Do you know which flowmeters correspond to different media? I believe that all gods can be beaten. Do you have any advantages with other flowmeters? The shortcomings are even less known. I want to explain to you what are the advantages and disadvantages of the 8 commonly used flow meters, and what are the disadvantages.Primary pressure flow meterThe differential pressure flowmeter has a long history and is a flow measuring instrument with rich practical experience, mature, complete standard specifications, and complete varieties and specifications. The differential pressure flowmeter uses the principle of Bernoulli equation to measure. When the fluid filled with the pipeline passes through the differential pressure device in the pipeline, the flow will form a local contraction on the differential pressure device, which will increase the flow rate and reduce the static pressure, resulting in a differential pressure. The front and back of the pressure device or the neck produces differential pressure. The greater the medium flow, the greater the differential pressure generated. Therefore, the fluid flow can be measured by measuring the differential pressure. Differential pressure flow meters are divided into two types: standard deviation differential pressure flow meters and non-standard differential pressure flow meters. The standard standard flowmeter is recognized by the International Organization for Standardization and the International Legal Metrology Organization, and is recognized as a universal flowmeter by the international community. It was the only natural gas flow meter before the 1950s, and now it occupies a more important position.The advantages of differential pressure flow meters are as follows:The structure is simple, sturdy, stable in performance, long in use and low in price.Inspection products and differential pressure display instruments can be produced in different production plants, specialization is easy to form scale economy production, and their combination is very flexible and convenient.Standard inspection products are universally used worldwide and are recognized by the International Standards Organization.The standard differential pressure device does not require real flow calibration. As long as the actual calibration is not required for the standard design and processing, the flow measurement can be performed within the known uncertainty range to meet the needs of engineering measurement.The disadvantages of differential pressure flow meters are as follows.The measurement accuracy is generally low.The range is narrow, generally only: 1 to 433601.The site installation conditions should be high.The pressure loss is great.In response to this shortcoming, domestic production plants have introduced a series of improvements in recent years, including integral differential pressure flow meters, fixed throttles, replaceable orifice throttling devices, and the use of standard nozzles. According to the characteristics of the differential pressure flowmeter, if you want to obtain accurate measurement results in work, you must fully grasp the flow measurement method, measurement medium, measurement device, fluid condition, inspection standard, etc. It can be widely used in electric power, chemical industry, petrochemical, petroleum, natural gas, metallurgical light industry and other fields, and is particularly advantageous for flow measurement of high temperature and high pressure media.2 volumetric flowmeterPositive displacement flow meters (also known as constant displacement flow meters) are one of the more accurate types of flow measuring instruments, which use mechanical measuring elements to continuously divide the fluid into a known volume part. It is a flowmeter that repeatedly fills and discharges this volume of fluid, and accumulates the total amount of fluid. Advantages of volumetric flowmeter 3360The measurement accuracy is high.The installation piping conditions will not affect the measurement accuracy of the flowmeter, and there is no need for a straight pipe section in front of the flowmeter.It can be used for the determination of high viscosity liquids.Measuring range width.The direct-reading instrument can directly obtain the cumulative total without external energy, and the operation is clear and convenient.Disadvantages of volumetric flow meters:The machine has a complex structure and large volume.The types, calibers, and working conditions of the tested media are very limited.Not suitable for high temperature and low temperature conditions.Most meters are only suitable for clean single-phase fluids.Cause noise and vibration.The flowmeter uses a long history and complete standard specifications. It is a high-precision instrument suitable for small and medium flow ranges. It is widely used in the determination of the total amount of expensive media such as crude oil, diesel, liquefied petroleum gas, natural gas, and natural gas.Three float flowmeterThe float flowmeter is the flowmeter with the largest range after the differential pressure flowmeter, and plays an important role especially in the small and fine flow. The working principle of the float flowmeter is that the change of flow is directly related to the corresponding flow area of the float position. When the measured fluid passes through the circulation area formed by police officer Li and the rich man from bottom to top, the pressure difference generated at the bottom of the rich forms the rising force of the rich. When the rising force of the rich is greater than the weight of the rich man in circulation, the rich As people rise, the circulation area increases, the flow velocity on the circulation area decreases, and the pressure difference between the upper and lower ends of the rich decreases, and the upward force acting