A forklift (10-ton capacity) will operate continuously at the plant. This machine will unload full racks from trucks and place them onto a conveyor into the plant for direct processing, or stack these racks in at-plant storage. It will then load empty racks onto the truck for return to the field. Empty racks will be removed from the conveyor and stacked in the storage yard until they are loaded onto trucks.

The operational plan calls for two forklifts at the plant, identified as a “work horse” and a “backup”. The workhorse will operate continuously and the backup will operate during the day when trucks are backed up in the queue. Key point — the system must have a backup forklift because, if a forklift is not available to handle racks, all operations cease.

The handling of the racks emulates the handling of bins at a sugar mill in South Florida. (The Rack System Concept is actually an adaptation of the successful commercial technol­ogy used for sugarcane.) In the bin system, a truck has three bins, two on the first trailer and one on a “pup” trailer. The bins are side-dumped if material is needed directly, or they are off-loaded and stacked two-high on the storage yard for nighttime operation. (A bin system is also used for the sugar industry in Texas. Figure 13.13 shows bins being off-loaded at a sugar mill in Texas, and Figure 13.14 shows bins being stacked on the storage yard at this mill.) When the bins are dumped directly, it takes 3 min to unload a truck. For normal operation, one truck hauls 10 loads (30 bins) a day. At 37 tons/load, each truck hauls 370 ton/d. Sugar cane is 80% moisture content, so 370 ton = 74 dry ton/d/truck. The reader is asked to record this figure for later comparison.

The receiving facility operates 6 d/wk, thus, on average, the daily delivery will be:

For this example, plant size (23 dry ton/h) was chosen to optimize the operation of the two forklifts at the plant. One forklift is expected to unload full racks and load empties

at the rate of one truck every 27 minutes averaged over the 24-h day. The design of the storage yard has to facilitate this operation. A larger at-plant storage will lower the forklift productivity (ton/h) because average cycle time to move an individual rack is greater.