaller diameter are usually used, which means lower costs for the purchase of the pipeline, its maintenance and installation work (denote K 1). With an increase in speed, there is an increase in head losses due to friction and in local resistances, which leads to an increase in the cost of pumping liquid (denote K 2).
For pipelines of large diameters, the costs of K 1 will be higher and the costs during operation of K 2 are lower. If we add the values \u200b\u200bof K 1 and K 2, then we get the total minimum costs K and the optimal diameter of the pipeline. The 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 \u003d (m C M K M) / n
m is the mass of the pipeline, t;
C M - cost of 1 ton, rub / ton;
K M - coefficient that increases the cost of installation work, for example 1.8;
n - service life, years.
The indicated operating costs are related to energy consumption:
K 2 \u003d 24 N n days C E rub / year
N - power, kW;
n ДН - number of working days per year;
С Э - costs for one kWh of energy, rubles / kW * h.
Pipeline sizing formulas
An example of general formulas for sizing pipes without considering possible additional influencing factors such as erosion, suspended solids, etc.
| Name | The equation | Possible limitations |
|---|---|---|
| Pressurized liquid and gas flow | ||
| Loss of friction head Darcy-Weisbach |
d \u003d 12 · [(0.0311 · f · L · Q 2) / (h f)] 0.2 |
Q - volumetric flow rate, gal / min; d is the inner diameter of the pipe; hf - friction head loss; L is the length of the pipeline, feet; f is the coefficient of friction; V is the flow rate. |
| Total fluid flow equation | d \u003d 0.64 √ (Q / V) |
Q - volumetric flow rate, gal / min |
| Pump suction line size to limit frictional head losses | d \u003d √ (0.0744 Q) |
Q - volumetric flow rate, gal / min |
| Total gas flow equation | d \u003d 0.29 √ ((Q T) / (P V)) |
Q - volumetric flow rate, ft³ / min T - temperature, K Р - pressure lb / in² (abs); V - speed |
| Gravity flow | ||
| Manning Equation for Calculating Pipe Diameter for Maximum Flow | d \u003d 0.375 |
Q - volumetric flow; n is the roughness coefficient; S is the slope. |
| Froude number ratio of inertial force and gravity | Fr \u003d V / √ [(d / 12) · g] |
g is the acceleration of gravity; v is the flow rate; L - pipe length or diameter. |
| Steam and evaporation | ||
| The equation for determining the pipe diameter for steam | d \u003d 1.75 · √ [(W · v_g · x) / V] |
W is the mass flow; Vg is the specific volume of saturated steam; x - steam quality; V is the speed. |
Optimum flow rate for various piping systems
The optimal pipe size is selected from the condition of the minimum costs for pumping the medium through the pipeline and the cost of pipes. However, the speed limits must also be considered. Sometimes, the size of the piping line must match the requirements of the process. Likewise, piping size is often related to pressure drop. In preliminary design calculations, where pressure losses are not considered, the size of the process pipeline is determined by the allowable speed.
If there are changes in the flow direction in the pipeline, this leads to a significant increase in local pressures at the surface perpendicular to the flow direction. This type of increase is a function of fluid velocity, density, and initial pressure. Since velocity is inversely proportional to diameter, high velocity fluids require special attention when sizing and configuring piping. The optimal pipe size, for example, for sulfuric acid, limits the fluid velocity to a value that prevents wall erosion in the pipe bends, thus preventing damage to the pipe structure.
Liquid flow by gravity
Calculating the size of the pipeline in the case of a gravity flow is rather complicated. The nature of movement with this form of flow in a pipe can be single-phase (full pipe) and two-phase (partial filling). Two-phase flow occurs when both liquid and gas are 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 bubble to dispersed.
| bubble flow (horizontal) | slug flow (horizontal) | wave flow | dispersed flow |
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The driving force for the fluid when moving by gravity is provided by the difference in the heights of the start and end points, and a prerequisite is the location of the start point above the end point. In other words, the difference in heights 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 \u200b\u200bat the start and end points. An increase in the pressure drop entails an increase in the fluid flow rate, which, in turn, allows the selection of a pipeline with a smaller diameter, and vice versa.
