National Cranberry Cooperative

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Background
National Cranberry Cooperative (NCC) had faced operational problems at Receiving Plant #1 (RP1) during the peak harvest season in the fall of 1995, which had resulted in unhappiness of the owners of the Co-operatives and high labour cost, despite the purchase of an additional dumper. To avoid the same problems in the coming peak season, it is important to analyse the plant operations based on predicted demands and make recommendations if new equipment should be purchased before the fall of 1996.

Problem
During the peak seasons, RP1 faces 2 key operational problems: 1. Long idling time of trucks and drivers prior to unloading berries at the plant; and 2. High overtime cost due to the long plant operation hours.

The long idling time of trucks and drivers caused extra cost and much unhappiness among the growers, who are the owners of the cooperative. In spite of this, NCC’s profits are not affected. On the other hand, high overtime cost will negate the revenue from the sales of berries, affect profits and is a more crucial problem to be solved.

Plant Operations Analysis
The process flow diagram for RP1 up to the separation processes, including the process and storage capacities, is shown in Appendix A. Following assumptions were made to calculate the capacities: 1. There are 2 continuous flow processes in RP1, 1 for wet berries and 1 for dry berries; 2. Berries flow continuously at a constant rate throughout the entire process; 3. There is negligible flow time at the receiving and testing process, and the process is treated as an inventory; and 4. Trucks spend 7 to 8 minutes to empty their contents and leave the platform and it was assumed that an average of 7.5 minutes was required to unload a truck carrying 75 barrels of cranberries at each of the dumping units.

The process capacities are calculated and shown in Table 1.
Process| Type of Berries Processed| Calculation| Capacity (bbls/h)| Dumping| Dry/Wet| (75bbls / (7.5 min/60)) * 5 units| 3,000| Destoning| Dry| 1,500bbls/h * 3 units| 4,500|
Dechaffing| Dry| 1,500bbls/h * 1 units| 1,500|
Dechaffing | Wet| 1,500bbls/h * 2 unit| 3,000|
Drying| Wet| 200bbls/h * 3 units| 600 (Bottleneck)|
Separating | Dry/Wet| 400bbls/h * 3 units| 1,200|
Table 1 Processing Capacity

It is given that 16,800 barrels of berries are delivered in a typical peak harvest day, of which 70% are wet berries and 30% are dry berries. Throughout the 12 hours of receiving process, the demand for wet berries is 980 barrels per hour and that for dry berries is 420 barrels per hour. The total demand for all the berries is 1,400 barrels per hour. Table 2 shows the implied utilization for each of the processes.

Process| Type of Berries Processed| Calculation| Implied Utilization (%)| Dumping| Dry/Wet| 1,400 / 3,000| 47|
Destoning| Dry| 420 / 4,500| 9|
Dechaffing| Dry| 420 / 1,500| 28|
Dechaffing | Wet| 980 / 3,000| 33|
Drying| Wet| 980 / 600| 163 (Bottleneck)|
Separating | Dry/Wet| 1,400 / 1,200| 117|
Table 2 Implied Utilization
From the implied utilizations, it was determined that the operations at RP1 is process constrained, with the capacities of both the drying and separating processes lower than their demands. It was also identified that the drying process is the bottleneck of the operations and will require 63% more capacity to process the demand of wet berries. Although not the bottleneck, the separating process requires 17% more capacity to process the demand of berries.

NCC is concerned about the overtime cost incurred from the peak harvest season and the plant operation time would be determined to address this concern. Another concern is the waiting time for the trucks and drivers before unloading berries at the dumpers and the waiting time required for the last truck would be determined. The following assumptions were made: 1. There are no berries inside the holding...
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