Calculation and selection of pipelines. Optimum pipeline diameter

In some cases, one has to face the need to calculate the flow of water through a pipe. This indicator indicates how much water the pipe can pass, measured in m³ / s.

For organizations that have not put the meter on the water, the charge is based on the patency of the pipe. It is important to know how accurately these data are calculated, for what and at what rate you have to pay. Individuals this does not apply, for them, in the absence of a meter, the number of registered people is multiplied by the water consumption of 1 person according to sanitary standards. This is a fairly large volume, and with modern tariffs it is much more profitable to install a meter. In the same way, in our time it is often more profitable to heat the water yourself with a column than to pay utilities for their hot water.
Calculation of pipe permeability plays a huge role when designing a house, when bringing communications to the house .

It is important to make sure that each branch of the water supply can receive its share from the main pipe, even during peak water consumption hours. Plumbing was created for comfort, convenience, and ease of work for a person.

If every evening water will practically not reach the inhabitants of the upper floors, what kind of comfort can we talk about? How can you drink tea, wash dishes, swim? And everyone drinks tea and bathes, so the volume of water that the pipe could provide was distributed over the lower floors. This problem can play a very bad role in fire fighting. If firefighters connect to the central pipe, and there is no pressure in it.

Sometimes calculating the flow of water through a pipe can come in handy if, after repairing the water supply by unfortunate masters, replacing part of the pipes, the pressure has dropped significantly.

Hydrodynamic calculations are not an easy task, usually carried out by qualified specialists. But, let's say you are engaged in private construction, designing your cozy spacious house.

How to calculate the flow of water through the pipe yourself?

It would seem that it is enough to know the diameter of the pipe hole in order to get, maybe, rounded, but generally fair figures. Alas, this is very little. Other factors can change the result of calculations at times. What influences maximum flow water through a pipe?

Pipe section. obvious factor. Starting point of hydrodynamic calculations.
Pipe pressure. As the pressure increases, more water passes through a pipe with the same cross section.
Bends, turns, change in diameter, branching block the flow of water through the pipe. Different variants to varying degrees.
Pipe length. Longer pipes will carry less water per unit of time than shorter ones. The whole secret is in the force of friction. Just as it delays the movement of objects familiar to us (cars, bicycles, sleds, etc.), the force of friction impedes the flow of water.
A pipe with a smaller diameter has more area of water contact with the pipe surface in relation to the volume of water flow. And from each point of contact there is a force of friction. Just like in longer pipes, in narrower pipes the speed of water movement becomes less.
Pipe material. Obviously, the degree of roughness of the material affects the magnitude of the friction force. Modern plastic materials(polypropylene, PVC, metal-plastic, etc.) are very slippery compared to traditional steel and allow water to move faster.
Duration of pipe operation. Lime deposits, rust greatly impair the throughput of the water supply. This is the most tricky factor, because the degree of clogging of the pipe, its new internal relief and friction coefficient are very difficult to calculate with mathematical accuracy. Fortunately, water flow calculations are most often required for new construction and fresh, unused materials. And on the other hand, this system will be connected to already existing, existing communications for many years. And how will she behave herself in 10, 20, 50 years? The latest technology greatly improved this situation. plastic pipes do not rust, their surface practically does not deteriorate over time.

Calculation of water flow through a tap

The volume of fluid flowing out is found by multiplying the cross section of the pipe opening S by the outflow velocity V. The cross section is the area of a certain part of the volumetric figure, in this case, the area of a circle. It is found according to the formula S = πR2. R will be the radius of the pipe opening, not to be confused with the radius of the pipe. π is a constant value, the ratio of a circle's circumference to its diameter, approximately 3.14.

The flow rate is found by the Torricelli formula: . Where g is the free fall acceleration, on the planet Earth equal to approximately 9.8 m/s. h is the height of the water column above the hole.

Example

Let us calculate the water flow through a tap with a hole with a diameter of 0.01 m and a column height of 10 m.

Hole cross section \u003d πR2 \u003d 3.14 x 0.012 \u003d 3.14 x 0.0001 \u003d 0.000314 m².

