01float flow meterUsed for small diameters and low flow rates. Commonly used instruments have a diameter of 40-50mm or less, with the smallest diameter being 1.5-4mm. They are suitable for measuring low flow rates and small flow rates. Taking liquids as an example, the nominal diameter of a glass tube float flowmeter with a diameter of 10mm or less for full flow rates is only between 0.2-0.6m/s, or even below 0.1m/s; Metal tube float flow meters and glass tube float flow meters with a diameter greater than 15mm are slightly higher, with flow rates between 0.5-1.5m/s.
02. Float flow meters can be used for lower Reynolds numbers, and viscosity insensitive floats can be selected. As long as the Reynolds number at the flow gap is greater than 40 or 500, the flow coefficient remains constant when the Reynolds number changes, that is, changes in fluid viscosity do not affect the flow coefficient. This value is much lower than the requirement of standard orifice plates [3] and other throttling differential pressure instruments for low Reynolds numbers of 104-105.
03. Most float flowmeters do not have upstream straight pipe section requirements, or in other words, do not have high requirements for upstream straight pipe sections.
04. The float flowmeter has a wide flow range, generally 10:1, with a minimum of 5:1 and a maximum of 25:1. The output of the flow detection component is close to linear. Low pressure loss.
05. The glass tube float flowmeter has a simple structure and low price. As long as the flow indicator is convenient to use on site, the disadvantage is the risk of glass tubes being fragile, especially for unguided floats used for gas.
06. The metal tube float flowmeter has no risk of cone tube rupture. Compared with glass tube float flow meters, it has a wide range of temperature and pressure usage.
Most structural float flow meters can only be used for pipeline installation with vertical flow from bottom to top.
08. The application of float flow meters is limited to small and medium-sized pipe diameters. Ordinary full flow float flow meters cannot be used for large pipe diameters. Glass tube float flow meters have a maximum diameter of 100mm, while metal tube float flow meters have a diameter of 150mm. For larger pipe diameters, only shunt type instruments can be used.
When the fluid used is different from the calibrated fluid at the factory, flow indication correction should be performed. Float flow meters for liquids are usually calibrated with water, while those for gases are calibrated with air. If the actual fluid density and viscosity are different, the flow rate may deviate from the original division value and require conversion correction.