Pipe section on consumption. Calculation and selection of pipelines. The optimal diameter of the pipeline. Suitable liquid rate, depending on the type of pipeline

Enterprises and residential buildings consume a large amount of water. These digital indicators become not only evidence of a specific value indicating consumption.

In addition, they help to determine the diameter of the tubular sorting. Many believe that the calculation of water flow through the pipe diameter and pressure is impossible, as these concepts are completely unnecessary.

But practice showed that it is not. The capacity of the water supply network is dependent on many indicators, and the diameter of the tubular sorting and pressure in the highway will be the first in this list.

Perform the calculation of the bandwidth of the pipe, depending on its diameter, is recommended at the stage of designing the pipeline construction. The data obtained define the key parameters of not only home, but also the industrial highway. All this will go further.

We calculate the bandwidth of the pipe using an online calculator

ATTENTION! To correctly calculate, it is necessary to pay attention to that 1kgs / cm2 \u003d 1 atmosphere; 10 meters of water column \u003d 1kgs / cm2 \u003d 1atm; 5 meters of water column \u003d 0.5 kgf / cm2 and \u003d 0.5 atm, etc. Fractional numbers in an online calculator are entered through a point (for example: 3.5 and not 3.5)

Enter the parameters for calculating:

What factors affect the patency of fluid through the pipeline

Criteria affecting the described indicator make up a large list. Here is some of them.

Inner diameter, which has a pipeline.
The speed of movement of the flow, which depends on the pressure in the highway.
Material taken for the production of tubular sorting.

The determination of water flow at the outlet of the highway is performed on the diameter of the pipe, because this characteristic shared with others affects the bandwidth of the system. Also, calculating the amount of consumed fluid, it is impossible to discount the wall thickness, the definition of which is carried out on the basis of the intended internal pressure.

You can even declare that only the length of the network does not affect the definition of "tube geometry". And the section, pressure and other factors play a very important role.

In addition, some parameters of the system are not direct, but an indirect effect. This includes the viscosity and temperature of the pumpable medium.

By summing a small result, we can say that the definition of bandwidth allows you to accurately establish the optimal type of material for the construction of the system and make the choice of technology used for its assembly. Otherwise, the network will not function effectively, and it will take frequent emergency repairs.

Calculation of water consumption by diameter Round pipe depends on his size. Therefore, in a larger cross section, a significant amount of fluid will be performed for a certain period of time. But, performing the calculation and taking into account the diameter, it is impossible to discount the pressure.

If we consider this calculation on a specific example, it turns out that through a meter tube product through a hole in 1 cm there will be less fluid for a certain time period than through a highway reaching a couple of tens of meters. This is natural, because the highest level of water consumption on the site will reach the largest indicators at maximum pressure on the network and at the highest values \u200b\u200bof its volume.

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Calculations of the section on SNiP 2.04.01-85

First of all, it is necessary to understand that the calculation of the diameter of the water pipe tube is a complex engineering process. This will require special knowledge. But, by performing a domestic building of the water pipeline, often hydraulic calculation by section is carried out independently.

This form of the design calculation of the flow rate for the waterfront design can be carried out in two ways. First - tabular data. But, referring to the tables, it is necessary to know not only the exact number of cranes, but also tanks for a set of water (baths, sinks) and other things.

Only in the presence of these information about the waterproof system, you can use the tables that SNiP 2.04.01-85. On them and determine the volume of water to girth pipes. Here is one of these tables:

External volume of the tubular sorting (mm)

An approximate amount of water that is obtained in liters per minute

Approximate amount of water calculated in m3 per hour

If you can focus on the norms of SNiP, then you can see the following - the daily volume of water consumed by one person does not exceed 60 liters. This is provided that the house is not equipped with a water supply, and in a situation with a well-maintained housing, this volume increases to 200 liters.

Definitely, these data on the volume showing consumption are interesting as information, but a pipeline specialist will need a definition of completely other data - this is the volume (in mm) and the internal pressure in the highway. In the table it can be found not always. And more accurately learn this information to help formulas.

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It is already clear that the dimensions of the system cross section affect the hydraulic calculation of consumption. For home calculations, water flow formula is used, which helps to obtain the result, having pressure data and pipe diameter. Here is this formula:

Formula for calculating pressure on pressure and diameter of the pipe: Q \u003d π × d² / 4 × v

In the formula: Q shows water consumption. It is calculated by liters. D is the size of the pipe cross section, it is shown in centimeters. And v in the formula is the designation of the speed of movement of the flow, it is shown in meters per second.

If the water supply network is powered by the water tower, without the additional effect of the injection pump, the flow rate of the flow is approximately 0.7 - 1.9 m / s. If any injection device is connected, then in the passport there is information about the coefficient of the pressure of the pressure and the speed of moving the flow of water.

This formula is not the only one. There are also many others. You can easily find them in the Internet.

In addition to the formula represented, it should be noted that the inner walls of pipe products have a huge importance on the functionality of the system. For example, plastic products are distinguished by a smooth surface than steel counterparts.

For these reasons, the plastic resistance coefficient is significantly less. Plus, these materials are not affected by corrosion entities, which also has a positive effect on the capacity of the water supply network.

Determination of pressure loss

The calculation of the passage of water is produced not only by the diameter of the pipe, it is calculated by falling pressure. Calculate losses can be calculated by special formulas. What formulas to use, everyone will solve independently. To calculate the desired values, you can use various options. There is no single universal solution to this issue.

But first of all, it is necessary to remember that the inner lumen of the passage of the plastic and metal-plastic design will not change in twenty years of service. And the inner lumen of the passage of the metal structure will become less over time.

And this will entail the loss of some parameters. Accordingly, the velocity of water in the pipe in such structures is different, because the diameter is a new and old network in some situations will differ significantly. The magnitude of the resistance in the highway will also differ.

