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Pipe capacity: simple about the complex
How does the throughput of a pipe vary with diameter? What factors, besides the cross section, affect this parameter? Finally, how to calculate, albeit approximately, the permeability of a water supply system with a known diameter? In the article I will try to give the most simple and accessible answers to these questions.
Our task is to learn how to calculate the optimal cross-section of water pipes.
Why is it needed
Hydraulic calculation allows you to get the optimal minimum the diameter of the pipeline.
On the one hand, there is always a catastrophic shortage of money during construction and repair, and the price of a linear meter of pipes grows non-linearly with an increase in diameter. On the other hand, an underestimated section of the water supply will lead to an excessive drop in pressure at the end devices due to its hydraulic resistance.
With a flow rate at the intermediate device, the pressure drop at the end device will lead to the fact that the water temperature with the cold water and hot water taps open will change dramatically. As a result, you will either be doused with ice water or scalded with boiling water.
Restrictions
I will deliberately limit the scope of the tasks under consideration to the plumbing of a small private house. There are two reasons:
- Gases and liquids of different viscosities behave completely differently when transported through a pipeline. Consideration of the behavior of natural and liquefied gas, oil and other media would increase the volume of this material several times and would take us far from my specialty - plumbing;
- In the case of a large building with numerous plumbing fixtures, for the hydraulic calculation of the water supply system, it will be necessary to calculate the probability of using several water points at the same time. In a small house, the calculation is performed for peak demand by all available appliances, which greatly simplifies the task.
Factors
Hydraulic calculation of a water supply system is a search for one of two quantities:
- Calculation of the throughput of a pipe with a known cross section;
- Calculation of the optimal diameter with a known planned flow rate.
In real conditions (when designing a water supply system), the second task is much more often necessary.
Household logic suggests that the maximum flow of water through a pipeline is determined by its diameter and inlet pressure. Alas, the reality is much more complicated. The fact is that the pipe has hydraulic resistance: Simply put, the flow slows down due to friction against the walls. Moreover, the material and condition of the walls predictably affect the degree of braking.
Here is a complete list of factors that affect the performance of a water pipe:
- Pressure at the beginning of the water supply (read - pressure in the route);
- slope pipes (change in its height above the conditional ground level at the beginning and end);
- Material walls. Polypropylene and polyethylene have much less roughness than steel and cast iron;
- Age pipes. Over time, steel becomes overgrown with rust and lime deposits, which not only increase the roughness, but also reduce the internal clearance of the pipeline;
This does not apply to glass, plastic, copper, galvanized and metal-polymer pipes. They are in like new condition even after 50 years of operation. An exception is the silting of the water supply with a large amount of suspensions and the absence of filters at the inlet.
- Quantity and Angle turns;
- Diameter changes plumbing;
- Presence or absence welds, soldering beads and connecting fittings;
- Shut-off valves. Even full bore ball valves offer some resistance to flow.
Any calculation of pipeline capacity will be very approximate. Willy-nilly, we will have to use average coefficients that are typical for conditions close to ours.
Law of Torricelli
Evangelista Torricelli, who lived in the early 17th century, is known as a student of Galileo Galilei and the author of the very concept of atmospheric pressure. He also owns a formula describing the flow rate of water pouring out of a vessel through an opening of known dimensions.
For the Torricelli formula to work, it is necessary:
- So that we know the pressure of the water (the height of the water column above the hole);
One atmosphere under the earth's gravity is capable of lifting a column of water by 10 meters. Therefore, pressure in atmospheres is converted into head by simply multiplying by 10.
- For the hole to be significantly smaller than the diameter of the vessel, thus eliminating the loss of pressure due to friction against the walls.
In practice, Torricelli's formula allows you to calculate the flow of water through a pipe with an internal section of known dimensions at a known instantaneous head during flow. Simply put: to use the formula, you need to install a pressure gauge in front of the tap or calculate the pressure drop on the water supply at a known pressure in the line.
The formula itself looks like this: v^2=2gh. In it:
- v is the flow velocity at the outlet of the orifice, in meters per second;
- g is the acceleration of fall (for our planet it is equal to 9.78 m/s^2);
- h - head (height of the water column above the hole).
How will this help us in our task? And the fact that fluid flow through an orifice(the same throughput) is equal to S*v, where S is the cross-sectional area of the orifice and v is the flow velocity from the above formula.
Captain Evidence suggests: knowing the cross-sectional area, it is easy to determine the inner radius of the pipe. As you know, the area of a circle is calculated as π*r^2, where π is rounded to 3.14159265.
In this case, Torricelli's formula will look like v^2=2*9.78*20=391.2. The square root of 391.2 is rounded to 20. This means that water will pour out of the hole at a speed of 20 m / s.
We calculate the diameter of the hole through which the stream flows. Converting the diameter to SI units (meters), we get 3.14159265*0.01^2=0.0003141593. And now we calculate the water flow: 20 * 0.0003141593 \u003d 0.006283186, or 6.2 liters per second.
