Coriolis mass flow meter
Coriolis mass flowmeter in the domestic application started late, but it can directly measure the mass flow of fluids in the pipeline, its main features are as follows.
(1)Advantages: high measurement accuracy; wide range of measurement fluids, including liquids containing trace gases; installation of upstream and downstream straight pipe section without requirements.
(2) disadvantages: can not be measured for low-density media and low-pressure gases, the gas content of the liquid exceeds a certain limit will affect the measurement accuracy; sensitive to external vibration interference, in order to prevent the impact of pipeline vibration, most of the sensor installation and fixing requirements are higher; restricted pipeline caliber, can not be used for larger diameters; measurement of pipeline fouling or wear of the inner wall will affect the accuracy of the measurement; pressure loss is greater.
(3) Application. Coriolis mass flowmeter is particularly suitable for the viscosity of the medium, because of its accuracy and stability, therefore, developed countries in the chemical industry, pharmaceuticals, petroleum, energy, food and other industrial areas have been a large number of use of this type of flowmeter, in the transportation sector is commonly used in the measurement of fluid pipeline transmission.
Ultrasonic flowmeter
Ultrasonic flowmeter can be roughly divided into insertion type, pipe section type, external clamping type and portable type, etc., and its main features are as follows.
(1) Advantages: non-contact measurement, suitable for large caliber, large flow measurement; no pressure loss, does not interfere with the fluid; suitable for any liquid; easy installation and maintenance.
(2) Disadvantages: the measured fluid contains bubbles or murmurs, it will affect the measurement accuracy; the temperature range of the measurable fluid by the ultrasonic transducer and the coupling between the transducer and the pipeline temperature resistance degree of restriction, high temperature of the measured fluid sound transmission velocity of the original data is incomplete.
(3) Application. Ultrasonic flowmeter in the petroleum, chemical, metallurgy, electric power and other fields are widely used, often used in the factory discharge fluid, dirty process fluid and other flow measurement, as well as the operation area of the pipeline of the West-East gas pipeline measurement.
Electromagnetic flowmeter
(1) Advantages: suitable for measuring liquid-solid two-phase fluid containing solid particles; no pressure loss; not affected by fluid properties.
(2) Disadvantages: can not measure the conductivity of the liquid is low, such as petroleum products and organic solvents, etc.; can not be used for higher temperature measurement of liquids; can not measure the gas, steam, and contain more larger bubbles of liquid.
(3) Application. Electromagnetic flowmeter in large caliber instruments are often used in water supply and drainage projects; small and medium diameter instruments are often used in high requirements or difficult to measure occasions, such as strong corrosive liquids in the chemical industry, the paper industry to measure the pulp liquid and the black liquid; small diameter, tiny caliber is commonly used in the pharmaceutical industry, the food industry, the biochemical industry and other fields.
Vortex Flow Meter
Vortex flowmeter is one of the newest types of flowmeter, but its development is rapid, and now it has become a common category, its main features are as follows.
(1)Advantages: wide range of applications, can be applied to liquid, gas and steam and other flow measurement; pressure loss is small; easy to install, simple and solid structure.
(2) Disadvantages: poor anti-interference ability; installation requirements before and after the straight pipe section; in the pulsating flow, multiphase flow is still a lack of application experience.
(3) Application. Vortex flowmeter has a very wide range of applications, commonly used in factory water supply systems, the application of high viscosity, low flow rate, small diameter case will be limited.
General guidelines for the selection of liquid flow meters
In order to correctly select the liquid flowmeter, first of all, each type of flowmeter must have a basic understanding of the measurement principle, structure, performance, etc., and then combined with the specific measurement conditions, taking into account the accuracy of the measurement, economy and other factors, to determine the type of liquid flowmeter and specifications.
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Determine the characteristics of the measured fluid. Clearly measured fluid is what kind of media, that is, to understand the measured fluid is liquid, gas or steam; measured fluid properties, such as flow rate, density, viscosity, corrosion and compression, etc.; measured medium temperature, pressure, and its high and low changes in the normal operation range; measured flow range of fluids, including the minimum flow rate, the usual flow rate, the maximum flow rate; fluid flow state is laminar or turbulent; whether there is a pulsation; And whether the fluid flow is in a full pipe state, these factors will directly affect the selection of liquid flow meter.
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Determine the technical requirements for flow measurement. Define the accuracy of the flow meter, that is, to determine the accuracy of the measured fluid requirements; flow measurement of repeatability, that is, under certain conditions, many times repeatedly measure the same amount of the measured value is the same; flow measurement results of the expression, is the quality of flow or volume flow, is the instantaneous flow or cumulative flow; flow meter signal output, whether it is necessary to have a remote transmission function; flow measurement results of the display, is the mechanical meter Flow measurement results of the display mode, whether mechanical or electronic meter head. If the flow meter does not match the technical requirements of the measured fluid, it will also lead to measurement errors.
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Determine the installation conditions of the liquid flow meter. Flow meter measurement object is generally based on pipeline liquids, so the flow meter is generally installed in the pipeline for measurement, then before selecting the liquid flow meter, it is necessary to understand the site conditions, to determine whether or not the need for explosion-proof type of flow meter; instrumentation installation, whether outside the pipeline or in the closed pipeline, whether or not the need to break the pipe; if the break pipe, the process pipeline vibration and the ambient temperature and humidity Conditions, etc., try to choose a permanent pressure loss, easy to install and maintain the liquid flow meter. 4.
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Determine the economics of operation. Liquid flow meter structure of different prices and pressure losses are different, comprehensive consideration, the price is a one-time investment, but if the pressure loss is not selected properly, then the liquid flow meter will make the fluid flow in the long-term operation of the kinetic energy loss is huge, resulting in energy waste.