Pulsating flow is common in industrial pipe flow. It may be generated by rotating or reciprocating prime movers, compressors, blowers, pumps, and winged rotating machines can also generate small pulsations at blade passing frequencies. Some positive displacement flow meters can also produce pulsation. Vibration-induced resonances, oscillations in pipeline operation and control systems, and flow separation caused by valve â€œhunting vibrationsâ€, pipe fittings, valves, or rotating machines are also possible sources of flow agitation.
There are three ways to measure pulsating flow: one is to use a fast-response flowmeter; the other is to attenuate the pulsation to a small enough amplitude using an appropriate method, and then use an ordinary flowmeter to measure; third, to the pulsating flow state The measured flow value is corrected for errors. In some systems, the latter two methods must be combined to achieve measurement. This is because the pulsation amplitude is large and exceeds the applicable range of the estimation formula. If only the damping method is used, the attenuated pulsation amplitude fails to enter the stable flow range. .
When the electromagnetic flowmeter uses a higher excitation frequency, it can respond quickly to the pulsating flow. Therefore, the pulsating flow can be measured and often used to measure the outlet flow of reciprocating pumps, diaphragm pumps, etc. Electromagnetic flowmeters for pulsating flow measurements are usually designed in the following three areas and are properly commissioned when commissioned.
First, the excitation frequency is adjustable so as to obtain the excitation frequency in accordance with the pulsation frequency. Too high and too low are unfavorable.
Second, the analog signal processing part of the electromagnetic flowmeter should be prevented from entering saturation when the pulsation peak arrives. The pulsation peak of the pulsating flow is sometimes surprisingly high. If the peak occurs, the flow signal input channel of the electromagnetic flow meter enters a saturated state, just as the peak is eliminated, and the instrument indicates that the value is low.
Third, in order to read the average value, the display part should be smoothed. Because the measurement part of the electromagnetic flowmeter can quickly respond to the change of the pulsating flow, it truly reflects the actual flow, but if the display part actually displays the actual flow value, it will inevitably cause the display value to jump up and down greatly, and it is difficult to read, so the display should be taken The average of a period of time. The implementation method is usually a chain of inertia, after selecting the appropriate time constant, the instrument can be displayed stably. However, if the time constant is selected to be too large, the display part will be unresponsive when the average flow rate changes, causing an illusion to the observer.
The above is an introduction to the method of electromagnetic flowmeter measuring pulsation flow. If you still want to learn more about the flowmeter, or the purchase of flowmeter, the need for selection can be contacted with Shunda flowmeter manufacturers. We will serve you wholeheartedly. .
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