Comparison of advantages and disadvantages of the

Comparison of advantages and disadvantages of various flowmeters

1 turbine flowmeter

turbine flowmeter is the main type of speed flowmeter. It uses a multi blade rotor (turbine) to sense the average flow rate of fluid, and deduces the instrument of flow or total amount. Generally, it is composed of sensor and display instrument, and it can also be made into an integral type

turbine flowmeter, positive displacement flowmeter and Coriolis mass flowmeter are the three types of flowmeter with the best repeatability and accuracy. In 2017, the amount of imported waste paper fell by 10% year-on-year. As one of the top ten types of flowmeter, its products have developed into the scale of multi variety and multi series mass production

advantages: (1) high accuracy, belonging to the most accurate flowmeter among all flowmeters; (2) Good repeatability; (3) Good zero disturbance free ability; (4) Wide range; (5) Compact structure

disadvantages: (1) the calibration characteristics cannot be maintained for a long time; (2) The physical properties of fluid have a great influence on the flow characteristics

Application Overview: turbine flowmeter is widely used in the following measurement objects: petroleum, organic liquid, inorganic liquid, liquefied gas, natural gas and cryogenic fluid system. In Europe and the United States, turbine flowmeter is the natural metering instrument second only to orifice flowmeter in terms of consumption. Only the Netherlands has adopted more than 2600 gas turbine flowmeters with various sizes and pressures from 0.8 to 6.5MPa on natural gas pipelines, They have become excellent natural gas measuring instruments

2 vortex flowmeter

vortex flowmeter is an instrument that places a non streamlined vortex generator in the fluid, and the fluid alternately separates and releases two strings of regularly staggered vortex generators on both sides of the generator

vortex flowmeter can be divided into stress type, strain type, capacitance type, thermal type, vibrating body type, photoelectric type and ultrasonic type according to frequency detection mode

vortex flowmeter is the youngest type of flowmeter, but it has developed rapidly and has become a general type of flowmeter at present

advantages: (1) simple and firm structure; (2) There are many kinds of applicable fluids; (3) High accuracy; (4) Wide range; (5) Small pressure loss

disadvantages: (1) not suitable for low Reynolds number measurement; (2) Long straight pipe section is required; (3) The instrument coefficient is low (compared with the turbine flowmeter ethylene-4 fluoroethylene copolymer, which is highly transparent, highly stain resistant, easy to clean, high strength and corrosion resistant); (4) The instrument is still lack of application experience in pulsating flow and multiphase flow

3 electromagnetic flowmeter

electromagnetic flowmeter is an instrument for measuring conductive liquid made according to Faraday's law of electromagnetic induction

electromagnetic flowmeter has a series of excellent characteristics, which can solve the problems that other flowmeters are not easy to apply, such as the measurement of dirt flow and corrosion flow

in the 1970s and 1980s, electromagnetic flow made a major breakthrough in technology, making it a widely used type of flowmeter, and the percentage of its use in flow instruments continues to rise

advantages:

(1) the measurement channel is a smooth straight pipe, which will not be blocked. It is suitable for measuring liquid-solid two-phase fluids containing solid particles, such as pulp, mud, sewage, etc

(2) no pressure loss caused by flow detection and good energy saving effect

(3) the measured volume flow is actually not significantly affected by the changes of fluid density, viscosity, temperature, pressure and conductivity; (4) Large flow range and wide caliber range; (5) Corrosive fluids can be applied

disadvantages: (1) cannot measure liquids with low conductivity, such as petroleum products; (2) Gas, steam and liquid containing large bubbles cannot be measured; (3) Cannot be used at higher temperatures

Application Overview: electromagnetic flowmeter has a wide range of applications, and large-diameter instruments are mostly used in water supply and drainage projects; Small and medium caliber are often used in high demand or difficult to measure occasions, such as blast furnace tuyere cooling water control in the iron and steel industry, pulp liquid and black liquid measurement in the paper industry, strong corrosive liquid in the chemical industry, and pulp in the non-ferrous metallurgical industry; Small caliber and micro caliber are often used in places with health requirements, such as pharmaceutical industry, food industry, biochemistry, etc

4 differential pressure flowmeter

differential pressure flowmeter is an instrument that calculates the flow according to the differential pressure generated by the flow detector installed in the pipeline, the known fluid conditions and the geometric size of the detector and the pipeline

differential pressure flowmeter is composed of primary device (detector) and secondary device (differential pressure conversion and flow display instrument). Differential pressure flowmeter is usually classified in the form of detection parts, such as orifice flowmeter, venturi flowmeter, averaging tube flowmeter, etc

the secondary devices are various mechanical, electronic and electromechanical integrated differential pressure gauges, differential pressure transmitters and flow display instruments. It has developed into a large class of instruments with a high degree of Standardization (serialization, generalization and standardization) and a large variety of specifications. It can measure not only flow parameters, but also other parameters (such as pressure, material level, density, etc.)

the detection parts of differential pressure flowmeter can be divided into throttling device, hydraulic resistance type, centrifugal type, dynamic head type, dynamic head gain type and jet type according to its action principle

test pieces can be divided into two categories according to their degree of Standardization: standard and non-standard

the so-called standard test piece is designed, manufactured, installed and used in accordance with the standard documents, and its flow value and measurement error can be determined without real flow calibration

non standard test pieces are those with poor maturity and have not been listed in international standards

differential pressure flowmeter is the most widely used flowmeter, and its usage ranks first in all kinds of flow instruments. In recent years, due to the advent of various new flow meters, its usage percentage has gradually decreased, but at present, the most important polar 2 will become the first battery electric vehicle (Bev) class I flow meter of Volvo car group

advantages:

(1) the orifice plate flowmeter with the most applications has firm structure, stable and reliable performance and long service life

(2) it has a wide range of applications, and so far there is no type of flowmeter that can be compared with it

(3) the detection parts, transmitters and display instruments are produced by different manufacturers respectively, which is convenient for scale economic production

disadvantages: (1) the measurement accuracy is generally low; (2) The scope is narrow, generally only 3:1~4:1; (3) High requirements for on-site installation conditions; (4) Large pressure loss (refers to orifice, nozzle, etc.)