Also before calculating the necessary parameters of the fluid passage, it is necessary to take note that the flow rate of the water supply flow is associated with the number of turns, fittings, volume transitions, with the presence of shut-off reinforcement and friction force. Moreover, all this when calculating the flow rate should be carried out after thorough preparation and measurements.

Calculation of water consumption with simple methods is not easy. But, with the slightest difficulties, you can always seek help from specialists or use the online calculator. Then you can count on the fact that the laid water supply network or heating will work with maximum efficiency.

Video - how to calculate water consumption

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Why do you need such calculations

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

In addition, if the water supply is not equipped with water meters, then when paying for the services of public services, the settlement is taken. "Pettleness of the pipe." In this case, it is quite logical than the question of the tariffs applied at the same time.

It is important to understand that the second option does not apply to private premises (apartments and cottages), where in the absence of counters when calculating the payment take into account sanitary standards: it is usually up to 360 l / a day per person.

What depends on the passability of the pipe

What does water consumption depends on the round of the circular section? It seems that the search for the answer should not cause difficulties: the larger cross section has a pipe, the greater the volume of water it can skip over a certain time. A simple formula for the volume of pipe will allow you to know and this value. In this case, the pressure is also remembered, because the higher the water pole, with the greater speed, the water will be joined inside the communication. However, practice shows that this is not all factors affecting water consumption.

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

Length pipe. With an increase in its length, water turns more than its wall, which leads to a slowdown. Indeed, at the very beginning of the system, water is experiencing exclusively with pressure, but it is important and how quickly the following portions will have the opportunity to enter into communication. Braking inside the tube often reaches large values.
Water consumption depends on diameter In a much more difficult degree than it seems at first glance. When the size of the diameter of the pipe is small, the walls resist the aqueous stream an order of magnitude greater than in thicker systems. As a result, with a decrease in the pipe diameter, its benefit is reduced in terms of the ratio of the water flow rate to the index of the inner area on the fixed length section. If you say in a simple, thick water supply is much faster transported water than thin.
Material of manufacture. Another important point, directly affecting the speed of the water in the pipe. For example, smooth propylene contributes to the glide of water in much more than the rough steel walls.
Service duration. Over time, rust appears on steel water pipes. In addition, for steel, as for cast iron, it is characteristic of gradually accumulating lime deposits. The resistance to the water flow pipe with sediments is much higher than new steel products: this difference sometimes reaches 200 times. In addition, the tip of the pipe leads to a decrease in its diameter: even if you do not take into account the increased friction, it clearly falls. It is also important to note that products from plastic and metalplastic such problems do not have: Even after decades of intensive operation, the level of their resistance to the aqueous streams remains at the initial level.
Availability of turns, fittings, adapters, valves Promotes additional braking of water streams.

All of the above factors have to be considered, because it is not about some small errors, but about a serious difference several times. As an output, it can be said that a simple definition of the diameter of the pipe on water consumption is hardly possible.

New possibility of calculating water flow

If the use of water is carried out by means of a crane, it greatly simplifies the task. The main thing in this case is that the size of the water output holes were much smaller than the diameter of the water pipeline. In this case, the formula for calculating the water calculation by cross section of torrchelli V ^ 2 \u003d 2GH, where V is the speed of flow through a small hole, G is an acceleration of free fall, and H is the height of the water column over the crane (a hole having a cross section S, per unit of time Passes aqueous volume S * V). It is important to remember that the term "section" is not applied to designate the diameter, and its area. For its calculation, the formula Pi * R ^ 2 is used.

If the water column has a height of 10 meters, and the hole is the diameter of 0.01 m, the water consumption through the pipe at a pressure into one atmosphere is calculated in this way: V ^ 2 \u003d 2 * 9.78 * 10 \u003d 195.6. After removing the square root, V \u003d 13,98570698963767 comes out. After rounding, to get a simpler speed indicator, it turns out to be 14m / s. The cross section of the hole, having a diameter of 0.01 m, is calculated as: 3,14159265 * 0.01 ^ 2 \u003d 0.000314159265 m2. As a result, it turns out that the maximum water flow through the pipe corresponds to 0.000314159265 * 14 \u003d 0.00439822971 m3 / s (slightly less than 4.5 liters of water / second). As you can see, in this case, the calculation of water in the pipe cross section is quite simple. Also in free access there are special tables indicating the cost of water for the most popular plumbing products, with a minimum value of the diameter of the tap pipe.

As can already be understood, a universal simple way to calculate the diameter of the pipeline depending on the flow of water, does not exist. However, certain indicators for themselves can still be withdrawn. This is especially true if the system is equipped with plastic or metal-plastic pipes, and water consumption is carried out by cranes with a small exit cross section. In some cases, this method of calculation is applicable on steel systems, but it is primarily about new water pipelines that did not have time to be covered with internal sediments on the walls.

In order to properly mount the design of the water supply, starting the development and planning of the system, it is necessary to calculate the flow of water through the pipe.

The main parameters of the domestic water industry depend on the data obtained.

In this article, readers will be able to get acquainted with the main techniques that will help them independently calculate their water supply system.

The purpose of calculating the diameter of the pipeline by consumption: determination of the diameter and cross-section of the pipeline based on the flow data and the speed of longitudinal movement of water.

Perform such a calculation is quite difficult. It is necessary to take into account a lot of nuances associated with technical and economic data. These parameters are interconnected. The diameter of the pipeline depends on the type of fluid, which will roll over it.

If you increase the speed of movement of the stream, you can reduce the diameter of the pipe. Material consumption will automatically decrease. Introduction such a system will be much easier, the cost of work will fall.

However, the increase in the flow movement will cause pressure loss that require the creation of additional energy for pumping. If it is very reduced to reduce it, unwanted consequences may appear.

