Jarring and jolting at the dock is an issue 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 the 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 has often 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.
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 has also 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.
Lift truck jolting and jarring at the dock have also 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 (NIOSH) reports that shock (jarring and jolting) causes 36 percent of all head, neck, and back injuries associated with mobile equipment operators.
The forklift industry has also 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 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 have also suggested that sudden changes in elevation, such as when entering/exiting a rail car, result 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 (levelers) 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.
Spotting The Signs
With the wide range of factors influencing whether dock shock and trailer drop occur at a particular loading dock, there’s little question as to whether the issue is complicated. Yet it’s relatively easy to identify whether the problems exist. Telltale signs that point to potential problems include:
Forklift operator complaints: The average forklift driver transitions in and out of semi-trailers hundreds of times per shift, which amounts to serious levels of vibration over time. If forklift operators are complaining, take notice.
Forklift driving patterns: Forklift operators often comment that the worst bump experienced is when they transition in and out of trailers. Check whether forklift operators are purposely slowing down as they enter and exit trailers.
Noise: A forklift that encounters dock shock and/or trailer drop makes considerable noise. Dock shock is particularly noticeable when forklifts encounter large gaps between the warehouse floor and the trailer bed. The noise level also increases proportionately to the amount of trailer drop involved.
Trailer movement: Tests of air-ride suspension systems indicate that the average deflection of trailer bed height from center when a forklift travels in and out of a trailer is six inches. No devices are needed to visually identify up and down movement of this magnitude. If trailer movement exists, trailer drop is likely an issue.