Production Time

1_J

H

Oil pressure pump

Cylinder heater

Material dryer

Die temperature controller

| : ■ : i : ■ : i : ■ : ■ :| Under production | | In operation

| : ■ : i : ■ : i : ■ : ■ :| Under production | | In operation

Figure 3.3 Operational Procedure for Molding Machine components do not need to run all of the time. The purpose of a standard operational procedure is to prescribe the running status of single components during production stages.

As time goes by, the originally prescribed procedures and operational requirements often tend to be forgotten and more relaxed and convenient operational practices are applied instead.

Another important issue, for the energy/production relationship, is capacity utilization. Capacity utilization can be defined as the ratio between the actual production output and maximum production capacity. Even when operational procedures are strictly adhered to, if machines run at partial capacity, energy effectiveness will decrease, and energy cost per unit of product will increase.

This can be illustrated by an example, a hammer mill driven by an electric motor of more than 200 kW power, which displayed a particularly inefficient operation. Figure 3.4 shows the daily load profile as measured during the operation analysis. It reveals several points of concern:

1. Frequent idling (i.e. no load operation).

2. Low average capacity use - mostly at half of the nominal output level.

3. Frequent start/stop.

Hammer Mill #3 (24 hours)

Figure 3.4 Actual Daily Load Profile of Hammer Mill

The main reason for these problems is that the operational procedures for mill operation are not followed and strictly applied. As a result, the mill uses, on average, 40 % more electricity than is required by the actual design! Of course, things would be different if the mill operated at the nominal capacity and with strictly observed operational procedures, as prescribed by the original design. Neglecting standardized operational procedures owing to convenience or other reasons will always result in higher operational (including energy) costs, and will be reflected in a changed energy/production relationship. The usual deviations from prescribed operation procedures are

• operating time that is too long;

• machines left running when not required;

• operating at partial load, etc.

The issues emphasized by Figure 3.3 and Figure 3.4 may look simple and straightforward but cause most of the variations of energy use in production as well as increased energy and other operational costs. Therefore, it is of the utmost importance to have and then to understand and follow operational procedures, which must not be underestimated.

Understanding operational procedures and the consequences of less than strict adherence to them is at the heart of understanding variability in the energy/production relationship. This understanding provides the critical knowledge necessary for monitoring energy and environmental performance in production departments.

If standardized operational procedures do not exist, they need to be established and then followed. That is one of the aims and results of EEMS - to establish a best practice operation that is embodied in standardized operational procedures.

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