BEST PRACTICES IN PET INTERMEDIATE PROCESSING
Shipping/Truck Loading, Receiving and Weight Determination
Issue: Properly loaded trucks of PET bales and boxes of PET regrind can ensure regulatory compliance with maximum legal shipping weights, lessen the possibility of contamination, and prevent costly material losses and clean-up expenses due to improper loading. Proper paperwork and weight verification for shipments can help reduce disputes over material quality or quantity.
Best Practices: Prior to loading a truck with PET bales or regrind, the truck floor should be swept to remove any potential contaminants that may be present. Bales should never be pushed across the truck floor surface to prevent potential contaminants from becoming imbedded in the bales. Shipments of PET should always be accompanied with a completely filled out bill of lading, certified weight slips, and preferably, a detailed packing list or shipping manifest from the shipper.
The PET bale size proposed in these specifications (30" X 42" X 48") will allow for the most efficient truck loading and unloading. Standard 48-foot trailers, probably the most popular means of over-the-road transport, have interior loading dimensions of 47.5' long, 101.5" wide and 96"-108" high. With these bale dimensions and these truck dimensions it is possible to stack a truck “row” with six bales, that is, 2 bales wide (with the 48" side stacked in the horizontal direction), and three bales high (the 30" dimension in the vertical direction). This will result in a total of thirteen rows of bales, for a total of 78 bales/truclc (47.57421- 13.6 rows, therefore 13 rows). This bale configuration will not require special loading, such as standing bales on end, to achieve required minimum shipping weights.
Facility operators should never load broken or partially broken bales. Bales should never be “jammed,” or wedged into trucks, as this will adversely affect unloading and could possibly damage equipment.
Based on the actual bale density and the particular truck’s legal gross shipping weight, it may be necessary not to fill the truck to capacity. This can be determined by calculating the number of bales that can be accommodated without exceeding the maximum legal shipping weight provided to you by your carrier, based on the sum of individual bale weights. In addition, a best practice is to record individual bale weights on a packing list or shipping manifest that can be attached to the bill of lading for the shipment.
In cases where the truck cannot be filled to capacity, bales should be distributed evenly throughout the truck. This may require stacking some rows only two bales high instead of three bales high. The best practice is to distribute the bales along the entire track floor, that is, from the nose to the tail, even if the maximum stack height is not achieved. In addition, when scheduling tracks for outgoing shipment, a best practice is to always request that the carrier be equipped with “load locks” that are placed across the width of the track to prevent bales from falling and potentially breaking open during transport. It is also important to specify the track size you require when scheduling a shipment to make sure that you receive a track that can accommodate the required minimum shipping weight of your particular supplier. While most trades use either 48- or 53-foot trailers, there are still some carriers that use 45-foot trailers.
When loading tracks with bales it is recommended that the bottom bale of each stack in a row be loaded singly, with the remaining two bales placed on top as a pair in a separate pass. In this way, forklifts with two-stage hydraulic systems will not hit the roof of the track. Similarly, when unloading, operators should take off the top two bales of a stack first and then return for the bottom bale.
When loading regrind, boxes should be stacked in “rows” that are two boxes high and two boxes wide. When loading regrind for shipment, the same rales apply as for bales in terms of load distribution, preparation and documentation. Once again the individual weight of each box will determine how many can be put on the track without exceeding the legal shipping weight of the track. When loading regrind it extremely important that pallets are well matched to the box and that each stacked pair is stable. This means that boxes are matched such that the pallet under the top box is well positioned and completely straddles the top of the box underneath and that no pallet edge will fall inside the bottom box. If boxes “slip” in this fashion, the entire top box can fall causing material losses as well as costly and time-consuming clean-up. The use of box fids can further prevent boxes from falling into each other.
When receiving bales of PET, trained personnel should visually inspect the load prior to accepting it. The fact that most PET purchasers only accept bales of clear and transparent green PET bottles and containers means that trained facility personnel can usually identify excessive levels of contamination. Visual inspection will quickly identify the excessive presence of such contaminants as non-bottle materials, unacceptable colors, non-PET resins, etc. The basic rule of thumb throughout the industry is that if contamination is visible on the exterior of the bale it is likely to be contained in the interior of the bale. Therefore, poor bale appearance usually indicates poor overall material quality. Visual identification of excessive levels of contamination is grounds for load rejection. To avoid disputes, it is always best to take photographs of any rejected materials.
The best practice for determining the weight of a shipment is to have bucks weighed empty and full (referred to throughout the industry as the light and heavy weight) on certified 65-foot truck scales that are as close as possible to where the buck is being loaded or unloaded. This will eliminate weight discrepancies that might result from differing fuel levels in the truck. Certified scales are those that have been inspected by their respective regulatory agency for weights and measures for accuracy.
In cases where trailers are dropped for loading and unloading and picked up at a later time, light and heavy weights can be taken on the trailer only. Many carriers that provide trailers in this fashion have the trailer’s weight documented.
The sequence of weighing will vary depending on whether you are shipping or receiving. If you are shipping, the truck is first weighed empty, is loaded and then is weighed full. If you are receiving, the sequence is reversed. The difference in the empty and full weights will yield the net weight of PET bales. When shipping PET regrind, the difference in the two truck weights will yield the gross material weight from which the tare weight of the pallet/box pairs must be deducted for the net PET regrind weight. If individual tare weights for pallet/box pairs are not provided with the shipping paperwork, the PET recycling industry mle of thumb is to apply an average pallet/box tare weight of 65-70 lbs.
A general recommendation is that all plastics recycling facilities should be equipped with at least a platform scale, preferably with a digital read-out display. If platforms scales are employed, metal guards should be placed around the perimeter to prevent accidental damage from forklifts. If the forks on a forklift hit the side of a scale inadvertently it may throw off the accuracy of the scale. Most platform scales have a load cell in each comer. A quick way to check the accuracy of your scale is to stand on each comer of the scale. The weight that is displayed should be the same at each comer. If it is not, the scale should be readjusted.
A general mle within the recycling industry is that the receiver’s weight takes precedence. To ensure that the weights provided by your purchaser are accurate, or in cases where certified truck scales are not available or convenient to shipper or receiver, there are several ways that weights can be determined. If not using certified truck scales for weighing, the method used for determining weights should be determined by mutual consent of both the shipper and receiver. While it may require additional time, it will provide justification when there are disputes over a shipment’s weight.
If a shipping facility is equipped with a platform or forklift scale, the best practice is to weigh each bale after it is prepared, and to “tag” it with a bale number and the corresponding weight. If this is done, a detailed packing list can be prepared that itemizes the individual weight of each bale loaded onto a track. In this way, receivers have a double check against truck scale weights they receive.
Regardless of how bales are weighed, it should be noted that the accuracy of bale weights can be adversely affected by moisture, rain, snow and ice.
When shipping PET regrind, the best practice is to weigh and record the empty and full weight of the pallet/box pair and record these right on the box with a permanent marker. The difference in these two weights is the net PET regrind weight. Once again, a detailed packing list should be prepared from this information.
However, receivers also need to verify weights of incoming materials if they are not equipped with truck scales. One way to do this without weighing every single bale or box in the shipment is to check the accuracy of “tagged” bales or marked boxes. That is, if a bale supplier has supplied the weights of individual bales, weigh a few to verify that the weights provided are accurate. If bales or boxes of PET have not been marked with their individual weights, then it will be necessary to weigh a number of the incoming bales. One common practice is to weigh a representative sampling of approximately 10 bales or boxes. From these ten weights determine the average bale or box weight and then multiply by the total number of bales or boxes in