A Better Solution for Liquid (Pulp) Level and Froth Interface Control in Flotation Cells

HAWK’s New Solution for Accurate & Repeatable Pulp Level Measurement & Froth Height

As the primary mechanism of separation in almost all metal mineral mines (iron ore tending toward dry processing on my home continent), and even for fines recovery in thermal and metallurgical (coking) coal, the correct and efficient operation of flotation cells can make or break an operation. Incorrect setup can result in valuable mineral being sent to tailings, or tailings being sent to concentrate, either losing or diluting the very product the operation is designed to recover.

In general, cells are run in “trains,” where material passes through several flotation cells, with total extraction reducing at each stage further down the train. Typical setups include six flotation cells, with those at the start referred to as Roughers, which remove the majority of material, and those at the end referred to as Scavengers, configured to remove the last remaining amounts of mineral.

Most flotation cells have a practical maximum size because their surface area and perimeter-to-volume ratio are crucial to performance. For this reason, most applications utilize long trains rather than larger single cells (although exceptions, such as the Jameson Cell, exist). Consequently, even small sites with low throughput can operate more than 20 flotation cells, while large operations in South Africa, South America, and Australia may operate installations numbering into the low hundreds.

Each cell has an optimum liquid (pulp) level that operators must maintain to ensure an appropriately thick bubble column and achieve steady, predictable mineral extraction over the launders. Unfortunately, variations in ore quality, chemistry, and throughput rates make maintaining this level a constantly moving target.

Detecting the top of the bubble column is relatively straightforward because the material within the froth is highly reflective to radar waves and can be measured using many off-the-shelf instruments such as Senator S60W cost-effective radar. However, this same reflectivity makes the froth-to-liquid (pulp) interface difficult to detect using traditional level instrumentation. Furthermore, this is not a true level but a gradient interface, as the liquid transitions into the bubble column over several centimetres, depending on the proce

Traditionally, mechanical ball floats connected to arms with magnetic encoders have been used to measure this level. However, their size and shape make them susceptible to buildup and uplift forces from bubble flow, resulting in significant measurement inaccuracy. In addition, the large cross-sectional area of the ball float occupies valuable usable surface area within the cell.

By contrast, the Flotation PulpMaster (FPM) uses a compact, low-profile HDPE float designed to resist buildup, combined with an encapsulated sensing element that protects it from the harsh environment.

The system targets millimetre-level measurement performance (±3 mm accuracy, 1.0 mm resolution) while responding directly to the pulp level rather than the froth.

Hawk Measurement Systems (HAWK) has developed the FPM as an all-in-one solution for reliably controlling liquid (pulp) level in flotation cells, incorporating several features specifically designed for flotation applications.

At the heart of the FPM is HAWK’s pulse Guided Wave Radar float level technology, engineered to deliver a stable pulp level signal in turbulent, aerated slurry environments. The unit is specified for three measurements per second, supporting tight process control when valves are actively modulating.

The FPM integrates flotation-specific hardware, including a built-in water-jet cleaning system and a clamp-on 6-inch ANSI multi-fit flange with cleaner spray assembly. It measures the pulp interface up to 1 m below the launder, with a minimum blanking distance of 150 mm or less.

Pulp Level

Froth Height

Water Jet Cleaner

Key Features

Based on field-evaluated, proven Guided Wave Radar platform
Only one moving part
Air purge and water spray ready
Incorporates pulse radar for bubble column level tracking
Stainless steel and PVDF construction
Handrail or floor-grate mounting ready

Available with multiple output options, including analogue 4–20 mA, HART 7, Modbus (4-wire), Modbus TCP/IP, and PoE—the FPM is ready for straightforward integration into flotation cells today.

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