Differences between turbine flowmeters and electromagnetic flowmeters and how to choose the right one

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1 Performance of turbine flowmeters 1.1 Applications and features (1) Applications. The flow sensor used in the sand mixing vehicle receives electrical pulse signals, which constitute the turbine flowmeter of the sand mixing vehicle. It is mainly used for cementing and fracturing in oil and gas fields, and in particular it enables accurate measurement of the flow rate of the sand-carrying fluid during fracturing operations. (2) Characteristics. As this is a specialized flow meter, designed to withstand severe vibration and harsh operating conditions involving abrasive wear from sand particles, its sensor features a robust structure, wear resistance, shock resistance, as well as ease of disassembly, cleaning, and maintenance. In addition, this sensor is small in size, light in weight, and has a high throughput, making it suitable for intermittent use and in locations where it cannot be fixed in place. To ensure resistance to seismic forces and wear, this sensor is made of high-hardness cemented carbide material (composed of tungsten, chromium, cobalt, and tungsten carbide, etc.), and its impeller features a monolithic structure with increased blade thickness. 2 Structure and Working Principle 2.1 Working Principle The fluid under measurement impacts the turbine blades, causing the turbine to rotate. The speed of the turbine changes with the flow rate – that is, a higher flow rate results in a higher turbine speed. The turbine speed is then converted into electrical pulses of corresponding frequency using a magnetoelectric conversion device. After being amplified by a pre-amplifier, these pulses are sent to a display instrument for counting and showing. The instantaneous flow rate and cumulative flow rate can be determined based on the number of pulses per unit time and the total number of pulses. The working principle of the turbine transmitter is such that as the fluid flows along the axis of the pipe and impacts the turbine blades, the relationship Q = f k holds, where Q represents the flow rate through the transmitter in L/s, f is the frequency of the electrical pulses, and k is a calibration constant in pulses per liter. The force of the fluid flowing within the pipeline acts on the blades, driving the turbine to rotate. As the turbine rotates, the blades periodically cut through the magnetic field lines generated by the electromagnet, thereby changing the magnetic flux in the coil. According to the principle of electromagnetic induction, a pulsating potential signal is induced within the coil. The frequency of this pulsating signal is proportional to the flow rate of the fluid being measured. k is an important characteristic parameter of the turbine transmitter; it represents the instrument constant for each turbine transmitter, and this constant varies from one unit to another. It is usually determined by the manufacturer using clean water at normal temperature. The pulse signal generated by the turbine transmitter is amplified by a preamplifier and then sent to the display instrument, thereby enabling the measurement of flow rate. 2.2 Usage Characteristics Advantages: Turbine flowmeters feature high accuracy, good repeatability, no zero drift, and a high range ratio. Turbine flowmeters feature high-quality bearings and specially designed guide vanes, which greatly reduce wear; they are not sensitive to peak values, and can still provide reliable measurement data even under harsh conditions. Disadvantages: (1) Measuring gas-liquid mixtures or fluids with high viscosity can result in significant errors ； (2) The fluid containing particles to be measured needs to be filtered in advance to prevent the turbine from getting clogged. (3) It is inconvenient to install and remove; the flow meter needs to be taken apart frequently. 2.3 Installation and Use The installation and use of turbine flow sensors in sand mixing vehicles must meet the following conditions. (1) The sensor should be installed as horizontally as possible at the point on the pipeline to be tested; if vertical installation is necessary, the slurry flow must pass through the sensor from bottom to top. (2) Before installing the sensor, connect it to the display instrument or oscilloscope first. After powering it on, manually rotate the impeller at high speed and check whether there is any indication on the display. If so, remove the sensor and rinse the impeller with clean water to ensure the accuracy of the flow rate. The turbine flow sensor used in the sand mixing vehicle was thoroughly washed and checked to ensure there were no abnormalities or damage. 2.4 Problems encountered during construction During fracturing operations, when working at a low flow rate (flow rate