During the Soviet era, water could be used in unlimited quantities for a very small fee. But unfortunately, water resources are not endless and their number is decreasing. Today, water is becoming closer to oil in importance, which means that accounting for its consumption is stricter. Currently, there is a federal law according to which all consumed water must be counted using special devices. To ensure the operation of such devices or meters, there is a water meter unit.
What it is?
A water metering unit is considered to be a section of a pipe with various constituent elements, coming from the entrance of the central water supply to an apartment or private house. With its help, the water supply company controls the amount of water used by consumers at a specific facility. For consumers, the installation of a water metering unit allows not only to control the use of water, but also to save money by analyzing the flow for a certain period of time.
A water metering unit is a whole system consisting of different elements that have their own purpose. The main component of the node is the counter. Equally important parts of the system are fixing fittings with a locking mechanism, a strainer, a valve with a fixed control and trigger mechanism, compensation pipe sections in the form of branch pipes and other elements that perform a connecting function.
The meter shows the amount of consumed water in cubic meters. The purpose of the tap is to drain water and control the pressure in the internal network, with its help, you can check the accuracy of the installed meter and determine the place of water leakage in the internal system.
With the help of valves, water access to the house from the central highway is blocked. It is used when dismantling the meter or completely draining the system. A strainer is necessary for additional purification of the water entering the internal system from impurities resulting from corrosive changes in pipes or emergencies at a waterworks. Flanged nozzles are used for mounting individual sections of the system. And the rest of the connecting elements perform an auxiliary function.
To equip the water metering unit, it is necessary to comply with a number of requirements specially developed and adopted in the Russian Federation.
- For the installation of a water metering unit, a non-residential premises with a relative air humidity of 75-80% and a temperature of at least +5? C are used. The location of the nodal system should be accessible for inspection, taking readings, replacing or dismantling the device for verification. In apartment buildings and public buildings, units are most often located in central heating points, basements or specially equipped pits. For private houses, installation in a well is possible.
- Installation of the unit is impossible without preliminary preparation of the system, namely, pressure testing and flushing of pipes. Direct installation is started only after filling the system pipes with water. Pipes and other components used for assembly and subsequent installation must be rigidly fixed to the surface of the floor or wall. In order that the water pressure does not decrease with the commissioning of the unit, it is recommended to use a minimum number of bends and fittings during the installation process.
- The design of the unit and the installation of the metering device should be carried out in accordance with regulatory documents and accepted standards (SNiP, technical passport of the meter). The measuring device is always installed on a straight section and at a certain height from the floor level, as a rule, it fluctuates in the range of 300-1000 mm. The length of the sections on each side of the measuring device must comply with state standards for measuring devices (SNiP).
- The installed device must have a passport of the manufacturer with the date of issue and a state-recognized certificate. After installation, the device must be protected from unauthorized interference by installing a seal. Sealing of the meter with the issuance of an official permit for operation is carried out by a company that provides water supply services.
- To estimate the volume of cold water, a device marked with cold water supply is installed, and for calculating hot water, a meter marked with hot water supply is installed. The cold water meter is subject to verification every 6 years, and the operation of the hot water meter is checked every 4 years.
- Calibration of measuring devices is carried out either by organizations with appropriate accreditation, or by a company that provides maintenance of this unit, with the issuance of an appropriate conclusion. To check the measuring device, you can use special equipment that excludes the possibility of dismantling. Typically, ultrasonic, electromagnetic and mobile testing devices are used.
The classification of the gauge units depends on the number of lines and the design features of the measuring device installed on the line.
- Depending on the number of lines in the structure, the water metering units are divided into simple, consisting of one line, and complex, with a bypass line . Structures with a bypass line must be installed at facilities with one water inlet. This system is also provided if the installed meter is not designed to pass water in sufficient quantity for fire extinguishing systems. In order to provide water to the fire extinguishing system, a gate valve is additionally mounted on the bypass line, which is automatically set in motion due to an electric drive.
- Depending on the meters used in the design, the units are divided into tachometric, electromagnetic, vortex and ultrasonic . The tachometer is one of the most common and typical metering devices installed directly in pipes with a diameter not exceeding 400 mm. Water consumption is measured by rotating the working fluid, driven by the flow. The higher the rotation speed, the greater the volumetric flow rate of water. The division of tachometer metering devices depends on the internal device.
Today there are: vane, turbine and combined meters.
- For buildings with a small volume of consumed water, where the diameter of pipes is in the range of 15-40 mm, vane sectional water meters are installed . These meters are mounted exclusively on horizontal sections, the connecting elements of which are connected to each other by means of a thread. This setting is associated with their internal structure. For a more accurate measurement of the consumed volume of water, the axis of the device must be perpendicular to the liquid flow. Meters for hot water can withstand temperatures up to +150 degrees, and those used in cold water supply units can withstand temperatures no more than +40 degrees.
