Advantages of mass flow meters:1. Direct measurement of mass flow meter with high measurement accuracy.2. It can measure a wide range of fluids, including various liquids with high viscosity, slurries containing solids, liquids containing trace gases, and medium and high pressure gases with sufficient density.3. The vibration amplitude of the measuring tube is small, which can be regarded as a non-moving part, and there are no obstructing parts and moving parts in the measuring pipeline.4. The pair is not sensitive to the flow velocity distribution of the upstream flow, so there is no requirement for the upstream and downstream straight pipe sections.5. The measured value is not sensitive to fluid viscosity, and the change of fluid density has little effect on the measured value.6. It can do multi-parameter measurement, such as measuring the density at the same time, and derive the concentration of the solute in the measurement solution.Disadvantages of mass flow meters:1. Zero point instability forms zero point drift, which affects the further improvement of its accuracy, so that many types of instruments have to divide the total error into two parts: basic error and zero point instability measurement.2. The measurement error of low-density medium and low-pressure gas is large; the gas content in the liquid exceeding a certain limit (varies according to the model) will significantly affect the measured value.3. Coriolis mass flow meter is more sensitive to external vibration interference. In order to prevent the influence of pipeline vibration, most types of flow sensors have higher requirements for installation and fixation.4. It cannot be used for larger pipe diameters and is currently limited to less than 300mm.5. The wear and corrosion of the inner wall of the measuring tube or the deposition and scaling will affect the measurement accuracy, especially for the thin-walled measuring tube.6. Some products have large pressure loss, which is equivalent to volumetric instruments, and some models are even 100% larger than volumetric instruments.7. Most models of CMF are larger in weight and volume.Sincerity Group has developed over years to manufacture the Coriolis Mass Flow Meters industries. Through continuous research, development and transformation, we have become the leader of the Coriolis Mass Flow Meters industries in China.Sincerity mass flow meter manufacturers has powerful technology knowledge over the flow meter industries. The Coriolis Mass Flow Meter are suitable for different kinds of industries--- high requirements testing experiments of universities, research institutes; and also the petroleum, medicine, metallurgy, electricities industries.In addition, the Coriolis mass flow meter can be also functioning as a general density meter which does not necessarily require further preference of temperature, viscosity.
The ultrasonic flow meter is used in conjunction with the weir tank to measure the flow of water in the open channel. It is mainly used to measure the sewage discharge outlets of sewage plants, enterprises and institutions, the flow of urban sewers and the channels in farmland water conservancy. Since our ultrasonic flow meter company's instrument uses ultrasonic waves to pass through the air, it measures in a non-contact method. Therefore, it is suitable for the measurement of flow and liquid level under the conditions of sticky and corrosive liquids.What are the reference factors for selecting an ultrasonic flow meter?1. Selection of range and accuracy The water level range of open channel flowmeters used in agricultural irrigation channels and sewage discharge channels is within the range of 2-4m, and the blind area of the probe is within the range of 0.3-0.5m. The accuracy is selected according to the actual application needs to achieve economic benefits.2. The choice of power supply type includes 24VDC.12VDC.5VDC.220VAC, etc. If there is a municipal power supply on site, select the 220V/AC power supply type. If there is no municipal power supply on site, 12V/DC is preferred, and the supporting DTU/RTU is 12V/DC power supply to ensure the consistency of the on-site power supply.3.Selection and installation of the weir tank. There are three common water weirs: triangular weirs, rectangular weirs and Parshall troughs. Parshall troughs are recommended for agricultural irrigation and sewage discharge. The level-flow relationship of the Parshall trough is calibrated experimentally, and the data are relatively accurate. As long as it is ensured that the water level in the downstream of the Parshall trough is poor, the discharge is smooth, and there is no stagnant water. The water level-flow relationship between triangular weirs and rectangular weirs comes from theoretical calculations, and it is easy to ignore some operating conditions, resulting in additional errors and requirements for the upstream and downstream drop.4. Select the signal transmission type.Digital signal: The digital signal shall determine the data interface and communication protocol. Data interface RS485.RS232, etc. Protocols include HART protocol, Modbus protocol, Profibus protocol, etc.Analog signal: Analog signal includes current (DC4-20ma), voltage, resistance (resistance and voltage are usually rarely used), etc.Ultrasonic flow meters are mainly used for flow measurement in reservoirs, rivers, water conservancy projects, farmland irrigation and culverts. Since it mainly uses the weir-trough method and the velocity area method to calculate the flow of the water delivery section, its installation method will directly affect the measurement results and accuracy.The low cost ultrasonic flow meter consists of an instrument for measuring the liquid level and a water tank, which is manufactured according to documents published by the Metrology Institute. Liquid level gauges directly measure the liquid level in a