Back to reality
Dear reader, I would venture to suggest that you do not have a pressure gauge installed in front of the mixer. It is obvious that some additional data are needed for a more accurate hydraulic calculation.
Usually, the calculation problem is solved from the opposite: with known water flow through plumbing fixtures, the length of the water pipe and its material, a diameter is selected that ensures the pressure drop to acceptable values. The limiting factor is the flow rate.
Reference data
The flow rate for internal water pipes is considered to be 0.7 - 1.5 m / s. Exceeding the latter value leads to the appearance of hydraulic noise (primarily at bends and fittings).
Water consumption rates for plumbing fixtures are easy to find in the regulatory documentation. In particular, they are given by the appendix to SNiP 2.04.01-85. To save the reader from lengthy searches, I will give this table here.
The table shows data for mixers with aerators. Their absence equalizes the flow through the sink, washbasin and shower faucets with the flow through the faucet when taking a bath.
Let me remind you that if you want to calculate the water supply of a private house with your own hands, sum up the water consumption for all installed appliances. If this instruction is not followed, surprises will await you, such as a sharp drop in the temperature in the shower when you open the hot water tap on.
If there is a fire water supply in the building, 2.5 l / s for each hydrant is added to the planned flow. For fire water supply, the flow velocity is limited to 3 m/s: in case of fire, hydraulic noise is the last thing that will unnerve the residents.
When calculating the pressure, it is usually assumed that on the device extreme from the input it must be at least 5 meters, which corresponds to a pressure of 0.5 kgf / cm2. Some plumbing fixtures (flowing water heaters, filling valves of automatic washing machines, etc.) simply do not work if the pressure in the water supply is below 0.3 atmospheres. In addition, it is necessary to take into account the hydraulic losses on the device itself.
In the photo - instantaneous water heater Atmor Basic. It includes heating only at a pressure of 0.3 kgf/cm2 and above.
Flow rate, diameter, speed
Let me remind you that they are linked to each other by two formulas:
- Q=SV. The water flow in cubic meters per second is equal to the cross-sectional area in square meters multiplied by the flow rate in meters per second;
- S = r ^2. The cross-sectional area is calculated as the product of the number "pi" and the square of the radius.
Where can I get the values for the radius of the inner section?
- For steel pipes, it is, with a minimum error, equal to half of the control(conditional pass, which is marked pipe rolling);
- For polymer, metal-polymer, etc. the inner diameter is equal to the difference between the outer one, with which the pipes are marked, and twice the wall thickness (it is also usually present in the marking). The radius, respectively, is half the inner diameter.
- The inner diameter is 50-3 * 2 = 44 mm, or 0.044 meters;
- The radius will be 0.044/2=0.022 meters;
- The area of the internal section will be equal to 3.1415 * 0.022 ^ 2 \u003d 0.001520486 m2;
- At a flow rate of 1.5 meters per second, the flow rate will be 1.5 * 0.001520486 = 0.002280729 m3 / s, or 2.3 liters per second.
head loss
How to calculate how much pressure is lost on a water supply system with known parameters?
The simplest formula for calculating the pressure drop is H = iL(1+K). What do the variables in it mean?
- H is the cherished pressure drop in meters;
- i - hydraulic slope of the water pipe meter;
- L is the length of the water supply in meters;
- K- coefficient, which makes it possible to simplify the calculation of the pressure drop on the stop valves and . It is tied to the purpose of the water supply network.
Where can I get the values of these variables? Well, except for the length of the pipe - no one has canceled the roulette yet.
The coefficient K is taken equal to:
With a hydraulic slope, the picture is much more complicated. The resistance offered by a pipe to flow depends on:
- Internal section;
- Wall roughness;
- Flow rates.
A list of 1000i values (hydraulic slope per 1000 meters of water supply) can be found in Shevelev's tables, which, in fact, are used for hydraulic calculation. The tables are too large for an article as they give 1000i values for all possible diameters, flow rates and life corrected materials.
Here is a small fragment of the Shevelev table for a 25 mm plastic pipe.
The author of the tables gives the values of the pressure drop not for the internal section, but for the standard sizes that mark the pipes, adjusted for the wall thickness. However, the tables were published in 1973, when the corresponding market segment had not yet formed.
When calculating, keep in mind that for metal-plastic it is better to take values corresponding to a pipe one step smaller.
Let's use this table to calculate the pressure drop on a polypropylene pipe with a diameter of 25 mm and a length of 45 meters. Let's agree that we are designing a water supply system for household purposes.
- With a flow velocity as close as possible to 1.5 m/s (1.38 m/s), the value of 1000i will be equal to 142.8 meters;
- The hydraulic slope of one meter of pipe will be equal to 142.8 / 1000 \u003d 0.1428 meters;
- The correction factor for domestic water pipes is 0.3;
- The formula as a whole will take the form H=0.1428*45(1+0.3)=8.3538 meters. This means that at the end of the water supply at a water flow rate of 0.45 l / s (the value from the left column of the table), the pressure will drop by 0.84 kgf / cm2 and at 3 atmospheres at the inlet it will be quite acceptable 2.16 kgf / cm2.