on the rich also decreases. The lift is equal to being submerged by fluid.The advantages of float flow meters are:It can measure the flow of almost all fluids such as liquid, gas, and steam.Simple structure, suitable for on-site indication of flow.As an on-site indicating type flowmeter, it does not require a power source, so the flammable and explosive environment is inherently safe.The pressure loss is small.The requirements for the upstream straight pipe section are lower.It is not affected by various noises (electricity, chemical, fluid, etc.) contained in the liquid.Low price and easy installation.The disadvantages of float flow meters include:Moving parts, pressure loss, etc.Accuracy is affected by changes in fluid physical parameters.Float flowmeter is an intuitive flow indicator or on-site indicator with low measurement accuracy. It is widely used in the measurement and process control of liquid, gas, and steam media in the petroleum, chemical, metallurgical, electric power, food, pharmaceutical, papermaking and other industries.Four-impeller flowmeterThe impeller flowmeter is a velocity flowmeter with complete standard specifications. It has developed into a flowmeter with multiple varieties, full series, multiple specifications, and mass production scale. The measuring fluid impacts the blades and rotates the impeller, and the speed of the impeller changes with the change of the flow. In other words, the flow rate is large, the speed of the impeller is also large. Advantages of impeller flowmeter:The accuracy level is high.The measurement range is wide and the repeatability is good.The pressure loss is small.Easy to install and maintainDisadvantages of impeller flowmeter:Because there are moving parts, the calibration characteristics cannot be maintained for a long time, so regular verification is required.Fluid physical properties (density, viscosity) have a great influence on flow characteristics.The cleanliness of the tested medium is very demanding.The rectifier with high-efficiency rectification function is combined with the impeller flow sensor to form an integrated gas impeller flowmeter. Its characteristic is that under the condition that the upstream resistance flow is an elbow or half-open stop valve, as long as the length of the two-dimensional straight pipe section, the installation space is limited. narrow. The European and American impeller flowmeter is the second legal natural gas flowmeter after the orifice flowmeter. It has developed into a multi-variety, full-series, multi-specification, and large-scale production of natural gas flowmeters, and the standard specifications are also very complete. Impeller flowmeters are also widely used in various departments such as petrochemical industry, scientific research, national defense measurement and so on.5 Electromagnetic flowmeterAccording to Faraday’s law of electromagnetic induction, the electromagnetic flowmeter produces induced electromotive force at both ends when the conductor cuts the magnetic field lines in a magnetic field, and its magnitude can be proportional to the flow rate to measure the flow value.The biggest advantages of electromagnetic flowmeters are:The accuracy level is high.The simple structure of the pipeline has no resistance and almost no pressure loss.It can measure both liquid and solid flows, pulp, mine, coal slurry, etc.Wide range of calibers.The biggest disadvantage of electromagnetic flowmeter:Cannot be used to measure gas, steam and non-conductive liquids.Cannot be used for high temperature medium measurement.It is susceptible to external electromagnetic interference.As a current new type of instrument, the electromagnetic flowmeter has been widely recognized by the market for its excellent measurement performance, and it has been increased to one of the largest flowmeters at present. It is widely used in chemistry, environmental protection, metallurgy, medicine, papermaking, drainage and other industrial technology and management departments.6 Fluid Vibration FlowmeterFluid vibration is one of the physical phenomena peculiar to fluids. Under certain conditions, according to the corresponding relationship between the frequency of fluid vibration and the flow rate, instruments that use the method of measuring fluid vibration frequency to achieve flow measurement are collectively referred to as fluid vibration flow meters.Advantages of fluid vibration flowmeter:The accuracy level is high.Immovable parts, high reliability and long life.The structure is simple, the installation is convenient, and the maintenance is low.It has a wide range of applications and can be used for flow measurement of liquid, gas, and steam.Disadvantages of fluid vibration flow meter:Difficulty in high temperature and high pressure measurement.External vibration will hinder the normal operation of the flowmeter.The fluid vibration flowmeter is a vortex flowmeter, a vortex flowmeter, and a jet flowmeter. It has a wide range of applications and has become a general-purpose flowmeter. 