Comparative performance of new, repaired, and remanufactured

The pallet repair industry has been growing at significant rates in the United States. It has been estimated that therepair industryreceived 299 million pallets in 2001, and a majority went back into the marketplace as repaired or remanufactured pallets. Many question how well these pallets perform when compared to new pallets. The purpose of this research was to provide a benchmark for the relative performance (strength, stiffness, and durability) of new, repaired, and remanufactured 48by 40-inch, three-stringer, partial four-way, flush, non-reversible, Grocery Manufacturers of America (GMA)-type pallets. GMA-type pallets were selected because they are the most common wood pallets repaired and remanufhctured in the United States. The pallets in this study were sampled in 1995 from locations throughout the United States. Repaired pallets were separated into three grades. Performance tests showed differences between new, repaired, and remanufactured pallets. Bending strength and stifhess spanning pallet stringers declined and variation increased as repair quality decreased. This was expected because repair quality is segregated according to stringer repair level. There was little difference in the bending strength and stiffness of new and used GMA-style pallets spanning the deckboards. Stringer repair had a small effect on performance when spanning deckboards. Remanufactured pallets were less strong and stiff due to nail holes inmany ofthe used parts. The new, remanufactured, and Grade A GMA-type wood pallets performed similarly when tested for structural durability and should have comparable service life inuse. Greater standardization of repair practices would result in performance improvements of repaired wood pallets. I n 2001, an estimated 433 million new wood pallets were manufactured in the United States, consuming an estimated 6.6 billion board feet (BBF) of hardwood and softwood lumber, cants, and parts (Bejune et al. 2002). Subsequently, another industry has emerged that specializes in the repair and remanufacture of wood pallets. This rise of the wood pallet repair and remanufacture industry is in large part the result of increasing landfill fees, recycling mandates, and a perceived market opportunity. In 1999, pallet recyclers recovered an estimated 299 million wood pallets, or approximately 4.46 BBF of recovered pallet parts for repair (Bejune et al. 2002). Of the pallets received for repair, 66 percent were multiple-use grocery pallets, or so-called Grocery Manufacturers of America "(GMA)-type" 48by 40-inch, three-stringer, non-reversible, partial four-way, flush pallets (Bejune et al. 2002). Standard grades and repair methods for repaired pallets are specified in the American Society of Mechanical Engineers (ASME) MH1 -Part 3 Wood Pallets, but the performance of repaired pallets is undocumented (ASME 2000). A previous study investigating the performance of pallet parts recovered from used wood pallets concluded that average flexural strength and stiffness of used pallet parts varies significantly, but is generally less than parts manufactured from new material when adjusted for moisture content. This lower strength and stiEness were due to the presence of nail holes (Clark et al. 2001). This study also indicated that the quality of The authors are, respectively, Sales Executive, Nelson Company, Baltimore, MD; Professor, Dept. of Wood Sci. and Forest Prod., Virginia Tech, Blacksburg, VA ([email protected]); and Project Leader, USDA Forest Serv., SouthernRes. Sta., Blacksburg, VA. This paper was received for publication in October 2004. Article No. 9944. *Forest Products Society Member. OForest Products Society 2005. Forest Prod. J. 55(12):83-88. FOREST PRODUCTS JOURNAL VOL. 55, NO. 12 used hardwood parts was better than that of used softwood parts, and that there is no significant difference in the grade characteristics of new and used hardwood and softwood pallet parts in general. However, the presence of significant variation in used pallet part deckboard thickness and stringer width indicates the need for dimension sorts prior to using salvaged parts. Also, due to the difficulty of separating parts on the basis of species, it is most practical to group parts into simple hardwood and softwood categories since further species separations would contribute little to pallet performance criteria (Clark et al. 2001). replaced stringer removal of damaged stringer and replacement with a fill length new or used stringer. Top and bottom deckboards were nailed to replaced stringers. f i l l companion stringer full length (approx. 48 in) new or used stringer placed adjacent to the damaged stringer. Top and bottom deckboards were nailed to the companion stringer (Fig. 1). halfcompanion stringerhalf length (approx. 24 in) new or used stringer segment placed adjacent to the damaged stringer and connected by nailing the applicable top and bottom deckboards to the half stringer (Fig. 2). plug companion any wood companion shorter than a half stringer or any unnotched block placed adjacent to the damaged stringer and connected by nailing the applicable top and bottom deckboards to the plug (Fig. 3). metalplate similar to metal plates used in the roof and floor truss industry. Typically, a pair of plates were used, one on each side of a stringer split, and plate teeth were hydraulically pressed into the damaged stringer (Fig. 4). Repair practices vary considerably. The number of repaired pallet grades used by manuhcturers varied from 1 to 1 1. However. the most common number of mades was 3. The names asThe purpose of the present study is to benchmark the relative performance (strength, stiffness, and durability) of new, repaired, and remanufactured GMA-type pallets sampled from locations throughout the United States. The test specimens were sampled and tested during 1995 and 1996. Although this research was previously accepted for publication, the authors postponed resubmission until now to allow a similar study by Clark et al. to publish first (Clark et al. 2001). Changes in raw material and repair procedures may have occurred since the time of this study. Readers are cautioned when applying the results fiom this study to new and repaired pallets that differ from those tested. The pallets tested, however, were in compliance with current industry standards (ASME 2000). Materials and methods signed to pallet repair grades also v7;ried considerably. Standard repair practices are lacking in commerce. Although stringer repair was the industry-accepted method of separating grades, the Pallets tested All of the test pallets were GMA-type, 48by 40-inch, three-stringer, partial four-way, flush, non-reversible designs. Three distinct groups new, repaired, and remanufactured were sampled. The description of each group is: New pallets manufactured of new, unused lumber, cants, or parts. Repaired "Used" pallets, or pallets that have supported at least one unit load, been recovered, repaired if necessary, and returned to the marketplace. Deckboards and stringers may have been renailed, repaired, or replaced. Repaired pallets were W e r differentiated into three quality grades, described later in the text. Remanufacturedpallets manufactured of parts salvaged from disassembled, used pallets. Figure 1. Example of full companion stringer repairs adjacent to center and outer stringers. New pallets were sampled from 1 1 locations in California, Florida, Missouri, New York, Ohio (two mills), Oregon, Pennsylvania, Texas, Virginia, and Wisconsin. Remanufactured pallets were obtained from nine locations in Arizona, California, Illinois, Minnesota, Missouri, Ohio, Texas, West Virginia, and Wisconsin. Repaired pallets were sampled from 13 locations in Arizona, California, Florida (two mills), Illinois, Minnesota, New Hampshire, Ohio, Pennsylvania, Tennessee, Texas, Viginia, and Wisconsin. Repaired pallets were typically differentiated by quality. Representative pallets of each repair quality or grade were sampled at each location. The two general types of pallet repair were deckboard repair and stringer repair. Deckboard repairs included replacement with new or used boards, or simply re-nailing a loose deckboard to stringer connection. Although deckboard repairs were more prevalent, the repair industry typically segregated pallet grades according to the type and number of stringer repairs. The stringer repairs observed in the test pallets were: Figure 2. Example of half companion stringer repair.