Business: Industrial
Setting up an Energy Management Program
1.2.3 Auditing
Gathering information
While you are measuring and recording energy consumption data, also examine
current foundry practices and procedures. Interview workers and staff. Observe
how the job is performed. If necessary and feasible, ask for a demonstration.
Compare information obtained from different sources and verify its validity.
You want to obtain information that is objective and verifiable.
do check the essentials. Ensure that the contacts on power bars are tightened;
that there are no hot spots and excessive heat on the leads and that they
are of proper length as specified by the equipment manufacturer; that furnaces
are not run on two phases only; that switches are cleaned of sand; and
that phase reversals have not occurred on (wrongly) installed motors and
equipment; etc.
Balances
It is useful in the course of an energy audit to establish energy and material
(mass) balances. They serve to account for all energy inputs and outputs (including
waste streams) for a given balance type. They serve to cross-check and reconcile
energy data as one of the means to verify the accuracy of the audit observations
and support its conclusions. They are useful for evaluation of the impact of
foundry development plans and certain types of energy-saving projects.
Balances
include the following:
- Power balance
- Natural gas (and/or oil) balance
- Steam and condensate balance
- Water balance
- Material balance (raw material to good castings)
- Sand balance, etc.
The balances can be undertaken for the entire foundry or
can be limited to key equipment affected (e.g., the melting furnace, usage
of compressed
air, boiler efficiency, etc.). It is useful to use process flow diagrams
and, for factual as well as visual representation, to enter the calculations
in the appropriate streams on the flow diagram.
on where the energy is most expensive – at
the point of end use.
Practical production considerations
In the course of auditing gas-fired and oil-fired furnaces, the auditors
may often find that there is a lack of controls for these furnace
types. In uncontrolled
burning, the fuel-air mixture is not optimized, so fuel is wasted
whether the mixture is too rich or too lean. In the former case,
furnace temperatures
are
frequently excessive. In addition, there may be metallurgical problems
associated with uncontrolled burning, such as excessive hydrogen
content in molten aluminum.
The audit may point out several ways
in which electrical energy is wasted or why payments for power used are needlessly
high. Lack of
monitoring
and controlling
power demand and power factor may often be highlighted. These subjects
will be dealt with later on in this guidebook.
influence energy efficiency and should be examined during the audit.
To account for energy
losses, the auditor should also pay attention to the process equipment and
how it is used. For example, assess
melting and holding
furnaces and their lids; the state of their repair; how the ladles
are
preheated; how the molten metal is conveyed, handled and poured;
what the temperature
gradients are at each stage; etc.
As well, an energy audit should
consider examining casting yield and scrap rate (see the ratio between good
castings and metal melted
in
Appendix 5.2) and how the scrap is utilized. Clearly, casting yield
greatly influences
materials and energy consumption (and primarily, of course, the foundry’s
profit).