7 Ultrasonic flowmeterUltrasonic flowmeter is an instrument that detects the influence of fluid flow on the ultrasonic beam and measures the flow rate. The ultrasonic flowmeter, like the electromagnetic flowmeter, does not set any obstacles on the flow channel of the instrument, so it is an unobstructed flowmeter and a flowmeter suitable for solving the difficulty of flow measurement, especially in large-caliber flow measurement. Has more prominent advantages. In recent years, it is one of the rapidly developing flow meters.Advantages of ultrasonic flowmeter:Can carry out non-contact measurement.In order to measure without flow interference, there is no pressure loss.Can measure non-conductive liquids.Wide range of calibers.shortcoming:The measurement of high temperature media has some limitations.The temperature requirements for the flow field are very high.There are requirements for the length of the straight line.The method of measuring flow with ultrasound has been widely used in developed countries, and the technology has also matured. At present, the market for liquid ultrasonic and gas ultrasonic flowmeters is growing rapidly, and it is continuously expanding in heating, electric power, metallurgy, and municipal applications.Multi-channel gas ultrasonic flowmeters began to be used in the natural gas industry and attracted great international attention with their excellent characteristics. They have become an important natural gas flowmeter after the orifice plate. (William Shakespeare, opera, gas, gas, ultrasound, ultrasound, ultrasound, ultrasound, ultrasound, ultrasound, ultrasound).8 mass flow meterThe flow meter that can directly measure the mass value is currently the most widely used force mass flow meter in Korea. The Coriolis effect refers to the fact that when particles move relative to each other in the radial direction in the rotating reference system, an inertial force different from the usual centrifugal force acts on this particle, which is called the Coriolis force. (William Shakespeare, Coriolis, Coriolis, Coriolis, Coriolis, Coriolis, Coriolis, Coriolis) Due to the Coriolis force, the vibrating tube Forced vibrations consistent with the vibration frequency will occur on the side surface. A mass flow meter that uses the principle of Coriolis force that is proportional to the mass flow rate when fluid flows from a vibrating pipe is called a Coriolis force mass flowmeter. The development of mass flow meters based on the principle of Coriolis force began in the 1950s, but it was not until the 1970s that breakthroughs were made. The mass flow meter that directly measures the medium flowing in the rotating pipe is one of the most advanced flow meters in the world today.Features of mass flow meters:Direct measurement of mass flow, high measurement accuracyMass flow measurement, indirect measurement method used in the past. That is to say, use a velocity flow meter or a volume flow meter to measure the volume flow of the medium, introduce a number of intermediate parameter measurements, and then use the method of calculating and modifying the mass flow of the medium. Because these measurement methods introduce a lot of intermediate parameters and introduce a lot of error factors, they may be suitable for situations where the measurement accuracy is not high, but in some cases where the measurement accuracy is high, the strength seems to decrease. (David Asher, Northern Exposure (American TV series), measurement quote) The accuracy of mass flow meters is generally better than 0.2% (R) within the range of 10336601, and the highest is 0.05% (R). Compared with other instruments that indirectly measure mass flow, the advantage of accuracy is obvious. Therefore, at present, users have higher and higher preference for mass flowmeters in measurement places with high measurement accuracy (such as product packaging, loading and unloading truck measurements, etc.), and mass flowmeters can be used for measurement under almost all conditions. Strong adaptability to measurement media, suitable for most media measurement.Mass flow meters are highly adaptable to measuring media and are suitable for flow measurement of almost a variety of media such as high-viscosity media, solid-containing slurry, liquid containing trace gas, low-temperature medium, medium and high-pressure gas, etc. As the measurement of high-viscosity media, mass flow meters have obvious advantages. This is determined by the structural characteristics (pipeline flowmeter) and measurement principle. In addition, many pipes in high-viscosity media require pipe insulation, and the structure of the mass flow meter is easier to heat insulation. The mass flow meter is also more adaptable to the temperature of the measuring medium. The self-adaptive medium temperature of ordinary mass flowmeters is generally -50 to 200, the special high-temperature type can reach 350, and the low-temperature type can reach -240, which can meet the flow measurement of most fluid media.Simultaneous measurement of medium density and temperatureThe mass flow meter can not only accurately measure the mass flow of the medium, but also measure the density of the medium, and it can also measure the temperature of the medium. This can realize the group concentration measurement of 2 trillion mixed media and the mass flow measurement of each component. This is difficult to achieve in other flow measuring instruments.Simple structure, high reliability, simple maintenanceThe measuring sensor of the mass flowmeter has no driving parts and sealing rings on the medium pipeline, and the structure is relatively simple, the reliability is high, and the maintenance is convenient.Easy to installUnlike general velocity flow meters, the flow field distribution does not affect the normal measurement of mass flow meters. Therefore, the installation of the mass flowmeter does not require the length of the straight line between the upstream and downstream, so the mass flowmeter is easy to install and use.Can be used for bidirectional flow measurementThe mass flow meter can be used to indicate the direction of the medium flow, and can measure the dual flow measurement separately. This function is useful in certain situations (for example, to measure the flow into and out of the tank).The production process of mass flow meters is more complicated and strict, and the materials used require relatively high prices, so the prices are relatively high. Good quality and high price determine the main direction of use. The following are some common applications.
Post time: 21-09-21