channel or tank. When used for open channel flow measurement, install a weir groove on the open channel. Weir grooves convert water flow in open channels into liquid levels. The instrument measures the water level in the weir tank, and then calculates the flow according to the relationship between the water level and the flow rate in the corresponding weir tank.There must be a certain gap between the actual measurement accuracy of the high temperature ultrasonic flow meter and the theoretical accuracy (that is, the calibration accuracy of the instrument when it leaves the factory), which is mainly due to factors such as installation location, installation accuracy, data processing method and calibration method.Therefore, the improvement of measurement accuracy mainly starts from the following points:1. Adjust the installation position.Try to choose a straight channel with a standard section to meet the requirements (the upstream straight section of the instrument is 10 times the channel width, and the downstream straight section is 5 times the channel width). If this requirement is not met, the flow state of the water will not be very stable, and the measurement result will be too large or too small. At this time, it needs to be corrected, usually by multiplying a correction factor (generated by on-site calibration) or adjusting the installation position.2. Improve installation accuracyIt is mainly aimed at the accuracy of the installation angle and position of the speed probe. If the installation angle is deviated, the result will have a fixed error factor. At this time, in order to improve the measurement accuracy, it is necessary to adjust the installation angle or multiply by a correction factor.3. Data processing methodMainly refers to the fact that in the actual measurement process, there will be various disturbances on site (such as fish swimming near the flow rate probe during the measurement process), making individual data inaccurate or completely distorted. If the measurement time interval is large, these distorted data will have a greater impact on the measurement results, so it is necessary to increase the density of the measurement time interval and remove or smooth the distorted data.4. Calibration methodWhen calibrating the ultrasonic density meter, it is necessary to ensure that the flow rate of the section at the measurement site remains unchanged for a certain period of time, otherwise the same water level will correspond to different flow rates during the process of rising or falling water, resulting in the calibration coefficient being too large (falling water) or too small (rising water). water). Another point to note is that one or several suitable water levels should be selected for calibration, and special water levels cannot be selected. When the exact value of the actual section flow cannot be obtained, the system error can be offset by installing the instrument by the symmetrical method or the reverse method.
Notes and summary of mass flow meter installation:1. Since the mass flow meter relies on the Coriolis principle of vibration when the fluid flows through the pipeline to achieve the measurement purpose, the installation state of the gas mass flow meter should be a stress-free state, and the installation of the flowmeter should be on the same axis as the pipeline. Moreover, it should be supported near the mass flow meter sensor, and the sensor cannot be used to support the pipeline, which can eliminate vibration and reduce errors.2. The selected installation site should be far away from large transformers or motors, because the cable connected between the sensor and the transmitter is covered or close to the electromagnetic field emitted by the motor, etc., which will cause interference, inaccurate readings and errors. In addition, different installation orientations should be selected according to the different properties of the fluid during installation, that is, the fluid in the sensor tube should always be kept in a full state.3. Entrained air bubbles. When used for liquid flow measurement, when the content of mist gas exceeds 1% to 5% of the volume content, the mass flow meter will stop working. These bubbles damp the vibration of the flow tube used to generate the Coriolis force and should dissipate the gas before the sensor. If this is difficult to achieve, minimize the gas content (increase the pressure within the sensor as much as possible) to ensure that the bubbles are evenly dispersed into smaller bubbles (maintain a high liquid flow rate). Bubbles are created when the pressure of a liquid is lower than its vapor pressure. The pressure drop across the sensor caused by the geometry of the flow tube and the flow of the liquid can reduce the effective pressure of the liquid below its vapor pressure, and gas in the liquid in the pipe can have the same effect on the sensor as a fog bubble. Once the sensor is sized, the back pressure required to maintain the liquid state can be calculated. Install the sensor in a location that can meet the required back pressure.4. Sediment and suspended matter. Thermal gas mass flow meters can calculate the mass content of one component in a solution or slurry of two components. Accurate density measurement needs to be avoided: sediments adhering to the measuring tube wall or solid particles settling out of the suspension (flow rate too low).5. Vibration. The introduction of the double-pipe design greatly reduces but does not completely eliminate the effect of common mode vibration on the coriolis mass flow meter. External vibrations introduced by the pipeline system can cause undesired vibration patterns of the sensor. If the external vibration frequency is equal to or close to the frequency of the sensor drive system, it will interfere with the drive control system of the instrument, causing the flow tube to vibrate unstable or