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Not all media can be measured with ultrasonic flow meters
2012-4-14 13:08:39

的相关知识,将会帮大家全面的了解相关的超声波流量计的基本原理以及相关的使用知识。 Jiangsu Dongxiang Instrument will introduce to you the relevant knowledge of ultrasonic flowmeters today, and will help you comprehensively understand the basic principles of related ultrasonic flowmeters and related knowledge. The problems related to the measurement of liquid flow using ultrasonic flowmeters focus on explaining the measurement principle, installation, use and calibration of ultrasonic flowmeters. Principle introduction: Currently there are two types of ultrasonic flowmeters, one is Doppler ultrasonic flowmeter and the other is One type is the time difference ultrasonic flowmeter. The Doppler type uses the phase difference method to measure the flow velocity, that is, a certain frequency of motion in a sonic fluid. The liquid itself has a speed of movement, which causes a relative change in the frequency or phase between the two ultrasonic receivers (or transmitters). The velocity of the liquid can be obtained as soon as the relative change occurs; the time difference type uses the time difference method to measure the flow velocity, that is, a certain speed of the acoustic wave fluid changes the propagation time between the two receivers (or transmitters), and this relative change can be measured. Obtain fluid flow rate. Currently, a time difference ultrasonic flowmeter is used.

相关的安装知识相关的方法介绍: 目前通常采用三种安装方式:W型,V型,Z型。 The following introduces the related installation methods related to the ultrasonic flow meter : At present, three installation methods are generally used: W type, V type, and Z type. Different pipe diameters and fluid characteristics are used to choose the installation method. Generally, W type is suitable for small diameter (25 ~ 75mm), V type is suitable for medium diameter (25 ~ 250mm), and Z type is suitable for large diameter (above 250mm). In short, improve measurement accuracy and sensitivity, and choose a suitable installation method to make the measurement signal (that is, the difference) match the secondary meter. I currently use a Z-mount installation. To ensure the accuracy of meter measurement, you should choose a location that meets certain conditions: Usually, straight pipe sections above 10D upstream and downstream 5D are selected; pumps, valves and other disturbance equipment cannot be installed within 30D upstream. For the installation of our company's Z-type, I will talk about the installation method of the ultrasonic flowmeter probe, specifically using the "coordinate installation", that is, first clean the outer surface of the pipe, apply a special coupling agent, first fix one of the probe positions, and wrap it with paper tape. Measure the perimeter of the pipe and mark it in half. Determine the position of the other probe track at 1/2 of the perimeter. Similarly, the track should be parallel to the axis of the pipe. The meter displays the installation distance to determine the relative distance between the two probe tracks. The ultrasonic wave has sufficient signal strength. Usually, the signal strength displayed on the panel is greater than 2%. When the reading is stable, it indicates that the instrument can work normally after the installation and debugging. The ultrasonic flowmeter is mainly used for liquid medium flow measurement of pipeline diameters below DN300 in industrial enterprises. Its advantage is that it is not necessary to saw the pipe open, as long as a pair of sensor probes are installed on the pipe, and then connected to the host, the flow can be measured. Its measurement accuracy is mainly related to the quality of the instinct product and the installation of the field probe and the relevant characteristics of the medium. Not all media can be measured with ultrasonic flow meters.

现场故障现象常见有4种:1.流速显示不正常数据剧烈变化;2.读数不正确;3.传感器是好的,但流速低或没有流速;4.故障现象:当控制阀门部分关闭或降低流量时读数反会增加。 There are four common types of on-site failure phenomena of ultrasonic flowmeters : 1. Abnormal flow rate display and dramatic changes in data; 2. Incorrect readings; 3. The sensor is good, but the flow rate is low or no flow rate; 4. Failure phenomenon: When the control valve part The reading will increase when the flow is turned off or decreased. 1. On-site failure phenomenon: Abnormal flow rate display data changes dramatically; On-site cause analysis: The sensor is installed in a place with a large vibration in the pipeline or the flow device (such as a regulating valve, pump, downflow hole) is treated properly. Move away from the source of vibration or move upstream of the device that changes the flow regime 2. Field failure phenomenon: incorrect readings, analysis of the cause of the field failure: A. The sediment installed on the top and bottom of the horizontal pipe interferes with the ultrasonic signal. B. The sensor is installed on the pipe where the water flows downward, and the pipe is not full of fluid. Correct handling method: A. Install the sensor on both sides of the pipe B. Install the sensor on the pipe section full of fluid Cause analysis of field failure: A. Make the flow state strong The devices such as Levi ’s fluctuations: venturi, orifice plate, vortex street, turbine or partially closed valve, which are in the range of the sensor transmitting and receiving, make the reading inaccurate. B. The input pipe diameter of the flowmeter is not the same as the inner diameter of the pipe The correct processing method: A. Install the sensor away from the above device, the sensor upstream from the device 30D, downstream from the device 10D or move to the above device B. Modify the pipe diameter to match 3. Field failure phenomenon: the sensor is good, but the flow rate is low or no, the analysis of the cause of the field failure: A. The paint and rust outside the pipeline have not been removed. B. The pipeline The surface is uneven or installed at the welding seam. C. The roundness of the pipe is not good, the inner surface is not smooth, and there is lining fouling. This may occur if the pipe is cast iron. D. The measured medium is pure Or solid suspended matter is too low. E. The sensor is installed on the fiberglass pipe. F. The sensor is installed on the casing, which will weaken the ultrasonic signal. G. The sensor is not well coupled to the pipe, and there are gaps or bubbles on the coupling surface. Correct Treatment method: A. Clear the pipeline again and install the sensor. B. Grind the pipeline flat or away from the welding seam. C. Select the place where the inner surface of the pipeline is smooth, such as the material or lining of the pipeline. D. Choose another suitable type of instrument. E. Remove the glass fiber. F. Move the sensor to the pipe section without casing. G. Reinstall the coupling agent 4. Field failure phenomenon: When the control valve is partially closed or the flow is reduced, the reading will increase the field failure Cause analysis: sensor Hold It is too close to the downstream of the control valve. When the valve is partially closed, the flowmeter actually measures the reduced flow rate of the control valve, which increases the flow rate, and the flow rate increases due to the decrease in the diameter. The correct processing method: Move the sensor away from the control valve, and the sensor upstream from the control valve 30D Or move the sensor to the control valve 5D upstream of the control valve. When selecting the ultrasonic flowmeter, we must fully consider some physical and chemical properties of the medium, and make reasonable choices based on the user's measurement requirements. Good product quality and reasonable selection Only when the installation is correct can accurate metering be guaranteed.