Plant Services - November 2007 - (Page 51)

Material handling SAFETY Trailer stabilization Gaining prominence Figure 1. A trailer that isn’t properly stabilized moves substantially in both the vertical and horizontal directions, causing problems such as damaged equipment and products, chronic back injuries to forklift operators, serious accidental injuries, and greatly decreased productivity. again causing serious incidents. The first vehicle restraints addressed the problem effectively. When a trailer is backed up to a dock, a hook inside a wall-mounted housing rotated up to grab the rear impact guard (RIG), holding the truck in place. If the trailer was secure, forklift drivers saw a flashing green light. When the RIG was released, they saw a flashing red light. Truckers, meanwhile, saw a red light when the trailer restraint was engaged. When it disengaged, they saw a green light, which told them they were cleared to leave. This configuration, built on a national survey of thousands of trailers and five years of development, worked on 95% of trucks. In 1981, OSHA recognized the restraints as an acceptable alternative to wheel chocks. Companies of every size and across industries adopted the technology, which became fundamental to dock designs. When supply chain efficiency became universally recognized as a key to competitive advantage, business saw a safe, productive loading dock as a key link in the distribution chain. Yet new hazards emerged at the loading dock. Trailers with air-ride suspensions have a bed height that can fluctuate by several inches as lift trucks add or remove loads (Figure 2). These trailers have a natural tendency to bounce with the weight of loads and progressively move away from the dock. The bouncing can cause some restraint designs to lose their grip on the RIG. Trailers spotted at the dock and supported by landing gear are another source of danger. Lift truck traffic can rock the trailer until the landing gear collapses, causing the trailer to pitch forward or fall to the side. The weight of a lift truck at the trailer’s front end can force the nose down and the back end up and away from the building. If the tandem wheels are in a forward position, a lift truck entering can cause the rear of the trailer to scoot forward and drop. This, in turn, causes the trailer nose to pop up. It’s clear that vehicle restraints must do more than resist trailer movement straight out and away from the building. In effect, they have to trap the RIG so that it can’t move outward, rise or tip (Figure 3). The resulting technological advance is improved rotating hook designs, ensuring that the hook wraps around the RIG, providing two-point entrapment that protects against every form of trailer separation. Addressing ergonomics Changing landscape Then, life at the loading dock began to change. Through the 1980s, companies pushed for more efficient supply chains and preferred trucks that could carry bigger payloads. Trailers were switched to low-profile tires and rims to increase box size without increasing clearance height. Air suspensions cushion the ride, protect cargo and extend trailer life. These new trailers – longer, wider and taller, with lower beds – challenged lift truck drivers. At the same time, plants demanded more productivity on the dock. Faster servicing of new trailers carrying wider, taller loads added to safety concerns. Vehicle restraints had to adapt, holding on to RIGs at the typical 30 in. above the road, yet reaching down to secure low-bed trailers with RIGs as low as 12 in. above the ground. Modifications such as a low-profile nose extension on the restraint housing provided the necessary working range. Adding complexity, some trucks had hydraulic rear liftgates for use at facilities that had no dock levelers. These units had no RIGs for traditional restraints to grab. The response was wheel-locking restraints. As the trailer backs in, an automatic barrier rod is positioned against and ahead of a rear tire. These restraints can secure virtually every trailer. Industry now looks beyond catastrophic dock accidents and focuses on addressing long-term wellness issues, including Fluctuating bed heights Figure 2. With the advent of air-ride suspension trailers in the early 1990s, bed heights could fluctuate by several inches as left trucks added or removed loads. Such trailers could bounce and progressively “walk” away from the dock, a serious problem for forklift operators. November 2007 www.PLANTSERVICES.com 51 http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - November 2007

Plant Services - November 2007 Contents New Tools Letters Let Us Know Where to Put the Gas Up and Running How are you Fighting Crisis? What Works Why is the Best Practice Transfer so Hard? Who are you Going to Call? Chained to Power Mobile Mindset Making Money in the Lube Lab Grabbing a Moving Target Bagging the BTUs Keeping Mellow Preserving Health and Safety The Power of Reliability Excellence

Plant Services - November 2007

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