If the end point is connected to a pressurized system such as a distillation column, the equivalent pressure must be subtracted from the available 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 total differential pressure must also be taken into account when selecting the pipeline. The final pipe sizing is carried out using differential pressure, taking into account all of the above factors, and not based solely on the difference in heights of the start and end points.
Hot liquid flow
Process plants typically face various problems when handling hot or boiling media. The main reason is the evaporation of part of the hot liquid flow, that is, the phase transformation of the liquid into vapor within the pipeline or equipment. A typical example is the phenomenon of cavitation of a centrifugal pump, accompanied by a point boiling of a liquid followed by the formation of vapor bubbles (vapor cavitation) or the release of dissolved gases into bubbles (gas cavitation).
Larger piping is preferred because of the reduced flow rate over smaller piping at a constant flow rate because of the higher NPSH at the pump suction line. Cavitation caused by pressure loss can also be caused by sudden changes in flow direction or reduction in pipeline size. The resulting vapor-gas mixture creates an obstacle to the passage of the flow and can cause damage to the pipeline, which makes the cavitation phenomenon extremely undesirable during pipeline operation.
Equipment / Instrument Bypass Piping
Equipment and devices, especially those that can create significant pressure drops, that is, heat exchangers, control valves, etc., are equipped with bypass pipes (so that the process is not interrupted even during maintenance work). Such pipelines usually have 2 shut-off valves installed in the line of the installation and a valve that regulates the flow in parallel to the installation.
During normal operation, the fluid flow passing through the main units of the apparatus experiences an additional pressure drop. In accordance with this, the discharge pressure for it is calculated, created by the connected equipment, for example, a centrifugal pump. The pump is selected based on the total pressure drop across the installation. While moving through the bypass, this additional pressure drop is absent, while the running pump delivers the same force flow 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 pressure equivalent to the main unit.
Sampling line
Usually a small amount of liquid is taken for analysis to determine its composition. Sampling can be carried out at any stage of the process to determine the composition of raw materials, intermediate products, finished products, or simply transported substances such as waste water, heat carrier, etc. The size of the piping section that is sampled will usually depend on the type of fluid being analyzed and the location of the sampling point.
For example, for gases at elevated pressure, small pipelines with valves are sufficient to take the required number of samples. Increasing the diameter of the sampling line will reduce the proportion of the sample taken for analysis, but such sampling becomes more difficult to control. At the same time, 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 sample line for the analysis of suspensions is largely dependent on the size of the solid particles and the characteristics of the medium. Similar conclusions apply to viscous fluids.
When sizing the sampling line, usually consider:
- characteristics of the liquid to be taken;
- loss of the working environment during selection;
- safety requirements during selection;
- ease of use;
- location of the sampling point.
Coolant circulation
High speeds are preferred for piping with circulating coolant. This is mainly due to the fact that the cooling liquid in the cooling tower is exposed to sunlight, which creates conditions for the formation of an algae-containing layer. A part of this algae-containing volume enters the circulating coolant. At low flow rates, algae will start to grow in the piping and after a while make it difficult for the coolant to circulate or to pass into the heat exchanger. In this case, a high circulation rate is recommended to avoid the formation of algal blockages in the pipeline. Typically, the use of highly circulating coolant is found in the chemical industry, which requires large pipe 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 enters another reservoir rather than spilling out of the original reservoir);
- preventing unwanted liquids from leaking out of the tank;
- maintaining the liquid level in the tanks.
In all the aforementioned cases, the overflow pipes are designed for the maximum allowable flow of liquid entering the tank, regardless of the flow rate of liquid at the outlet. Other principles of pipe selection are similar to the selection of pipelines for gravity fluids, that is, in accordance with the available vertical height between the start and end point of the overflow pipeline.