When the pipeline design is performed, in most cases, the water consumption is immediately set. Two values \u200b\u200bremain unknowns:

Pipe diameter;
Flow speed.

Make fully technical and economic calculation is very difficult. This requires relevant engineering knowledge and a lot of time. To facilitate such a task when calculating the necessary diameter of the pipe, use reference materials. They are given the values \u200b\u200bof the best flow rate obtained by experimentally.

The final calculation formula for the optimal diameter of the pipeline is as follows:

d \u003d √ (4q / πw)
Q - flow of pumped liquid, m3 / s
D - pipeline diameter, m
W - flow rate, m / s

Suitable liquid rate, depending on the type of pipeline

First of all, the minimum costs are taken into account, without which it is impossible to pump the liquid. In addition, the cost of the pipeline is necessarily considered.

When calculating, you should always remember about the limitations of the speed of the moving environment. In some cases, the size of the main pipeline must meet the requirements laid down in the technological process.

On the size of the pipeline also affect possible pressure jumps.

When preliminary calculations are made, the change in the calculation is not taken. As the basis of the design of the process pipeline takes permissible speed.

When in the designed pipeline there are changes in the direction of movement, the pipe surface begins to experience a large pressure, directed perpendicular to the movement of the flow.

Such an increase is associated with several indicators:

Fluid speed;
Density;
Source pressure (pressure).

Moreover, the speed is always in the reverse proportion to the pipe diameter. That is why high-speed fluids require the right choice of configuration, the competent selection of the dimensions of the pipeline.

For example, if sulfuric acid is pumped, the speed value is limited to the value, which will not cause erosion on the walls of the tube knees. As a result, the structure of the pipe will never be broken.

Water speed in the formula pipeline

The volume flow V (60m³ / hour or 60 / 3600m³ / s) is calculated as a product of the flow velocity W on the cross section of the pipe S (and the cross section in turn is considered as S \u003d 3.14 d² / 4): V \u003d 3.14 W d² / 4. From here we obtain w \u003d 4V / (3.14 d²). Do not forget to translate the diameter of millimeters to meters, that is, the diameter will be 0.159 m.

Water consumption formula

In general, the methodology for measuring water consumption in rivers and pipelines is based on a simplified form of the continuity equation for incompressible liquids:

Water consumption through pipe table

Pressure flow dependence

There is no such dependence of the flow of fluid from pressure, but is from the pressure drop. Formula is displayed simply. There is a generally accepted pressure drop equation during fluid in the pipe Δp \u003d (λl / d) ρw² / 2, λ is the friction coefficient (it is selected depending on the speed and diameter of the pipe in terms of or appropriate formulas), L - the length of the pipe, D is its diameter , ρ - the flow of the liquid, W is the speed. On the other hand, there is a calculation of the flow G \u003d ρwπd² / 4. We express the speed from this formula, we substitute it into the first equation and find the dependence of the flow rate G \u003d π SQRT (ΔP D ^ 5 / λ / L) / 4, SQRT is a square root.

The friction coefficient is looking for a selection. Initially, you specify a certain value of the fluid velocity from the lantern and determine the number of Reynolds Re \u003d ρwd / μ, where μ is the dynamic viscosity of the fluid (do not confuse with kinematic viscosity, these are different things). By Reynolds, looking for the friction coefficient λ \u003d 64 / re for laminar mode and λ \u003d 1 / (1.82 LGRE - 1.64) ² for turbulent (here LG is a decimal logarithm). And take the value that is higher. After you find the flow of fluid and speed, it will be necessary to repeat the entire calculation re-with the new coefficient of friction. And this recalculation is repeated until the rate specified to determine the friction coefficient does not coincide to some error with the meaning that you find at the rate.

Method of calculating Table Sheveleva Theoretical hydraulics SNiP 2.04.02-84

Initial data

Pipeline material: New steel without an internal protective coating or with bitumen protective coating New cast iron without an internal protective coating or with bitumen protective coating Nen steel and cast-iron without an internal protective coating or with bitumen protective coating asbestos-cement reinforced concrete vibrohydropressed reinforced concrete centrifuges steel and cast iron with ext. Plastic or polymercient cover, applied by the centrifugation of steel and cast iron, with an internal cement-sand coating applied by spraying steel and cast iron, with an internal cement-sand coating applied by centrifuging from polymeric materials (plastic) glass

Estimated flow

L / s m3 / hour

Outside diameter mM.

Wall thickness mM.

Length of the pipeline m.

Average water temperature ° C.

Eq. Roughness inside. Pipe surfaces: Stretched or with big deposits steel or cast iron old rusted steel otsink. After several years old after several years old cast iron steel galvanized new steel welded new steel seamless new brass, lead, copper glass

Amount of K-Tov Local Resistance

Payment

Pressure loss dependence on pipe diameter

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When calculating the water supply system or heating, you encounter the task of selecting the diameter of the pipeline. To solve such a task, you need to make a hydraulic calculation of your system, and for an even simpler solution - you can use hydraulic calculation onlineWhat we will do now.
Operating procedure:
1. Choose a suitable calculation method (calculation on Shevelev's tables, theoretical hydraulic or SNiP 2.04.02-84)
2. Choose pipelines material
3. Set the calculated water consumption in the pipeline
4. Set the outer diameter and thickness of the pipeline wall
5. Set the pipeline length
6. Set the average water temperature
The result of the calculation will be the graph and the values \u200b\u200bof the hydraulic calculation below.
The graph consists of two values \u200b\u200b(1 - water pressure loss, 2 - water velocity). The optimal values \u200b\u200bof the pipe diameter will be written green under the schedule.

Those. You must set the diameter so that the point on the chart is strictly over your green values \u200b\u200bof the pipeline diameter, because only such values \u200b\u200bthe water speed and pressure loss will be optimal.