This value can be used to determine consumption according to the Torricelli formula. The calculation method with an example is given in the corresponding section of the article.
In addition, in order to calculate the maximum flow through a water supply system with known characteristics, one can select in the “flow rate” column of the complete Shevelev table such a value at which the pressure at the end of the pipe does not fall below 0.5 atmospheres.
Conclusion
Dear reader, if the above instructions, despite the extreme simplification, still seemed tedious to you, just use one of the many online calculators. As always, more information can be found in the video in this article. I will be grateful for your additions, corrections and comments. Good luck, comrades!
July 31, 2016If you want to express gratitude, add a clarification or objection, ask the author something - add a comment or say thanks!
Working with the calculator is simple - enter data and get the result. But sometimes this is not enough - an accurate calculation of the pipe diameter is possible only with manual calculation using formulas and correctly selected coefficients. How to calculate the diameter of the pipe according to the water flow? How to determine the size of the gas line?
When calculating the required pipe diameter, professional engineers most often use special programs that can calculate and give an accurate result using known parameters. It is much more difficult for an amateur builder to perform the calculation on his own to organize water supply, heating, gasification systems. Therefore, most often, when building or reconstructing a private house, the recommended pipe sizes are used. But not always standard advice can take into account all the nuances of individual construction, so you need to manually perform a hydraulic calculation in order to choose the right pipe diameter for heating and water supply.
Calculation of pipe diameter for water supply and heating
The main criterion for selecting a heating pipe is its diameter. From this indicator depends on how effective the heating of the house will be, the life of the system as a whole. With a small diameter in the lines, increased pressure can occur, which will cause leaks, increased stress on pipes and metal, which will lead to problems and endless repairs. With a large diameter, the heat transfer of the heating system will tend to zero, and cold water will simply ooze from the tap.
pipe capacity
The diameter of the pipe directly affects the throughput of the system, that is, in this case, the amount of water or coolant passing through the section per unit time matters. The more cycles (movements) in the system for a certain period of time, the more efficient the heating. For water supply pipes, the diameter affects the initial water pressure - a suitable size will only maintain pressure, and an enlarged one will reduce it.
According to the diameter, a plumbing and heating scheme is selected, the number of radiators and their sectionality, and the optimal length of the mains is determined.
Since the throughput of the pipe is a fundamental factor when choosing, you should decide what, in turn, affects the permeability of water in the line.
| Consumption | Bandwidth | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| DN pipe | 15 mm | 20 mm | 25 mm | 32 mm | 40 mm | 50 mm | 65 mm | 80 mm | 100 mm |
| Pa/m - mbar/m | less than 0.15 m/s | 0.15 m/s | 0.3 m/s | ||||||
| 90,0 - 0,900 | 173 | 403 | 745 | 1627 | 2488 | 4716 | 9612 | 14940 | 30240 |
| 92,5 - 0,925 | 176 | 407 | 756 | 1652 | 2524 | 4788 | 9756 | 15156 | 30672 |
| 95,0 - 0,950 | 176 | 414 | 767 | 1678 | 2560 | 4860 | 9900 | 15372 | 31104 |
| 97,5 - 0,975 | 180 | 421 | 778 | 1699 | 2596 | 4932 | 10044 | 15552 | 31500 |
| 100,0 - 1,000 | 184 | 425 | 788 | 1724 | 2632 | 5004 | 10152 | 15768 | 31932 |
| 120,0 - 1,200 | 202 | 472 | 871 | 1897 | 2898 | 5508 | 11196 | 17352 | 35100 |
| 140,0 - 1,400 | 220 | 511 | 943 | 2059 | 3143 | 5976 | 12132 | 18792 | 38160 |
| 160,0 - 1,600 | 234 | 547 | 1015 | 2210 | 3373 | 6408 | 12996 | 20160 | 40680 |
| 180,0 - 1,800 | 252 | 583 | 1080 | 2354 | 3589 | 6804 | 13824 | 21420 | 43200 |
| 200,0 - 2,000 | 266 | 619 | 1151 | 2486 | 3780 | 7200 | 14580 | 22644 | 45720 |
| 220,0 - 2,200 | 281 | 652 | 1202 | 2617 | 3996 | 7560 | 15336 | 23760 | 47880 |
| 240,0 - 2,400 | 288 | 680 | 1256 | 2740 | 4176 | 7920 | 16056 | 24876 | 50400 |
| 260,0 - 2,600 | 306 | 713 | 1310 | 2855 | 4356 | 8244 | 16740 | 25920 | 52200 |
| 280,0 - 2,800 | 317 | 742 | 1364 | 2970 | 4356 | 8566 | 17338 | 26928 | 54360 |
| 300,0 - 3,000 | 331 | 767 | 1415 | 3076 | 4680 | 8892 | 18000 | 27900 | 56160 |
Factors influencing the patency of the highway:
- The pressure of water or coolant.