- Turbine meters , unlike vane meters , can be mounted not only horizontally, but also vertically. In this case, the flow of water is parallel to the axis of rotation. The vertical arrangement of the device is possible if the incoming water flows in an ascending manner. Water meter units with a turbine-type meter are installed in buildings with a high water flow rate, where pipes have a diameter of 50-250 mm.
- Combined metering devices contain elements of a vane and turbine meter. Such structures are indispensable if the building has an uneven consumption of water resources, as well as there are sharp fluctuations in consumption.
The method of supplying water to the device allows tachometric meters to be subdivided into single-jet and multi-jet types. The stream of water passing through the mechanism of the single-jet meter causes the spring to rotate around the impeller. To set the impeller in motion, the flow of water in multi-jet meters is first divided into small flows and only then falls on the blades. Multi-jet types are among the most accurate metering devices of this class.
To measure large volumes of consumed water at large enterprises, electromagnetic metering devices are installed. Their work is based on the analysis of changes in the magnetic field created inside the meter by the flow of water. Electromagnetic models of water meters refer to high-precision measuring instruments capable of withstanding any pressure inside the system, giving accurate indicators of water consumption over a certain period of time. By connecting to a laptop, you can draw up a graph of consumption for different periods in dynamics.
The work of vortex meters is based on the analysis of the speed and intensity of vortices, measured by a piezoelectric element located inside the device. In ultrasonic devices, water consumption is measured by analyzing the displacements of the ultrasonic wave generated by the water flow. The wave propagation interval is fixed using a piezoelectric receiver. Ultrasonic devices are used in units where it is impossible to install electromagnetic meters due to impurities in the water, in particular, for calculating the volume of wastewater. To trap impurities, a DN 100 mesh filter is most often used; the use of filters with a smaller cross-section can lead to a pressure drop.
The project of a water metering unit is a diagram on which the location of all constituent elements and connections is drawn in detail. There are different layouts of water metering units. But the sequence for any scheme should remain unchanged: first there is a locking device (valve, tap), then - a section of a pipe with a filter, and only then a metering device. When installing meters, certain requirements must be observed. The length of straight connecting elements emanating from the device in both directions must correspond to the value specified in the document for a specific meter model. Similar requirements are imposed on the diameters of the sections and the nominal diameter of the device, they must correspond to each other.
The length of the straight connecting elements is formed by the fittings with union nuts included in the kit with the meter. If they provide the length indicated in the instrument passport, and the diameter of the conditional bore of the meter corresponds to the diameter of the straight sections, then there is no need to install a transition element. If there is a discrepancy in length, and the diameters are the same, then an elongated fitting with union nuts is mounted. If the diameter does not match, a transition element is installed.
To increase the length in straight sections, if the declared value does not correspond to the declared value, couplings and bends (straight or angular) are used, and if the diameters do not match, a transition element is also used. A combined installation of additional elements is also allowed. The squeegee can be installed between the filter device and the meter, or between the shut-off and filter device.
The scheme also provides for the presence of tanks, circulation systems, and in case of difficult draining of water, a second locking device is also allowed , installed after the meter. Additionally, a drain valve or a plug is included in the assembly diagram if it is planned to drain water directly from the assembly and monitor the water pressure at the outlet of the device. To control the pressure, a regulator can be included in the circuit, located between the shutter device and the meter. It is turned on if ball valves, shut-off and rotary devices cannot provide smooth flow control, to protect the meter from water hammer, and also if it is necessary to periodically reduce the pressure to the optimal value.
On projects, they draw not only a diagram of a water metering unit with all its components. If there are several nodes, indicate the location of each with a designation of the diameters of the underwater mains.
The selection of a meter for a water metering unit should be carried out taking into account several factors.
- It is necessary to take into account the pressure and temperature of the water, the sensitivity limit and the permissible head loss. The most important characteristic is the sensitivity limit, it depends on it for which pipe diameter the meter is purchased. It makes no sense to buy a meter with a large diameter for low water consumption, since it simply will not fix them, its sensitivity threshold is higher.
- For apartments and private houses with small pipe diameters, conventional tachometers are suitable. But it is worth remembering that all mechanical models are sensitive to electromagnetic fields, and their accuracy is directly dependent on the quality of the supplied water. Electromagnetic models are much more accurate than mechanical models, but they cost several times more and require a power supply to operate.
- Meters for hot water can be installed in units with cold water supply, as their temperature range is wider than that of models designed to measure the volume of cold water, but not vice versa.
- It is better to buy a metering device in specialized stores. When buying, you should pay attention to the release date indicated in the technical passport. The verification date is counted precisely from the date of issue, and not from the date of installation. The more time this device has been on the counter, the sooner the verification date will come.
- It is better to entrust the installation of a meter in an apartment to specialists with an appropriate license, and the company servicing this object should carry out the sealing and registration of the device.
For information on how to properly mount the water meter unit, see the next video.