Outflow velocity = √2gh = √2 x 9.8 x 10 = √196 = 14 m/s.

Water consumption \u003d SV \u003d 0.000314 x 14 \u003d 0.004396 m³ / s.

In terms of liters, it turns out that 4.396 liters per second can flow out of a given pipe.

In order to properly mount the water supply structure, 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 home conduit depend on the data obtained.

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

The purpose of calculating the diameter of the pipeline by flow: Determining the diameter and section of the pipeline based on data on the flow rate and the speed of the longitudinal movement of water.

It is rather difficult to perform such a calculation. It is necessary to take into account a lot of nuances related to technical and economic data. These parameters are interconnected. The diameter of the pipeline depends on the type of liquid that will be pumped through it.

If you increase the flow rate, you can reduce the diameter of the pipe. Material consumption will automatically decrease. It will be much easier to mount such a system, the cost of work will fall.

However, an increase in flow movement will cause head losses, which require the creation of additional energy for pumping. If you reduce it too much, undesirable consequences may appear.

When designing a pipeline, in most cases, the amount of water flow is immediately set. Two quantities remain unknown:

Pipe diameter;
Flow rate.

It is very difficult to make a complete technical and economic calculation. This requires appropriate engineering knowledge and a lot of time. To facilitate this task when calculating the desired pipe diameter, reference materials are used. They give the values of the best flow rate obtained empirically.

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

d = √(4Q/Πw)
Q is the flow rate of the pumped liquid, m3/s
d – pipeline diameter, m
w is the flow velocity, m/s

Suitable liquid velocity, depending on the type of pipeline

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

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

The dimensions of the pipeline are also affected by possible pressure surges.

When preliminary calculations are made, the change in pressure is not taken into account. Permissible speed is taken as the basis for designing a process pipeline.

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

This increase is due to several indicators:

Fluid speed;
Density;
Initial pressure (pressure).

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

For example, if sulfuric acid is being pumped, the velocity value is limited to a value that will not cause erosion on the walls of the pipe bends. As a result, the structure of the pipe will never be broken.

Water velocity in pipeline formula

The volume flow V (60m³/h or 60/3600m³/sec) is calculated as the product of the flow velocity w and the cross section of the pipe S (and the cross section in turn is calculated as S=3.14 d²/4): V = 3.14 w d²/4. From here we get w = 4V/(3.14 d²). Don't forget to convert the diameter from millimeters to meters, i.e. the diameter will be 0.159 m.

Water consumption formula

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

Water flow through pipe table

Flow vs pressure

There is no such dependence of fluid flow on pressure, but there is - on pressure drop. The formula is simple. There is a generally accepted equation for the pressure drop during the flow of liquid in a pipe Δp = (λL / d) ρw² / 2, λ is the coefficient of friction (it is searched depending on the speed and diameter of the pipe according to the graphs or the corresponding formulas), L is the length of the pipe, d is its diameter , ρ - fluid density, w - speed. On the other hand, there is a definition of flow G = ρwπd²/4. We express the speed from this formula, substitute it into the first equation and find the dependence of the flow rate G = π SQRT(Δp d^5/λ/L)/4, SQRT is the square root.

The coefficient of friction is sought by selection. First, you set a certain value of the fluid velocity from the lantern and determine the Reynolds number Re=ρwd/μ, where μ is the dynamic viscosity of the fluid (do not confuse it with the kinematic viscosity, these are different things). According to Reynolds, you are looking for the coefficient of friction λ = 64 / Re for laminar mode and λ = 1 / (1.82 lgRe - 1.64)² for turbulent (here lg is the decimal logarithm). And take the value that is higher. After you find the flow rate and speed, you will need to repeat the entire calculation again with a new coefficient of friction. And you repeat this recalculation until the speed value specified for determining the friction coefficient coincides to some error with the value that you find from the calculation.

Water flow parameters:

The value 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 consumption is the length of communications.

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

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

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

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

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

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

Reference data in the calculation of water

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

Standard consumption rates:

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

Why calculate water according to SNiP?

