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Given the ever increasing high costs associated with workman's compensation payouts and the increased focus on increasing worker safety in today's workplace, I find it puzzling that some companies still insist on using mechanical dock levelers at their shipping and receiving docks in lieu of hydraulic units. In Europe, where worker safety has been a mantra for the past 20 years or more, more than 95% of the levelers in use today are hydraulic. However, in the US, mechanical dock levelers still account for more than 50% of all new leveler sales year after year.
Simply put, hydraulic levelers outperform mechanical levelers hands down in regards to ease of use which in turn helps to decrease user accidents and injuries. All hydraulic dock levelers sold today now come standard with a central main lifting cylinder that is equipped with either an external or internal velocity fuse system that keeps the leveler from falling should a truck pull away from the dock prematurely.
Mechanical units simply do not have this feature. Instead they rely on mechanical fall-safe legs that work best only if they have been properly maintained and when the dock leveler in a raised above dock position. In some documented cases where a truck has left the dock prematurely where a mechanical leveler was in use, the safety legs have been reported to some times not engage dock levellers quickly enough to prevent the board from crashing to the bottom of the pits. These incidents have resulted in both minor and major injuries to some employees and even in some recorded deaths.
Another problem with mechanical levelers is that they are known to be prone to a condition called "Stump Out". "Stump Out" occurs when a trailer bed is below dock height, which means that the safety legs on a mechanical leveler are in a retracted position to allow the leveler board to fall below the dock so that the board lip can make contact with the truck bed. When a truck is being loaded or unloaded, the weight of the fork truck can cause the truck's suspension to rise and fall thus lifting and lowering the dock board as well as the truck rises and falls. "Stump Out" occurs when the truck rises to a sufficient height that causes the fall safety legs of the dock board to engage thus causing the lip of the dock board to rise above the truck bed.
When this happens, the fork truck driver, must maneuver his fork truck off of the leveler, raise the leveler manually, and push the safety legs back again so that the dock board lip again rests upon the truck bed. Dealing with "Stump Out" not only poses safety issues for the fork lift driver, but also promotes potential damage to the fork truck's tires and the dock board lip should the driver not notice that "Stump Out" has occurred and thus backs his fork truck into the raised dock board lip. While some manufacturers of mechanical dock levelers do offer self-retracting fall safe legs as an option, these still need to be maintained properly to work properly, and simply stated, they are still not as reliable at keeping workers safe as the hydraulic levelers which employ the velocity fuse as part of their system.
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