- The inner diameter (section) of the pipe.
- The total length of the system.
- pipeline material.
- Pipe wall thickness.
On the old system, the patency of the pipe is aggravated by lime, silt deposits, the effects of corrosion (on metal products). All this together reduces the amount of water passing through the section over time, that is, used lines work worse than new ones.
It is noteworthy that this indicator does not change for polymer pipes - plastic is much less than metal, allowing slag to accumulate on the walls. Therefore, the throughput of PVC pipes remains the same as on the day they were installed.
Calculation of pipe diameter by water flow
Determining the right amount of water
To determine the diameter of the pipe by the flow rate of the passing liquid, you will need the values of the true water consumption, taking into account all plumbing fixtures: a bathtub, a kitchen faucet, a washing machine, a toilet bowl. Each individual section of the water supply system is calculated according to the formula:
qc = 5× q0 × α, l/s
where qc is the value of water consumed by each device;
q0 is a normalized value, which is determined by SNiP. We accept for the bath - 0.25, for the kitchen faucet 0.12, for the toilet bowl -0.1;
a is a coefficient that takes into account the possibility of simultaneous operation of plumbing fixtures in the room. Depends on the probability value and the number of consumers.
In sections of the highway where the water flows for the kitchen and the bath, for the toilet and the bath, etc., are combined, the probability value is added to the formula. That is, the possibility of simultaneous operation of a kitchen faucet, bathroom faucet, toilet bowl and other appliances.
The probability is determined by the formula:
Р = qhr µ × u/q0 × 3600 × N,
where N is the number of water consumers (devices);
qhr µ is the maximum hourly water consumption that can be taken according to SNiP. We choose for cold water qhr µ = 5.6 l / s, the total flow is 15.6 l / s;
u is the number of people using plumbing.
Example of water consumption calculation:
The two-storey house has 1 bathroom, 1 kitchen with installed washing machine and dishwasher, shower, 1 toilet. A family of 5 lives in the house. Calculation algorithm:
- We calculate the probability P = 5.6 × 5 / 0.25 × 3600 × 6 = 0.00518.
- Then the water flow for the bathroom will be qc = 5 × 0.25 × 0.00518=0.006475 l/s.
- For the kitchen qc \u003d 5 × 0.12 × 0.00518 \u003d 0.0031 l / s.
- For a toilet, qc = 5× 0.1 × 0.00518=0.00259 l/s.
We calculate the diameter of the pipe
There is a direct dependence of the diameter on the volume of the flowing liquid, which is expressed by the formula:
where Q is water consumption, m3/s;
d – pipeline diameter, m;
w is the flow velocity, m/s.
By transforming the formula, we can select the value of the diameter of the pipeline, which will correspond to the volume of water consumed:
Yulia Petrichenko, expert
d = √(4Q/πw), m
The flow rate of water can be taken from Table 2. There is a more complex method for calculating the flow rate - taking into account losses and the coefficient of hydraulic friction. This is a rather voluminous calculation, but in the end it allows you to get the exact value, unlike the tabular method.
| Pumped medium | Optimum speed in the pipeline, m/s | |
|---|---|---|
| LIQUIDS | Gravity movement: | |
| Viscous liquids | 0,1-0,5 | |
| Low viscosity liquids | 0,5-1 | |
| pumped: | ||
| Suction pipeline | 0,8-2 | |
| Discharge pipeline | 1,5-3 | |
| GASES | Natural traction | 2-4 |
| Low pressure (fans) | 4-15 | |
| High pressure (compressor) | 15-25 | |
| COUPLES | Overheated | 30-50 |
| Saturated vapors at 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 | |
Example: Calculate the diameter of the pipe for the bathroom, kitchen and toilet, based on the obtained water flow rates. We select from table 2 the value of the water flow rate in the pressure water supply - 3 m / s.
When laying water mains, it is most difficult to calculate the throughput of pipe sections. Correct calculations will ensure that the water flow is not too large and its pressure does not decrease.
The importance of correct calculations
Calculation of water consumption allows you to choose the right material and pipe diameter
When designing a cottage with two or more bathrooms or a small hotel, one must take into account how much water can be supplied by pipes of a selected section. After all, if the pressure in the pipeline drops with high consumption, this will lead to the fact that it will be impossible to take a shower or bath normally. If the problem arises during a fire, you can completely lose your home. Therefore, the calculation of the patency of highways is carried out even before the start of construction.
It is also important for small business owners to know throughput rates. Indeed, in the absence of metering devices, utilities, as a rule, present an invoice for water consumption to organizations according to the volume passed by the pipe. Knowing the data on your water supply will allow you to control the flow of water and not pay too much.
What determines the permeability of the pipe
Water consumption will depend on the configuration of the water supply, as well as the type of pipes from which the network is mounted
The permeability of pipe segments is a metric value that characterizes the volume of fluid passed through the pipeline for a certain time interval. This indicator depends on the material used in the production of pipes.
