Getting Ideas for Energy Management Opportunities

2.3.4 Core making

The choice of core-making technology is influenced by the type of metal cast, size and complexity of the casting, desired casting finish quality, type of production equipment, productivity required and the source of available energy. There are advantages and disadvantages to the six most common technologies. From the energy usage point of view, per unit of product (which is the commonly used base for comparison), the core-making process can be ranked, from the highest to the lowest, as follows:

• Oil as the sand binder. The process requires high temperatures for curing, and the cores need to get a refractory coating and paste;
• Green sand, when used for cores, closely follows, with similar requirements;
• Hotbox, also requiring hot curing for binder setting, and usually the refractory coating. It produces solid cores;
• Coldbox requires heated sand and amine gas mixture and no wash;
• Nobakes - depends on air setting of the binder and catalyst and precisely controlled attemperated sand. Usually, refractory coating is necessary; and
• Shell process – coating is not usually required.

TABLE 4:
Relative energy use in core making

An innovative core making was used by a grey iron foundry in Ontario, which is using removable cores made of interlocking steel components.

Since a foundry must be profitable, any changes to the process must be justified based on the full assessment of variable and fixed costs, capital requirements, adequate payback, etc. A proposal should look into the energy consumption implications as well as the future availability of the chosen energy source.

Other EMOs
Housekeeping

• Switch off the heating equipment (core ovens) when not needed.
• Prevent cold air infiltration into the area (windows and doors).
• Prevent spillage of shell sand.
• Control and analyse core defects/rejects.
• Investigate whether turning off core-making machines using gas or power at the end of the shift is more economical than reheating of the core boxes, and enforce the implementation of the correct approach (or use timers or programmable controls).
• Maintain and calibrate the monitoring and controlling equipment on the core-making machinery and supply streams, and on core drying/baking ovens.

Low cost

• Improve oven insulation.
• Install moisture sensors on water-based wash drying ovens.
• Consider installing automatic programmable controls for the oven (temperature, time, conveyor speed in continuous ovens) and for the control of the fuel consumption by the burners (air ratio, throttling, shut-offs).
• Investigate whether insertion of removable, reusable steel cores would be possible in your foundry (as it is elsewhere) to improve productivity, quality and reduce costs.

Retrofit; high cost

• Consider improving core baking/drying by the application of:
  • Convection drying;
  • Infrared heating;
  • Microwave heating;
  • High-velocity hot air drying to distribute heat quickly and evenly in the oven;
  • Direct firing of the burners into the oven; and
  • Continuous drying.
• Consider the advantages and economics of changing the technology of core making.
• Consider heat recovery on the drying/baking oven exhausts.

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