Calculation of water pressure in the pipeline. Example of calculating the pressure in the pipe
Comfort in the house is hard to imagine without running water. And the emergence of new technology in the form of laundry, dishwashers, Boilers and other units have further enhanced its role in housing housing 21 century. But these units require, that water came from a water supply system with a certain pressure. Therefore, man, who decided to equip her house with a water supply system, must know, how to calculate the required water pressure in the pipeline, that all devices work normally.
For the normal functioning of the water supply system, the pressure in it must meet the standards
Definition of the indicator
The pressure in the pipeline is divided into the following types: working, conditionally, trial and calculation. Without knowledge of their differences to calculate the pressure drop of the fluid transported from the engineering communication will be difficult. In accordance, when selecting the appropriate elements of the water supply system, the owner will face difficulties, that do not allow to provide a comfortable stay in the living space.
- Working. It is external or internal, necessarily the maximum excess pressure, which is fixed at standard components of process of transportation of water in normal conditions.
- Conditionally. Use this indicator when calculating the strength of pipelines and vessels), which operate under a certain pressure at water temperature 20?WITH.
- Try it. This simple indicator is measured during the design test. Based on it, the behavior of system elements when changing the pressure in the water supply is monitored. This approach serves as a kind of general insurance before laying the network.
- Estimated. This means the maximum excess pressure in the cavity of the pipeline, produced substance transported through it. It should be taken into account, that actions are exposed not only to pipes, but also all the elements, which are a part of engineering communication. It is on the basis of the design pressure that the wall thickness of the water pipe is determined. Functionality depends on it, as well as the service life of the system and, of course, safety of the occupants of the house.
The water pressure in the tap depends on the pressure in the water supply system
A simple example of calculating the pressure in the pipe
As you know, not so long ago the water supply was connected to the water tower. Thanks to this structure, pressure is created in the water supply network. The unit of measurement of this characteristic is the atmosphere. And, the size of the tank located at the top does not affect the value of this parameter, it depends only on the height of the tower.
Useful to know! In practice, the pressure is measured in meters of water. When pouring water into the pipe height 10 meters, the pressure will be fixed at the lower point, equal to one atmosphere.
Consider the example of a house in 5 floors. Its height - 15 meters. That is, on one floor 3 meters. The tower is tall 15 meters will create pressure on the ground floor 1,5 atmosphere. The value of this figure in the pipe on the second floor will be already 1,2 atmosphere. It turns out by subtracting from the number 15 height of one floor - 3 meters, and dividing the result by 10. Having made the further calculation, it will become clear to us, that on the 5th floor there will be no pressure. Logic tells, that to provide water to people, living on the top floor need to build a higher tower. And if it comes, example, about a 25-storey building? Nobody will build such big buildings. For this purpose, modern water supply systems are equipped with submersible pumps.
The outlet pressure of such a unit is calculated very simply. Example, if the submersible pump, whose power is enough to raise the water to the mark 50 meters of water column, immerse in a well on 15 meters, at ground level it will create pressure 3,5 atmosphere (50-15/10 = 3,5).
It is possible to provide the necessary indicator of pressure in system by means of the pump
How to calculate the thickness of the pipe from the action of pressure
When water moves through a pipe, there is resistance to its friction against the walls, as well as various obstacles. This phenomenon is called hydraulic resistance of the pipeline. Its numerical value is in direct proportion to the flow rate. We already know from the previous example, that at different altitudes the water pressure is different, and this feature should be taken into account when calculating the inner diameter of the pipe, that is, its thickness. Simplified formula for calculating this parameter for a given head loss (pressure) looks like this:
Dvn = KGSopr?Dl. tr. / PD?(Ud.vaga?Sk / 2g),
where: Dvn. - inner diameter of the pipeline; КГСопр. - coefficient of hydraulic resistance; Dovzh.tr - the length of the pipeline; PD - set or allowable pressure loss between the final and initial sections of the highway; Ud.vaga. - specific weight of water - 1000 kg / (9815 m /; Sk. - flow rate, m / sec.; g – 9,81 m / sec2. Everyone knows the constant - the acceleration of gravity.
The pressure loss in the fittings and fittings of the pipeline is determined with sufficient accuracy by the losses in the straight pipe of equivalent length and with the same conditional passage.
How to calculate the walls of the pipe by pressure
Accurate calculation of this indicator of steel pipes, operating under the influence of excessive internal pressure, includes two stages. First, the so-called estimated wall thickness is calculated. Then the thickness of wear from corrosion is added to the received number.
The calculation of the pressure is necessary to select the wall thickness of the pipe
Council! Manufacturing and assembling the pipeline, do not install individual random inserts. In order not to provoke an accident, work only with those, the sizes of which coincide with the estimated ones.
So, the generalized formula for calculating the wall thickness is as follows:
T = RTS + PC,
where: T - the desired parameter - the thickness of the walls; RTS - estimated wall thickness; PC - allowance for corrosion wear.
The calculated wall thickness depending on the pressure is calculated by the following formula:
RTS = VID × Dsun /230× DR × KPSH + R ,
where: TYPE - internal excess pressure; Dnar. - outer diameter of the pipe; IN - allowable breaking voltage; KPS - weld strength factor. Its value depends on the technology of pipe production. At the final stage of calculating the wall of the pipe by pressure, we add to the RTS the value of the PC parameter. Taken from the directory.
