However, they are used for a long time and in a variety of applications requiring precise accounting of running water.Counters are used for commercial metering of water consumption in the municipal and household sector, chemical, Pharmaceuti-tion, food and other industries.With their help, we keep records of drinking water, network and waste water (both cold and hot), as well as keeping the coolant - a part of heat meters.Accordingly, a wide range of applications there is considerable diversity in CCA-design feature of these devices and in different sizes.
On the device mechanism water meters water meters are on-Subsection tachometer, electromagnetic, Volumetric, Ultrasound-kovye, combined counters and differential pressure or diaphragm.
tach water meters
All tachometer water meters include your device mechanism (ta-tachometer), in which the flow of water directly through the WHO-mechanical pressure acts on the blades of the turbine vane wheel or causing rotation.This rotation through the gear re
The single-jet and multi-jet water meters tachometer plane of the blades of the impeller wheel in its lowest position is perpendicular to the direction of water flow.The turbine water meters (meters Woltman) has blades with respect to the direction of water flow at an angle less than 90 °, as in classical turbine.Multi-jet water meters
different from the single-jet so that the flow of water before reaching the blade of the impeller is divided into several jets.This greatly reduces the error turbulence.And as a result, multi-jet meters are more accurate taking into account the flow of water, but they are more expensive than single-jet.
single-jet and multi-jet water meters, and there are also "dry" and "wet."Counters wet type - this is the most simple, yet effective enough water meters, counting device by which the flow stream not isolated.Ease of execution and accompanying cheapness at a sufficiently high reliability - these are the main advantages of a wet-type counters.However, these water meters can not be used for metering water abundantly polluted by suspended mechanical particles.
dry-type counters have this drawback.They Counter hermetically separated from the water of the nonmagnetic wall, whereby it does not form deposits of suspended particles.Transmission as readings from BPA--rotating impeller or turbine at a counting mechanism by means of a magnet mounted on them.Such an apparatus suitable for making the counter account of any water contamination, but at the same time considerably increases its cost.Therefore, "dry" is equipped with a mechanism often-and so are more expensive multi-jet meters, which are used in cases where you really need especially accurate metering of water."Dry" mechanism in the single-jet meters installed rarely: it would deprive these instruments of their main advantages cheapness.In addition, indications of "dry" water meters in connection with the features of their devices most often subjected to tampering by the user.
compromise solution is a "semi-dry" counter, developed by ABB.In this device, a counting mechanism is separated from the water jet baffle impeller rotation is transmitted to it through a gear train, but the water inside the counter mechanism does not penetrate.This effect is achieved by filling the chamber counter mechanism viscous hydrophobic filler is not miscible with water, which prevents movement of the gears, but isolates them from the water.
Another kind of constructive counter-tachometer are combined water meters, in which the device is usually combined conventional turbine vane counter and placed on a parallel layering.When the water pressure in the water supply is low, the water moves through the impeller counter, but when the pressure increases, the pipeline with the valve and the meter is covered by water flows through the turbine layering.In the most modern models and a turbine impeller and counters are located in one plane.Under the same principle, taking into account the additional water side slips in such devices is not required.
Places application of different types of water meters tachometer
normal diameter of the pipeline, which are set single-jet water meters - 15-20 mm (flat), multijet -15-50 mm turbine -40-500 mm.Accordingly, the apparent potential and the point of use.In Europe, single-jet water meters are commonly used for pokvar-Tierney water meters.In Russia, because of poor water quality, possibly for the same purpose are often applied more reliable and durable BUILD-WIDE counters, but the price factor may adversely affect the breadth of their distribution.At the moment, multi-jet model with a diameter of 25-50 mm are installed in the water supply of office buildings, single family houses, schools, nurseries, gas stations and other facilities of this type.
Turbine water meters of large diameter (over 50 mm), usually installed at water intakes, water supply systems at the entrances industrial-governmental enterprises, inputs and high-rise buildings in the system of water canals.
Combination water meters are used primarily in the water systems of hotels, hotels and industrial facilities, where depending on the season (increase or decrease in the number of consumers) or the conditions of the process water flow can vary significantly.
