Ultrasonic flowmeter advantages and disadvantages

Ultrasonic flowmeter (hereinafter referred to as USF) is a meter that measures the volumetric flow rate by detecting the effect of an ultrasonic beam (or ultrasonic pulse) on fluid flow. This article focuses on the USF used to measure the liquid flow in closed pipes.

Closed-pipe USF is classified according to the measurement principle: 1 propagation time method; 2 Doppler effect method; 3 beam offset method; 4 correlation method; 5 noise method. This article will discuss the most widely used instrument for the propagation time method and the Doppler effect method.

First, advantages:

USF can be used for non-contact measurement. The clip-on transducer USF can be installed without stopping the flow pipe, as long as the transducer is installed outside the existing pipeline. This is the unique advantage that USF has in industrial flow meters. It can therefore be used for mobility (ie, non-stationary, fixed installations) measurements. It is applicable to the assessment of pipe network flow conditions. The USF is measured without flow obstruction and without additional pressure loss.

The meter coefficient of the flow meter can be obtained from the actual measurement of the geometric dimensions of the pipeline and the channel, and can be calibrated by dry method. Except for the measurement of the pipe type, no real flow verification is required.

The USF is applicable to large circular pipes and rectangular pipes, and in principle is not limited by the pipe diameter, and its construction cost is basically independent of the pipe diameter. Not only is it convenient for a large pipe, it can be considered as a preferred option when real-flow verification cannot be achieved.

The Doppler USF can measure liquids that contain more solids or contain bubbles.

The USF measures non-conductive liquids and complements the electromagnetic flowmeter in terms of unobstructed flow measurement.

Due to the ease of implementation and testing methods (such as velocity-area velocity-area method, tracer method, etc.), some special measurement problems can be solved, such as measurement of severe distortion of velocity distribution, measurement of non-circular cross-section pipelines, etc.

Some of the time-of-flight methods, the USF, have the function of measuring the travel time of sound waves, ie, the sound velocity of the liquid can be measured to determine the type of liquid being measured. For example, a tanker pumping oil ashore can check whether the measured oil or bottom water is measured.

Second, disadvantages:

The time-of-flight method USF can only be used to clean liquids and gases and cannot measure suspended particles and bubbles over a range of liquids; instead, the Doppler USF can only be used to measure liquids that contain a certain phase.

USFs with externally mounted transducers cannot be used for lining or pipes with too thick a scale, and cannot be used for peeling of the lining (or rust layer) from the inner tube wall (if the sandwich is trapped with gas, the ultrasonic signal will be severely attenuated) or the rust is severe (Change the ultrasound propagation path) of the pipeline.

Doppler USF measurement accuracy is not high in most cases.

Domestic production of existing varieties can not be used for pipes with a diameter of less than DN25mm.