Pressure loss in the pipeline show pressure loss on a given area of \u200b\u200bthe pipeline. The higher the loss, the more you have to work to deliver water to the right place.
The characteristic of the hydraulic resistance shows how efficiently the diameter of the pipe depending on the pressure loss.
For reference:
- If you need to know the speed of fluid / air / gas in the pipeline of various sections - use

Pipelines for the transportation of various liquids are an integral part of the units and installations in which workflows relating to different applications are carried out. When choosing pipes and pipe configuration, the cost of both the pipes and pipeline fittings are of great importance. The final cost of pumping 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 with the help of specially developed formulas specific for certain types of operation.

The pipe is a hollow cylinder of metal, a tree or other material used to transport liquid, gaseous and bulk media. Water, natural gas, steam, petroleum products, etc. can act as a movement medium. Pipes are used everywhere, starting from various industries and ending with household use.

For the manufacture of pipes, a variety of materials can be used, such as steel, cast iron, copper, cement, plastic, such as ABS plastic, polyvinyl chloride, chlorinated polyvinyl chloride, polybucenen, polyethylene, etc.

The main dimensional pipe indicators are its diameter (outdoor, internal, etc.) and wall thickness, which are measured in millimeters or inches. It is also used as a conditional diameter or conditional passage - the nominal value of the inner diameter of the pipe, also measured in millimeters (denoted by DN) or inches (denoted by DN). The values \u200b\u200bof the conditional diameters are standardized and are the main criterion in the selection of pipes and the connecting reinforcement.

Compliance of the values \u200b\u200bof the conditional passage in mm and inches:

The pipe with a circular cross section is preferred to other geometric sections for a number of reasons:

The circle has the minimum perimeter ratio to the square, and applies to the pipe this means that with an equal bandwidth, the consumption of material in the pipes of the round form will be minimal in comparison with the pipes of another form. From here, the minimum possible costs of insulation and protective coating should also be
The circular cross section is most beneficial to move the liquid or gas medium from a hydrodynamic point of view. Also due to the minimum possible inner area of \u200b\u200bthe pipe per unit of its length, minimization of friction between the movable medium and the pipe is achieved.
The round form is most resistant to the effects of internal and external pressure;
The process of manufacturing round-shaped pipes is quite simple and easily present.

Pipes can be very different in diameter and configuration, depending on the purpose and application area. So the main pipelines for moving water or petroleum products are capable of reaching almost a half-meter in diameter with a sufficiently simple configuration, and heating coils, also constituting a pipe, with a small diameter, have a complex shape with a plurality of turns.

It is impossible to submit any industry without a network of pipelines. The calculation of any such network includes the selection of pipe material, drawing up the specification, where data about the thickness, pipe size, route, etc. are listed. Raw materials, intermediate and / or finished product undergo production stages, moving between various devices and installations that are connected using pipelines and fittings. The correct calculation, the selection and installation of the pipeline system are necessary for the reliable implementation of the entire process, ensuring safe transfer of media, as well as to seal the system and prevent leaks of the pumped substance into the atmosphere.

There is no uniform formula and rules that could be used to select the pipeline for any possible application and work environment. In each individual area of \u200b\u200bapplication of pipelines, there is a number of factors requiring accounting and capable of providing a significant impact on the requirements for the pipeline. For example, when working with sludge, the large pipeline does not only increase the cost of the installation, but also create workers difficulties.

Usually the pipes are selected after optimizing the costs of material and operating costs. The larger the diameter of the pipeline, that is, the above initial investment, the lower the pressure drop and, accordingly, less operating costs. Conversely, the small size of the pipeline will reduce the primary costs for the pipes themselves and pipe fittings, but the increase in speed will entail an increase in the losses, which will lead to the need to spend additional energy to pump the medium. Speed \u200b\u200bnorms fixed for various applications are based on optimal calculated conditions. The size of the pipelines is calculated using these norms, taking into account the applications.

Design pipelines

When designing pipelines, the following main structural parameters are taken as the basis:

required performance;
entrance place and place of pipeline outlet;
the composition of the medium, including viscosity and proportion;
topographic conditions of the pipeline route;
maximum allowable working pressure;
hydraulic calculation;
the diameter of the pipeline, the thickness of the walls, the yield strength of the material of the walls during tension;
number of pumping stations, distance between them and power consumption.

Reliability of pipelines

Reliability in the design of pipelines is ensured by compliance with the proper design standards. Also training personnel is a key factor in ensuring a long service life of the pipeline and its tightness and reliability. Permanent or periodic control of the pipeline operation can be carried out by control systems, accounting, management, regulation and automation, personal control devices, safety devices.

Additional pipeline coating

The corrosion-resistant coating is applied to the outer part of most pipes to prevent the destructive corrosion action from the external environment. In the case of pumping corrosion media, the protective coating can be applied to the inner surface of the pipes. Before commissioning, all new pipes intended for transporting hazardous liquids are tested for defects and leaks.

Basic provisions for calculating the flow in the pipeline

The nature of the flow of the medium in the pipeline and when streamlining obstacles is able to differ much from fluid to the liquid. One of the important indicators is the viscosity of the medium characterized by such a parameter as a viscosity coefficient. The Irish Physicist Engineer Osborne Reynolds held a series of experiments in 1880, according to which he managed to remove a dimensionless value, characterizing the nature of the flow of viscous fluid, called Reynolds criterion and denoted Re.

Re \u003d (v · L · ρ) / μ

where:
ρ - liquid density;
v - flow rate;
L is the characteristic length of the flow element;
μ is a dynamic viscosity coefficient.

