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DHR - SAFETY ALERT MEMO 96-02
|DATE: January 26,
INCIDENT TYPE: Sander Rack Failure
LOCATION: District 9
THE ACCIDENT: At approximately 9:30 am on January 10, 1996, two employees unloaded an in-bed sander from a four yard dump truck onto a hanging type storage rack. As they drove away, two of the four support chains on the rack failed allowing one end of the sander to fall approximately 3 feet to the ground. Fortunately, both employees were clear of the sander when it fell and there were no injuries.
CONCLUSION: Upon investigation, it was determined that the support chains were used incorrectly. The sander rack was designed with two chains hanging down from the sander support rack at each of the four corners. These chains are attached by a 1/2 inch bolt that passes through the support beam. One chain was fastened at the head end of the bolt and the other is fastened at the nut end of the bolt. One chain is designed to be passed through the support eye on the sanders corner and then pulled up to take out the slack and fastened to the other chain forming a loop. This was to be done at each of the four corners. Instead, one chain at each corner was passed through the eye and then hooked back to itself. This resulted in all the sanders weight being supported by only one chain fastened to only one end of each bolt at each of the four corners. The result was a failure of two of the four bolts. Although the design of the sander rack was adequate to handle the load when used properly, it was determined that the design was such that it became far too easy for someone to use it incorrectly.
RECOMMENDATION: All employees using support type sander racks must be trained in the proper use of the rack. All support rack hardware should be inspected to ensure that the proper size and grade of chain and bolts are used. Chain should be either 3/8 inch for racks with two support chains at each corner) or 1/2 inch (for single support chains) and either grade 40 or 80 (chain grade is marked on at least one link in every 24 inches of chain). Bolts should be either grade 5 or grade 8 (grade 5 bolts have three marks on the bolt head and grade 8 bolts have six marks on the bolt head). The rack and all hardware should also be inspected periodically to ensure they are in good working condition.
A diagram is attached (from District 9) detailing a single support chain system that is being used on sander racks in District 9. This design eliminates the bolt as a means of support and uses the bolt only to keep the chains in place.
HEADQUARTERS OFFICE OF SAFETY AND HEALTH (916) 227-2640