The Information Presented Here Came from a 1995 Study Conducted

Over 135 million wooden pallets were repaired for reuse in 1995. Notched stringers are one of the most commonly damaged components. Metal plates, half companion stringers, and full companion stringers are repair methods described in the U.S. industry standard published by the American Society of Mechanical Engineers. This study evaluated the effect of these three stringer repair methods on the bending strength and stiffness of 48x40 GMAstyle pallets spanning the pallet stringTable 1: Effect of Stringer Repair Method and Frequency of Repair on the Bending Strength of 48 x 40-inch GMA-style Pallets. ers. Pallets with up to two stringers repaired with full-companion stringers were stronger and stiffer than new, undamaged pallets. In general, pallets with one or two repaired stringers using up to two metal plates or half-companion stringer repairs were as strong or stronger, but less stiff, than the original pallets without stringer repairs. On the other hand, on average pallets with two stringers repaired with metal plates or half-companions were less strong and less stiff than pallets with only one such repair. These results indicate that all three repair practices (metal plates, half-companions, and full companions), when properly applied, will reTable 2: Effect of Stringer Repair Method and Frequency of Repair on the Bending Stiffness of 48 x 40-inch GMA-style Pallets. store pallet strength when used to repair one notch on one or two stringers of a 48x40 partial 4-way, three stringer pallet. There may be an additional species effect on repair performance that warrants further evaluation. Current repaired pallet grades group metal plate repairs in upper grades, while companion member repairs are placed in lower grades. Based on functionality with material handling equipment, these grades do not reflect the racking performance of these repair methods. Introduction In 1995, an estimated 171 million pallets were retrieved by pallet suppliers for repair, reuse, or recycling. Approximately 75% were reused, and 63% required repair before reuse. One of the most common damages to a GMA-style pallet is a fracture in the stringer notch fillet. According to ASME MH1a, Part 3 (1996) there are four standard repair methods for damaged pallet stringers: replacement, metal connector plates, fulllength companion stringers, and halflength companion stringers. Replacement is the process of removing a damaged stringer and nailing a similar new or used stringer in its place. Stringer replacement is rarely used to repair GMA 68 PALLET ENTERPRISE pallets and was not included in the study. Metal connector plates are applied to each side of a stringer fracture using specialized equipment. Only horizontal or diagonal stringer splits may be repaired. Plates must be 20-gauge steel, galvanized, a minimum of 2.75 inches in length and 11 square inches in area, and have at least four teeth per square inch. A pair of plates is used for each repair, one per stringer side over the fracture. A full-length companion stringer (full-companions) can be placed adjacent to the damaged stringer and nailed to all top and bottom deckboards. Full companion stringers should be equal in length and slightly less in height to the damaged stringer to be supported. Halflength companion stingers (half-companions) are cut one inch shorter than half of the stringer length, and are slightly less in height than the damaged stringer being repaired. A half-companion is placed adjacent to the damaged portion of a stringer and nailed to applicable top and bottom deckboards. Full and half-companion stringers should be notched for forklift tine entry similar to the damaged stringer. ASME MH1a, part 3(1996) describes four grades of pallet repairs based on the method and number of stringer repairs: R-l Component replacement with similar elements R-1P Component replacement and appropriate proper stringer metal plating R-2 Single full or half-companion stringer and metal plating R-3 Multiple half-stringer companions and metal plating Although stringer repair practices for each grade are detailed in this standard, no performance levels are implied. Little has been known of the relative effect of each stringer repair practice on pallet performance. The effect of metal connector plate repair on the performance of individual stringers has been studied. These plates, when properly applied, were found to restore the strength of stringers fractured between stringer notches at the notch fillet. Stiffness, however, was only restored by using an L-shaped plate that extended over the stringer notch. Most plates in use are rectangular, not Lshaped. The three researchers previously compared the performance of three grades of repaired GMA pallets from throughout the United States. The repair practice performance levels they measured constitute a bench mark of performance for comparing changes in future practices. They found that the quality of current repair practices did not meet the minimum quality specified in ASME MH1. Because of the level variation of repair methods observed between each grade of repaired pallets, the researchers were not able to determine the relative impacts of various stringer repair procedures on pallet performance. Most pallet recyclers have established proprietary grades that resemble, but are not identical, to the standard ASTM grades. In general, used pallets with no repairs or metal plate repairs are higher in grade than pallets with half or fullcompanion stringer repairs. Companion stringers reduce the opening sizes for materials handling equipment, decreasing the functionality with material handling equipment. Therefore, the lower grade ranking given to pallets with companion stringer repairs is due more to this loss of functionality than to any