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Selection of Flow Meters for Measuring Water

The measurement of water flow is not very difficult. Most flow meters of different principles can be used to measure the flow of water, but they are not necessarily good enough to be installed casually.  Normally  we choose magnetic flow meters, vortex flow meter, liqid turbine flow meters to measure different kind of water . We may have to measure slurry flow ,RO water , portable water flow , we choose different kinds of flow meters according to different waters .The following is a simple analysis of the advantages and disadvantages of the flow meters used to measure various water quality flows.

flow meter

1. The measured medium with high sediment content. Flow measurement medium with high sediment content are common in raw water. If throttle differential pressure flow meter or uniform-speed pipe differential pressure flow meter is selected, the pressure and discharge valves are often blocked by sediment, which affects the use. In contrast, insertion type vortex flow meter and insertion type electromagnetic flow meter will not occur such a situation.
Large caliber flow meter usually has low flow velocity, and sediment in the water is easy to deposit in the inner wall of the measuring tube, which reduces the flow cross-section area and leads to high flow indication. Therefore, it should be cleaned up regularly.

2. Measuring medium for process monitoring and control.
Water flow meters used for process monitoring and control generally require less accuracy than those used for custody transfer, mainly considering reliability, price and the type of output signals. The orifice plate flow meter is still the most widely used device in industrial and mining enterprises. In the new device, people prefer to use vortex flow meter, magnetic flow meter and liquid turbine flow meters, because the traditional orifice plate flow meter installation complex, maintenance workload, pressure loss, open-air installation of the instrument also need to consider anti-freezing, and vortex flow meter,mag meter, liquid turbine flow meter installation and maintenance are very simple,. Orifice plate has been squeezed out of the market. However, vortex flow sensor, electromagnetic flow meter and turbine flow sensor can only solve the problem of partial flow measurement, because the larger diameter vortex flow sensor is more expensive than the same diameter electromagnetic flow meter, and the largest diameter vortex flow meter can only be DN300 ~ DN400. The smallest diameter vortex flow meter is now DN15, with a minimum measurable flow rate of 0.32/m3h, while the electromagnetic flow meter has a diameter of DN2.5-DN3000 and a measurable flow rate of 0.0053-305000m3/h, thus covering a much wider area than the vortex flow meter. The vortex street can only reach about 0.4m/s at the lowest velocity that can be measured, while the electromagnetic flow meter can measure normally at 0.1m/s.

Large-aperture electromagnetic flow meter is also very expensive, and the saving scheme is to select the plug-in flow meter, which is commonly used in the uniform speed tube, insertion type vortex flow meter and insertion type electromagnetic flow meter, etc. The insertion type vortex flow meter can measure the velocity of the lower limit of 0.32m/s, and the electromagnetic flow probe can measure the flow of the lower limit is unlimited, but the error is slightly larger. Some, about (+ 0.2%R+1mm/s).

3. Measuring medium in gas-liquid equilibrium state. To measure the flow rate of water in a vapor-liquid equilibrium state, such as the outlet water of boiler deaerator tank, the flow meter should be installed after the booster pump. If it is installed before the booster pump, because the flow meter always has a certain pressure loss, the water in the vapor-liquid equilibrium state will cause partial liquid vapor due to the pressure reduction. The higher the value of the flow meter is.

4. Sewage flow measurement. Sewage is characterized by dirt, and some of them are corrosive. The sewage transported by pipeline can be measured by electromagnetic flow meter, and the sewage discharged by open channel is suitable for measurement by open channel flow meter.

5. deionized water flow measurement. Deionized water and high-purity distilled water are extremely pure water, and their conductivity is about three orders of magnitude less than that of general electromagnetic flow meter, so they can not be measured by electromagnetic flow meter.We can choose vortex flowmeter and liquid turbine flow meter to measure clean water with low conductivity.
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