March 24, 2020
Advantages of Rotameter:
Rotameter is used for small pipe diameter and low flow rate. Commonly used instruments with a caliber below 40-50mm and a small caliber of 1.5-4mm. It is suitable for measuring low flow rate and small flow rate. Taking liquid as an example, the nominal pipe diameter of glass tube rotor flowmeter full-scale flow rate with a diameter of less than 10mm, the flow rate is only between 0.2-0.6m / s, even lower than 0.1m / s; metal Rotary flowmeters and glass tube rotor flowmeters with a diameter greater than 15mm are slightly higher, and the flow rate is between 0.5-1.5m / s. Rotary flowmeters can be used for lower Reynolds numbers. If a rotor with a viscosity-insensitive shape is selected, as long as the Reynolds number at the circulation ring gap is greater than 40 or 500, the flow coefficient of the Reynolds number change will remain constant, that is, the change of fluid viscosity will not affect the flow coefficient. This value is far lower than the requirements of low orifice Reynolds number 104-105 for throttle differential pressure instruments such as standard orifice plates.
Most of the rotor flowmeters do not have upstream straight pipe requirements, or the upstream straight pipe requirements are not high. Rotary flowmeters have a wide flow range, generally 10: 1, low zui is 5: 1, high zui is 25: 1. The output of the flow detection element is close to linear. Low pressure loss. The glass tube rotor flowmeter has a simple structure and a low price. As long as the flow indicator is convenient at the scene, the disadvantage is the risk of fragility of the glass tube, especially the non-guided structure rotor for gas. There is no risk of rupture of the cone tube with the metal rotor flowmeter. Compared with glass tube rotor flowmeters, the operating temperature and pressure range is wide. Most structured rotor flowmeters can only be used for pipe installations with vertical flow from bottom to top.
Disadvantages of rotor flowmeters:
When the fluid used is different from the factory calibrated fluid, the flow value should be corrected. Rotary flowmeters for liquids are usually calibrated with water, and gases are calibrated with air. If the density and viscosity of the fluid used are different, the flow rate should deviate from the original graduation value and conversion correction should be made.
Rotor flowmeter applications are limited to small and medium pipe diameters. Ordinary full-flow type rotor flowmeters cannot be used for large pipe diameters. Glass rotor flowmeters have a large diameter of 100mm, and metal rotor flowmeters have a diameter of 150mm. Larger diameters can only be used with flowmeters .
