Wedge wire centrifuge baskets and screens

Centrifuge basket overview

The centrifuge basket is the working screen of a centrifuge. Feed is spread over the inside face of the rotating basket, the liquid is thrown outward through the slots, and the retained solids are scrolled, pushed or discharged from the machine. Separation depends on the basket holding its slot width and shape under high vibrating centrifugal load and abrasive media.

SIMO Screens manufactures centrifuge baskets and centrifuge screen baskets in welded wedge wire for coal, mineral, sugar and chemical centrifuges. Every wire and rod intersection is resistance welded on high-frequency transformer machines, so the basket acts as one rigid structure and the V-shaped slot drains freely without pegging.

Features and benefits

• Internal profile construction. The flat face of the profile wire lines the inside of the basket and the slot widens outward, so particles that enter a slot clear through instead of lodging in it.
• Welded at every intersection. A full-penetration weld at each wire and rod crossing holds the slot geometry under cyclic load and resists weld cracking, a common cause of basket failure.
• Controlled slot width. Slots are checked with feeler gauges at set-up, during the run and at the end of each screen, to a standard tolerance of plus or minus 5 percent of nominal.
• Profile selected for abrasion. A heavier profile wire extends service life on abrasive coal and ore, while a lighter profile gives higher open area where drainage governs.
• Built to fit the machine. Complete baskets and segmented screen sections are made to the OEM drawing or a worn sample, so the replacement fits without rework at site.

Applications

• Coal washery centrifuges, including vibrating and screen scroll machines that dewater fine and small coal, where axial slots are typical. See coal centrifuge baskets.
• Iron ore and mineral centrifuges dewatering concentrate and fines in mining and mineral processing.
• Sugar centrifugals, continuous and batch, separating crystal from molasses, for which SIMO supplies complete screens. See centrifugal screens.
• Crystal slurry centrifuges in chemical, fertiliser and pharmaceutical plants.

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Construction and specifications

A centrifuge basket works in radial flow with an internal profile, inside to outside. The solids slide or are scrolled over the smooth wire faces while the liquid passes outward through the widening slot.

SIMO builds in the forms that centrifuges use: conical baskets for continuous, vibrating and screen scroll machines, cylindrical baskets for batch machines, and screen sections shaped to fit an existing basket frame. Flanges, end rings and reinforcing rings are fabricated and machined to the fit dimensions of the machine.

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Materials

SS 304 and SS 316L cover most coal and ore applications, where abrasion governs and the profile wire is selected heavier before the alloy is upgraded. Sugar centrifugal screens use stainless grades suited to hot massecuite and wash water. Duplex 2205 and Super Duplex 2507 add strength and chloride resistance for corrosive crystal slurries. The material selector and the centrifuge basket guide set out the selection in more detail.

Engineering and quality

Each order is reviewed for slot, profile wire, support rods and ring sections against the speed, diameter and vibration of the machine, and FEA is used for structural validation of custom designs. For a replacement, SIMO engineering prepares a drawing from the OEM drawing or from measurements of the worn basket, and production begins after the customer approves it.

Profile wire is formed in house to SIMO profile codes and checked with calibrated micrometers before welding. The final inspection report records the minimum, maximum and mean slot together with cone angle, diameters, flange faces and bolt holes. Each basket is identified with the job number, item and slot on a QR-coded tag, laser marked where the client requires it, and heat numbers are traceable from the Mill Test Certificate to the finished basket.

The Mill Test Certificate is supplied as standard, while the dimensional inspection report and quality assurance plan are supplied on request. Dynamic balancing is arranged through an approved agency when specified.

What to send for a quotation

1. Centrifuge make, model and type: vibrating, screen scroll, pusher, continuous or batch.
2. The OEM basket drawing, or the worn basket or a sample for measurement.
3. Product handled: coal size range, ore, sugar grade or crystal slurry.
4. Existing slot and wire orientation, and any problems you see in service.
5. Operating speed, if known.
6. Slurry chemistry, temperature and wash water quality.
7. Material grade, inspection and document requirements, and whether dynamic balancing is required.