Pipelines made of plastic retain almost the same patency throughout the entire operational period. Plastic, in comparison with metal, does not rust, thanks to which the lines do not become clogged for a long time.
For metal models, throughput decreases year after year. Due to the fact that the pipes rust, the inner surface gradually peels off and becomes rough. Because of this, much more plaque is formed on the walls. In particular, hot water pipes clog quickly.
In addition to the material of manufacture, the permeability also depends on other characteristics:
- Plumbing lengths. The greater the length, the lower the flow velocity due to the effect of friction, and the head decreases accordingly.
- Pipe diameter. The walls of narrow highways create more resistance. The smaller the cross section, the worse the ratio of the flow velocity to the value of the internal area in a section of a fixed length will be. In wider pipelines, water moves faster.
- The presence of turns, fittings, adapters, taps. Any shaped details slow down the movement of water flows.
When determining the throughput rate, it is necessary to take into account all these factors in combination. In order not to get confused in the numbers, it is worth using proven formulas and tables.
Calculation methods
The coefficient of friction is affected by the presence of locking elements and their number
To determine the permeability of the water supply system, you can use three calculation methods:
The last method, although the most accurate, is not suitable for calculating ordinary household communications. It is quite complex, and for its application you will need to know a variety of indicators. To calculate a simple network for a private house, you should resort to the help of an online calculator. Although it is not as accurate, it is free and does not need to be installed on a computer. You can achieve more accurate information by comparing the data calculated by the program with the table.
How to Calculate Bandwidth
The tabular method is the easiest. Several counting tables have been developed: you can choose the one that is suitable depending on the known parameters.
Calculation based on pipe section
In SNiP 2.04.01-85, it is proposed to find out the amount of water consumption by the girth of the pipe.
In accordance with the norms of SNiP, daily water consumption by one person is not more than 60 liters. This data is for a house without plumbing. If a water supply network is installed, the volume increases to 200 liters.
Calculation according to the temperature of the coolant
As the temperature rises, the permeability of the pipe decreases - the water expands and thereby creates additional friction.
You can calculate the necessary data using a special table:
| Pipe section (mm) | Bandwidth | |||
| By heat (gcl/h) | By heat carrier (t/h) | |||
| Water | Steam | Water | Steam | |
| 15 | 0,011 | 0,005 | 0,182 | 0,009 |
| 25 | 0,039 | 0,018 | 0,650 | 0,033 |
| 38 | 0,11 | 0,05 | 1,82 | 0,091 |
| 50 | 0,24 | 0,11 | 4,00 | 0,20 |
| 75 | 0,72 | 0,33 | 12,0 | 0,60 |
| 100 | 1,51 | 0,69 | 25,0 | 1,25 |
| 125 | 2,70 | 1,24 | 45,0 | 2,25 |
| 150 | 4,36 | 2,00 | 72,8 | 3,64 |
| 200 | 9,23 | 4,24 | 154 | 7,70 |
| 250 | 16,6 | 7,60 | 276 | 13,8 |
| 300 | 26,6 | 12,2 | 444 | 22,2 |
| 350 | 40,3 | 18,5 | 672 | 33,6 |
| 400 | 56,5 | 26,0 | 940 | 47,0 |
| 450 | 68,3 | 36,0 | 1310 | 65,5 |
| 500 | 103 | 47,4 | 1730 | 86,5 |
| 600 | 167 | 76,5 | 2780 | 139 |
| 700 | 250 | 115 | 4160 | 208 |
| 800 | 354 | 162 | 5900 | 295 |
| 900 | 633 | 291 | 10500 | 525 |
| 1000 | 1020 | 470 | 17100 | 855 |
For summing up the plumbing system, this information is not extremely important, but for heating circuits it is considered the main indicator.
Finding Data Depending on Pressure
The pressure of the water flow of the common line is taken into account when selecting pipes
When selecting pipes for installing any communication network, it is necessary to take into account the flow pressure in the common line. If a high pressure head is provided, it is necessary to install pipes with a larger cross section than when moving by gravity. If these parameters are not taken into account when selecting pipe sections, and a large water flow is passed through small networks, they will make noise, vibrate and quickly become unusable.