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

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

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

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

Water head loss calculation

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

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

The friction index varies from the following values:

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

Ease of calculation

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

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

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

In addition, they help determine the diameter of the pipe assortment. Many people believe that it is impossible to calculate water flow by pipe diameter and pressure, since these concepts are completely unrelated.

But practice has shown that this is not the case. The capacity of the water supply network is dependent on many indicators, and the first in this list will be the diameter of the pipe range and the pressure in the line.

It is recommended to calculate the throughput of a pipe depending on its diameter even at the design stage of pipeline construction. The data obtained determine the key parameters of not only the home, but also the industrial highway. All this will be discussed further.

We calculate the throughput of the pipe using an online calculator

ATTENTION! To calculate correctly, you need to pay attention that 1kgf / cm2 \u003d 1 atmosphere; 10 meters of water column \u003d 1kgf / cm2 \u003d 1 atm; 5 meters of water column \u003d 0.5 kgf / cm2 and \u003d 0.5 atm, etc. Fractional numbers in the online calculator are entered through a dot (For example: 3.5 and not 3.5)

Enter parameters for calculation:

What factors affect the permeability of the liquid through the pipeline

The criteria that affect the described indicator make up a large list. Here are some of them.

The inner diameter that the pipeline has.
The flow rate, which depends on the pressure in the line.
Material taken for the production of pipe assortment.

The determination of the water flow at the outlet of the main is carried out by the diameter of the pipe, because this characteristic, together with others, affects the throughput of the system. Also, when calculating the amount of fluid consumed, one cannot discount the wall thickness, the determination of which is carried out based on the estimated internal pressure.

It can even be argued that the definition of "pipe geometry" is not affected by the length of the network alone. And the cross section, pressure and other factors play a very important role.

In addition, some system parameters have an indirect rather than a direct effect on the flow rate. This includes the viscosity and temperature of the pumped medium.

Summing up a little, we can say that the determination of throughput allows you to accurately determine the optimal type of material for building a system and make a choice of technology used to assemble it. Otherwise, the network will not function efficiently and will require frequent emergency repairs.

Calculation of water consumption by diameter round pipe, depends on it size. Therefore, over a larger cross section, a significant amount of fluid will move over a certain period of time. But, performing the calculation and taking into account the diameter, one cannot discount the pressure.

If we look at this calculation specific example, it turns out that less liquid will pass through a meter-long tubular product through a hole of 1 cm over a certain time period than through a pipeline reaching a height of a couple of tens of meters. This is natural, because the highest level of water consumption in the area will reach the highest rates at the maximum pressure in the network and at the highest values of its volume.

Watch the video

Section calculations according to SNIP 2.04.01-85

First of all, you need to understand that calculating the diameter of a culvert is a complex engineering process. This will require special knowledge. But, when performing a domestic construction of a culvert, often a hydraulic calculation for the section is carried out independently.

This type of design calculation of the flow velocity for a culvert can be done in two ways. The first is tabular data. But, referring to the tables, you need to know not only the exact number of taps, but also containers for water collection (baths, sinks) and other things.

Only if you have this information about the culvert system, you can use the tables provided by SNIP 2.04.01-85. According to them, the volume of water is determined by the girth of the pipe. Here is one such table:

External volume of tubulars (mm)

The approximate amount of water that is received in liters per minute

Approximate amount of water, calculated in m3 per hour

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

Definitely, this volume data showing consumption is interesting as information, but a pipeline specialist will need to define completely different data - this is the volume (in mm) and the internal pressure in the line. This is not always found in the table. And formulas help to find out this information more accurately.

Watch the video

It is already clear that the dimensions of the system section affect the hydraulic calculation of consumption. For home calculations, a water flow formula is used, which helps to get a result, having data on the pressure and diameter of the tubular product. Here is the formula:

Formula for calculating pressure and pipe diameter: q = π × d² / 4 × V

In the formula: q shows the flow of water. It is measured in liters. d is the size of the pipe section, it is shown in centimeters. And V in the formula is the designation of the speed of the flow, it is shown in meters per second.

