Emerging Safety Threats at Loading Docks

Feb. 21, 2006
Dock shock and trailer drop are two emerging issues that pose serious health and safety risks.

A first-time back injury can cost as much as $10,000 when drugs, doctor's visits and physical therapy are factored into the ailment. And it gets worse. According to one recent study published by Ohio State University, more-severe back injuries that occur when a person is hurt over and over again can cost as much as $300,000.

But whether it's a first-time incident or an ongoing problem, facility decision-makers need to protect their employees against the potential for chronic spinal injuries. It's also why facility decision-makers need to focus their attention on dock shock and trailer drop two emerging issues that pose serious health and safety risks and adversely affect the profitability of virtually every facility with a loading dock.

Here's what every decision-maker needs to know about dock shock and trailer drop, as well as advice on to how to protect against the problems they create.

Dock Shock and Trailer Drop Defined

Dock shock and trailer drop are terms coined by Rite-Hite to describe unsafe situations that occur during the process of unloading and loading semi-trailer trucks.

Dock shock describes jarring that occurs when a lift truck (stand-up walkie or forklift) crosses between the warehouse floor and the trailer bed due to the bumps and gaps that exist on traditional dock levelers. Dock shock is a source of vibration, which is known to pose a serious health and safety risk.

Trailer drop describes vertical trailer bed movement or "drop" that occurs with the weight of lift trucks traveling in and out trailers due to trailer suspension systems. Trailer drop causes lift truck operators to experience significant jolts, which can lead to chronic back and neck injuries.

Rite-Hite began to research the issues in 2001, when customers expressed concerns about the adverse affects that jarring and jolting have on the health of forklift drivers. Facility decision-makers also have voiced concern about the negative impact on product and dock equipment.

A Common Problem

At virtually any traditional loading dock configuration, lift truck operators encounter significant jarring and jolting as they transfer materials within a facility's shipping/receiving/staging area and move in and out of trailers. This area often is referred to as the material transfer zone (MTZ).

Jarring and jolting that occurs within the MTZ is an issue that is closely tied to occupational vibration. There are two types of occupational vibration: segmental, such as hand-arm, and whole-body vibration (WBV), which is transmitted to entire body through supporting surfaces, such as the legs when standing and the neck, lower back and buttocks when sitting.

WBV exists in many environments. At the loading dock, WBV exposure often has been associated with forklifts. According to documented reports, back disorders are more prevalent and more severe in forklift operators exposed to WBV versus non-exposed operators.

It's also important to note that problems with vibration have not gone unchecked. The International Organization for Standardization (ISO) has issued various guidelines for vibration exposure levels. ISO2631/1, for example, outlines acceptable vibration standards. The European community also has taken notice. In 2002, the European Parliament and the Council of the European Union issued Directive 2002/44/EC to provide minimum health and safety requirements regarding the exposure of workers to the risk arising from vibration.

A Contributing Factor

For years, the forklift industry has worked to address problems associated with WBV. Just some of the forklift innovations designed to minimize vibration include pneumatic tires, contoured and pivoting seats, vibration-dampening engines, anti-vibration seats and advanced seat-suspension systems and seat cushions. However, many studies indicate that loading dock equipment not just forklifts contribute to WBV and chronic injuries at the loading dock.

Key factors often cited as being problematic within the MTZ are the warehouse floor surface, as well as undulations and sudden, unexpected movements or loads. Published reports show that the amount of vibration transmitted to lift truck operators is primarily a factor of how smooth the driving surface is.

Leading researchers also have suggested that sudden changes in elevation, such as when entering/exiting a rail car, results in harmful high-impact loads. These same reports suggest that special attention be paid to the design of entry points into trailers. Additionally, researchers recommend that bridges used to span the space between the dock and the trailer (or a rail car) be designed to minimize any shock, especially if the height of the dock is higher/lower than the floor of the trailer.

Problems with lift truck jolting and jarring at the dock also have caught the attention of key industry organizations. The Occupational Health Clinics for Ontario Workers Inc. recommends that employees minimize the undulations of the surface over which lift trucks must travel as a way to reduce the effects of WBV. At the same time, the National Institute of Occupational Safety and Health reports that shock (jarring and jolting) causes 36 percent of all head, neck and back injuries associated with mobile equipment operators.

Shedding Light on the Issue

No single culprit is responsible for jarring and jolting at the dock, which is one of the primary reasons why the problem has gone unchecked. Instead, the dynamics of lift trucks (both forklifts and stand-up walkies) and their interaction with semi-trailer trucks play a key factor.

An understanding of this basic premise drove Rite-Hite to further study how dock levelers and vehicle restraints influence the situation. Dock levelers serve as a bridge between the dock floor and a semi-trailer. Vehicle restraints are devices that latch onto a trailer's rear-impact guard (RIG) to keep them from separating from the dock during loading/unloading. The restraints help to prevent a variety of catastrophic accidents.

Research showed that a lift truck experiences significant jarring as it encounters bumps and gaps found on standard dock levelers during the loading and unloading process. Subsequent Rite-Hite studies showed conclusively that dock shock serves as a significant source of vibration.

When analyzing the interaction of vehicle restraints and trailers, Rite-Hite found that trailer beds move vertically, or "drop," due to the weight of lift trucks traveling in and out of unstable trailers. Trailer drop often is severe when trailers with air-ride suspension systems are involved because the systems float up and down to maintain a consistent trailer height when loaded or unloaded. The situation causes lift truck operators to experience significant jolts.

In addition to safety issues, trailer drop contributes to product damage. As a lift truck enters a trailer, fragile loads can be damaged or fall off the pallet if not properly secured. Driving forklifts over unstabilized, steeply inclined levelers and bumpy terrain also accelerates wear on brakes, tires, transmission, steering axle and other components.

The situation also is hard on dock levelers, seals, shelters and bumpers. The cost for repairs to a single dock seal as a result of trailer movement can be as high as $2,000. Productivity also is hampered because lift trucks need to slow down to avoid problems created by dock shock and trailer drop.

Taking the Right Approach

The severity of dock shock and trailer drop varies from dock to dock and industry to industry. But there's little doubt that dock shock and trailer drop exist at a facility that operates loading docks and lift truck equipment.

Given the magnitude of the safety risks involved and the employer's responsibility to control the environment where lift trucks operate, consider having a trained loading dock equipment representative inspect your dock situation to assess the severity of dock shock and trailer drop and the risk involved. If the problem warrants attention, don't overlook technology. Some dock levelers and vehicle restraints are now designed specifically to minimize dock shock and trailer drop and create a smooth transition between the warehouse floor and the trailer.

Understanding these new chronic safety issues and taking a proactive approach will provide a safer, more profitable loading dock.

Joe Manone is vice president, Rite-Hite Corp. He is responsible for marketing, product positioning and sales development, and works with customers, industry leaders and representatives to identify trends and new product requirements.

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