What I’m Seeing in Froth Handling: A Field Note on the VFD Vertical Froth Pump

If you run flotation, you already know: foam is money and headaches at the same time. In the last year, several sites asked me about a vertical froth pump that can live in a hostile sump, swallow air-slurry without choking, and still be easy to service. Enter the VFD Vertical Froth Pump (Repalce AF) from Beisu Industrial Park, Wuji County, Shijiazhuang, Hebei. I’ve seen it on test stands and—more importantly—on real flotation cells where the froth never takes a day off.

Quick specs (real-world use may vary)

Product	VFD Vertical Froth Pump (Repalce AF)
Size range	2–8 inches
Capacity	≈7–570 m³/h
Head	≈5–25 m
Wet-end materials	Cr27, Cr28 (high-chrome white iron), CD-4MCu duplex SS
Air handling	Designed for entrained air typical in flotation froth (often 10–30%)

Industry trends (and what operators actually say)

Two trends keep popping up: higher air loads and tighter OPEX targets. Plants are pushing recoveries, so froth is thicker; meanwhile maintenance teams want fewer unplanned stops. Many customers say the vertical froth pump with semi-open impeller and a de-aeration barrel helps avoid air-locking and keeps NPSH requirements manageable. To be honest, I was skeptical about “plug-and-play” promises—but the sump-level tolerance on these VFD units is better than I expected.

Where it fits

- Flotation cells and launders in base metals, PGM, and gold
- Phosphate and potash froth transfer
- Coal prep fines circuits
- Smelter slag and converter foams (with CD-4MCu where corrosive)
- Pulp/paper foam skimming (select duties)

Process, materials, and testing

Wet ends in Cr27/Cr28 are typically sand-cast per ASTM A532 with heat treatment to hit hardness around 58–65 HRC (≈). Duplex CD-4MCu is used when chlorides bite. Rotors are dynamically balanced (I’ve seen G6.3 targets per ISO 1940-1). Hydraulic performance tests usually reference ISO 9906 (Grade 2B tolerance in most purchase specs). Hydrostatic tests are commonly 1.5× rated pressure. Service life? In moderately abrasive Cu flotation, users report ≈6–12 months on impellers; in harsh silica-rich ore, it can be shorter—your slurry chemistry decides.

Why this vertical froth pump gets short-listed

- Vertical cantilever design: no submerged bearings, fewer panic calls
- Froth-specific inlet geometry to break air cores
- VFD-friendly: easy tuning to froth swings without throttling losses
- Material flexibility: Cr27/Cr28 for abrasion, CD-4MCu for corrosion-abrasion

Vendor snapshot (informal comparison)

Vendor	Capacity/Head (≈)	Materials	Customization	Lead time	Certs
Kingmech VFD (Repalce AF)	7–570 m³/h, 5–25 m	Cr27/Cr28, CD-4MCu	Shaft length, liners, seal options	≈4–8 weeks (stock-dependent)	ISO 9001 (supplier-declared)
Global Brand AF-type	10–600 m³/h, 6–30 m	Hi-chrome, rubber (select)	Broad global options	≈6–12 weeks	ISO 9001, CE
Local Fabricator	Varies	Often 27% Cr only	High (bespoke)	≈2–10 weeks	Varies

Customization (what engineers usually tweak)

- Shaft length and sump cover geometry
- Impeller diameter trims for BEP alignment
- Liners: switch between Cr28 and CD-4MCu depending on chlorides
- Seal/deflector packages and splash guards
- Coatings for borderline corrosive slurries (trial-based, honestly)

Mini case study

Copper concentrator, rougher froth sump. Replaced an older unit with this vertical froth pump, 4-inch discharge, Cr28 wet end. After commissioning, air-lock trips dropped from 5–7 per week to near zero. Measured availability rose ≈4.2%, and impeller wear rate improved ≈18% over 6 months. Caveat: slurry solids averaged only 32% w/w; your mileage will vary if you’re running >45% solids.

What to ask before you buy

- Air volume fraction at operating point?
- Target BEP and expected turndown with VFD?
- Slurry pH, Cl- ppm, and top-size—material choice hinges on these.
- Required test protocol: ISO 9906 Grade 2B or equivalent?

Origin: Beisu Industrial Park, Wuji County, Shijiazhuang City, Hebei Province.

References

1. [1] ISO 9906:2012, Rotodynamic pumps — Hydraulic performance acceptance tests.
2. [2] ASTM A532/A532M, Standard Specification for Abrasion-Resistant Cast Irons.
3. [3] ISO 1940-1:2003, Mechanical vibration — Balance quality requirements for rotors.
4. [4] ISO 5199:2002, Technical specifications for centrifugal pumps — Class II (general guidance).