Application brief: Assess the froth reaching the pump—not simply whether the pump operates in a flotation plant.

A froth pump should be evaluated when persistent, air-rich flotation slurry prevents a conventional slurry pump from delivering the required flow and head reliably. Typical concerns include unstable discharge, repeated loss of delivery and a rising feed-hopper level despite an operating pump.

However, not every flotation stream requires a froth pump. Flotation feed, tailings and concentrate can reach their transfer pumps with different amounts of retained air. The decision depends on the material at the pump inlet, the system layout and the proposed pump’s capability.

Start by separating unavoidable process froth from air introduced by suction leaks, vortices or poor intake conditions. A specialized pump cannot replace that investigation.

Why Flotation Froth Is Different from Ordinary Slurry

Ordinary slurry selection primarily considers liquid and solids. Flotation froth introduces a substantial gas phase, making the volume and inlet behaviour more difficult to characterize.

Gas can interfere with centrifugal pumping, reducing delivered performance or causing unstable operation. Hydraulic Institute guidance identifies entrained air and inadequate priming among the reasons a pump may fail to develop its expected pressure. 

The amount of air reaching the pump may also change as operating conditions change. Flotation research examines gas dispersion under different frother concentrations and gas rates, reinforcing the need to characterize the actual stream rather than assume constant behaviour. 

Two streams with similar solids concentration can therefore present different pumping challenges. Solids percentage alone does not describe the froth duty.

When Should a Froth Pump Be Considered?

Evaluate a froth pump for flotation slurry when the required duty includes persistent process froth and the proposed conventional pump cannot reliably accommodate it.

Useful warning signs include:

• Discharge repeatedly falls while frothy material accumulates in the hopper.
• Pump performance varies with flotation froth conditions.
• Required delivery cannot be maintained despite verified speed and system conditions.
• A pump selected using ordinary slurry data performs poorly on the actual aerated feed.

These observations justify further assessment; they do not establish the cause by themselves.

A standard slurry pump may remain suitable when little air reaches the inlet or when the selected arrangement is confirmed for the measured duty. Equipment should be selected for the stream, not solely for its location in a flotation plant.

Check the Hopper and Inlet Before Changing the Pump

Process froth and accidentally introduced air require different responses.

Air may enter through a suction leak or be drawn into the inlet by a vortex at insufficient liquid submergence. Cavitation is another mechanism: it involves liquid vaporization under low pressure and should not be treated as synonymous with flotation air. Pumps.org

Review the hopper geometry, feed entry, available inlet head, suction restrictions and level behaviour. Ask whether the layout provides the inlet conditions required by the selected pump.

Hydraulic Institute intake guidance emphasizes steady, uniform inlet flow without unwanted swirl or entrained air. For an unavoidable froth duty, this makes the inlet arrangement and pump design a combined engineering problem. Pumps.org

Increasing speed or installing a larger conventional pump should not be the automatic response. First establish whether the limiting factor is hydraulic duty, retained gas or an installation problem.

Report Froth Volume Separately from De-aerated Slurry Flow

A froth duty needs more information than a conventional liquid–solid flow estimate.

Distinguish:

• De-aerated slurry flow: liquid and solids volume after air removal.
• Aerated feed volume: bulk volume including retained gas at stated conditions.
• Froth persistence: how readily the material releases air before reaching the pump.

If a froth volume factor is reported, state its definition and sampling procedure. Measurements can change as froth drains or collapses; an undefined factor is difficult to use for selection.

Do not apply a universal air-content threshold or multiply a water-curve capacity by an arbitrary froth factor. Ask the supplier to explain how the reported froth conditions affect its proposed selection.

The slurry pumps for mineral processing used elsewhere in the circuit may handle different streams and should not be assumed interchangeable.

Illustrative Example: Stable Froth at a Concentrate Transfer Point

Illustrative example only; this is not a customer case or product rating.

A concentrate transfer duty has a de-aerated slurry flow of 70 m³/h and an estimated system requirement of 18 m head. The stream contains 25% solids by mass, operates at 30°C and has a measured pH of 8.

The receiving hopper accumulates persistent froth while discharge becomes intermittent. Inspection finds no obvious suction restriction or air leak.

These observations justify evaluating a froth-handling design, but the data are not yet sufficient to select a model. The engineering team still needs representative aerated-volume information, particle data, reagent details and the range of hopper conditions.

The 70 m³/h figure describes de-aerated slurry; it does not establish the volume occupied by the incoming froth. Similarly, the preliminary head estimate does not guarantee that a pump will deliver that duty on aerated feed.

What to Confirm Before Ordering

Request a review of the pump and hopper arrangement together. Provide:

• Application and transfer points.
• De-aerated slurry flow and available aerated-volume measurements.
• Required head and piping layout.
• Solids concentration, particle sizes and slurry density.
• Froth persistence and operating variations.
• pH, relevant reagents and temperature.
• Existing pump information and observed delivery problems.

Confirm wet-end materials and the proposed replacement slurry pump parts as part of maintenance planning. A froth-handling design must still suit abrasive solids and slurry chemistry.

Frequently Asked Questions

👉Does every flotation plant need a froth pump?

No. Assess the particular stream at the pump inlet. Some duties contain little retained air, while others carry persistent froth.

👉Can a normal slurry pump handle some froth?

Possibly, depending on the pump design, inlet arrangement and actual feed. There is no universal air-content limit applicable to all slurry pumps.

👉Is air binding the same as cavitation?

No. Retained air can interfere with pumping without liquid vaporization. Cavitation involves vapor formation and collapse; the causes require separate investigation.

👉Can adding water solve a froth pumping problem?

It may change the feed, but it also changes volume, concentration and the process water balance. Review the effect on flotation and downstream equipment before using dilution as a solution.

👉Can a clear-water curve confirm froth performance?

Not by itself. Request the supplier’s selection basis for the measured slurry and froth conditions, including operating limits and inlet requirements.

Request a Froth-Duty Review

If persistent froth is disrupting transfer, provide flow, required head, solids data, reagent information and photos or video of the feed and hopper behaviour. Include how the problem changes during operation.

Use the pump application inquiry to distinguish measured values from estimates so the proposed pump and inlet arrangement can be reviewed together.