The highest point of the overflow pipe, which is also its starting point, is at the point of connection to the tank (tank overflow pipe), usually almost at the top, and the lowest end point may be near the drain gutter, almost at the very ground. However, the overflow line may end at a higher elevation. In this case, the available differential head will be lower.
Sludge flow
In the case of mining, the ore is usually mined in areas that are difficult to access. In such places, as a rule, there is no rail or road connection. For such situations, hydraulic transportation of media with solid particles is considered as the most acceptable, including in the case of mining processing installations located at a sufficient distance. Slurry pipelines are used in various industrial fields for transporting crushed solids together with liquid. Such pipelines have proven to be the most cost-effective in comparison with other methods of transporting solids in large volumes. In addition, their advantages include sufficient safety due to the lack of several types of transportation and environmental friendliness.
Suspensions and mixtures of suspended solids in liquids are kept under intermittent agitation to maintain uniformity. Otherwise, a delamination process occurs, in which suspended particles, depending on their physical properties, float to the surface of the liquid or settle to the bottom. Agitation is achieved through equipment such as a stirred tank, 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 blockage in the pipeline and a change in the concentration of the transported solid in the stream. Intensive mixing in the flow volume is facilitated by the turbulent flow regime.
On the other hand, excessive pipeline size reduction also often leads to pipeline blockages. Therefore, the choice of the size of the pipeline is an important and crucial step that requires preliminary analysis and calculations. Each case must be considered individually, as different slurries behave differently at different fluid speeds.
Pipeline repair
During the operation of the pipeline, various types of leaks may occur in it, which require immediate elimination to maintain the system's operability. Repair of the main pipeline can be carried out in several ways. This can include replacing an entire pipe segment or a small section where a leak has occurred, or patching 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 only to repair, but to change the route of the pipe to prevent its repeated damage.
The first stage of repair work is to locate the pipe section that requires intervention. Further, depending on the type of pipeline, a list of the necessary equipment and measures necessary to eliminate the leak is determined, as well as the collection of the necessary documents and permits if the pipe section to be repaired is located on the territory of another owner. Since most of the pipes are located underground, it may be necessary to remove part of the pipe. Further, the pipeline coating is checked for general condition, after which part of the coating is removed for repair work directly with the pipe. After the repair, various verification measures can be carried out: ultrasonic testing, color flaw detection, magnetic powder flaw detection, etc.
While some repairs require a complete shutdown of the pipeline, often a temporary interruption is sufficient to isolate the repair section or prepare a bypass. However, in most cases, repair work is carried out with a complete shutdown of the pipeline. Isolation of the pipeline section can be carried out using plugs or shut-off valves. Next, the necessary equipment is installed and the repair is carried out directly. Repair work is carried out in the damaged area, freed from the medium and without pressure. At the end of the repair, the plugs are opened and the integrity of the pipeline is restored.
Carrying capacity 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, how much fluid the pipe passes through the section also depends on the pipeline diagram. 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 designations that are important in determining the throughput of a pipe:
Outside diameter - the physical size of the pipe section from one edge of the outer wall to the other. When calculating it is designated as Dn or Dн. This parameter is indicated in the marking.
Nominal bore is an approximate value of the diameter of the inner section of the pipe, rounded to the nearest whole number. In calculations, it is designated as Du or Du.
Physical methods for calculating the throughput of pipes
The values \u200b\u200bof the throughput of pipes are determined by special formulas. For each type of product - for gas, water supply, sewerage - the calculation methods 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 accuracy is not required, so values \u200b\u200bcan be applied without complex calculations. But this table does not take into account the decrease in throughput due to the appearance of sediment build-up inside the pipe, which is typical for old highways.
