The concepts of theoretical and effective capacity also are applicable to throughput capacity. Throughput is based on time, but because throughput usually refers to the flow of material through a machine, the units may be different from those used for capacity. For example, the performance of a hay baler could be evaluated using units of bales per hour or tons per hour.
Problem: What is the throughput of a baler if it baled 150.0 tons in one week while operating an average of 6.0 hr per day?
Solution: With the information given, different units could be used for the output. These include tons/week, tons/day, or bales/day. The "correct" units are the ones that match the input units. For this example, assume that the manufacturer advertises that the baler has a capacity of 6 tons/hr. This means we need to determine the output (effective throughput) in units of ton/hr.
ton 150.0 ton 1 week 1 day 150 5 0 ton hr week 5 day 6.0 hr 30 ' hr
Knowing the actual throughput for the baler, the throughput efficiency can be determined. The throughput efficiency is:
5 0 ton
input 6 0 ton
Assuming the advertised throughput of the baler is a reasonable value, this operation is only 83% efficient in baling hay.
The throughput of a baler also can be evaluated in units of bales per hour (bales/hr). To use these units additional information is required, including the weight of the hay (lb/bale) and two unit conversion values.
Problem: Determine the effective throughput in units of bales per hour when each bale weighs 1,200.0 lb.
Solution : No equation has been presented to solve this problem. This is an example where units cancellation should be used.
bales 150.0 ton 1 week 2,000 lb 1 bale x - x - x hr week 30 hr 1 ton 1,200.0 lb
3.0 E5 bales
Obviously, throughput can be expressed in many different ways depending on the values being compared. Remember that efficiency is a ratio—both values must have the same units. In addition, these examples illustrate the usefulness of units cancellation for solving problems of this type.
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