Float and Tape Level Gauge

Float and tape gauges have measured storage tanks for a century, and they are still fitted where a simple, visible reading is wanted without wiring or calibration. A float on the liquid surface is connected by a perforated tape to a counterweight; as the level changes the tape runs over pulleys to a gauge head mounted at eye level on the tank side, where a pointer or counter displays the level. The float can be guided by wires or a guide pipe so it works in agitated or windy tanks.

Gauges cover ranges to 20 m for process conditions to 25 bar and 300 °C. The indicator head is aluminium and the guide tube and float are 316 or 316L stainless steel; guide pipes, guide wires, fittings and pulleys are supplied to suit the tank. Where a signal is required the head can carry a transmitter for 4–20 mA HART output and relays for high and low alarms, turning the mechanical gauge into a backup for electronic level measurement or a simple inventory signal.

Typical applications are water tanks, fuel and diesel tanks, reservoirs and cooling towers in power generation, water treatment, marine and general industry. For large storage tanks with pulleys and wires exposed to the weather, see the mechanical float and board gauge.