Loading docks have always been dangerous places to work. However, thanks to technological innovations and improved best practices, they are safer now than they used to be. Nonetheless, there are still hundreds of things that can – and do – go wrong.
Chronically damp loading dock floors are one common dock problem, particularly in regions with hot, humid and/or wet climates. Whether they are caused by precipitation or condensation, wet dock floors typically become slippery and can cause accidents that injure workers, damage products and reduce productivity.
There are several ways to address this dilemma. Smart facility managers are discovering that proper dock seals and shelters can greatly reduce the amount of precipitation and contaminants that enter the loading dock. Correspondingly, floor condensation can be minimized with the strategic use of high-volume, low-speed (HVLS) fans.
The starting point for most dampness elimination efforts is establishing a complete seal along the perimeter of the facility.
Gaps at loading dock openings
When trailers are positioned at the dock being loaded or unloaded, gaps often exist between the trailer and the edges of the dock opening. Many dockworkers are all too familiar with the “waterfall” that can happen when precipitation flows down the top of a trailer and dumps down the gap between the trailer and the facility. Not only is it an annoyance for workers loading and unloading, the resulting puddles and wet spots can create slip hazards on the dock floor.
Gaps can exist along the tops of trailers, at the upper corners, down the sides, as well as around and beneath the dock leveler and exterior dock bumpers. Besides allowing precipitation to enter, gaps can let in dust, bugs and other pests to the facility. In addition, these seemingly innocuous gaps can lead to thousands of dollars flying out the door in the form of wasted heating/cooling.
Protecting the entire area with a solid system of sealing products is essential to maintaining the integrity of products, equipment and operations. The goal is to seal all gaps that are created, 24/7, when trailers are in place or not, and when overhead doors are open or closed. Besides proper top and bottom sealing of the overhead door itself, all four sides of the opening must be considered separately. With the help of a qualified environmental control specialist, follow these steps to achieve the best results:
1) Look for daylight
Visible daylight at loading dock openings indicates a gap in the seal that needs to be plugged. When standing on the inside of the dock, examine the perimeter around all sides of the trailer and dock leveler and note areas where you can see light when a trailer is in place and the dock door is opened. Because different gaps will need to be sealed by different products, understanding what kinds of gaps exist will lead to more informed decisions on properly sealing them.
2) Seal the top
Even brand new enclosures can leave gaps along the top if they’re not designed and fit to prevent them. To get the best seal possible in this area, choose a foam compression dock seal with a pleated-face head pad or head curtain, or a dock shelter with a heavily weighted head curtain. A gravity-based design guarantees the tightest, most consistent seal across the full width of the trailer, allowing it to maintain contact as the trailer bounces during loading and unloading. Today’s advanced dock shelters incorporate this type of weighted head curtain, accomplishing a tight seal without the need for an additional overhead rain diversion device.
3) Seal the corners
For the best seal at the top corners of the trailer, choose a dock shelter that is specially designed to seal this problem area. Most dock shelters leave gaps where the side curtains and head curtain meet. Technologically advanced shelters fix this problem with integral fabric pockets in the side curtains that receive the head curtain and block all daylight in this area.
4) Seal the sides
Foam compression style dock seals generally offer a very good seal along the sides of the trailer, but often suffer significant wear-and-tear due to the constant pressure and friction from the trailer. Additionally, foam and other material can protrude inside of the trailer when compressed, interfering with forklift loading. In contrast, perimeter-sealing dock shelters offer full access loading as they seal along the sides of the trailer, with nothing protruding into the trailer opening. Unless the right model is selected, however, gaps often exist, especially in situations with swing-open trailer doors. The solution is a shelter with side curtains featuring a fabric-covered hook on the leading edge. This seals the trailer hinge gap and minimizes the intrusion of outside elements.
5) Remember the fourth side
While it is critical to effectively seals gaps at the top and along the sides of the dock opening using a dock seal or shelter, a seal isn’t complete until the fourth side of the opening is addressed. Gaps typically remain below and around the dock leveler and exterior bumpers, presenting stubborn challenges for sealing out contaminants. Installing a complete under-leveler pit seal with complementary filler pads and other components helps fill tough-to-seal gaps where the dock enclosure, leveler, and bumpers all meet. Inside the facility, leveler lip corner seals, weather seal, door seals and other gap-sealing, daylight-blocking products finish the job.
6) Consider vertical-storing levelers
Utilized in many food facilities that require clean environments, vertical levelers differ from pit-style levelers in that they allow the loading dock door to close directly onto the pit floor. This minimizes outside air infiltration, helps reduce contaminants like rain from entering a building, and also helps protect the dock door from damage. Additionally, their vertical design makes it easy to clean or wash down the pit floor when the leveler is in the upright and stored position.
The Slippery Science of Sweating Slab Syndrome
Another common cause of slippery loading docks is sweating slab syndrome (SSS). This is a phenomenon that occurs when moisture intermittently develops on the surface of an interior concrete slab.
Dew point condensation is a common cause of this moisture accumulation, which typically occurs in spring and summer, when warm, humid air enters the structure through open dock doors, improperly sealed dock doors, doorways and windows.
One of the ways to reduce SSS is with a steady breeze. Although high-speed ceiling or floor fans can help (by increasing air movement), they use high amounts of energy and produce a high wind speed, which can be disruptive. In addition, having multiple floor fans can increase clutter and the chance of mishaps involving equipment and electrical cords – which makes them particularly impractical in loading docks.
The HVLS difference
Not only does the gentle 2 to 3 mph breeze they produce provide a cooling effect of 7 to 11 degrees F, HVLS ceiling fans can help reduce or eliminate slab sweating by minimizing ceiling-to-floor temperature differentials and increasing the surface evaporation rate.
Through a process called destratification, HVLS fans mix the air to create more uniform air temperatures from ceiling to floor. Warm air near the ceiling is pushed downward to the floor, replacing the cool air that settles along the floor. When that air heats up and rises, it’s pushed downward again. This process minimizes temperature differentials that can lead to condensation.
HVLS fans can move large volumes of air over an area up to 22,000 square feet, meaning a single HVLS fan can replace as many as 20 floor fans. In air-conditioned facilities, the breeze from an HVLS fan typically allows up to a 5 degrees F increase in thermostat setting with no change in employee comfort.
In addition, commercial dehumidification units can alter the interior environment to help reduce or eliminate SSS.
Keeping the dock dry and safe
Loading docks can be dangerous. Facility managers who take steps to keep dock floors dry are helping make them less slippery and, therefore, safer.
The right combination of dock seals and shelters can provide a complete seal and greatly reduce precipitation that infiltrates a loading dock area. HVLS fans will not only provide a nice breeze that workers appreciate on a hot day, they can aid in the evaporation of condensation on dock floors.
The next time you see a wet spot developing on the loading dock floor, contact a loading dock expert with a background in seals, shelters and HVLS fans to examine possible solutions.
The information herein is provided as a general reference regarding the use of the applicable product(s) in specific applications. This information is provided without warranty. It is your responsibility to ensure that you are using all mentioned products properly in your specific application and in accordance with all laws and regulations.