stop vibrating.6. Hazardous location installations. If you want to install the instrument in an explosive place, you must first pay attention to whether the instrument is an intrinsically safe instrument, and determine whether it is allowed to be installed according to the on-site explosion-proof level requirements and the instrument's immediate certification documents. In the process of installation, the influence of ambient temperature on related components such as sensors, transmitters, and cables should also be considered. Consider waterproofing when installing outdoors, and consider the length of the special cable for the split-type mass flow meter (refer to the corresponding product manual for details).7. The flow field is based on the principle of step by step. In principle, the Coriolis flow meter is not affected by the flow field distribution, and does not require front and rear straight pipe sections. In actual field applications, not all types of flowmeters are not affected by the flow field distribution. Although the Coriolis force mass flowmeter does not have high requirements for the flow field distribution, for the double vibrating tube type Coriolis force mass flowmeter, when the flow field changes too drastically, it may cause inaccurate measurement.8. Other notes.In addition to the above points to be considered, the following principles should also be followed when choosing an installation site: when using a Coriolis mass flow meter price to measure liquid media, especially easily vaporized liquids or liquid media containing a small amount of gas, The flow sensor should be installed at the lower part of the pipeline, not at the higher part of the pipeline to prevent the inclusion of gas from accumulating in the measuring tube and causing measurement errors; when using the Coriolis mass flow meter side face For gaseous media, especially non-dry gas or gaseous media that is easy to liquefy under high pressure, the flow sensor should be installed at the higher part of the pipeline, not at the lower part of the pipeline, so as to avoid the accumulation of liquid in the measuring tube. The accuracy of image measurement.In addition, if conditions permit, the convenience of mass flow meter installation, routine maintenance and disassembly should also be considered. For example, install the flow meter downstream of the steam purge line, and be careful not to install the sensor too high or in a place with many and complicated surrounding lines. These practices will provide convenience for the installation and routine maintenance of the flowmeter.
Ultrasonic flow meters have many advantages such as high measurement accuracy, low maintenance and maintenance costs, and self-diagnosis functions. Multi-channel ultrasonic flowmeters are more and more widely used in the field of natural gas measurement.There are many factors that affect the uncertainty of the steam flow measurement results of the ultrasonic flow meter, such as the roughness of the inner wall of the upstream straight pipe section of the flowmeter, gas composition, the length of the upstream straight pipe section, fluid flow state upstream of the flowmeter, noise interference, and airflow pulsation. The most common for operators is that noise in the pipeline can interfere with the operation of the ultrasonic flowmeter, which in turn affects the performance of the meter. The typical place where this noise Z is generated is where there is a pressure drop, such as a flow control valve.The impact of noise on clamp on ultrasonic flow meters and measures to eliminate or reduce the impact of noise. At the beginning of the project, if the engineering designers can recognize these influencing factors and take corresponding measures, the project cost can be greatly reduced, but once all the equipment is installed, and the problems are found and measures are taken, it will generally cost a lot of money. cost. Therefore, it is very necessary to understand these measures to reduce the impact of noise, which can guide the user to apply the ultrasonic flowmeter correctly.The influence of noise on ultrasonic flow meter:Noise is generated during the operation of process units, such as high-velocity gas passing through pipes, fittings, protruding temperature sensors, regulating valves, etc. . The study found that the biggest noise is the large pressure drop regulating valve. If this noise is not dealt with, it will interfere with the signal detection system of the flowmeter and cause transmission detection errors. The size and nature of the noise generated by the control valve are related to the design of the control valve. In order to achieve the characteristics of "low noise", some control valves deliberately increase the noise frequency, but the high frequency reaches the operating frequency range of the ultrasonic slurry density meter, which seriously affects the normal operation of the ultrasonic flowmeter. Although the control valve can reduce the noise signal by means such as cage design, the characteristics of the control valve also determine that any valve with throttling characteristics is a potential source of ultrasonic noise. Studies have shown that the energy loss of the valve body is proportional to the pressure drop through the valve body and the actual flow rate, and the noise increases with the increase of the energy loss through the valve body.Once the noise is generated, it will propagate upstream and downstream of the regulating valve, so just installing the ultrasonic flow meter before the regulating valve does not guarantee that the flowmeter will not be disturbed by the noise of the regulating valve. The experimental results show that when the control valve is installed downstream of the flow meter, the noise interference of the sensor near the control valve is 2-4 times larger than that of the sensor far from the control valve.