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Greensand back to coreshop reclamation

A leading foundry in Turkey has invested in a new Omega Sinto greensand thermal reclamation plant to improve casting surface finish and achieve significant reductions in bentonite addition and new sand consumption. Inspired by a serious commitment to the production of quality castings and a pledge to environmental sustainability, Döktas Dökümcülük Ticaret ve San Inc turned to Omega Sinto Foundry Machinery Ltd to design a new state-of-the-art reclamation plant that could meet fierce production and raw material consumption targets. Prior to this, the foundry was working with sand scrubbing machines that had served their purpose but were in need of replacement. The foundry had a low reclamation capacity and cores were being made with 70/30 mixed sand but increased binder content was necessary. There was an experienced sand testing laboratory which had highlighted the need for an investment in newer technology. With a long track record in the Turkish foundry sector, Omega Sinto was an ideal supply partner for the project.

Having looked at the potential, four tons of the foundry’s waste sand was sent to Omega’s UK-based test plant for trials on a USR secondary attrition unit. Following the sand trials, it became apparent that the proposed reclamation plant, incorporating ceramic scrubbing units and dedusting via a fluidised bed, could achieve the highest capacity of its type in the world. Trials highlighted that the sand characteristics would be vastly improved by the third scrub process. This would enable water jacket cores to be made with cold box resin and one hundred per cent reclaimed sand.

In comparison with the existing equipment, the advantages of the new plant were vast, most notably an improved continuous capacity to 15 ton/hour, much higher grade reclaimed sand thanks to the adjustable scrubbing parameters, and less sand grain loss with correct dust separation through the fluidised system. Of particular benefit was the possibility to separate chromite sand to prevent chromite contamination and the opportunity of being able to use one hundred per cent reclaimed sand in the circulation system. In addition, the rounding operation during the process results in less binder requirement for core and moulding production.

Increased sample weight

Surface quality improvements are achieved thanks in part to the rounder shape and perfect silica distribution achieved from the new plant, which leads to a reduction in molten metal to sand interaction surface area. In addition, the reduced surface contact also means that less coke material and lustrous carbon is required which will result in a reduced consumption of coal dust.

Increased green compression strength

The new plant offers a 40 per cent increase in strength, measured with the same rate of bentonite addition, resulting in a reduced bentonite addition.

Increased green shear strength

With the rounder grains, the shear strength of moulding sand is increased. This will also improve the flowability and reduce the risks of broken moulds. During test conditions a 55 per cent increase in strength of moulding sand was achieved.

Increased wet tensile strength

In terms of wet tensile strength, the test measurement promised a 26 per cent increase. Döktas is mindful that with increased sand weight and compacting density, the risk for scabbing increases. However, this will be compensated with increased WTS values. Under test conditions Omega reclaimed sand requires higher demand for moisture. Döktas is confident that this will not be a problem in the foundry as they intend to run the system at lower active clay levels thus resulting in less moisture demand.

Key benefits of the new system

  • Improved casting surface finish.
  • Reduced fettling times.
  • Reduced consumption of coal dust.
  • A 20 per cent reduction in bentonite addition.
  • Increased green strength of cores.
  • A 20-25 per cent reduction in resin addition in the coreshop.
  • Reduced new sand consumption.

Döktas Dökümcülük Ticaret ve San Inc is a leading company in Turkey specialised in manufacturing pig, ductile and aluminium castings for the automotive, heavy commercial vehicles, construction and agricultural machinery industries.

This article is compiled from a presentation by Bülent Sirin, Arif Yalçin Yildiz and Adnan Demirel of Döktas.

Contact: Omega Sinto Foundry Machinery Ltd, Morely Way, Woodston, Peterborough, Cambridgeshire PE2 7BW, UK. Tel: +44 (0) 1733 232231, email: [email protected] web: