What is a mass flow meter used for and how does it work?

The mass flow meter is a thermally sensitive measurement, and the flow rate is measured by the molecular mass taken away by the split molecules, because it is a thermally sensitive measurement, so it will not affect the measurement results due to changes in gas temperature and pressure. Mass flow meter is a more accurate, fast, reliable, efficient, stable and flexible flow measurement instrument, which will be more widely used in petroleum processing, chemical industry and other fields, and is believed to show great potential in promoting flow measurement. The mass flow meter cannot control the flow rate, it can only detect the mass flow of liquids or gases, and output the flow value through analog voltage, current or serial communication.

However, a mass flow controller is an instrument that can detect and control at the same time. In addition to the measuring part, the mass flow controller itself is equipped with a solenoid regulating valve or piezoelectric valve, so that the mass flow control itself constitutes a closed-loop system for controlling the mass flow of the fluid. The setpoint of the mass flow controller can be provided by analog voltage, analog current, or by computer or PLC.

Here are some of the well-known brands recognized in the flowmeter industry that are widely recognized and have a great reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following are the top ten domestic first-line valve brand manufacturers in 2022-2023, but for reference only: Suzhou Neway Valve Co., Ltd., Shanghai Guanlong Valve Machinery, Shanghai Qizhong Valve Manufacturing, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

The structure and principle of the mass flow meter are introduced as follows:

The structure of the mass flow meter consists of a sensor and a transmitter for signal processing, which together with the flow totalizer form a flow measurement system.

In the housing of the sensor there is a pair of parallel measuring tubes, which are mounted on an electromagnetic drive coil at the end of the tube. The measurement principle of the mass flow meter is based on Newton's second law of motion, and the specific principle is: the mass flow meter adopts thermal measurement, and the flow rate is measured by the molecular mass taken away by the split molecules, because it is measured by the thermal inductive method, so it will not affect the measurement results because of the change of gas temperature and pressure.

Advantages and disadvantages of mass flow meters:

First, the advantages. 1. The mass flow meter directly measures the mass flow rate of the fluid, and the current signal converted by the transmitter does not need to be opened.

2. Long service life and low maintenance rate: the measuring body of the mass flow meter is a U-shaped pipe, the two open ends of the U-shaped pipe are fixed, and the fluid flows in and out, there are no obstacles in the pipeline, there are no moving parts, there are few fault factors, and it is convenient to install and maintain.

Second, the shortcomings. 1. **Higher: For users who are used to rotameters, mass flowmeters are indeed more expensive.

2. High maintenance costs: in principle, the measurement products should be calibrated regularly; Although the failure rate of the product is different for different brands, there is a possibility of failure, so it is generally necessary to have some calibration maintenance costs. Due to the different charging policies of each manufacturer, the different use of users, and the different product failure rates, the maintenance expenses of users may be different.

1 What is a mass flow meter:

Mass flow meter

English Mass Flow Meter (MFM) is a precision sensor used to quickly and accurately measure the flow rate of process gas. The mass flow meter mentioned here is mainly used in low pressure, small flow of single or mixed gas, low pressure is generally below 1MPa, up to 3MPa; The flow range is generally as follows:; Single gases such as common air, helium, argon, etc., are required to be relatively dry and pure; For gas mixtures, the type and proportion of gases need to be specified.

Mass flow meter

What parameters are available:

The Ease Mass Flow Meter can accurately obtain the five parameters of the gas: real-time temperature, pressure, working condition flow, standard flow rate and cumulative flow rate.

Mass flow meter

The units are: generally: SLPM (liter minutes under standard conditions) and SCCM (milliliter minutes under standard conditions), both are volume flow units under standard conditions, and the ease standard condition is defined as and 25.

4. The composition of the mass flow meter:

Ease laminar flow mass flow meter

It is mainly composed of six parts: laminar flow element, differential pressure sensor, pressure sensor, temperature sensor, circuit design, and software algorithm.

The working principle of 5 laminar flow differential pressure mass flow meter:

The principle of laminar differential pressure, based on Hagenpoisauer's law.

When the gas is in a laminar flow state when the temperature, pipe diameter and other parameters are constant, the volume flow rate is calculated by obtaining the pressure difference signal at both ends of the laminar flow element, and then the standard volume flow rate is obtained by correcting the temperature, pressure and other parameters.

Ease of flow meter

Schematic diagram of the structure:

6. Communication of mass flow meter:

Ease of flow meter

Through RS485, PROFIBUS and other digital signals, 0-5V-20mA analog signals or touch display panels can be used to switch media, change standard definitions, display parameters and other operations.

