The dangers at loading docks are many: forklifts racing in and out of truck trailers and making sharp turns to avoid staged pallet loads, open doors that lead to 3-foot drops to the driveway below and stacked pallets that can tumble over on passersby. Perhaps the worst among these is the peril of wet, slick dock floors.
Statistics point to the dock being a danger zone, where 25 percent of accidents leading to injuries occur. According to research conducted at the University of Wisconsin at Stevens Point, slips and falls accounted for 34 percent of workers' compensation claims, putting these incidents as the No. 2 leading cause for claims.
The costs of these claims add up. In 2007, the Liberty Mutual Safety Index revealed that these kinds of accidents cost the industry $6.6 billion annually. The study found that while the incidence of other injuries was dropping, the number of injuries caused by slips and falls was growing.
The problem is that there can be dozens of typical doorways along the dock, each creating 8-by-10-foot holes in the wall. These doors can permit moisture — rain and snow — to enter the area, mixing with dirt, debris and oil to create a dangerously slick surface. Additional moisture results when indoor/outdoor temperature differentials create condensation that drips to the floor. The moisture mixes with debris and oil, coating the floor surface.
OSHA regulation CFR 1910.22 distinctly recommends that floors should be kept clean and dry, which is a good, common-sense rule. Smart facilities practicing 5S and other strategies apply discipline to keep the dock floors clean and swooping in on spills and slicks when they happen.
But the dock's design and operation presents special challenges. Chief among them is the lack of time to stop traffic and wipe up the floor on busy docks. The additional problem of bringing the cleanup crew onto the dock adds an extra element of danger because it exposes them to forklift traffic.
Therefore, it is essential to prevent moisture from entering the dock in the first place, reducing the need to bring in the cleanup crew.
DOCK DOORS — ENSURING A CLOSED CASE
Almost anyone managing a dock knows that completely blocking these roughly 80-square-foot holes in the wall can be tough. Stroll past a typical dock door and the light shining between the door panels, around the doorframe and under the door is a sign that eventually, precipitation will find its way onto the dock.
Doors always are the first to suffer damage from the fast-moving forklifts that prowl the confined dock spaces. Collisions can damage doors outright, or the hammering can compromise their ability to seal the doorway. The resulting misalignment between the door panels and the doorframe creates gaps that enable the invasion of moisture.
Common dock doors with garage-style roller guides and light-gauge metal tracks cannot stand up to the beating. In some situations, replacing lower panels with “flex panels” will ensure the doorway is covered. Other times, management finds damage occurring at all points of the door and decides it is best to install a fully impactable dock door.
Impactable dock doors are built to stand up to both the occasional bump and the most severe collision. Rather than becoming damaged from the force of a major impact, the door panels release and easily can be set back in place.
Fully impactable models have the weatherseal attached to the door panel rather than the doorframe. The door and weatherseal can roll up out of harm's way, allowing the door to maintain a consistent seal.
Door guide or track design is another important element of sealing effectiveness. When traditional light-gauge metal tracks are hit by forklifts, they become deformed and can capture the guide rollers. The seized rollers make the door difficult to operate and tempt dock workers to leave the doorway open between truck loads to avoid back strain.
Impactable doors that feature rolling, retractable plungers riding along V-groove tracks ensure the door will operate easily, regardless of the impacts suffered by the guides. Some door models have guide tracks made of high-impact plastic. These doors offer durability over standard doors, but also can prevent the transmission of heat from the outside, preventing chilled air from condensing and dripping on the floor.
Even when the doorway is completely covered, moisture from condensation still can form on the dock floor, especially in cold-storage warehouses. It's important that the dock door match the thickness of the dock walls. Utilizing a thicker, insulated impactable dock door is the ideal defense in cold storage applications.
CLOSING THE AVENUES FOR MOISTURE
Standard, pit-mounted dock levelers provide safe trailer access for forklifts, but the pit cut into the concrete dock floor includes small gaps that act as a passageway for moisture. Even a tightly closed and sealed door will not totally block moisture.
Both new and existing pit-style dock levelers can be outfitted with an advanced weatherseal system — a combination of durable open-cell foam and heavy-duty vinyl. This system effectively fills the gaps around the sides and rear of the dock leveler and provides a seal around the perimeter.
As an alternative to pit-style dock levelers, vertical-storing powered levelers and modular dock bridges store upright when not in use. Their design allows the dock door to close tightly against the concrete floor, sealing in energy and locking out the elements. Vertical levelers and dock bridges provide the added benefit of a full perimeter seal while also acting as a steel barrier when stored, protecting overhead doors from forklift assaults.
DOOR SEALS AND PARKED TRAILERS
Even when forklift drivers are working as fast as they can to load or unload, a trailer can be parked at the dock for hours at a time. Docks depend on seals and shelters to close the gap between the dock wall and the trailer and prevent the invasion of outdoor moisture. As with damaged dock doors, a poorly specified seal or shelter also permits considerable infiltration.
Dock seals have fabric-covered foam pads that compress when the trailer backs into them, providing a tight seal around the sides of the trailer and closing the gaps between the trailer's door hinges. Dock shelters consist of fabric attached to side and head frames to create a canopy around the perimeter of the trailer, allowing full, unimpeded access to the trailer interior.
Trailers expose seals and shelters to damage through impact and compression thousands of times a year. It is important that dock seals are made of durable material and inspected regularly for signs of wear, or they ultimately will provide no seal at all.
Because rain and snow can build up on the roof of a trailer, moisture also can spill into the dock through the top of the doorway. Dock seals and shelters can be combined with rain-sealing systems to literally wipe off moisture from the roof of backing trailers, keeping it out of the dock area. These rain-sealing systems attach to the top or header of the dock seal or shelter and are fitted with a special wiper pad that sweeps rain, snow and condensation off the roof of the trailer.
Many docks use rubber wheel chocks in an attempt to hold trailers in place during loading and unloading, but these chocks are no match for the forces exerted by forklifts driving in and out of trailers. This force gradually can cause a trailer to “walk” away from the dock, forming a doorway gap. A powered vehicle restraint ensures that the trailer is held snugly to the dock with the back end of the trailer fully enveloped by the dock seal or shelter.
Growing numbers of dock owners are installing high volume/low speed (HVLS) fans to reduce their energy costs. These fans move large volumes of air at low speeds over very large areas, dissipating moisture and creating drier dock floors. The fan blades produce a massive column of air that flows down to the floor and outward in all directions, creating a deep, horizontal floor jet that ultimately circulates air up vertically and gets drawn back through the top of the fan.
The equipment on the loading dock always has been focused on safety. Adding the additional benefit of keeping the dock floor dry contributes yet another dimension to the well-being of the work force in facilities. The effective use of loading dock equipment turns dock floors from a potential liability into an instrument of productivity.
Michael Brittingham is marketing communications manager for 4Front Engineered Solutions. If you'd like to contact him, e-mail [email protected].