Business: Industrial
Getting Ideas for Energy Management Opportunities
2.1.4 Production scheduling, productivity and process control
We deal with production scheduling, productivity and process control throughout
this guide, hence these few additional points.
cost of one hour of down time in your foundry?
During a normal workweek, production
shutdowns on Friday night and start-ups on Sunday midnight or Monday morning
cause energy losses in furnaces, holding
furnaces, ovens, ladles, etc. With market demand supporting steady production
and after considering the economics, some foundries adopted continental shifting.
There are often overlooked benefits from continental shifting in maintenance
and energy savings. The regular plant maintenance is done on Tuesdays, for
example, and contractors are brought in at regular hourly rates, not at weekend
premiums, as before. Secondly, the plant’s power demand during the week
is reduced, and an advantage may be obtained in cheaper weekend power rates.
In foundries that use electricity for melting, analysing electrical demand
and the associated charges may provide a valuable input to production scheduling.
Electrical demand charge may be considered a fixed cost on a monthly basis.
Also, there is usually a predictable pattern to the general power demand in
the plant. Often, there is a high coincidence of the melt deck demand combining
at the same time with the general plant demand, with the resultant high peak
demand penalty applying for the entire month. With another way of scheduling
the production, it may be possible to shift the melting demand to another period
of the day, thus reducing the peak demand charges. In fact, this could create
a “free” demand zone, where the melting department could operate
without incurring the excessive penalty.
the foundry: productivity, yield, safety, scrap, production plan attainment
(in foundries with profit-sharing plans: monthly payouts,
accumulated total). All this will help keep employees motivated and interested
in improving results.
A boost in productivity means better
utilization of plant and equipment and the energy they require. Often, the
hidden benefit of lower specific energy
(and, of course, not-so-hidden labour costs!) due to higher productivity
is overlooked. A case to illustrate the compounding of losses is the transfer
of molten metal from the furnace to the pouring station. Often, there may
be
a distance involved, and the ladle holding the metal may not be properly
lined and/or covered to limit the significant convection and radiation losses.
To
ensure that the metal is poured at the right temperature, the furnace may
need to heat the metal to a much higher temperature. Not only is the energy
wasted
at the furnace, but also its lining is exposed to excessive wear, so productivity
suffers in the end.
Improved productivity resulted at an Ontario foundry when
it converted to cell-based manufacturing, with good results. Among other
benefits claimed
are better awareness
of quality, improved customer relationships, increased pride and process
buy-in.
Use of robotics for repetitive operations, such as handling of forms
and castings, finishing operations, cutting off gates and risers, removal
of flash, etc.,
leads to an improvement in quality; can be combined with automated inspection,
enabling product tracing; generally improves quality through the consistency
and repeatability of operations; and increases productivity several times
over the manual way.
Better process control also means better cost control
that involves monitoring and accounting for energy costs. Further on we deal
with how the use
of electricity and fuels can be maximized with proper controls. More
of the
saved funds
may be directed to energy efficiency improvements as a result.
Very
illustrative is a case of a large iron foundry in Ontario, where, at strategic
points, per-pound costs of ingredients and other materials
used
by the foundry
are prominently posted. The implicit message: do not waste resources!