Why rotameter is tapered

This type of rotameter is very cheap, and it can be used for a very wide variety of fluid measurements. This type of rotameter is widely used for many industrial applications.

This type is used for small flow measurements and it is used to measure liquids and gases and this type of rotameters is capable to accurately measure low flow rates. Home Forum Tool Contact Us. Facebook Twitter Linkedin Youtube.

Primary Menu AutomationForum. Search for: Search. Home Flow Measurement What is a rotameter and how does it work. What is a pitot tube and what is it used for. This device is easy to install with no electrical connections and gives a direct reading of flow rate. The bob is free to move inside the tube and is heavier than the fluid it displaces.

At any point of time, the float experiences three fundamental forces; drag, buoyancy and its own weight. With increase in flow velocity, the drag force increases and the flow velocity reduces with increase in cross-sectional area in the tapered tube. With no flow, the float sits at the bottom of the tube, as the fluid flow increases the float begins to rise until an equilibrium is maintained with the viscous forces and gravity. Calibration: Rotameter calibration is undertaken for a given gas or fluid at a given set of conditions.

These conditions are normally written on the side of the flowmeter, along with flow range and measurement units. The larger the flow, the higher the float will be raised.

The tapered tube allows the annular area between the ball and the tube to be proportionate to the flow, in a balanced condition. The accuracy of a rotameter is established by the accurateness of the temperature, pressure, and flow control when it is initially calibrated.

If there is any change to the weight and density of the float, there will be an impact on the reading of the flowrate.

Also, if there are any changes that affect the liquid, like a change in temperature or pressure, the accuracy of the rotameter will be affected. All rotameters consist of a tapered tube and a float, but what those components are made of and where they are best used can vary.

The tubes may be made of glass, metal, or plastic, and float materials can vary. The following will provide more information about different rotameter designs:. The glass for these tubes is safety-shielded borosilicate glass, which is safe for water and air applications up to 60gpm flowrate for water and scfh for air. These tubes are typically made of stainless steel.

To detect the position of the float, magnetic followers are used inside the tube along with readings on the outside of the tube. Metal tubes can be utilized for hot and strong alkalis, water, steam, fluorine, slurries, hydrofluoric acid, molten metals, and more. The tube itself can be made from polysulfone, perfluoroalkoxy PFA , or polyamide. Other float materials include sapphire, carboloy, and tantalum.