| Liquid type | Speed \u200b\u200b(m / s) |
| City water supply | 0,60-1,50 |
| Pipeline water | 1,50-3,00 |
| Central heating water | 2,00-3,00 |
| Pressure water in the pipeline | 0,75-1,50 |
| Hydraulic fluid | up to 12m / s |
| Oil line pipeline | 3,00-7,5 |
| Oil in the pressure system of the pipeline | 0,75-1,25 |
| Steam in the heating system | 20,0-30,00 |
| Steam central piping system | 30,0-50,0 |
| Steam in a heating system with a high temperature | 50,0-70,00 |
| Air and gas in the central piping system | 20,0-75,00 |
There is an accurate flow rate calculation table, called the Shevelev table, which takes into account the pipe material and many other factors. These tables are rarely used when laying a water supply system around an 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, 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 read 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 has the property of being compressed and therefore able to escape through the smallest gaps in pipes. There are special requirements for calculating the throughput of gas pipes (as well as for designing the gas system as a whole).
The formula for calculating the throughput of a gas pipe
The maximum throughput of gas pipelines is determined by the formula:
Qmax \u003d 0.67 Du2 * p
where p is equal to the operating pressure in the gas pipeline system + 0.10 MPa or the absolute gas pressure;
Du - nominal pipe bore.
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 \u003d 196.386 Du2 * p / z * T
where z is the coefficient of compressibility;
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 pushes against the walls. Therefore, when calculating large pipelines, 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 formed at high temperatures in summer (for example, at + 38 ... + 45 degrees Celsius), then damage to the pipeline is likely. This entails the leakage of valuable raw materials, and creates the possibility of an explosion of the pipe section.
Table of flow rates of gas pipes depending on pressure
There is a table for calculating the throughput of a gas pipeline for commonly used pipe diameters and nominal working pressure. To determine the characteristics of a gas pipeline of non-standard dimensions and pressure, engineering calculations will be required. The outside air temperature also affects the pressure, speed and volume of gas.
The maximum speed (W) of the gas in the table is 25 m / s, and the z (coefficient of compressibility) is 1. The temperature (T) is 20 degrees Celsius or 293 Kelvin.
| Pwork. (MPa) | Pipeline throughput (m3 / h), at wgas \u003d 25m / s; z \u003d 1; Т \u003d 20 ° С \u003d 293 ° К | |||||||
|---|---|---|---|---|---|---|---|---|
| DN 50 | DN 80 | DN 100 | DN 150 | DN 200 | DN 300 | DN 400 | DN 500 | |
| 0,3 | 670 | 1715 | 2680 | 6030 | 10720 | 24120 | 42880 | 67000 |
| 0,6 | 1170 | 3000 | 4690 | 10550 | 18760 | 42210 | 75040 | 117000 |
| 1,2 | 2175 | 5570 | 8710 | 19595 | 34840 | 78390 | 139360 | 217500 |
| 1,6 | 2845 | 7290 | 11390 | 25625 | 45560 | 102510 | 182240 | 284500 |
| 2,5 | 4355 | 11145 | 17420 | 39195 | 69680 | 156780 | 278720 | 435500 |
| 3,5 | 6030 | 15435 | 24120 | 54270 | 96480 | 217080 | 385920 | 603000 |
| 5,5 | 9380 | 24010 | 37520 | 84420 | 150080 | 337680 | 600320 | 938000 |
| 7,5 | 12730 | 32585 | 50920 | 114570 | 203680 | 458280 | 814720 | 1273000 |
| 10,0 | 16915 | 43305 | 67670 | 152255 | 270680 | 609030 | 108720 | 1691500 |
Sewer pipe throughput
The throughput of a sewer pipe is an important parameter that depends on the type of pipeline (pressure or gravity). The calculation formula is based on the laws of hydraulics. In addition to the laborious calculation, tables are used to determine the throughput of the sewage system.
For the hydraulic calculation of the sewage system, it is required to determine the unknowns:
- pipeline diameter DN;
- average flow velocity v;
- hydraulic slope l;
- the degree of filling h / Du (in the calculations, they are repelled by 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 rest of the parameters are easy to calculate. In preliminary calculations, the hydraulic slope 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 \u200b\u200bas well as the maximum h / DN values \u200b\u200bfor domestic networks can be found in Table 3.
