Loading Dock Safety: No More Risky Business
Busy loading docks can create a dangerous work environment. But recent advances in dock safety technology help keep workers safe on the job.
Safety is a key consideration in all parts of a distribution center, but one area typically concerns facilities managers the most: loading docks. In today’s fast-paced logistics environment, loading and unloading semi-trailers can pose safety risks for everyone from forklift operators and dock attendants to service technicians and bystanders.
No across-the-board solution to loading dock safety exists because no two facilities are exactly the same. Several recent advances in dock safety technology, however, can help address the issue.
Wheel Chocks Aren’t the Answer
One common loading dock accident occurs when drivers mistakenly pull away while a forklift is still inside the trailer. Another common problem is “trailer creep,” which happens when trailers (particularly those with air-ride suspension) gradually move away from the dock because of the ongoing impact and momentum of forklifts traveling in and around them.
In both cases, the first step in accident prevention is to secure the trailer to the dock using a locking device on either the trailer’s rear impact guard (RIG) or rear wheel. Unfortunately, many loading docks still use old-fashioned wheel chocks in front of trailer tires as a means of restraint.
This approach can create a host of problems, including insufficient pullout resistance, chock slippage, and time and safety concerns related to placing wheel chocks by hand. Additionally, chocks don’t have an embedded communication system to let the truck driver, lift operator, and dock personnel know they are in place.
RIG-based vehicle restraints may provide a better option. These restraints feature a full rotating hook that automatically locks to the trailer’s RIG, using the backing trailer’s energy. RIG-based restraints help prevent all types of trailer separation, including early departure, trailer creep, trailer tip-over from landing gear collapse, and trailer up-ending.
Most RIG-based restraints also incorporate communications systems that indicate when they are engaged and when it is safe to load and unload the trailer.
RIG-based restraints don’t work in all situations, however. For example, the retail, beverage, and grocery industries operate docks that handle a large volume of trailers with hydraulic gates. They typically can’t use RIG-based restraints because those gates block access to the RIG.
International shipping container and intermodal chassis traffic is another consideration, particularly because volumes are expected to increase when the Panama Canal expansion is completed. Intermodal chassis often have RIG obstructions, but a new type of rotating-hook RIG-based restraint alleviates this problem. These newest models incorporate a “shadow hook” to offer another layer of protection, ensuring the chassis is secured to the dock.
For applications where RIG-based restraints are inappropriate, wheel-based restraints—which engage trailer wheels and secure vehicles in place—can provide a solution. They work with virtually any trailer, and, like RIG-based restraints, eliminate dangers associated with early departure and trailer separation. They also provide communication, using lights and audible alarms. Operators can select either automatic or manually operated units.
Show Some Restraint
Although automatic units are generally considered the safest and most productive option, many manual wheel-based restraints deliver safety and cost benefits similar to RIG-based restraints. Several types of manual wheel restraints are available, providing varying levels of protection.
One design uses a steel barrier positioned along a frame assembly in front of the trailer’s tire. The barrier securely locks into place and doesn’t require adjustments. This is the best option.
Another design uses an articulated arm with springs for positioning the barrier. The arm folds against the dock face when not in use. When a trailer is ready for service, one end of the arm is detached from the dock face and extended out to the trailer’s rear tire. The barrier at the end of the arm is then placed on a grade-level plate located in front of a trailer’s rear tire, where the barrier and plate engage to lock the wheel in position.
The articulated arm style does require adjustments, however, and dirt, debris, snow, and ice can prevent the teeth from properly engaging. Additionally, without a frame assembly, the barrier can disengage and move off to the side if the truck driver aggressively pulls the trailer away.
Integrated into most wheel-based restraints are systems that automatically and clearly communicate the status of the restraint so that both the lift truck operator and truck driver know when they can safely perform their duties. The systems generally include sensors that detect when the trailer is present and the barrier is safely engaged; LED lights inside the dock that signal when the barrier is safely engaged, and it is safe for the lift truck operator to begin unloading or loading; and LED lights outside the dock that signal when the operator has finished loading or unloading, and it is safe for the driver to pull away.
The Importance of Communication
Communications systems follow a logical sequence that provides a clear, visual message to forklift operators and truck drivers. Once the restraint is safely engaged, the light on a control panel inside the dock automatically changes from red to green to indicate that trailer servicing can begin. The light outside turns red, signaling to the truck driver not to pull away.
Some restraints can be equipped with advanced systems to enhance trailer loading and unloading safety. In addition to performing the same functions as a traditional communications system, the most recent technology uses lights around the corners of the dock doors to show restraint status directly in the forklift driver’s line of sight, free from any visual obstructions. It also offers lights at the rear of the leveler to confirm the restraint’s status to forklift operators where they are most at risk—inside the trailer.
Wheel-based restraints’ communications systems are often incorporated into a single dock-control system that integrates multiple loading dock components, including the leveler and door. Interconnected or interlocked components ensure proper equipment sequencing for added safety and productivity.
Loading dock accidents happen every day, producing devastating consequences. Modern vehicle restraints with visual communications systems safely secure trucks so loading and unloading at the dock becomes a less risky procedure.
Joe Manone is president/CEO of Rite-Hite Products.
Choosing Manual Wheel Restraints
Facilities managers considering manual wheel restraints must take a number of factors into consideration when deciding which model to use. These factors include:
Trailer tire dimension. Trailer tire dimension influences barrier height because it is one of several factors that determine the restraining force required to securely lock the trailer in place. Advanced restraints are designed to match the latest tire diameter specifications, which range from 34.25 to 42.5 inches.
Axle configuration. Numerous axle configurations are used on different trailer types, including vehicles with single and multiple axles. A key factor incorporated into restraint design is the distance between the rear of the trailer and the front end of the tire where the barrier is positioned. Some wheel-based restraints provide a range of 43 inches to 12 feet to accommodate common axle configurations and virtually any other configuration encountered.
Trailer design. In addition to lift gates, trailers may include design features that can impact the restraint’s ability to properly engage the tire, such as fenders, mud flaps, or hydraulic trailer jacks. The most recent restraint designs accommodate the widest possible range of issues associated with unique trailer designs.
Truck centering and side-to-side movement. Wheel-based restraints that incorporate the use of a frame assembly help the truck driver accurately and consistently center the trailer to the dock, which, in turn, ensures proper restraint engagement. The design also eliminates the potential for the barrier to pop out the side of the tire toward the operator or a bystander.
Barrier height. Another key variable is barrier height. The higher the barrier, the more force required to drive over it. Advanced wheel-based restraints are engineered so that the barrier height is at or close to the tire’s center line. Some restraints feature barrier heights as high as 19 inches.
Pullout resistance. The energy required to pull over a barrier is referred to as pullout resistance. Though there is no standard for pullout resistance, 32,000 pounds is a frequently quoted guideline.
Weather resistance and visibility. Most restraints are designed to withstand the abuse of backing trailers, and incorporate a galvanized finish that holds up to extreme weather conditions. Many are also designed to be highly visible and allow for easy clearing of snow and debris.