Application Overview:

differential pressure flowmeter has a wide range of applications, and it is applied to various objects in the flow measurement of closed pipelines, such as fluid: single-phase, mixed phase, clean, dirty, viscous flow, etc; Working state: normal pressure, high pressure, vacuum, normal temperature, high temperature, low temperature, etc; Pipe diameter: from several mm to several m; Flow conditions: subsonic, sonic, pulsating flow, etc. Its consumption in various industrial sectors accounts for about half of the total consumption. (2) digital technology will deeply change the production mode and industrial form of manufacturing industry, accounting for 1/4~1/3 of the total consumption of metrology

5 rotameter

rotameter, also known as rotameter, is a kind of variable area flowmeter. In a vertical cone tube expanded from bottom to top, the gravity of the float with circular cross-section is borne by hydrodynamic force, so that the float can rise and fall freely in the cone tube

rotameter is the flowmeter with the widest application range next to differential pressure flowmeter, especially in small and micro flow

in the mid-1980s, the sales amount of Japan, Western Europe and the United States accounted for 15% - 20% of the flow meters. China's output was estimated to be 120000-140000 units in 1990, of which more than 95% were glass cone tube rotameters

features: (1) the glass cone tube rotameter is simple in structure and easy to use, with the disadvantage of low pressure resistance and great risk of glass tube fragility; (2) Suitable for small diameter and low flow rate; (3) Low pressure loss

6 positive displacement flowmeter

positive displacement flowmeter, also known as constant displacement flowmeter, referred to as PD flowmeter, is the most accurate type of flow instruments. It uses mechanical measuring elements to continuously divide the fluid into a single known volume part, and measures the total volume of the fluid according to the number of times that the measuring chamber repeatedly fills and discharges the fluid in this volume part

the positive displacement flowmeter can be divided into elliptical gear flowmeter, scraper flowmeter, double rotor flowmeter, rotary piston flowmeter, reciprocating piston flowmeter, disk flowmeter, liquid seal rotary drum flowmeter, wet gas meter and membrane gas meter according to its measuring elements

advantages: (1) high measurement accuracy; (2) The installation conditions of pipelines have no influence on the measurement accuracy; (3) It can be used for the measurement of high viscosity liquids; (4) Wide range; (5) The direct reading instrument can be accumulated directly without external energy. The total amount is clear and easy to operate

disadvantages: (1) complex results and huge volume; (2) The type, diameter and working state of the measured medium are relatively limited; (3) Not suitable for high and low temperature occasions; (4) Most instruments are only applicable to clean single-phase fluid; (5) Generate noise and vibration

Application Overview:

volumetric flowmeter, differential pressure flowmeter and rotameter are the three types of flowmeter with the largest use, which are often used for the total amount measurement of expensive media (oil products, natural gas, etc.)

in recent years, the sales amount of PD flowmeter (excluding household gas meter and household water meter) in industrial developed countries accounts for 13% to 23% of flow instruments; China accounts for about 20%. In 1990, the output (excluding household gas meters) was estimated to be 340000 units, of which oval gear type and waist wheel type accounted for about 70% and 20% respectively

7 ultrasonic flowmeter

ultrasonic flowmeter is an instrument that measures flow by detecting the effect of fluid flow on ultrasonic beam (or ultrasonic pulse)

according to the principle of signal detection, ultrasonic flowmeter can be divided into propagation velocity difference method (direct time difference method, time difference method, phase difference method and frequency difference method), beam offset method, Doppler method, cross-correlation method, spatial filtering method and noise method

ultrasonic flowmeter, like electromagnetic flowmeter, is an unimpeded flowmeter because there are no obstructions in the instrument flow channel. It is a kind of flowmeter suitable for solving the difficult problem of flow measurement, especially in large-diameter flow measurement. In recent years, it is one of the rapidly developing types of flowmeter

advantages:

(1) it can be used for non-contact measurement; (2) No flow obstruction measurement, no pressure loss; (3) It can measure non-conductive liquids, which is a supplement to the electromagnetic flowmeter without obstruction

disadvantages:

1) the propagation time method can only be used to clean liquids and gases; Doppler method can only be used to measure the liquid containing a certain amount of suspended particles and bubbles; (2) The accuracy of Doppler method is not high

Application Overview:

(1) the propagation time method is applied to clean, single-phase liquids and gases. Typical applications include factory discharge liquid, strange liquid, liquefied natural gas, etc

(2) gas application has good experience in the field of high-pressure natural gas

3) Doppler method is applicable to two-phase fluids with low heterogeneous content, such as untreated sewage, factory discharge fluid, and dirty process fluid; Usually not suitable for very clean liquids

8 Coriolis mass flowmeter

Coriolis mass flowmeter (hereinafter referred to as CMF) is a direct mass flow instrument made by using the principle of Coriolis force proportional to the mass flow when the fluid flows in the vibrating tube

the application of CMF in China started late. In recent years, several manufacturers (such as Taihang instrument factory) have developed and supplied the market by themselves; Several other manufacturers set up joint ventures or introduce