The Feature of Ultrasonic Flowmeters
Similar to the electromagnetic flowmeter, the ultrasonic flowmeter is a kind of unobstructed flowmeter, which is applicable to the flow monitoring of most pure liquids. Because it does not need to break the pipe and the measurement installation method is simple, it has become a solution to a large class of flow monitoring problems, especially in the large diameter flow measurement.
The Classification of Ultrasonic Flowmeters
The ultrasonic flowmeter is mainly divided into hand-held, clamp-on type, and wall-mounted ultrasonic flowmeters. The main advantage of an ultrasonic flowmeter is that it is portable, easy to carry, easy to install and use, and the flow detection range is relatively large. It can detect the flow of multiple pipe diameters. Unlike a pipe flowmeter, it is limited to measuring the flow of one diameter. Advantages are bound to be accompanied by disadvantages. The greatest disadvantage of an ultrasonic flowmeter may be that its accuracy is not as high as that of a pipeline flowmeter. However, the steady flow of fluid is conducive to measurement stability, thus ensuring measurement accuracy. The fluid with a chaotic flow state will make the measurement data unstable or unable to measure.
The Selection of Ultrasonic FlowmetersWhen measuring pipes with a diameter greater than DN300, extended supports shall be selected. The pipe diameter measured with extended support shall not be less than DN700. The extension bracket can be installed by the V method and Z method, and the Z method is generally recommended for installation so that the signal strength will be greater.
Installation MethodsThe installation methods of external clip ultrasonic sensors include the V method and Z method.
1. The V method
The V method is preferred for DN15mm-200mm pipes. During installation, the two sensors should be aligned horizontally, and the center line should be parallel to the pipe axis. Note that the emission direction must be opposite (the two sensors face inward). V method has the characteristics of convenient use and accurate measurement. For pipes with a diameter less than DN50mm, the installation accuracy is high. Please pay attention to the signal strength, signal quality, and transmission time ratio.
2. The Z method
For the DN200mm-6000mm pipeline, the Z method is preferred, and the Z method can also be used when the V method cannot measure signal or signal quality is poor. During installation, make the vertical distance between the two sensors along the tube axis equal to the installation distance, and ensure that the two sensors are on the same axial plane. Note that the transmission direction must be opposite (the two sensors face inward). Since the Z method is the direct transmission and reception of ultrasonic waves in the medium transmission, the signal has no reflection, so the attenuation of signal strength is minimum. Therefore, the signal strength of the Z method is high, and it is suitable for occasions with a large caliber, medium containing impurities or bubbles, pipeline scaling, and other ultrasonic signal attenuation.