Sand Reclamation

Attrition Process

Environmental considerations and new molding sand costs make sand reclamation a necessity. To make quality molds, the reclamation system must produce sand with lower binder content, without foreign materials or metals, at low temperatures and with even grain size distribution.

Dependable systems achieve these results through attrition – by wearing binder from the sand grain through a series of mechanical processes. By keeping residual binder levels low, the Dependable process ensures sand of excellent rebondability with high tensile strength. In turn, casting surface finish and overall quality are improved.

The beauty of the Dependable System is that it operates at a lower cost-per-ton than any method of comparable quality. To date, nearly 200 Dependable reclamation systems have been installed, allowing foundries in some cases to recycle up to 90% of their sand. The result: new sand additions of only 10% without a loss in mold quality.

Today’s Dependable system is the result of 35 years of testing and experience. It includes five separate steps to meet the requirements for rebondability without damage to grain structure or adding dust to the sand mix. They handle up to 40 tph (36.4 mtph) and consist of shakeout/lumpreducing, scrubbing, screening, cooling and classifying to remove dust or broken grains.

The proven 5-step attrition process by Dependable recycles up tp 90% of used sand for rebonding:

Step 1:

Molds breaks down on Shakeout grid
		Sand passes through shake out grid in lumps held together by binder and is then reduced to grain size.
	VIBRACLAIM

VIBRACLAIM – Hot castings are broken free of the mold upon a vibratory grid. Loose sand and lumps fall down through the grid along with risers and other tramp metal. The Vibraclaim’s interior is lined with hard metal lugs and holes which help to break up the lumps and allow discharge of free-flowing sand to further processing. Large metallic pieces or unbroken lumps can be easily removed through a cleanout door.

Step 2:

	Shakeout sand and lumps in	Dust out
Waste Discharge
			To Rotaclaim
			Sand exits Lumpreducer in granular form with most binder intact.
	HLD LUMPREDUCER

LUMPREDUCER – Loose sand and lumps from the shakeout or other demolding process are fed into the Lumpreducer. Two vibratory motors shake the lumps and sand down through screening decks and up an inclined section of wear plates for initial binder removal. Only near-grain-size sand and particles under .06 inch (1.5mm) can successfully climb out to discharge. Other material is retained for periodic cleanout. Units are available with capacities to 20 tph (18.2 mtph).

Step 3:

Sand in	Sand in
		Liner plate
		Sand exits Rotaclaim with reduced and fractured binder coat.
ROTACLAIM

ROTACLAIM – Sand conditioning or scrubbing performs the most significant single binder removal function. Here, sand is fed into a rotating array of hard cast chrome alloy hammers. Impact with the hammers fractures the sand’s binder coating. The sand is then thrown outward at high speed against wear plates for further attrition. Additional binder is scrubbed away by thousands of impacts with other grains within the cyclonic Rotaclaim environment.

The speed of the spinning disc ( in the Rotaclaim units) can be adjusted by changing a sheave. This enables us to alter the impact velocity of the sand grain on the inner liner plates. The ability to perform this adjustment is most advantageous when a foundry is using sub-angular sands that may otherwise fracture upon impact with a wear surface.

Next: Attrition Process Step 4:

Core Machines | Mixers
Sand Reclamation | Additional Equipment

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Dependable Foundry Equipment Company - Redford-Carver Foundry Products Company
Divisions of Tromley Industrial Holdings, Inc.