Yulia Petrichenko, expert
In addition, there is a standardized value for the minimum slope for pipes with a small diameter: 150 mm
(i \u003d 0.008) and 200 (i \u003d 0.007) mm.
The formula for the volumetric flow rate of liquid looks like this:
where a is the flow area,
v - flow velocity, m / s.
The speed is calculated using the formula:
where R is the hydraulic radius;
C is the wetting coefficient;
From here you can derive the formula for the hydraulic slope:
According to it, this parameter is determined if a calculation is required.
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 normal radius, but only when the pipe is completely filled. In other cases, use the formula:
where A is the cross-flow area of \u200b\u200bthe liquid,
P is the wetted perimeter, or the transverse length of the inner surface of the pipe that touches the liquid.
Tables of throughput of non-pressure sewer pipes
The table includes all the parameters used to perform the hydraulic calculation. The data is selected by the value of the pipe diameter and substituted into the formula. Here, the volumetric flow rate of the liquid q passing through the pipe section has already been calculated, which can be taken as the throughput of the main.
In addition, there are more detailed Lukins' tables containing ready-made values \u200b\u200bof throughput for pipes of different diameters from 50 to 2000 mm.
Tables of throughput of pressure sewerage systems
In the tables of the capacity of the sewage pressure pipes, the values \u200b\u200bdepend on the maximum degree of filling and the calculated average wastewater velocity.
| Diameter, mm | Filling | Accepted (optimal slope) | Waste water speed in the pipe, m / s | Consumption, l / s |
| 100 | 0,6 | 0,02 | 0,94 | 4,6 |
| 125 | 0,6 | 0,016 | 0,97 | 7,5 |
| 150 | 0,6 | 0,013 | 1,00 | 11,1 |
| 200 | 0,6 | 0,01 | 1,05 | 20,7 |
| 250 | 0,6 | 0,008 | 1,09 | 33,6 |
| 300 | 0,7 | 0,0067 | 1,18 | 62,1 |
| 350 | 0,7 | 0,0057 | 1,21 | 86,7 |
| 400 | 0,7 | 0,0050 | 1,23 | 115,9 |
| 450 | 0,7 | 0,0044 | 1,26 | 149,4 |
| 500 | 0,7 | 0,0040 | 1,28 | 187,9 |
| 600 | 0,7 | 0,0033 | 1,32 | 278,6 |
| 800 | 0,7 | 0,0025 | 1,38 | 520,0 |
| 1000 | 0,7 | 0,0020 | 1,43 | 842,0 |
| 1200 | 0,7 | 0,00176 | 1,48 | 1250,0 |
Water pipe throughput
Plumbing pipes are most commonly used in the home. And since they are under heavy load, then the calculation of the throughput of the water main becomes an important condition for reliable operation.
Pipe permeability depending on diameter
Diameter is not the most important parameter when calculating the permeability of a pipe, 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 the water against the pipe walls (tabular value for each material), the length of the pipeline and the difference in fluid pressure at the inlet and outlet. In addition, the number of elbows and fittings in the pipeline will greatly affect permeability.
Table of throughput of pipes by temperature of the coolant
The higher the temperature in the pipe, the lower its throughput, since the water expands and thereby creates additional friction. This is not important for the water supply system, but in heating systems it is a key parameter.
There is a table for calculations for heat and coolant.