That is, Reynolds's criterion characterizes the ratio of inertia forces to the forces of viscous friction in the fluid flow. The change in the value of this criterion displays the 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 allocate three stream modes depending on the value of the Reynolds Criteria. 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 23004000 There is already a steady mode characterized by disorderly change of speed and direction of flow in each individual point, which in sum gives alignment of flow rates throughout the volume. This mode is called turbulent. The Reynolds number depends on the pressure specified by the pump, the viscosity of the medium at operating temperature, as well as the dimensions and form of the pipe cross section through which the flow passes.

Speed \u200b\u200bprofile in the stream
laminarian mode	transient mode	turbulent mode

The nature of the flow
laminarian mode	transient mode	turbulent mode

Reynolds Criterion is the criterion of similarity for the flow of viscous fluid. That is, it is possible to simulate a real process in a reduced size, convenient for study. This is extremely important because it is often extremely difficult, and sometimes it is impossible to study the character of fluid flows in real devices due to their large size.

Calculation of the pipeline. Calculation of the diameter of the pipeline

If the pipeline is not thermally insulated, then there is a heat exchange between the moved and the environment, the character of the stream in it may vary even at a constant speed (consumption). This is possible if the input is pumped medium has a sufficiently high temperature and flows in turbulent mode. In the length of the pipe, the temperature of the transferred medium will fall due to thermal losses into the environment, which can lead to a change in the flow mode to laminar or transient. The temperature at which the mode changes occurs is called a critical temperature. The value of the viscosity of the fluid directly depends on the temperature, so for such cases such a parameter is used as a critical viscosity, corresponding to the point change point of the flow mode during the critical value of the Reynolds Criterody:

v k \u003d (v · d) / re kru \u003d (4 · q) / (π · d · re cr)

where:
ν cr - critical kinematic viscosity;
RE CR - the critical value of the Reynolds criterion;
D - pipe diameter;
v - flow rate;
Q - Consumption.

Another important factor is friction arising between the pipe walls and the moving stream. At the same time, the friction coefficient largely depends on the roughness of the pipe walls. The relationship between the friction coefficient, the Reynolds criterion and roughness is set by the Moody diagram, which allows you to determine one of the parameters, knowing the other two.

The Colebruck-White formula is also used to calculate the friction coefficient of the turbulent flow. Based on this formula, it is possible to build graphs for which the friction coefficient is installed.

(√λ) -1 \u003d -2 · log (2.51 / (Re · √λ) + k / (3.71 · d))

where:
k - the coefficient of the roof of the pipe;
λ - friction coefficient.

There are also other formulas for approximate calculation of friction losses at a pressure flow of fluid in the pipes. One of the most frequently used equations in this case is considered to be the Darcy-Weisbach equation. It is based on empirical data and is used mainly when modeling systems. Friction losses are the function of the fluid velocity and the pipe resistance to the movement of the fluid expressed through the value of the roughness of the walls of the pipeline.

ΔH \u003d λ · L / d · V² / (2 · G)

where:
ΔH - pressure loss;
λ is the friction coefficient;
L is the length of the pipe section;
D - pipe diameter;
v - flow rate;
G - Acceleration of free fall.

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

ΔH \u003d 11.23 · L · 1 / s 1.85 · Q 1.85 / D 4.87

where:
ΔH - pressure loss;
L is the length of the pipe section;
C - coefficient of Haysen-Williams roughness;
Q - consumption;
D - pipe diameter.

Pressure

The operating pressure of the pipeline is an emerging overpressure that provides a specified pipeline operation mode. The decision on the size of the pipeline and the number of pumping stations is usually accepted, based on the operating pressure of the pipes, the performance of the pump and costs. The maximum and minimum pipeline pressure, as well as the properties of the working medium, determine the distance between the pumping stations and the required power.

The nominal pressure PN is a nominal value corresponding to the maximum pressure of the working medium at 20 ° C, in which long-term operation of the pipeline with specified sizes is possible.

With increasing temperature, the load capacity of the pipe is reduced, as well as the allowable overpressure due to this. The value of PE, ZUL shows the maximum pressure (either) in the pipeline system with an increase in the operating temperature.

Graph of permissible excess pressures:

Calculation of pressure drop in the pipeline

The calculation of the pressure drop in the pipeline is produced by the formula:

Δp \u003d λ · L / D · ρ / 2 · V²

where:
Δp - pressure drop on the pipe section;
L is the length of the pipe section;
λ is the friction coefficient;
D - pipe diameter;
ρ is the density of the pumped medium;
V - flow rate.

Transported workers

Most often, the pipes are used to transport water, but they can also be used to move sludge, suspensions, steam, etc. In the oil industry, pipelines serve to pump a wide range of hydrocarbons and mixtures that are very different in chemical and physical properties. Crude oil can be transported for more distances from deposits on land or oil towers on the shelf to terminals, intermediate points and refineries.

On pipelines also transmit:

oil refining products, such as gasoline, aviation fuel, kerosene, diesel fuel, fuel oil, etc.;
petrochemical raw materials: benzene, styrene, propylene, etc.;
aromatic hydrocarbons: xylene, toluene, kumol, etc.;
liquefied petroleum fuel, such as liquefied natural gas, liquefied petroleum gas, propane (gases with standard temperature and pressure, but liquefied with pressure applying);
carbon dioxide, liquid ammonia (transported as fluids under pressure);
bitumen and viscous fuel is too viscous for transportation through pipelines, therefore distillate oil fractions are used to dissolve this raw material and obtaining a mixture that can be transported by pipeline;
hydrogen (for short distances).

The quality of the transported environment

Physical properties and parameters of transported environments are largely determined by the design and operating parameters of the pipeline. Specific, compressibility, temperature, viscosity, pouring point and vapor pressure are the main parameters of the working medium that must be considered.

The proportion of fluid is its weight per unit volume. Many gases are transported in high pressure pipelines, 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 the design of pipelines and to determine throughput performance.