If the water supply network is fed from a water tower, without the additional influence of a pressure pump, then the flow velocity is approximately 0.7 - 1.9 m / s. If any pumping device is connected, then in the passport to it there is information about the coefficient of the created pressure and the speed of the water flow.

This formula is not unique. There are many more. They can be easily found on the Internet.

In addition to the presented formula, it should be noted that the inner walls of tubular products are of great importance for the functionality of the system. For example, plastic products differ in a smooth surface, rather than analogs from steel.

For these reasons, the drag coefficient of plastic is substantially lower. Plus, these materials are not affected by corrosive formations, which also has a positive effect on the throughput of the water supply network.

Determining head loss

The calculation of the passage of water is carried out not only by the diameter of the pipe, it is calculated by pressure drop. Losses can be calculated using special formulas. Which formulas to use, everyone will decide for themselves. To calculate the desired values, you can use various options. There is no single universal solution to this issue.

But first of all, it must be remembered that the internal clearance of the passage of a plastic and metal-plastic structure will not change after twenty years of service. And the inner lumen of the passage metal structure will become smaller over time.

And this will entail the loss of some parameters. Accordingly, the speed of water in the pipe in such structures is different, because in some situations the diameter of the new and old network will differ markedly. The amount of resistance in the line will also be different.

Also, before calculating the necessary parameters for the passage of a liquid, it must be taken into account that the loss in the flow rate of a water supply system is associated with the number of turns, fittings, volume transitions, with the presence of shutoff valves and friction force. Moreover, all this when calculating the flow rate should be carried out after careful preparation and measurements.

Water consumption calculation simple methods not easy to carry out. But, at the slightest difficulty, you can always seek help from specialists or use online calculator. Then you can count on the fact that the laid water supply or heating network will work with maximum efficiency.

Video - how to calculate water consumption

Watch the video

Why do we need such calculations

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

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

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

What determines the permeability of the pipe

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

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

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

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

New possibility of water consumption calculations

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

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

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

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

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

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

After all, hydrodynamic calculations are extremely complex ...

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

What is it for?

When self-calculation of plumbing systems.

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

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

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

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

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

Factors affecting the patency of the pipe

What affects the maximum water flow in a round pipe?

The obvious answer

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

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

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

Is there really something else needed?

Correct answer

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Beam of light in the dark realm

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

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

The master left you a gift

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

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

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

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

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

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

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

Conclusion

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

How to calculate pipe throughput

Throughput calculation is one of the most challenging tasks when laying a pipeline. In this article, we will try to figure out exactly how this is done for different types pipelines and pipe materials.

High capacity pipes

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

Methods for calculating the throughput of pipelines

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

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

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

Physical methods for calculating the throughput of pipes

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

Tabular calculation methods

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

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

Calculation using programs

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

How to calculate the throughput of a gas pipe

Gas is one of the most difficult materials to transport, in particular because it tends to compress and therefore can flow through the smallest gaps in pipes. To the calculation of the throughput of gas pipes (as well as to the design gas system in general) have special requirements.

The formula for calculating the throughput of a gas pipe

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

Qmax = 0.67 DN2 * p

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

Du - conditional passage of the pipe.

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

Qmax = 196.386 Du2 * p/z*T

where z is the compressibility factor;

T is the temperature of the transported gas, K;

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

Table of capacities of gas pipes depending on pressure

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

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

Capacity of the sewer pipe

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

Hydraulic Calculation Formula

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

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

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

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

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

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

where a is the free area of the flow,

v is the flow velocity, m/s.

The speed is calculated by the formula:

where R is the hydraulic radius;

C is the wetting coefficient;

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

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

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

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

where A is the area of the transverse fluid flow,

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

Capacity tables for non-pressure sewer pipes

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

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

Capacity tables for pressurized sewer systems

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

Capacity of the water pipe

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

Passability of the pipe depending on the diameter

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

Table of pipe capacity by coolant temperature

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

There is a table for calculations of heat and coolant.

Pipe capacity table depending on the coolant pressure

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

Pipe capacity table depending on diameter (according to Shevelev)

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

The tables take into account:

pipe diameters - internal and external;
wall thickness;
service life of the pipeline;
line length;
pipe assignment.

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

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