| Pipe diameter, mm | Bandwidth | |||
|---|---|---|---|---|
| By warmth | By coolant | |||
| Water | Steam | Water | Steam | |
| Gcal / h | t / h | |||
| 15 | 0,011 | 0,005 | 0,182 | 0,009 |
| 25 | 0,039 | 0,018 | 0,650 | 0,033 |
| 38 | 0,11 | 0,05 | 1,82 | 0,091 |
| 50 | 0,24 | 0,11 | 4,00 | 0,20 |
| 75 | 0,72 | 0,33 | 12,0 | 0,60 |
| 100 | 1,51 | 0,69 | 25,0 | 1,25 |
| 125 | 2,70 | 1,24 | 45,0 | 2,25 |
| 150 | 4,36 | 2,00 | 72,8 | 3,64 |
| 200 | 9,23 | 4,24 | 154 | 7,70 |
| 250 | 16,6 | 7,60 | 276 | 13,8 |
| 300 | 26,6 | 12,2 | 444 | 22,2 |
| 350 | 40,3 | 18,5 | 672 | 33,6 |
| 400 | 56,5 | 26,0 | 940 | 47,0 |
| 450 | 68,3 | 36,0 | 1310 | 65,5 |
| 500 | 103 | 47,4 | 1730 | 86,5 |
| 600 | 167 | 76,5 | 2780 | 139 |
| 700 | 250 | 115 | 4160 | 208 |
| 800 | 354 | 162 | 5900 | 295 |
| 900 | 633 | 291 | 10500 | 525 |
| 1000 | 1020 | 470 | 17100 | 855 |
Table of throughput of pipes depending on the pressure of the coolant
There is a table describing the capacity of pipes depending on the pressure.
| Consumption | Bandwidth | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Du pipes | 15 mm | 20 mm | 25 mm | 32 mm | 40 mm | 50 mm | 65 mm | 80 mm | 100 mm |
| Pa / m - mbar / m | less than 0.15 m / s | 0.15 m / s | 0.3 m / s | ||||||
| 90,0 - 0,900 | 173 | 403 | 745 | 1627 | 2488 | 4716 | 9612 | 14940 | 30240 |
| 92,5 - 0,925 | 176 | 407 | 756 | 1652 | 2524 | 4788 | 9756 | 15156 | 30672 |
| 95,0 - 0,950 | 176 | 414 | 767 | 1678 | 2560 | 4860 | 9900 | 15372 | 31104 |
| 97,5 - 0,975 | 180 | 421 | 778 | 1699 | 2596 | 4932 | 10044 | 15552 | 31500 |
| 100,0 - 1,000 | 184 | 425 | 788 | 1724 | 2632 | 5004 | 10152 | 15768 | 31932 |
| 120,0 - 1,200 | 202 | 472 | 871 | 1897 | 2898 | 5508 | 11196 | 17352 | 35100 |
| 140,0 - 1,400 | 220 | 511 | 943 | 2059 | 3143 | 5976 | 12132 | 18792 | 38160 |
| 160,0 - 1,600 | 234 | 547 | 1015 | 2210 | 3373 | 6408 | 12996 | 20160 | 40680 |
| 180,0 - 1,800 | 252 | 583 | 1080 | 2354 | 3589 | 6804 | 13824 | 21420 | 43200 |
| 200,0 - 2,000 | 266 | 619 | 1151 | 2486 | 3780 | 7200 | 14580 | 22644 | 45720 |
| 220,0 - 2,200 | 281 | 652 | 1202 | 2617 | 3996 | 7560 | 15336 | 23760 | 47880 |
| 240,0 - 2,400 | 288 | 680 | 1256 | 2740 | 4176 | 7920 | 16056 | 24876 | 50400 |
| 260,0 - 2,600 | 306 | 713 | 1310 | 2855 | 4356 | 8244 | 16740 | 25920 | 52200 |
| 280,0 - 2,800 | 317 | 742 | 1364 | 2970 | 4356 | 8566 | 17338 | 26928 | 54360 |
| 300,0 - 3,000 | 331 | 767 | 1415 | 3076 | 4680 | 8892 | 18000 | 27900 | 56160 |
Table of pipe throughput depending on diameter (according to Shevelev)
F.A and A.F.Shevelev's tables 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 most often by hydraulic engineers.
The tables take into account:
- pipe diameters - inner and outer;
- wall thickness;
- service life of the water supply system;
- line length;
- the appointment of pipes.
Hydraulic calculation formula
For water pipes, the following calculation formula applies:
Online calculator: calculation of pipe throughput
If you have any questions, or you have any reference books that use methods not mentioned here, write in the comments.