In the light of the reform of housing and communal services much attention is paid tachometric water meter with pulse output.In such devices totalizer readings are converted into an electrical signal and a pulse (digital) form can be transmitted and displayed on the final recording device remote from the direct flow metering consumer.This creates prerequisites for the establishment of common computerized automatic control points, and probably it is such water meters will in the future, the most common counters for every apartment water meters.
electromagnetic water meters
operating principle of electromagnetic (magnetic induction) water meters based on the measurement of EMF induction, suggestive, according to Faraday's law, in an electrically conductive liquid (in Vol. H. In water), which moves in a magnetic field produced by an electromagnetdevice.This emf is proportional to the flow velocity and the flow meter is converted to the electronic unit into an electrical analog or digital signal to be displayed on the display device itself or the broadcast controller or computer.Obviously, the flow of this type is much more expensive described above tachometer and therefore almost every apartment are used for household registration of drinking water and municipal services can be used as water meters for houses.Most such devices are designed to measure the flow of water in the food, beverage, pharmaceutical, sometimes quite slow-tion, as well as wastewater streams.
volumetric flowmeters type in Russia are rarely used.In these devices, the water is supplied under pressure into the chamber defined volume, which rotates, passing for each revolution of the same volume of water.It is rotated by the gear counter reports, the registration number of the consumed water.In the UK Volumetric water meters are used by organizations as the main supply of instruments for measuring flow rate.They are used in special systems, industrial buildings and laboratories for monitoring the water flow is very weak.
Measuring the difference of time spent on the passage of the ultrasonic signal in the direction of fluid flow and opposite to it, as the basis of the principle of operation of this type of flow.Two sensors mounted on the pipe and emit a signal generated by the piezoelectric crystal in opposite directions.Ultrasonic signal sent downstream, first reaches arranged oppositely in a counter-end portion of the pipeline converter, and the difference VRE-passage of both signals to time the flow rate is calculated.Naturally, in the absence of both the flow sensor signal is recorded simultaneously.The recording device can be mounted on the device removed Mr. range and is equipped with a display.
There are two types of ultrasonic flowmeters, one mounted on the outer surface of the pipe (Clamp on), the other is in contact with the medium (mortise type, Insertion).The first type is applied when dealing with aggressive liquids, for him there is no limit on the pressure and temperature.Mounted on the outer surface of the pipe does not require stopping the process.The second type often used for flow-measurement of fluid flow within the pipeline, made of material with low conductivity alarm.Water for industrial plants-prises and waste water - the main areas of application of ultrasonic flowmeters.
As we know from the course of fluid dynamics, flow around obstacles fluid flow turbulence occur (Karman vortex street), which cause on the body surface pressure drops.Frequency differences proportional to flow velocity and volumetric flow rate of the liquid or gas.On the registration number of differential pressure and convert them to analog or digital electrical signal based principle of the vortices revyh-meters used for metering, not only water and other low-viscosity liquids, but also vapor and gases.
such devices are used most often for process control and management.
Counters of hot water
For the calculation of hot water use the same types of flowmeters that cold.Household water meters of hot water - it's all the same vane tachometer counters Woltman meters and combined.Distinguish them from the tachometer cold water meters are used in materials and a high degree of permissible error.If the allowable error counters for cold water at a flow rate between the minimum (Qmin) and transition (Qt) is ± 5% and between Qt and maximum (Qmax) ± 2%, to hot water meters respectively ± 6% and ± 3%.
Nominal flow rate (Qn) for options counters with hot and cold water the same size from a single source, usually the same.According to government standard minimum service life counters with hot and cold water is 12 years with two optional calibration (recalibration period of 5-6 years) for cold water and three (recalibration period of 4 years) hot.All tachometer counters for hot water is required to dry type.
in the industry for the calculation of hot water, where necessary, take-nyayutsya electromagnetic and ultrasonic flowmeters.
diversity of manufacturers of water meters in the Russian market
Today in Russia there are all types of water meters on a variety of foreign and Russian companies registered in the State Register of the Russian Federation and certified more than 500 kinds water meters.Among the largest producers, whose products are in demand in the Russian market, companies such as: ABB, "Zenner-Vodopribor", Viterra, Wehrle, a group of companies "Mytischinskaya heating system", "Rise ER" and others. Among them are companies that collect theirproducts in Russia from imported components and licenses for foreign companies, firms that use domestic developments and own components, as well as those used to-torye products completely made by another manufacturer, but by arrangement with him which put its stamp on the device.A variety of water meters reflects the urgent need for the Russian market in these devices.
Qmax - maximum flow rate (flow rate) at which the meter can work normally no more than 1 hour.
Qn - nominal flow rate (flow rate), which is equal to half of the maxi-mum flow rate.Is the design flow rate for vodoschet Chica - flow rate at which the device should function normally in Techa-of all life.
Qmin - minimum flow rate (flow rate) at which the meter readings are rejected within the margin of error.
Qt - Transition flow (flow rate) at which the maximum permissible error of a water meter is changed.
dimension flow rate (flow) - m3 / h.
AB Preobrazhensky, MD
On materials "Aqua-Therm"