Discussion on how to carry out selection technique for liquid flowmeter

In recent more than 10 years with the rapid development of integrated circuit technology, as well as China's economic and technological strength, many well-known domestic enterprises have developed a variety of series of ultrasonic flowmeter, cost-effective advantage. So in recent years in metallurgy, power generation, cement and other industries have been widely used.

Flow meter selection should be based on production requirements, from the actual situation of product supply, comprehensively consider the safety, accuracy and economy of the measurement, and according to the nature and flow of the measured fluid to determine the flow sampling device and the type and specifications of the measuring instrument.  

There are many kinds of measuring liquid flowmeter, but it is widely used in electromagnetic flowmeter and ultrasonic flowmeter. The characteristics of these two types of traffic are described below.

First, the electromagnetic flowmeter:

1. principle of electromagnetic flowmeter
The basic principle is Faraday's law of electromagnetic induction, that is, the conductor in the magnetic field when cutting the magnetic line movement in its two ends of the induction electromotive force, through the detection of inductive electromotive force, and calculated to obtain the measured flow.

2. type of electromagnetic flowmeter:
Electromagnetic flowmeter in charge of the channel flowmeter and the plug-in flowmeter

3. characteristics of electromagnetic flowmeter:

A, the front straight pipe segment is less demanding than most other flow meters.
B, measuring range is large, usually -:1~ -:1, and the optional flow range is wide. The full-value liquid flow rate can be0.5~10m/sselected within. Some models can expand and reduce traffic as needed on-site(For example, a4Digit potentiometer Set instrument constant)do not have to be removed for offline real stream.
C, caliber range than other varieties of flow meter wide, from a few millimeters to3m. Measurable positive and negative two-way flow, but also measured pulsating flow, as long as the pulsation frequency is less than the excitation frequency. The instrument output is essentially linear.
D, easy to select with fluid contact parts of the material variety, can be applied to corrosive fluids.

4, electromagnetic flowmeter disadvantages :

A, pipe-type electromagnetic flowmeter installation, maintenance is not convenient, plug-in electromagnetic flowmeter installation is convenient, but the measurement accuracy, reliability is lower than the pipeline type flowmeter.
b, the electrode of the electromagnetic flowmeter is more susceptible to fouling, especially in the pipeline after the pump stopped operation, the dirt in the medium is easy to attach to the measuring electrode, causing the flow meter false signal issued.

Second, ultrasonic flowmeter

1. principle of ultrasonic flowmeter

When the ultrasonic wave travels in the flowing fluid, the liquid has a small effect on the ultrasonic transmission time, and the change of the transfer time is proportional to the liquid velocity. Therefore, the received ultrasonic wave can detect the flow rate of the fluid, which translates into flow. According to the method of detection, it can be divided into different types of ultrasonic flowmeter such as propagation velocity difference method, Doppler method, beam offset method, noise method and correlation method.

2. Characteristics of Ultrasonic flowmeter

A, ultrasonic flowmeter is a non-contact instrument, suitable for measuring difficult to contact and observe the fluid and large diameter flow. It is linked to the water level meter for flow measurement of open flow. The use of ultrasonic flow without installing the measuring element in the fluid will not change the flow state of the fluid, no additional resistance, the installation and maintenance of the instrument can not affect the production pipeline operation, thus is an ideal energy-saving flowmeter.
b, ultrasonic measuring instrument flow measurement accuracy is almost unaffected by the measured fluid temperature, pressure, viscosity, density and other parameters, due to non-contact measurement characteristics, and then with a reasonable electronic circuit, a meter can adapt to a variety of pipe diameter measurement and a variety of flow range measurement. The adaptability of ultrasonic flowmeter is also incomparable with other instruments. Ultrasonic flowmeter has some of the above advantages so it is more and more attention and product serialization, general development, has been made into different channels of the standard, high-temperature, explosion-proof, wet-type instrument to adapt to different media, different occasions and different pipeline conditions of flow measurement.

3, the shortcomings of the ultrasonic flowmeter

Ultrasonic flowmeter disadvantage is that the price is more expensive, the past ultrasonic flowmeter is mainly used in power plants, such as: water Turbine inlet volume, steam turbine circulating water, such as large diameter flow.

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Discussion on how to carry out selection technique for liquid flowmeter