To find the highest design water flow, a pipe capacity table is used depending on the diameter and different indicators of water pressure:
| Consumption | Bandwidth | |||||||||
| Pipe section | 15 mm | 20 mm | 25 mm | 32 mm | 40 mm | 50 mm | 65 mm | 80 mm | 100 mm | |
| Pa/m | Mbar/m | Less than 0.15 m/s | 0.15 m/s | 0.3 m/s | ||||||
| 90,0 | 0,900 | 173 | 403 | 745 | 1627 | 2488 | 4716 | 9612 | 14940 | 30240 |
| 92,5 | 0,925 | 176 | 407 | 756 | 1652 | 2524 | 4788 | 9756 | 15156 | 30672 |
| 95,0 | 0,950 | 176 | 414 | 767 | 1678 | 2560 | 4860 | 9900 | 15372 | 31104 |
| 97,5 | 0,975 | 180 | 421 | 778 | 1699 | 2596 | 4932 | 10044 | 15552 | 31500 |
| 100,0 | 1000,0 | 184 | 425 | 788 | 1724 | 2632 | 5004 | 10152 | 15768 | 31932 |
| 120,0 | 1200,0 | 202 | 472 | 871 | 1897 | 2898 | 5508 | 11196 | 17352 | 35100 |
| 140,0 | 1400,0 | 220 | 511 | 943 | 2059 | 3143 | 5976 | 12132 | 18792 | 38160 |
| 160,0 | 1600,0 | 234 | 547 | 1015 | 2210 | 3373 | 6408 | 12996 | 20160 | 40680 |
| 180,0 | 1800,0 | 252 | 583 | 1080 | 2354 | 3589 | 6804 | 13824 | 21420 | 43200 |
| 200,0 | 2000,0 | 266 | 619 | 1151 | 2488 | 3780 | 7200 | 14580 | 22644 | 45720 |
| 220,0 | 2200,0 | 281 | 652 | 1202 | 2617 | 3996 | 7560 | 15336 | 23760 | 47880 |
| 240,0 | 2400,0 | 288 | 680 | 1256 | 2740 | 4176 | 7920 | 16056 | 24876 | 50400 |
| 260,0 | 2600,0 | 306 | 713 | 1310 | 2855 | 4356 | 8244 | 16740 | 25920 | 52200 |
| 280,0 | 2800,0 | 317 | 742 | 1364 | 2970 | 4356 | 8568 | 17338 | 26928 | 54360 |
| 300,0 | 3000, | 331 | 767 | 1415 | 3078 | 4680 | 8892 | 18000 | 27900 | 56160 |
The average pressure in most risers varies from 1.5 to 2.5 atmospheres. The dependence on the number of floors is regulated by dividing the water supply network into several branches. The injection of water through pumps also affects the change in flow rate.
Also, when calculating the flow of water through a pipe according to the table of pipe diameter and pressure values, not only the number of taps is taken into account, but also the number of water heaters, bathtubs and other consumers.
Hydraulic calculation according to Shevelev
For the most accurate identification of indicators of the entire water supply network, special reference materials are used. They define running characteristics for pipes made of different materials.
Throughput is an important parameter for any pipes, canals and other heirs of the Roman aqueduct. However, the throughput is not always indicated on the pipe packaging (or on the product itself). In addition, it also depends on the pipeline scheme how much liquid the pipe passes through the section. How to correctly calculate the throughput of pipelines?
Methods for calculating the throughput of pipelines
There are several methods for calculating this parameter, each of which is suitable for a particular case. Some notations that are important in determining the throughput of a pipe:
Outer diameter - the physical size of the pipe section from one edge of the outer wall to the other. In calculations, it is designated as Dn or Dn. This parameter is indicated in the marking.
Nominal diameter is the approximate value of the diameter of the internal section of the pipe, rounded to the nearest 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.
| Liquid type | Speed (m/s) |
| City water supply | 0,60-1,50 |
| Water pipeline | 1,50-3,00 |
| Central heating water | 2,00-3,00 |
| Water pressure system in the pipeline line | 0,75-1,50 |
| hydraulic fluid | up to 12m/s |
| Oil pipeline line | 3,00-7,5 |
| Oil in the pressure system of the pipeline line | 0,75-1,25 |
| Steam in the heating system | 20,0-30,00 |
| Steam central pipeline system | 30,0-50,0 |
| Steam in a high temperature heating system | 50,0-70,00 |
| Air and gas in the central piping system | 20,0-75,00 |
There is an exact capacity calculation table, called the Shevelev table, which takes into account the pipe material and many other factors. These tables are rarely used when laying water pipes around the apartment, but in a private house with several non-standard risers they can come in handy.
Calculation using programs
At the disposal of modern plumbing firms there are special computer programs for calculating the throughput of pipes, as well as many other similar parameters. In addition, online calculators have been developed that, although less accurate, are free and do not require installation on a PC. One of the stationary programs "TAScope" is a creation of Western engineers, which is shareware. Large companies use "Hydrosystem" - this is a domestic program that calculates pipes according to criteria that affect their operation in the regions of the Russian Federation. In addition to hydraulic calculation, it allows you to calculate other parameters of pipelines. The average price is 150,000 rubles.
How to calculate the throughput of a gas pipe
Gas is one of the most difficult materials to transport, in particular because it tends to compress and therefore can flow through the smallest gaps in pipes. Special requirements are imposed on the calculation of the throughput of gas pipes (as well as on the design of the gas system as a whole).
The formula for calculating the throughput of a gas pipe
The maximum capacity of gas pipelines is determined by the formula:
Qmax = 0.67 DN2 * p
where p is equal to the working pressure in the gas pipeline system + 0.10 MPa or the absolute pressure of the gas;
Du - conditional passage of the pipe.