1. The basic principle of the mass flow meter is to use an external heat source to heat the measured fluid in the pipeline, and the heat energy flows with the fluid, and the mass flow rate of the fluid is reflected by measuring the heat (temperature) change caused by the fluid flow.

2. When the composition of the fluid is determined, the specific heat of the constant pressure of the fluid is a known constant. Therefore, it can be seen from Yu Yu's above equation that if the heating power is kept constant, the mass flow rate can be obtained by measuring the temperature difference; If the constant temperature difference method is used, i.e., the temperature difference between the two points is kept unchanged, the mass flow rate can also be calculated by measuring the heating power. Because the constant temperature difference method is relatively simple and easy to implement, it has many practical applications.

This type of flow meter is mostly used for the measurement of larger gas flows.

3. In order to avoid the temperature measurement element being polluted and corroded by the fluid due to direct contact with the measured fluid of the erected old section, a non-contact measurement method can be adopted, that is, the heater and the temperature measuring element are installed outside the thin-walled tube, and the fluid passes through the thin-walled tube.

4. Non-contact measurement method, suitable for small diameter pipeline micro flow measurement. When used for large flow measurements, the shunt method can be used, that is, only a partial flow rate is measured, and then the total flow rate is obtained to expand the measuring range.

The mass flow meter package includes both direct and indirect mass flow meters. The indirect mass flow meter is a flow meter that measures the mass flow rate by combining the ordinary volumetric flow meter and the density meter. Direct mass flow meters can directly measure the mass flow of fluids, mainly Coriolis mass flow meters such as slip volume flow meters and thermal gas mass flow meters.

Xiamen Hongkong Instrument specifically introduces the working principle of these two direct mass flow meters.

Different flow meters work differently.

The Chaozheng Hall Acoustic Flowmeter adopts the principle of time-difference measurement: after the signal emitted by one probe passes through the pipe wall, the medium, and the other side of the pipe wall, it is received by another probe, and at the same time, the second probe also transmits the signal and is received by the first probe. Due to the influence of the medium flow velocity, there is a time difference δt between the two, and the conversion relationship between the flow velocity v and the time difference δt can be obtained according to the estimation v=(C2 2L) δt, and then the flow value q can be obtained.

The working principle of the turbine flowmeter orange lift is the main type of velocity flowmeter, when the measured fluid flows through the turbine flowmeter sensor, under the action of the fluid, the impeller rotates under the force, and its speed is proportional to the average flow rate of the pipeline, at the same time, the blade periodically cuts the magnetic field lines generated by the electromagnet, changes the magnetic flux of the coil, according to the principle of electromagnetic induction, the first circle will induce a pulsating potential signal, that is, the electric pulse signal, the frequency of the electric pulsation signal is proportional to the flow rate of the measured fluid.

The working principle of the open channel flowmeter is to use ultrasonic technology to measure the fluid level height, and then calculate the flow rate through the microprocessor inside the instrument. Due to their non-contact measurements, open channel flow meters can be used in harsh environments. Under the control of the microcomputer, the open channel flowmeter emits and receives ultrasonic waves, and calculates the distance between the open channel flowmeter and the measured liquid level according to the transmission time, so as to obtain the liquid level height, because there is a certain proportional relationship between the liquid level and the flow rate, the liquid flow rate q can be finally obtained according to the calculation formula.

The English name of the flowmeter is flowmeter, which is defined by the National Committee for the Examination and Approval of Scientific and Technical Terminology as: an instrument that indicates the measured flow rate and/or the total amount of fluid in a selected time interval. In simple terms, it is a meter used to measure the flow of fluid in a pipe or open channel.

The unit m3 h is commonly used in engineering, which can be divided into instantaneous flow rate and cumulative flow rate, instantaneous flow is the amount of effective cross-section of closed pipeline or open channel per unit time, and the material flowing through can be gas, liquid and solid; The cumulative flow rate is the cumulative amount of fluid flowing through the effective section of a closed pipe or open channel at a certain interval (one day, one week, one month, one year). The cumulative flow can also be obtained by integrating the instantaneous flow with the time, so the instantaneous flowmeter and the cumulative flowmeter can also be converted to each other.

The working principle of the flowmeter is confirmed according to the type of flowmeter, like the working principle of the electromagnetic flowmeter is measured by electromagnetic induction.

Differential pressure flowmeters are measured according to the principle of differential pressure.