The temperature is indirectly and directly affects the performance of the pipeline. This is expressed in the fact that the fluid increases in the volume after an increase in temperature, provided that the pressure remains constant. A decrease in temperature can also have an impact on the performance and on the overall efficiency of the system. Usually, when the fluid temperature decreases, it is accompanied by an increase in its viscosity, which creates an additional friction resistance along the inner wall of the pipe, requiring more energy to pump the same amount of fluid. Very viscous media are sensitive to operating temperatures. Viscosity is the resistance of the course of the flow and is measured in SST centistoxes. The viscosity determines not only the selection of the pump, but also the distance between the pumping stations.

As soon as the temperature of the medium falls below the loss point of fluidity, the operation of the pipeline becomes impossible, and some options are being taken to resume its functioning:

heating medium or thermal insulation of pipes to maintain the operating temperature of the medium above its flow point;
change in the chemical composition of the medium before entering the pipeline;
dilution of the movable water medium.

Types of main pipes

Main pipes are made welded or seamless. Seamless steel pipes are made without longitudinal welds with steel cuts with thermal processing to achieve the desired size and properties. The welded pipe is manufactured using several production processes. These two types differ from each other by the number of longitudinal seams in the pipe and the type of welding equipment used. Steel welded pipe is the most commonly used type in the petrochemical application.

Each pipe segment is connected by welded sections together to form a pipeline. Also in the main pipelines, depending on the application of the application, pipes made of fiberglass, a variety of plastic, asbate cement are used, etc.

To connect direct sections of pipes, as well as for the transition between the sections of the pipeline of different diameters, specially made connective elements are used (knee, taps, shutters).

knee 90 °	distribution 90 °	transient branch	branching

knee 180 °	tire 30 °	transitional fitting	tip

For the installation of individual parts of pipelines and fittings, special compounds are used.

weld	flange	threaded	coupling

Temperature lengthening of the pipeline

When the pipeline is under pressure, its entire inner surface is exposed to a uniformly distributed load, which is why the longitudinal domestic efforts arise in the pipe and additional loads on end supports. Temperature oscillations also affect the pipeline, causing changes in pipe sizes. Efforts in the fixed pipeline with temperature fluctuations can accommodate the allowable value and lead to excess voltage dangerous for the strength of the pipeline both in the material of pipes and in flange connections. The fluctuation of the temperature of the pumped medium also creates a temperature voltage in the pipeline, which can pass onto the reinforcement, pumping station, etc. This may entail the depressurization of the joints of the pipelines, the failure of the reinforcement or drring elements.

Calculation of the size of the pipeline when temperature changes

The calculation of the change in linear dimensions of the pipeline with a change in temperature is carried out by the formula:

ΔL \u003d A · L · ΔT

a - coefficient of temperature elongation, mm / (m ° C) (see table below);
L is the length of the pipeline (the distance between fixed supports), m;
ΔT is the difference between Max. and min. The temperature of the pumped medium, ° C.

Table linear expansion of pipes from various materials

These numbers are average indicators for listed materials and to calculate the pipeline from other materials, data from this table should not be taken as a basis. When calculating the pipeline, it is recommended to use a linear elongation coefficient indicated by the pipe manufacturer in the accompanying technical specifications or a technical support.

The temperature elongation of pipelines is eliminated both by the use of special compensation sections of the pipeline, and using compensators that may consist of elastic or moving parts.

Compensation areas consist of elastic direct parts of the pipeline, located perpendicular to each other and fitting with the help of taps. With a temperature elongation, an increase in one part is compensated by the deformation of the bending of another part on the plane or deformation of bending and twist in space. If the pipeline itself compensates for the temperature expansion, it is called self-compensation.

Compensation occurs also due to elastic discharges. Part of the elongation is compensated by the elasticity of the taps, the other part is eliminated due to the elastic properties of the material of the area behind the tap. Compensators are installed where it is not possible to use compensating areas or when the piping self-compensation is insufficient.

According to the constructive execution and the principle of operation, compensators are four species: P-shaped, lenzovy, wavy, salon. In practice, flat compensators with L-, Z or U-shaped form are often used. In the case of spatial compensators, they are usually 2 flat mutually perpendicular sections and have one common shoulder. Elastic compensators produce from pipes or elastic disks, or bellows.

Determination of the optimal size of the diameter of pipelines

The optimal pipeline diameter can be found on the basis of technical and economic calculations. The size of the pipeline, including the size and functionality of the various components, as well as the conditions under which the pipeline should occur, determines the transporting ability of the system. Larger pipe pipes are suitable for a more intense mass flow of the medium, provided that the other components in the system are chosen and are designed for these conditions properly. Usually, the longer the segment of the trunk tube between pumping stations, it takes a larger pressure drop in the pipeline. In addition, changing the physical characteristics of the pumped medium (viscosity, etc.), there can also be a big impact on the pressure in the highway.

The optimal size is the smallest of the appropriate sizes of the pipe for a particular application, cost-effective throughout the service life of the system.

Formula for calculating pipe performance:

Q \u003d (π · d²) / 4 · v

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

In practice, for calculating the optimal diameter of the pipeline, the values \u200b\u200bof the optimal velocities of the pumped medium, taken from reference materials, composed on the basis of experimental data are used:

Purchased medium		Range of optimal velocities in the pipeline, m / s
Liquids	Movement Self:
	Viscous liquids	0,1 - 0,5
	Low viscosity liquids	0,5 - 1
	Pumping pump:
	Suction side	0,8 - 2
	Inspection side	1,5 - 3

Gases	Natural traction	2 - 4
	Small pressure	4 - 15
	Big Pressure	15 - 25

Couple.	Overheated par	30 - 50
	Saturated Pressure 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 obtain a formula for calculating the optimal diameter of the pipe:

d O \u003d √ ((4 · q) / (π · v o))

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 rate, the pipes of smaller diameter are usually used, which means a decrease in the cost of purchasing the pipeline, its maintenance and installation work (we denote K 1). With an increase in the speed, an increase in the threads of the pressure on friction and in local resistances, which leads to an increase in the cost of pumping the fluid (we denote K 2).