There is a complex formula for calculating the throughput of a gas pipe. When carrying out preliminary calculations, as well as when calculating a domestic gas pipeline, it is usually not used.
Qmax = 196.386 Du2 * p/z*T
where z is the compressibility factor;
T is the temperature of the transported gas, K;
According to this formula, the direct dependence of the temperature of the transported medium on pressure is determined. The higher the T value, the more the gas expands and presses against the walls. Therefore, when calculating large highways, engineers take into account possible weather conditions in the area where the pipeline passes. If the nominal value of the DN pipe is less than the gas pressure generated at high temperatures in summer (for example, at + 38 ... + 45 degrees Celsius), then the line is likely to be damaged. This entails the leakage of valuable raw materials, and creates the possibility of an explosion of the pipe section.
Table of capacities of gas pipes depending on pressure
There is a table for calculating the throughput of a gas pipeline for commonly used diameters and nominal working pressure of pipes. Engineering calculations will be required to determine the characteristics of a gas pipeline of non-standard dimensions and pressure. Also, the pressure, speed of movement and volume of gas is affected by the temperature of the outside air.
The maximum velocity (W) of the gas in the table is 25 m/s and z (compressibility factor) is 1. The temperature (T) is 20 degrees Celsius or 293 Kelvin.
| Pwork(MPa) | Throughput capacity of the pipeline (m? / h), with wgas \u003d 25m / s; z \u003d 1; T \u003d 20? C = 293? K | |||||||
|---|---|---|---|---|---|---|---|---|
| DN 50 | DN 80 | DN 100 | DN 150 | DN 200 | DN 300 | DN 400 | DN 500 | |
| 0,3 | 670 | 1715 | 2680 | 6030 | 10720 | 24120 | 42880 | 67000 |
| 0,6 | 1170 | 3000 | 4690 | 10550 | 18760 | 42210 | 75040 | 117000 |
| 1,2 | 2175 | 5570 | 8710 | 19595 | 34840 | 78390 | 139360 | 217500 |
| 1,6 | 2845 | 7290 | 11390 | 25625 | 45560 | 102510 | 182240 | 284500 |
| 2,5 | 4355 | 11145 | 17420 | 39195 | 69680 | 156780 | 278720 | 435500 |
| 3,5 | 6030 | 15435 | 24120 | 54270 | 96480 | 217080 | 385920 | 603000 |
| 5,5 | 9380 | 24010 | 37520 | 84420 | 150080 | 337680 | 600320 | 938000 |
| 7,5 | 12730 | 32585 | 50920 | 114570 | 203680 | 458280 | 814720 | 1273000 |
| 10,0 | 16915 | 43305 | 67670 | 152255 | 270680 | 609030 | 108720 | 1691500 |
Capacity of the sewer pipe
The capacity of the sewer pipe is an important parameter that depends on the type of pipeline (pressure or non-pressure). The calculation formula is based on the laws of hydraulics. In addition to the laborious calculation, tables are used to determine the capacity of the sewer.
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 domestic networks can be found in Table 3.
Yulia Petrichenko, expert
In addition, there is a normalized value for the minimum slope for pipes with a small diameter: 150 mm
(i=0.008) and 200 (i=0.007) mm.
The formula for the volumetric flow rate of a liquid looks like this:
where a is the free area of the flow,
v is the flow velocity, m/s.
The speed is calculated by the formula:
where R is the hydraulic radius;
C is the wetting coefficient;
From this we can derive the formula for the hydraulic slope:
According to it, this parameter is determined if calculation is necessary.
where n is the roughness factor, ranging from 0.012 to 0.015 depending on the pipe material.
The hydraulic radius is considered equal to the usual radius, but only when the pipe is completely filled. In other cases, use the formula:
where A is the area of the transverse fluid flow,
P is the wetted perimeter, or the transverse length of the inner surface of the pipe that touches the liquid.
Capacity tables for non-pressure sewer pipes
The table takes into account all the parameters used to perform the hydraulic calculation. The data is selected according to the value of the pipe diameter and substituted into the formula. Here, the volumetric flow rate q of the liquid passing through the pipe section has already been calculated, which can be taken as the throughput of the pipeline.
In addition, there are more detailed Lukin tables containing ready-made throughput values for pipes of different diameters from 50 to 2000 mm.
Capacity tables for pressurized sewer systems
In the capacity tables for sewer pressure pipes, the values depend on the maximum degree of filling and the estimated average flow rate of the waste water.
