BEST PRACTICES IN PET INTERMEDIATE PROCESSING
Storage: PET Regrind (dirty flake)
Issue: Properly stored boxes of PET regrind help maintain the quality of prepared post¬consumer PET plastic regrind prior to sale and further processing, improve workplace safety, and limit the economic losses associated with improper storage. Improperly stored PET regrind subjects it to contamination, causing it to be rejected by a purchaser. Improperly stacked boxes can fall causing serious injury to workers, damage to PET processing equipment, or costly material losses.
Best Practices: PET plastic regrind produced by PET processors should be ground into and stored in clean, cardboard boxes (referred to throughout the recycling industry as gaylords and which are approximately one cubic yard ท volume and capable of holding quantities of PET flake in the range of 600-1000 pounds) and on shipping pallets of adequate size and strength that will maintain their integrity during handling, storage, and transport. If the intermediate processing facility is equipped with a platform scale, tare weights should be determined for each pallet and box pair and recorded in some fashion on the box. This will help in determining the net weight of the PET contained in each box when full.
PET regrind should be stored indoors to keep it clean and dry with limited exposure to sunlight. Boxes of regrind should be stored in locations that limits introduction of contamination. This is best accomplished by “capping” and “strapping” all full boxes of PET regrind by strapping a cardboard top to each full box. In addition the use of lids helps prevent top boxes from falling into bottom boxes and splitting them when stacked. In cases where used boxes of sufficient quality are used to store PET regrind --a common reuse practice within the plastics recycling industry -- it is best to line them with a plastic liner bag to prevent possible contamination from the previous contents of the box . The use of box liners eliminates the need for caps as they can
be tied off when full. In lieu of the use of plastic box liners, all boxes should be thoroughly cleaned prior to use.
If the intermediate processing facility is equipped with a platform scale, the weight of each full box should be recorded on the box. The tare weight previously recorded should be subtracted from the gross weight to determine the net weight of the PET contained in the box. These weights can then be used to prepare a detailed packing list or shipping manifest to accompany bills of lading for each shipment and avoid potential shipping weight disputes that sometimes occur.
Proper stacking of boxes is imperative to safe operations within a facility. Improperly stacked boxes can fall, causing serious injury to workers, damage to plant equipment, and loss of finished product. Forklift operators should have the proper experience in matching boxes and pallets when stacking boxes to ensure stack integrity. Boxes of regrind should not be stacked greater than three high. Stack heights greater than this can exceed the structural capacity of the lower boxes, causing them to fall. Safe regrind stacking height in a facility is a function of box and pallet integrity and ceiling height. In addition, there may be a number of regulatory limits to stack height and configuration based on local fire codes or building department regulations. For example, local fire codes may require proper clearances from sprinkler heads, or that stored materials do not block aisles or points of exit or egress. Building codes may have limits on the amount of floor space that can be occupied with stored materials, or the load capacity for storage floors that are not on grade. Finally, the federal Occupational Safety and Health Administration (OSHA) requires compliance with all local requirements.
For facilities that grind more than one type of post-consumer plastic resin, PET regrind should be stored in separate locations from other plastic resins. It is best to provide a physical barrier - - for example, plastic curtains —between the storage locations for different plastic resin types to prevent contamination if stacked boxes should fall.
Finally, extreme caution should be exercised for any facility storing PET regrind that is known to contain a high percentage of edible oil bottles. The presence of excessive levels of edible oil contamination is the suspected cause of a number of spontaneous combustion fires of stored plastic regrind throughout the recycling industry. While the number of these incidents is small, regrind suspected of containing high levels of edible oil contamination should be stored in well ventilated areas with adequate fire protection equipment capable of suppressing a spontaneous combustion fire.