Water consumption parameters:
- The size of the pipe diameter, which also determines the further throughput.
- The size of the pipe walls, which will then determine the internal pressure in the system.
The only thing that does not affect the expense is the length of the communications.
If the diameter is known, the calculation can be carried out using the following data:
- Structural material for pipe building.
- Technology influencing the pipeline assembly process.
The characteristics affect the pressure inside the water supply system and determine the water flow rate.
If you are looking for an answer to the question of how to determine water consumption, then you must learn two calculation formulas that determine the parameters of use.
- The formula for calculating per day is Q \u003d ΣQ × N / 100. Where ΣQ is the annual daily water use per inhabitant and N is the number of residents in the building.
- The formula for calculating per hour is q \u003d 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 an expense that will show the needs and requirements of a given home. There are tables that can be used in calculating the liquid.
Reference data in water calculation
When using tables, you should calculate all the taps, bathrooms and water heaters in the house. SNiP table 2.04.02-84.
Standard consumption rates:
- 60 liters - 1 person.
- 160 liters - for 1 person, if the house has a better water supply.
- 230 liters - for 1 person, in a house with a high-quality water supply and a bathroom.
- 350 liters - for 1 person with running water, built-in appliances, bathroom, toilet.
Why calculate water according to SNiP?
How to determine the water consumption for every day is not the most popular information among ordinary residents of the house, but specialists in the installation of pipelines need this information even less. And at most they need to know what the diameter of the connection is, and what pressure it supports in the system.
But in order to determine these indicators, you need to know how much water is needed in the pipeline.
Formula to help determine pipe diameter and fluid flow rate:
The standard fluid velocity in a system without pressure 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. With knowledge of the diameter, the flow rate in communications is determined.
Calculation of water pressure loss
The loss of water consumption is calculated taking into account the pressure drop using one formula:
In the formula, L - denotes the length of the joint, and λ - friction loss, ρ - malleability.
The friction index changes from the following values:
- the level of roughness of the coating;
- obstruction in the equipment at locking points;
- fluid flow rate;
- the length of the pipeline.
Simplicity of calculation
Knowing the pressure loss, the fluid velocity in the pipes and the volume of water required, how to determine the water flow 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 pipe diameter, q is the consumer water consumption, and V is the water speed, i is the course. To determine the values, they must be found in the table and connected in a straight line. The flow rate and diameter are also determined, taking into account the slope and speed. Therefore, the easiest way to calculate is using tables and graphs.
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. This article will focus on 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
- External diameter... This indicator is expressed as the distance from one side of the outer wall to the other side. In calculations, this parameter has the designation Day. The outer diameter of the pipes is always shown in the marking.
- Nominal diameter... This value is defined as the internal diameter, rounded to whole numbers. When calculating, the nominal size is displayed as DN.
The calculation of the permeability of the pipe can be carried out according to one of the methods, which must be selected depending on the specific conditions for laying the pipeline:
- Physical calculations... In this case, the formula for the throughput of the pipe is used, which makes it possible to take into account each indicator of the structure. The choice of the formula is influenced by the type and purpose of the pipeline - for example, for sewage systems there is a set of formulas, as for other types of structures.
- Tabular calculations... You can choose the optimal amount of permeability using a table with approximate values, which is most often used to arrange wiring in an apartment. The values \u200b\u200bindicated in the table are rather 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 the changes in the latter due to deposits, therefore, 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 the factors affecting the pipes. Such a table is great for the installation of highways on individual land plots.
- Calculation using programs... Many companies specializing in the laying of 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 free of charge. A good version of 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 of gas pipelines
Gas pipeline design requires a fairly high degree of accuracy - the gas has a very high compression ratio, due to which leaks are possible even through microcracks, not to mention serious ruptures. 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 using the following formula:
- Qmax \u003d 0.67 Du2 * p,
Where p is the value of the working pressure in the pipeline, to which 0.10 MPa is added;
Du is the nominal size 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, professionals 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 turns out to be less than the gas pressure in the system, then the pipeline is very likely to be damaged during operation, as a result of which there will be a loss of the transported substance and the risk of explosion on the weakened pipe section will increase.
