Department of Forest and Wood Science

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Browsing Department of Forest and Wood Science by browse.metadata.advisor "Berry, Tarl"

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    Improved pallet base designs for citrus export : a structural and airflow study
    (Stellenbosch : Stellenbosch University, 2023-12) Rust, Michiel; Wessels, Coenraad Brand; Berry, Tarl; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: The overall aim of this study was to investigate and develop pallet base designs for the citrus export industry that have sufficient mechanical strength and stiffness to handle the rigors of the export process. Pallet designs should also facilitate good airflow penetration for an efficient cold chain during shipping. Six existing pallet designs were tested for strength and stiffness performance to obtain a baseline data set. Airflow penetration was also modelled for these designs. An existing pallet testing rig that has the capability of testing various aspects of pallet strength and stiffness, was used to evaluate racking bending strength/stiffness, forklift bending strength/stiffness, and impact strength. Results from these tests assisted with the identification of weaknesses in each of the pallet designs. The information was used to create improved pallet designs which were subsequently manufactured and compared to the original designs. In designs where the thickness of the structural members were increased, it resulted, as expected, in a stiffer pallet. The most breakages occurred in the stringers and especially where there were knots present on the stringer, indicating that this specific member should be a focus of improvement. The orientation of the deck boards also played a role in the stiffness of the pallet as it affected the orientation of the corner blocks. If the corner blocks were parallel to the length of the pallet, they effectively reduced the span of bearers and therefore increased the pallet stiffness. In the improved designs, an extra nail was added on the corner block for better impact performance. This inadvertently increased pallet stiffness by aiding the connections between the bearer and the corner blocks. Mixed species pallets, where Eucalyptus grandis stringers were used with other members being Pinus, also resulted in stiffer pallets. The accuracy of the nailing pattern had a large effect on the performance of the pallet during impact testing. Airflow of all the improved pallets could be enhanced by better slat spacings. Apart from improving pallet designs, it is recommended that the manufacturers and buyers of pallets should implement more stringent quality control measures. A citrus pallet quality control working group consisting of users and manufacturers of pallets can aid in this process and should be considered by the South African citrus industry.