Variable Area Flowmeters

Method

Variable Area Flowmeters, also known as Rotameters, are simple, precisely engineered devices that visually display flow rates in small pipelines. Typically made from Perspex, they feature a sloped chamber where the flow passes through. The chamber’s design causes a small ball, which rises against gravity, to settle at a position proportional to the flow rate. As flow increases, the ball moves higher due to the expanding chamber area.

Advantages

• Suitable for various liquids and gases
• Cost-effective

Disadvantages

• Custom-built for specific ranges and applications
• Accuracy depends on constant pressure and temperature in gas applications
• Must be installed vertically

Considerations

For metal balls, proximity switches can be added to convert the meter into a flow switch, though set points cannot be adjusted afterward. Avoid over-tightening connections on plastic meters to prevent damage. Some manufacturers, like Yokogawa, offer variable area flowmeters with traditional gauges instead of vertical columns.