| Diameter, mm | Filling | Acceptable (optimal slope) | The speed of movement of waste water in the pipe, m / s | Consumption, l / s |
| 100 | 0,6 | 0,02 | 0,94 | 4,6 |
| 125 | 0,6 | 0,016 | 0,97 | 7,5 |
| 150 | 0,6 | 0,013 | 1,00 | 11,1 |
| 200 | 0,6 | 0,01 | 1,05 | 20,7 |
| 250 | 0,6 | 0,008 | 1,09 | 33,6 |
| 300 | 0,7 | 0,0067 | 1,18 | 62,1 |
| 350 | 0,7 | 0,0057 | 1,21 | 86,7 |
| 400 | 0,7 | 0,0050 | 1,23 | 115,9 |
| 450 | 0,7 | 0,0044 | 1,26 | 149,4 |
| 500 | 0,7 | 0,0040 | 1,28 | 187,9 |
| 600 | 0,7 | 0,0033 | 1,32 | 278,6 |
| 800 | 0,7 | 0,0025 | 1,38 | 520,0 |
| 1000 | 0,7 | 0,0020 | 1,43 | 842,0 |
| 1200 | 0,7 | 0,00176 | 1,48 | 1250,0 |
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 diameter, mm | Bandwidth | |||
|---|---|---|---|---|
| By warmth | By coolant | |||
| Water | Steam | Water | Steam | |
| Gcal/h | t/h | |||
| 15 | 0,011 | 0,005 | 0,182 | 0,009 |
| 25 | 0,039 | 0,018 | 0,650 | 0,033 |
| 38 | 0,11 | 0,05 | 1,82 | 0,091 |
| 50 | 0,24 | 0,11 | 4,00 | 0,20 |
| 75 | 0,72 | 0,33 | 12,0 | 0,60 |
| 100 | 1,51 | 0,69 | 25,0 | 1,25 |
| 125 | 2,70 | 1,24 | 45,0 | 2,25 |
| 150 | 4,36 | 2,00 | 72,8 | 3,64 |
| 200 | 9,23 | 4,24 | 154 | 7,70 |
| 250 | 16,6 | 7,60 | 276 | 13,8 |
| 300 | 26,6 | 12,2 | 444 | 22,2 |
| 350 | 40,3 | 18,5 | 672 | 33,6 |
| 400 | 56,5 | 26,0 | 940 | 47,0 |
| 450 | 68,3 | 36,0 | 1310 | 65,5 |
| 500 | 103 | 47,4 | 1730 | 86,5 |
| 600 | 167 | 76,5 | 2780 | 139 |
| 700 | 250 | 115 | 4160 | 208 |
| 800 | 354 | 162 | 5900 | 295 |
| 900 | 633 | 291 | 10500 | 525 |
| 1000 | 1020 | 470 | 17100 | 855 |
Pipe capacity table depending on the coolant pressure
There is a table describing the throughput of pipes depending on the pressure.
| Consumption | Bandwidth | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| DN pipe | 15 mm | 20 mm | 25 mm | 32 mm | 40 mm | 50 mm | 65 mm | 80 mm | 100 mm |
| Pa/m - mbar/m | less than 0.15 m/s | 0.15 m/s | 0.3 m/s | ||||||
| 90,0 - 0,900 | 173 | 403 | 745 | 1627 | 2488 | 4716 | 9612 | 14940 | 30240 |
| 92,5 - 0,925 | 176 | 407 | 756 | 1652 | 2524 | 4788 | 9756 | 15156 | 30672 |
| 95,0 - 0,950 | 176 | 414 | 767 | 1678 | 2560 | 4860 | 9900 | 15372 | 31104 |
| 97,5 - 0,975 | 180 | 421 | 778 | 1699 | 2596 | 4932 | 10044 | 15552 | 31500 |
| 100,0 - 1,000 | 184 | 425 | 788 | 1724 | 2632 | 5004 | 10152 | 15768 | 31932 |
| 120,0 - 1,200 | 202 | 472 | 871 | 1897 | 2898 | 5508 | 11196 | 17352 | 35100 |
| 140,0 - 1,400 | 220 | 511 | 943 | 2059 | 3143 | 5976 | 12132 | 18792 | 38160 |
| 160,0 - 1,600 | 234 | 547 | 1015 | 2210 | 3373 | 6408 | 12996 | 20160 | 40680 |
| 180,0 - 1,800 | 252 | 583 | 1080 | 2354 | 3589 | 6804 | 13824 | 21420 | 43200 |
| 200,0 - 2,000 | 266 | 619 | 1151 | 2486 | 3780 | 7200 | 14580 | 22644 | 45720 |
| 220,0 - 2,200 | 281 | 652 | 1202 | 2617 | 3996 | 7560 | 15336 | 23760 | 47880 |
| 240,0 - 2,400 | 288 | 680 | 1256 | 2740 | 4176 | 7920 | 16056 | 24876 | 50400 |
| 260,0 - 2,600 | 306 | 713 | 1310 | 2855 | 4356 | 8244 | 16740 | 25920 | 52200 |
| 280,0 - 2,800 | 317 | 742 | 1364 | 2970 | 4356 | 8566 | 17338 | 26928 | 54360 |
| 300,0 - 3,000 | 331 | 767 | 1415 | 3076 | 4680 | 8892 | 18000 | 27900 | 56160 |
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.
Hydraulic Calculation Formula
For water pipes, the following calculation formula applies:
Online calculator: pipe capacity calculation
If you have any questions, or if you have any guides that use methods not mentioned here, write in the comments.