Pipe pressure and diameter
Correct determination of pipe cross-section is no less important, than their choice of fabrication material. If the diameter and pressure in the pipe are incorrectly calculated, air turbulence will occur, it is present, and in a stream of water. Because of this, the movement of fluid through the pipe will be accompanied by increased noise, and on the inner surface of the branch of the water supply will form a large number of lime deposits. in addition, should be remembered, that the existence of pressure dependence on the diameter of the pipe can adversely affect the capacity of the water supply. In practice, many residents of apartments and houses faced the situation, when at simultaneous inclusion of several cranes water pressure sharply fell. This trouble occurs for two reasons: when the pressure in the whole system dropped and when the diameter of the connected pipes was underestimated.
The capacity of the water supply network depends on the diameter of the pipe
The following table for the maximum estimated water flow through the most common diameters at different pressure values.
Table 1
| Consumption | Bandwidth. Unit of measurement - kg / hour | |||||||||
| Du pipe | 100 | 80 | 65 | 50 | 40 | 32 | 25 | 20 | 15 | |
| mbar / m | Pa / m | 0,3 m / sec | 0,15 m / sec | <0,15 m / sec | ||||||
| 3,00 | 300 | 56160 | 27900 | 18000 | 8892 | 4680 | 3078 | 1415 | 767 | 331 |
| 2,80 | 280 | 54360 | 26928 | 17338 | 8568 | 4356 | 2970 | 1364 | 742 | 317 |
| 2,60 | 260 | 52200 | 25920 | 16740 | 8244 | 4356 | 2855 | 1310 | 713 | 306 |
| 2,40 | 240 | 50400 | 24876 | 16056 | 7920 | 4176 | 2740 | 1256 | 680 | 288 |
| 2,20 | 220 | 47880 | 23760 | 15336 | 7560 | 3996 | 2617 | 1202 | 652 | 281 |
| 2,00 | 200 | 45720 | 22644 | 14580 | 7200 | 3780 | 2488 | 1151 | 619 | 266 |
| 1,80 | 180 | 43200 | 21420 | 13824 | 6804 | 3589 | 2354 | 1080 | 583 | 252 |
| 1,60 | 160 | 40680 | 20160 | 12996 | 6408 | 3373 | 2210 | 1015 | 547 | 234 |
| 1,40 | 140 | 38160 | 18792 | 12132 | 5976 | 3143 | 2059 | 943 | 511 | 220 |
| 1,20 | 120 | 35100 | 17352 | 11196 | 5508 | 2898 | 1897 | 871 | 472 | 102 |
| 1,00 | 100 | 31932 | 15768 | 10152 | 5004 | 2632 | 1724 | 788 | 425 | 184 |
| 0,975 | 97,5 | 31500 | 15552 | 10044 | 4932 | 2596 | 1699 | 778 | 421 | 180 |
| 0,950 | 95,0 | 31104 | 15372 | 9900 | 4860 | 2560 | 1678 | 767 | 414 | 176 |
| 0,925 | 92,5 | 30672 | 15156 | 9756 | 4788 | 2524 | 1652 | 756 | 407 | 176 |
| 0,900 | 90,0 | 30240 | 14940 | 9612 | 4716 | 2488 | 1627 | 745 | 403 | 173 |
In most risers, the average pressure is in the range of atmospheres.
Calculation of home plumbing
From a practical point of view, the pressure in the water supply is most often associated with the volume of water, supplied per unit time, that is, with the capacity of the water supply branch. In this context, the issue of calculating domestic water supply will be considered. After studying the passport data of devices and units, consuming water, summed up the total cost. Then the cost of all installed and used water taps is added to the received figure.
For home plumbing, working from a well, the choice of pipes depends on the power of the pump
Useful Information! One such plumbing device passes through itself in one minute or so 5-6 liters of water.
After that, all numbers are summed, and the output is the total flow in the house water. Given this data, buy a pipe with a diameter, which will provide the right pressure and, in accordance, the amount of water in all water collection devices, working simultaneously.
If the home water supply is planned to be connected to the city network, the owner has no choice, he will be forced to enjoy it, that is. Another thing, if it is a private house, well-fed. Then you should buy a pump, able to provide water supply pressure, corresponding to the costs. The choice is made according to the passport data of such a unit. The table below will help you determine the diameter.
Table 2
| Pipe capacity | Diameter and length of the pipeline | ||
| Capacity, l / min | Pipe diameter | Pipe diameter | The length of the water supply, meters |
| Seventy five | Thirty eight | Thirty-two | More 30 |
| Fifty | Thirty-two | Twenty five | |
| Thirty | Twenty five | twenty | Less 10 |
Here are the parameters of only the most commonly used pipe products.
Modern means
If you don't have time or you are not prone to math, it is possible to calculate the flow of water through the pipeline taking into account the pressure drop, using an online calculator. The Internet is full of sites with the same tools. To make a hydraulic calculation, it is necessary to take into account the loss factor. This approach involves choice:
- pressure drop on the running meter of the pipeline;
- plot length;
- inner diameter of the pipe;
- type and material of water supply system (plastic, ferroconcrete, asbestos cement, cast iron, steel). Modern online calculators even take this into account, example, less roughness of a plastic surface in comparison with steel;
- methods of calculating resistance.
in addition, the user has options for accounting for additional characteristics of pipelines, in particular, such, as a type of coating. Example:
- cement-sand, applied by various methods;
- external polymer cement or plastic;
- new or worked for a certain period of time pipelines with a bituminous covering or without a protective internal covering.
If the calculation is done correctly, provided that the installation is carried out in compliance with all the requirements for the water supply system, no complaints will arise.
