Conveyor Hardening – Mesh Belt versus Cast Link Design: Reducing Carbon Footprint and Costs by: P. Kleinbrod, Aichelin GesmH

Conveyor belt furnaces are a proven technology for quenching and tempering fasteners (screws, bolts and nuts). The parts are fed as bulk material and transported on metal conveyor belts through the hardening and tempering furnace, as well as through the oil quenching unit and washers (Fig. 1).

Fig. 1: AICHELIN cast link belt furnace (750 kg/h / 1,700 lb/h)

Conveyor belt furnaces with mesh belts are ideal for small and medium capacities up to approximately 750 kg/h /1,700 lb/h. They are highly flexible and economical (M2x4 up to M14x180). However, the mesh belt furnace has higher energy costs due to the continuous cooling and reheating of the belt. For production, a line with an internal cast link belt is technically and economically the better alternative. These advantages are particularly significant for higher production capacities in the range of 750 to 2,500 kg/h / 1,700 to 5,500 lb/h (Fig. 2)

In addition to the technical advantages of the cast link furnace, such as twice the output per working area and 5 times the belt life, the reduced energy requirement for heating of the hardening and tempering furnace also results in a reduction in CO 2 emissions of 10-20 %(depending on working temperature and throughput).

The following table (Tab. 1) provides an overview of the energy consumption and the related energy costs and CO 2 emissions for the two different furnace types (mesh belt vs. cast link design) – based on an electric heating system and a production capacity of 1500 kg/h / 3,300 lb/h. The cast link belt hardening furnace shows a reduction in required heating power of 77 kW. This is primarily due to savings in belt reheating, to a lesser extent due to reduced process gas volume and minimized wall losses.

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