What Is a Digital Flow Meter?

The English name of the flowmeter is flowmeter, which is defined by the National Science and Technology Terminology Examination Committee as a meter that indicates the measured flow rate and / or the total amount of fluid in a selected time interval. Simply put, it is an instrument for measuring the flow of fluid in a pipe or open channel.

As early as 1738, the Swiss Daniel Bernoulli measured the water flow using the differential pressure method based on the first Bernoulli equation. Later, the Italian GB Venturi research used Venturi to measure the flow, and published the results in 1791.

In 1886, American Herschel applied Venturi control to a practical measuring device for measuring water flow.

From the beginning to the middle of the 20th century, the original measurement principle gradually matured. People no longer limited their ideas to the original measurement methods, but started a new exploration.

In the 1930s, the method of measuring the flow velocity of liquids and gases using sound waves appeared again, but the method of measuring the flow by sound waves did not make much progress until World War II. The introduction of the Sen flowmeter for measuring the flow of aviation fuel.

After the 1960s of the 20th century, measuring instruments began to develop in the direction of precision and miniaturization.

With the rapid development of integrated circuit technology, ultrasonic (wave) flowmeters with phase-locked loop technology have also been widely used, and the widespread use of microcomputers has further improved the capacity of flow measurement, such as the application of laser Doppler flow meters After the microcomputer, it can process more complex signals.

At industrial sites, instruments that measure fluid flow are collectively called flow meters or flow meters. Yes

Due to the lack of strong national support for the system and mechanism in this industry, China's instrumentation industry lacks high-level compound talents and comprehensive talents who are familiar with and proficient in various disciplines. The capacity for independent innovation is low, and independent intellectual property rights are scarce. The specific manifestation is the scarcity of domestic high-end automation products, and the market competitiveness is not strong.

Modern metrology is a highly integrated product of light, mechanics, electricity, computers, and many basic disciplines. It is sensitive to new technologies. It is one of the products that are updated quickly in modern industrial products. New products are introduced every year, especially in In today's era of rapid development of information technology, competition is becoming increasingly fierce, and a slightly slower development rate will be left behind. Although China has entered the 21st century, many things are still at the level of the early 1980s. Large-scale and high-end instruments and equipment are almost entirely imported. Some specialized instruments are still in the blank state in China, and the quality of low-end products is guaranteed. There are still many problems to be overcome.

Therefore, we must have the national strategic planning and the strong support of related resources to have the opportunity to continue to narrow the gap. If the test equipment company cannot achieve a relatively large scale, then it is difficult to have a long and short strength with the international giants, and the early growth requires huge long-term capital investment.

Flow measurement is widely used in industrial and agricultural production, national defense construction, scientific research and foreign trade, and in various areas of people's life. In the petroleum industry production, from oil extraction, transportation, smelting and processing to trade sales, flow measurement throughout the entire process, flow measurement can not be separated from the flow measurement, otherwise the normal production and trade communication of the oil industry will not be guaranteed . In the chemical industry, inaccurate flow measurement will cause the chemical composition distribution ratio to be out of balance, product quality cannot be guaranteed, and serious production safety accidents will occur. In the power industry production, the measurement and adjustment of liquid, gas, steam and other media flow occupy an important position.

CJ / T1017-1993 Submersible electromagnetic flowmeter 1993-12-01 Obsolete

CJ / T122-2000 Ultrasonic Doppler Flowmeter Construction Department

CJ / T3017-1993 Ministry of Construction of Submersible Magnetic Flowmeter

CJ / T3054.1-1995 Ministry of Construction of Water Flow Metering Mean Speed Tube Flowmeter

CJ / T3063-1997 Ultrasonic Flowmeter for Water Supply and Drainage (Propagation Velocity Difference Method)

GB / T12826-1991 Guidelines for Calculation of Ampacity of Coiled Cables for Mobile Equipment, National Technical Supervision Bureau, 1992-02-01

GB / T17286.1-1998 Verification system for dynamic measurement of volumetric flowmeters for liquid hydrocarbons Part 1: General principles

GB / T17286.2-1998 Verification system for dynamic measurement of liquid hydrocarbon volumetric flowmeters Part 2: Volume tubes

GB / T17286.3-1998 Verification system for dynamic measurement of volumetric flowmeters for liquid hydrocarbons Part 3: Pulse insertion technology National Technical Supervision Bureau 1998-10-01

GB / T17286.4-2006 Verification system for dynamic measurement of volumetric flowmeters for liquid hydrocarbons-Part 4: Guide for volume tube operators

GB / T17288-1998 liquid hydrocarbon volume measurement volumetric flow metering system National Technical Supervision Bureau 1998-10-01

