Basics of Variable Area Flowmeters (Rotameters)

Rotameter
(variable area flowmeter
courtesy of SIEMENS)

Rotameters (variable area flowmeters) can be used to measure many different types of liquids and gases passing through closed piping. The robust design means that it can also be used in harsh conditions. The various types of flange connections, linings and float materials satisfy the requirements of the pharmaceutical and chemical industries.

Flow measurement is performed according to the float principle. The flowing medium lifts the conical float in the measuring ring. This increases the ring gap until an equilibrium is established between the buoyant force of the medium and the weight of the float. The height of the float is directly proportional to the flow rate. The movement of the float is transmitted from one magnet to another magnet in the display unit outside of the measuring tube.

The devices are particularly suitable for measuring:

• Water
• Liquids
• Anti-corrosives and lubricants
• Solvents
• Saturated and superheated steam • Food and beverages
• Industrial gases

The video below provides and excellent understanding of how rotameters operate.