For pipelines of large diameters, the costs K 1 will be higher, and the costs during operation of the K 2 are lower. If you fold the values \u200b\u200bof k 1 and k 2, we obtain the total minimum cost k and the optimal diameter of the pipeline. Costs K 1 and K 2 in this case are given in the same time interval.

Calculation (formula) of capital costs for pipeline

K 1 \u003d (m · c m · k m) / n

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

These operating costs are associated with energy consumption:

K 2 \u003d 24 · n · n dn · C e rub / year

N - power, kW;
n Dn - Number of working days per year;
With e - the cost of one kW-h energy, rub / kw * h.

Formulas for determining the size of the pipeline

An example of general formulas for determining the size of pipes without taking into account possible additional factors of impact, such as erosion, weighted solid particles and so on:

Name	The equation	Possible restrictions
Fluid flow and gas under pressure
Friction Darcy Weisbach	d \u003d 12 · [(0.0311 · F · L · q 2) / (H f)] 0,2	Q - volume consumption, gal / min; d - the inner diameter of the pipe; HF - a loss of friction pressure; L is the length of the pipeline, the feet; F - friction coefficient; V - flow rate.
Equation of the total fluid flow	d \u003d 0.64 · √ (Q / V)	Q - Volumetric Consumption, Gal / Min
The size of the suction line of the pump to limit the pressure loss for friction	d \u003d √ (0,0744 · q)	Q - Volumetric Consumption, Gal / Min
Gas General Flow Equation	d \u003d 0.29 · √ ((q · t) / (p · v))	Q - Volumetric flow, foot³ / min T - Temperature, K P - pressure pound / inch (ABS); V - speed
Self-flow
Manding equation for calculating pipe diameter for maximum stream	d \u003d 0.375	Q - volume flow; n - roughness coefficient; S - bias.
The number of Frouda The ratio of the power of inertia and gravity	FR \u003d V / √ [(D / 12) · G]	g - acceleration of free fall; V is the flow rate; L - pipe length or diameter.
Couples and evaporation
Pipe diameter diameter determination equation	d \u003d 1.75 · √ [(w · v_g · x) / v]	W - mass flow; VG - specific volume of saturated steam; x - pair quality; V - speed.

Optimal flow rate for various pipeline systems

The optimal pipe size is selected from the condition of the minimum cost of pumping the medium through the pipeline and the cost of pipes. However, it is necessary to take into account the speed limitations. Sometimes, the size of the pipeline line must comply with the requirements of the technological process. The size of the pipeline is also associated with 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 the pipeline has changes in the direction of flow, this leads to a significant increase in local pressures on the surface perpendicular to the flow direction. This kind of increase is the function of the velocity of fluid, density and starting pressure. Since the speed is inversely proportional to the diameter, high-speed fluids require special attention when choosing the size and configuration of the pipeline. The optimal size of the pipe, for example, for sulfuric acid limits the environment of the medium to a value at which the erosion of the walls in the tube knees is not allowed so as to damage the pipe structure.

Fluid stream Self

Calculation of the size of the pipeline in the case of a flow moving in gravity 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). The two-phase flow is formed in the case when liquid and gas are present in the pipe at the same time.

Depending on the ratio of liquid and gas, as well as their speeds, the two-phase flux mode may vary from bubble to dispersed.

bubble stream (horizontal)	choose stream (horizontal)	waveflow	dispersed flow

The driving force for fluid during the movement is moved by the difference of the heights of the initial and endpoints, and the prerequisite is the location of the starting point above the ultimate. In other words, the height difference determines the difference in the potential energy of the fluid in these positions. This parameter is also taken into account when selecting the pipeline. In addition, the value of pressures in the initial and end point is affected by the magnitude of the driving force. An increase in the pressure drop entails an increase in fluid flow rate, which, in turn, allows you to select a smaller diameter pipeline, and vice versa.

If the end point is connected to a pressure system, such as a distillation column, it is necessary to subtract equivalent pressure from the existing difference in height to assess the actually created effective differential pressure. Also, if the initial point of the pipeline is under vacuum, its influence on the total differential pressure should also be taken into account when choosing a pipeline. The final selection of pipes is carried out using differential pressure, which takes into account all of the above factors, and not based only on the height of the initial and end point.

Stream hot liquid

Technological installations are usually encountered with various problems when working with hot or boiling media. Basically, the reason is to evaporate a part of the hot liquid flow, that is, the phase conversion of the fluid into steam inside the pipeline or equipment. A typical example is the phenomenon of cavitation of a centrifugal pump, accompanied by point boiling of the liquid, followed by the formation of steam bubbles (steam cavitation) or separation of dissolved gases into bubbles (gas cavitation).

The larger pipeline is preferable to reduce the flow rate in comparison with the smaller diameter pipeline at a constant flow rate, which is caused by the achievement of a higher NPSH indicator on the suction line of the pump. Also, the cause of cavitation in the loss of pressure may be the points of a sudden change of the direction of flow or cutting the size of the pipeline. The emerging steamed mixture creates an obstacle to the passage of the flow and may cause damage to the pipeline, which makes the cavitation phenomenon is extremely undesirable during the operation of the pipeline.

Pipeline for equipment / appliances

Equipment and devices, especially those that can create significant pressure drops, that is, heat exchangers, regulating valves, etc., equipped with bypass pipelines (for the possibility not to interrupt the process even during maintenance). Such pipelines typically have 2 shut-off valves installed in the installation line, and the valve that regulates the flow in parallel to this unit.