GB / T17288-2009 Volumetric metering system for liquid hydrocarbon volume measurement 2009-10-01 will be implemented

GB / T17289-1998 Liquid hydrocarbon volume measurement Turbine flow metering system National Technical Supervision Bureau 1998-10-01

GB / T17289-2009 Liquid hydrocarbon volume measurement turbine flowmeter metering system 2009-10-01 will be implemented soon

GB / T18604-2001 National Quality Supervision, Inspection and Quarantine for Natural Gas Flow Measurement with Gas Ultrasonic Flowmeter. 2002-08-01

GB / T18659-2002 Measurement of conductive liquid flow in closed pipelines. Performance evaluation methods of electromagnetic flowmeters. National Quality Supervision, Inspection and Quarantine.

There are many types of flow measurement methods and instruments, as well as many classification methods. Before 2011, there were as many as 60 types of flow meters for industrial use. The reason for so many varieties is that there is no one for any fluid, any

Ultrasound

General selection

Can be considered from five aspects, these five aspects are meter performance, fluid characteristics, installation conditions, environmental conditions and economic factors. The five factors are detailed as follows:

• Instrument performance: accuracy, repeatability, linearity, range, flow range, signal output characteristics, response time, pressure loss, etc .;

• In terms of fluid characteristics: temperature, pressure, density, viscosity, chemical corrosion, abrasiveness, scaling, mixed phase, phase transition, electrical conductivity, sound velocity, thermal conductivity, specific heat capacity, isentropic index;

• In terms of installation conditions: pipeline layout direction, flow direction, length of the straight pipe section on the upstream and downstream sides of the test piece, pipeline diameter, maintenance space, power supply, grounding, auxiliary equipment (filters, aerators), installation, etc

• Environmental conditions: ambient temperature, humidity, electromagnetic interference, safety, explosion protection, pipeline vibration, etc .;

• In terms of economic factors: instrument purchase costs, installation costs, operating costs, calibration costs, maintenance costs, instrument life, spare parts, etc.

(2) The selection steps of flowmeter instruments are as follows:

1. Primary selection of available instrument types based on fluid type and five considerations (there are several types for selection);

2. Collect data and price information for primary selection types, and prepare conditions for in-depth analysis and comparison;

3. Use the elimination method to gradually focus on 1 or 2 types, and repeatedly compare and analyze the five factors to determine the pre-selection target.

Precautions

1. The fluid characteristics mainly refer to the pressure, temperature, density, viscosity, and compressibility of the gas. As the volume of the gas changes with temperature and pressure, consideration should be given to whether to compensate for the correction.

2. Instrument performance refers to the accuracy, repeatability, linearity, range ratio, pressure loss, initial flow rate, output signal, and response time of the instrument. When selecting a flow meter, the above indicators should be carefully analyzed and compared to select the one that can meet the requirements of the measurement medium meter.

3. Installation conditions refer to the gas flow direction, pipeline direction, upstream and downstream straight pipeline length, pipe diameter, spatial location, and pipe fittings, etc., which will affect the accurate operation, maintenance and service life of the gas gas flow meter.

4. Economic factors refer to the purchase cost, installation cost, maintenance cost, calibration cost, and spare parts, etc., which are also affected by the performance, reliability, and life of the gas meter.

5. Accuracy level and function The accuracy level of the instrument is selected according to the measurement requirements and application occasions, so as to be economical and cost-effective. Such as for trade settlement, product transfer and energy metering,

In the selection of accuracy level, such as 1.0 level, 0.5 level, or higher, for the occasion of process control, select different accuracy levels according to the control requirements. In some cases, only the process flow is detected, and precise control and measurement are not required. You can choose a lower accuracy level, such as 1.5, 2.5, or even 4.0. At this time, you can choose a cheaper one.

(1) When the indication value of the flow control instrument system reaches the minimum, first check the on-site detection instrument. If it is normal, the fault is displayed on the instrument. When the indication of the on-site testing instrument is also the smallest, check the opening degree of the regulating valve. If the opening degree of the regulating valve is zero, it is often a failure between the regulating valve and the regulator. When the on-site testing instrument indicates the smallest and the opening degree of the regulating valve is normal, the failure may be caused by insufficient system pressure, system pipeline blockage, pump failure, medium crystallization, and improper operation. If it is a fault in the instrument, the reasons are: the orifice plate differential pressure flow meter may be a positive pressure induced pressure pipe blockage;

Drivers According to the International Energy Agency (IEA) forecast, from 2007 to 2030, the world will need to accumulate a total investment of 26.0 trillion US dollars in energy infrastructure (in 2007 dollars). Among them, the electric power industry invested 13.6 trillion US dollars, accounting for 52.3% of the total investment. By 2030, the oil, gas and electricity infrastructure in many parts of the world will need to be replaced. In the long run, foreseeable energy investment will bring a lot of development space for the application of flow meters in the oil and gas and energy industry sectors.