If necessary, you can determine the permeability of the 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 pipeline throughput calculated by the diameter has, namely, the inability to take into account the impact of external factors.
Calculation of the throughput of sewer pipes
When designing a sewerage system, it is imperative to calculate the throughput of the pipeline, which directly depends on its type (sewerage systems are pressurized and non-pressurized). For the calculations, hydraulic laws are used. The calculations themselves can be carried out both using formulas and through the corresponding tables.
For the hydraulic calculation of the sewer system, the following indicators are required:
- Pipe diameter - DN;
- Average speed of movement of substances - v;
- The value of the hydraulic slope - I;
- The degree of filling is h / DN.
As a rule, during calculations, only the last two parameters are calculated - the rest after that can be determined without any special problems. The amount of hydraulic slope is usually equal to the slope of the ground, which will ensure that the drains move at the speed necessary to self-clean the system.
The speed and maximum filling level of the domestic sewage system are determined according to the table, which can be written as follows:
- 150-250 mm - h / DN is 0.6, and the speed is 0.7 m / s.
- Diameter 300-400 mm - h / DN 0.7, speed 0.8 m / s.
- Diameter 450-500 mm - h / DN 0.75, speed 0.9 m / s.
- Diameter 600-800 mm - h / DN 0.75, speed 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 value of the 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.
The following formula is used to calculate the volume of effluent:
- q \u003d a * v,
Where a is the area of \u200b\u200bthe free flow area;
v is the speed of wastewater transportation.
You can determine the speed of transport of a substance using the following formula:
- v \u003d 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 derived, which will determine the value of the hydraulic slope:
- i \u003d v2 / C2 * R.
To calculate the wetting factor, use a formula like this:
- С \u003d (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 manufacture of the pipe).
The R value is usually equated to a normal radius, but this is only relevant if the pipe is completely filled.
For other situations, a simple formula is used:
- R \u003d A / P,
Where A is the cross-sectional area of \u200b\u200bthe water flow,
P is the length of the inner part of the pipe in direct contact with the liquid.
Tabular calculation of sewer pipes
It is also possible to determine the permeability of pipes of the sewer system using tables, and the calculations will directly depend on the type of system:
- Gravity sewerage... To calculate gravity 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 throughput of the pipeline. If necessary, you can use the Lukin tables, which indicate the throughput of all pipes with a diameter ranging from 50 to 2000 mm.
- Pressure sewerage... 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. Read also: "".
The table of throughput of polypropylene pipes allows you to find out all the parameters necessary for arranging the system.
Calculation of the throughput of the water supply
Water pipes in private construction are used most often. In any case, the water supply system has a serious load, therefore, 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 cross-country ability, but its influence cannot be ruled out. The increase in the inner diameter of the pipe is directly proportional to its permeability - that is, the 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 considered. For example, a very important factor is the coefficient of friction of the fluid against the inner part of the pipe (there are eigenvalues \u200b\u200bfor different materials). 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 water supply system.
The throughput of polypropylene water pipes can be calculated depending on several parameters by a tabular method. One of them is a calculation in which the main indicator is the water temperature. As the temperature rises in the system, the liquid expands, so the friction increases. To determine the patency of the pipeline, use the appropriate table. There is also a table that allows you to determine the permeability in pipes depending on the water pressure.
The most accurate calculation of water by the throughput of a pipe is made possible by Shevelev's 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 associated with hydraulic calculations, therefore, most professionals in this field most often use Shevelev's tables.
The main parameters that are taken into account in these tables are:
- External and internal diameters;
- Pipeline wall thickness;
- System operation period;
- The total length of the highway;
- Functional purpose of the system.
Conclusion
The calculation of the throughput of pipes can be performed 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 or less accurate calculation options, so both a professional specializing in laying pipelines and an owner who decides to lay the highway at home can find a suitable one.