In normal operation, the fluid flow, passing through the main components of the device, is experiencing an additional pressure drop. In accordance with this, the pressure of the discharge is calculated for it, created by the connected equipment, such as a centrifugal pump. The pump is selected based on the total pressure drop in the installation. During the movement on the bypass pipeline, this additional pressure drop is missing, while the working pump is thrown into the stream of the former force, according to its working characteristics. To avoid differences in the flow characteristics through the device and the watering line, it is recommended to use a smaller size of a smaller size with an adjusting valve to create pressure equivalent to the main installation.

Sampling Line

Usually a small amount of fluid is selected for analysis to determine its composition. The selection can be produced at any stage of the process to determine the composition of the raw materials, the intermediate product, the finished product, or simply transported substance, such as wastewater, coolant, etc. The size of the pipeline on which samples occurs, usually depends on the type of the analyzed working medium and the location of the sampling point.

For example, for gases under conditions of increased pressure, sufficiently small pipelines with valves for selecting the desired amount of samples. An increase in the diameter of the sampling line will reduce the proportion of the medium being taken to analyze the environment, but this selection becomes more difficult to control. At the same time, a small sampling line is poorly suitable for analyzing various suspensions, in which solid particles can beat the flow part. Thus, the size of the sampling line for the analysis of suspensions largely depends on the size of the solid particles and the characteristics of the medium. Similar conclusions are applicable to viscous fluids.

When selecting the size of the pipeline for sampling, usually takes into account:

characteristics of a liquid intended for selection;
loss of the working medium during the selection;
security requirements during selection;
ease of operation;
selection point location.

Circulation of coolant

High speeds are preferred for high speed circulating coolant. It is mainly due to the fact that the coolant in the cooling tower is exposed to sunlight, which creates conditions for the formation of an alpine-flowing layer. Some of this algae-containing volume enters the circulating coolant liquid. With low flow rate, algae is beginning to grow in the pipeline and after a while they create difficulties for circulating the coolant or its passage to the heat exchanger. In this case, high circulation rate is recommended to avoid the formation of algae congestion in the pipeline. Typically, the use of intensively circulating coolant is found in the chemical industry, which requires large-sized pipelines and length in order to provide nutrition from various heat exchanger.

Reservoir overflow

Reservoirs are equipped with pipes for overflow for the following reasons:

avoiding fluid loss (excess fluid enters another reservoir, and does not fall out beyond the initial tank);
preventing leaks of unwanted liquids outside the tank;
maintaining the level of fluid in tanks.

In all the aforementioned cases, the pipes for overflow are designed for the maximum allowable fluid flow entering the tank, regardless of the flow fluid flow. Other printing principles are similar to the selection of pipelines for self-e-liquids, that is, in accordance with the presence of an available vertical height between the initial and end point of the overflow pipeline.

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

Flow of sludge

In the case of mining industry, ore is usually mined in hard-to-reach areas. In such places, as a rule, there is no railway or road communication. For such situations, hydraulic transportation of media with solid particles is considered as the most acceptable, including in the case of the location of the mining processing plants at sufficient removal. Slurry pipelines are used in various industrial areas for transporting solid media in crushed form together with liquid. Such pipelines have proven themselves as the most economically beneficial compared to other methods of transporting solid media in large volumes. In addition, their advantages include sufficient safety due to the lack of several types of transportation and environmental friendliness.

Suspension and mixtures of suspended substances in liquids are stored in a state of periodic mixing to maintain homogeneity. Otherwise, a stratification process occurs, in which suspended particles, depending on their physical properties, float to the surface of the liquid or settle on the bottom. Stirring is ensured by equipment, such as a tank with a stirrer, while in pipelines, this is achieved by maintaining the turbulent conditions of the flow of the medium.

Reducing the flow rate during transportation of particles weighted in fluid is not desirable, since the phase separation process may begin in the stream. This can lead to closure of the pipeline and change the concentration of the transported solid in the stream. Intensive stirring in the volume of flow contributes to a turbulent flow mode.

On the other hand, an excessive decrease in the size of the pipeline also often leads to its blockage. Therefore, the choice of the size of the pipeline is an important and responsible step requiring preliminary analysis and calculations. Each case should be considered individually, since various sludge behave differently at different fluid speeds.

Repair of pipelines

During the operation of the pipeline, various types of leakage may occur in it, requiring immediate elimination to maintain the workability of the coat. Repair of the main pipeline can be carried out in several ways. This can be both replacing the entire segment of the pipe or a small area, in which leakage and the overlaying of the patchwork on the existing pipe occurred. But before choosing any method of repair, it is necessary to carry out a thorough study of the cause of leakage. In some cases, it may not be necessary to repair, but a shift of the pipeline to prevent its damage.

The first stage of repair work is to determine the location of the pipe area requiring intervention. Further, depending on the type of pipeline, the list of the necessary equipment and measures necessary to eliminate leakage is determined, and the necessary documents and permits are collected, if the pipe is repaired is located on the territory of another owner. Since most pipes are located underground, it may be necessary to extract part of the pipe. Next, the coating of the pipeline is checked for general condition, after which part of the coating will be removed to carry out repair work directly with the pipe. After repair, various checks may be carried out: ultrasound test, color flaw detection, magnetic powder flaw detection, etc.

Although some repairs require full pipeline disconnection, it often can only be enough time interruption to isolate the repaired site or preparation of the waterway path. However, in major cases, repair work is carried out with full pipeline disabling. Insulation of the pipeline portion can be carried out using plugs or shut-off valves. Next, install the necessary equipment and are repaired directly. Repair work is carried out on a damaged area freed from the medium and without pressure. At the end of repair, the plugs open and restore the integrity of the pipeline.