Faced with a fierce competition environment, and in order to respond to the global demand for energy conservation and emission reduction, users in various industries have paid more attention to the operating efficiency of production plants and reduced energy consumption as much as possible to improve competitiveness. Therefore, a large amount of investment is used to improve the automation level of the factory and the collection and real-time monitoring of field data to improve the process control efficiency of the factory. For example, in the oil and gas and energy industries, closed-flow transmission facilities require reliable fluid measurement equipment; in the chemical and pharmaceutical industries, high-precision flow meters are required. Various trends will definitely drive the development of sensors and field equipment (including flow meters). .

Electronic technology, such as digital signal processing (DSP) and microprocessors, is being introduced into the flowmeter, which enables the flowmeter to have self-diagnostic functions and better communicate with the production control level. The improved performance better meets the needs of industry users, creating more market application space for flow meters.

Inhibiting factors The current global economic situation needs to be further boosted, and demand for industrial products is not strong. Users in many industries have slowed investment in new projects or suspended equipment upgrades, waiting for signs of global economic recovery. Therefore, in the short term, this will have a certain impact on the development prospects of flow meters in their main application industries.

There are many manufacturers in the global flowmeter market, and the competition is extremely fierce. At the same time, manufacturers of flowmeters are facing more demanding prices from industry users. In order to allow products to penetrate the major industries of flowmeter applications, price competition between manufacturers is inevitable. This phenomenon is common in emerging economies, especially China. Price often becomes the most important determinant of purchasing behavior. In the long run, manufacturers pay more attention to price strategies, resulting in insufficient product innovation and hindering market development.

Challenges for flow meters

Traditional mechanical flow meter, example

Float meter

For example, differential pressure flowmeters, volumetric flowmeters, and variable area flowmeters are already in the popularization stage, with fierce price competition, decreasing profit margins, fewer technological innovations, and relatively mature markets. Realizing product differentiation and customized production is an important breakthrough point for manufacturers in the fierce competition in mature markets. According to Frost & Sullivan's analysis of the needs of industry users, the user community expects manufacturers to provide automated equipment that brings tangible benefits to the production process. Users will have specific requirements during the application of the product, such as: in the special environment of the petrochemical industry, they need a rugged design and explosion-proof certification; the user needs a Coriolis flowmeter with a straight tube design. How to effectively obtain the actual needs of users and improve traditional products is a big challenge for manufacturers to differentiate and customize the production process.

Guide users to accept and use new technology flowmeters, such as SBL target flowmeters, ultrasonic flowmeters, electromagnetic flowmeters, mass flowmeters, and V-cone flowmeters (orifice flowmeters). Strong yet another challenge.

In addition, while new technology flowmeters are being continuously introduced into various industries, fast and effective after-sales service is equally important for manufacturers. In particular, the use of flow meters based on FOUNDATION fieldbus and ProfibusPA bus has certain requirements for software technology, and effective services can provide users with more suitable solutions and be closer to users.

Flow meter looks to the future

The revolution from mechanical flow meters to electronic technology flow meters is one of the most important development trends of flow meters. Target flowmeters, electromagnetic flowmeters, ultrasonic flowmeters, vortex flowmeters, and V-cone flowmeters (orifice flowmeters) work using electrical principles, thereby avoiding moving parts that need to be replaced during mechanical flowmeter operation. At the same time, the self-diagnostic function is introduced into the flow meter, which makes the flow meter not only a simple measurement tool, but also more for system maintenance purposes, such as: empty pipe detection and self-checking. In addition, the combination of advanced communication technology in the electronic flow meter enables the control personnel to remotely obtain real-time flow data and historical data at the production site.

According to Frost & Sullivan's research, about 89.0% of the world's current flowmeters use the mAHART communication protocol, because the flowmeters using the mAHART communication protocol are lower than the flowmeters using the fieldbus protocol, and the introduction of fieldbus system It is also a significant cost for users. However, as industry users continue to improve their automation level, they hope to obtain more information besides flow data from flow measurement, such as diagnostic information and status detection. These data transmissions need to rely on fieldbus support. In addition, manufacturers such as Siemens and Emerson are working hard to implement fieldbus protocol flow measurement technology. It is believed that this will definitely promote the application prospect of fieldbus protocol flowmeters in various industries.

In addition, wireless technology flowmeters are gradually being accepted by users. Fluid measurement in harsh environments is a good application space for wireless technology. However, it will take some time for users to fully accept and popularize wireless technology flow meters.