Business: Industrial
Getting Ideas for Energy Management Opportunities
2.1.6 Scrap and recycling
The highest-cost component in a good casting is the material cost. That, in turn,
is influenced by the cost of the purchased scrap. Add to this the cost of energy,
electrical demand, consumables and labour to arrive at the unit spout cost – the
cost of castable metal per kilogram. The internal scrap, which is being returned
to the charge, is valuable raw material, and should be treated as such. The cost
of internal returns is often taken as equal to the spout cost, minus the credit
given for the consumables, which was added to the molten metal previously. It
means, that the metallic cost component is independent of either the yield or
the proportion of returns in the charge: the high value of internal returns is
being confirmed.
returns is, in fact, more than furnace spout costs.
Scrap has, of course, a high energy and labour content because
it went through the process once already. As well, it takes away from the yield.
From these points
of view, scrap represents big waste and a loss of sales opportunity. In Section
2.1.10, “Full cost accounting” (page 33), we argue that, in full
cost accounting, scrap costs exceed the nominal spout costs. Efforts to limit
the proportion of scrap at each stage of the casting process and convert it
into saleable product should be made. When simple records are kept of the incidence
and location of scrap, e.g., mould and core scrap, a picture will emerge of
where to focus improvement efforts.
Other EMOs
Housekeeping
- Prevent scrap generation by maintaining proper process controls
and correct operation practices (e.g., temperatures and degassing of
molten metal). - Recover all metal from rejects, cutoffs, shakeouts, etc.
- Reconsider the cost/benefits
of currently selling internal scrap to outside processors.