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The rotameter, also known as a float flow meter, is a type of variable-area flow meter. As the fluid flows upward within the meter’s scale tube, its buoyancy and upward force cause the float to rise; however, when these forces reach equilibrium with gravity, the float remains stable. The flow rate indicated at this point corresponds to the actual flow rate of the fluid. Rotary flow meters can sometimes experience certain faults, with three being the most common: First, large measurement errors in rotary flow meters: 1. Since gas media are greatly affected by temperature and pressure, it is recommended to use temperature and pressure compensation to obtain an accurate flow rate. 2. Prolonged use and pipe vibrations, among other factors, cause the moving parts of the float flow meter such as the sensing magnet, pointer, counterweight, and rotating magnet to become loose, resulting in significant errors. Solution: You can first verify by manually pushing the pointer. First, place the pointer at the RP position and check whether the output is 4 mA and whether the flow display shows 0%. Then verify it step by step along the scale. If any discrepancy is found, the position of the component can be adjusted. It is generally required that professionals make adjustments; otherwise, the position will be lost and it will be necessary to return to the manufacturer for correction. 3. Improper installation: For vertically installed rotameters, they must be kept vertical, with an inclination of no more than 20 degrees; for horizontally installed rotameters, they must also be kept horizontal, with an inclination of no more than 20 degrees. There should be no ferromagnetic objects within 100 mm around the rotameter. The installation location should be far away from valve diameter changes, pump outlets, and bends in the process pipelines. The requirement of a 5D front section and a 250 mm straight pipe section at the back must be maintained. 4. Large variations in the density of the liquid medium are also a cause of significant errors. Since, before calibration, the medium is converted to a density specified by the user in order to calibrate it using the flow rate of water under standard conditions, any significant change in the medium’s density can cause substantial errors in the measurements. The solution is to substitute the altered medium density into the formula to calculate an error correction factor, and then multiply the flow rate measured by the flow meter by this factor to obtain the actual flow rate. II. Oscillation of the pointer in rotameters: 1. Slight pointer oscillation: Usually caused by fluctuations in the medium. This can be overcome by increasing damping. 2. Moderate pointer jitter: usually caused by the flow condition of the medium. For gases, it is generally caused by unstable operating pressure of the medium. Voltage or current stabilizing devices can be used to overcome or increase the aerodynamic damping of rotameters. 3. Severe pointer oscillation: This is mainly caused by medium pulsations, unstable air pressure, or discrepancies between the pressure, temperature, and flow rates specified by the user for gas operation and the actual conditions of the rotameter, resulting in the rotameter operating outside its range. III. The pointer of the rotameter stops in a certain position and does not move: The main reason is that the rotor of the rotameter is stuck. Generally, this occurs because the valve is opened too quickly when using a rotameter, causing the rotor to rush upward toward the stopper at high speed; this leads to deformation of the stopper and thus the rotor gets stuck. However, it is also possible that the rotor gets stuck due to the rotor guide rod and the stop ring not being aligned. During processing, the gauge can be removed, the deformed stopper can be taken off and reshaped, and it should be checked whether it is concentric with the guide rod; if not, correction can be made. After that, the rotor should be reinstalled, and the rotor should be pushed by hand to ensure that it moves up and down smoothly without any obstruction. Additionally, when installing a rotameter, it must be installed vertically or horizontally – it cannot be tilted, as this can also cause problems with the meter and lead to measurement errors