Gauss vs Tesla in Magnetic Separators: How to Read a Spec Sheet

Magnetic separator data sheets advertise field strength in Gauss or Tesla, sometimes interchangeably. Bigger numbers look better, but separation performance depends on where the field is measured, how the gradient changes through the working zone, and what the particle actually experiences. This guide demystifies the units and shows how BAS reports fields so you can compare apples to apples.

Units and conversions

• Tesla (T) — SI unit of magnetic flux density. Used by physicists and most modern catalogs.
• Gauss (G) — CGS unit; 1 T = 10,000 G. Older catalogs and US-market literature still default to Gauss.
• Millitesla (mT) — practical sub-unit; 1 mT = 10 G. A magnet rated 300 mT delivers 3,000 G on the same probe.
• Kilogauss (kG) — sometimes seen on older drawings; 1 kG = 100 mT = 0.1 T.

Mental shortcut: divide Gauss by 10,000 for Tesla, divide millitesla by 10 for Gauss. A "high-intensity" wet drum at 1.2 T equals 12,000 G or 12 kG — large by industrial standards.

Field strength tiers (industrial reality)

• Plate magnets and basic permanent drums — 0.05–0.15 T (500–1,500 G). Tramp removal duty.
• Standard wet drum LIMS — 0.10–0.30 T (1,000–3,000 G). Magnetite recovery.
• Medium-intensity overband and drum — 0.30–0.60 T (3,000–6,000 G). Mixed scrap.
• Rare-earth roll separators — 1.0–1.6 T (10,000–16,000 G). Industrial mineral deironing.
• WHIMS and high-intensity wet electromagnets — 0.8–2.0 T (8,000–20,000 G). Paramagnetic mineral concentration.
• Lab-scale superconducting separators — 4–8 T. Research and specialty processing.

Surface vs effective field — the most-abused number

A spec sheet that brags "1.2 T pole face" tells you the value at zero millimeters distance, with a tiny Hall probe pressed onto a magnet pole. That number does not predict separation. What matters at the particle is:

• Effective field at the working air gap — typically 30–50% lower than pole-face peak depending on geometry.
• Field gradient (∂B/∂x) — a high gradient over a small distance separates fines better than a flat plateau at the same peak.
• Exposure time — burden depth and belt speed determine how long the particle is in the field.
• Matrix geometry (in WHIMS) — slot width, mat geometry, and rinse water determine real capture, not the coil current.

Red flags on data sheets

• No measurement distance stated — pole-face Gauss with no probe spacing is meaningless. Ask at what gap.
• Field reported but not gradient — for paramagnetic and fine separations, gradient is half the story. Reputable WHIMS sheets show both.
• No temperature condition — neodymium magnets weaken with temperature; specify operating temperature or expect degradation.
• No load condition — drums and overbands are weaker under burden; ask for "loaded" field measurements.
• Single-point bragging instead of curve — for industrial separators, a working-volume curve is more honest than a peak figure.

Practical reading tips

• Compare apples to apples — same probe gap, same load condition, same temperature.
• Demand pilot data on your feed — rather than relying on generic curves, ask the vendor to test a representative sample.
• Check the auxiliary specs — duty cycle for electromagnets, demagnetization curve for permanent magnets, water flow and matrix details for WHIMS.
• Match field to mineralogy — a 2 T claim is wasted if your ore is ferromagnetic; a 0.3 T spec misses everything paramagnetic.

How BAS documents field performance

BAS spec sheets and pilot reports include: pole-face peak value, field at stated air gap (typically 50 mm and 100 mm), gradient curve through the working volume, recommended burden depth and belt speed, and grade-recovery results from BAS solution center tests on the customer sample. Compare equivalent BAS high-intensity wet electromagnetic separators and dry magnetic drum separators using these consistent figures.

Frequently Asked Questions

Is more Gauss always better?

No. Above the field strength your mineral actually needs, additional Gauss adds capex and energy without lifting recovery. For magnetite, 0.2 T is plenty; for hematite, 1.0–1.5 T is right; for industrial mineral deironing, 1.5–1.8 T is typical. Past those, you are paying for marketing.

How do I convert Gauss to Tesla?

Divide Gauss by 10,000. So 5,000 G = 0.5 T. To go the other way, multiply Tesla by 10,000. 1.2 T = 12,000 G.

Why do older catalogs use Gauss instead of Tesla?

Gauss is a CGS unit historically used in engineering literature, especially in the US. Tesla is the SI unit and is more common in modern, international catalogs and academic work. Many catalogs report both for clarity.

What is the difference between magnetic field and magnetic flux density?

In casual industrial use the terms are used interchangeably. Strictly, magnetic field strength (H) is measured in A/m and magnetic flux density (B) is measured in Tesla. Separator performance is driven by B, so spec sheets quote Tesla or Gauss.

Does a higher Tesla rating mean lower throughput?

Often yes, but indirectly. Higher-field machines typically use smaller working zones (matrix slots, narrow gaps) for selectivity, which limits throughput per machine. In practice, plants stage multiple high-field machines in parallel to hit total capacity.