Business: Industrial
Getting Ideas for Energy Management Opportunities
2.1.5 Focusing on yield
of any foundry energy manager is to improve yield. This will automatically
reduce internal waste of energy, raw materials and labour, and generate
corresponding savings.
Casting yield has a great impact on the foundry’s profitability. Casting
yield should have already been considered at the design stage. The importance
of improving yield to reduce energy consumption is well illustrated in iron
foundries: the
average 50% yield means that for each tonne of saleable casting an extra tonne
has to be scrapped, handled, conveyed, re-melted and cast again.
Throughout the text of this guidebook, practices that result in better yield
are mentioned. It was stressed that the road to improving yield starts at the
casting and process design stage – see Section 2.3, "Foundry processes
and equipment (page 50) and Section 2.2.1, "Managing electricity" (page
36), etc. – and we mentioned several factors that help to improve yield.
One way to improve yield, which has been used in steel foundries, is to reduce
the riser weight by using riser insulation. If the riser solidifies much later
than the casting, it is probably too big; it wastes energy later on as well,
with extra thickness to cut, and bigger scrap to handle and re-melt.
Other EMOs
Housekeeping
- Re-examine and question current practices for justification and
EMOs. - Try to optimize the layout of patterns in the mould.
- Try to fit a smaller pattern
into the existing moulds. - Check the risers’ cooling rate with immersion
thermocouples and record the temperatures to establish whether the rate
of riser and patterns solidification is optimal.
Low cost
- Consider using oxygen enrichment in the melting furnace to increase
the
metal temperature and maintain chemistry: cold iron of poor chemical composition
accounts for many rejects, dragging the yield down.
Retrofit; high
cost
- Consider whether replacing your current hard-mould with high-pressure moulding
and the appropriate equipment and process would be advantageous. - As porosity
and voids due to shrinkage and casting defects increase the rejects rate,
consider a combination of effective metal degassing, fluxing and
metal filtration to ensure pore-free and oxide-free castings.