Sustainable operations and green buildings occupy a growing amount of attention from distribution center (DC) owners and managers, and the trend is not going to stop.
More companies are becoming aware of the need for a greener supply chain. A recent Material Handling Industry of America (MHIA) survey of material handling and logistics managers found that 79% have or are planning to institute sustainability goals for their operations. If a company isn't practicing sustainability yet, chances are someone who is part of their supply chain will either ask or demand that they do.
The natural point in the sustainable supply chain is the DC. Warehouses have long been on the sustainability track and not known it, simply by locating as close as possible to heavily traveled highways and to their customers.
Moreover, with these buildings enclosing hundreds of thousands of cubic feet, running a DC more efficiently can pay off in tremendous energy savings and a greener bottom line for the company. The owners of many DCs being constructed now are putting these projects on the path to LEED certification.
When it comes to sustainability and energy savings, many operations treat loading docks as an afterthought. Managers recognize that the doorway is a escape route for energy but generally feel they have done the job by installing seals and shelters to encase the door end of a parked trailer during loading and loading. But the typical 8 × 10 doorways at most docks present the biggest opportunities for saving energy.
JohnsonDiversey, a Sturtevant, Wis.-based provider of commercial cleaning, sanitation and hygiene solutions, is one company that has. Its recently built, 550,000-square foot facility has earned a LEED gold certification for new construction, and it's working on another LEED gold for existing buildings. The company is also urging contractors to practice sustainability while working to sell greener products to building maintenance customers throughout the world.
The JohnsonDiversey management team looked through all areas of the operation to discover ways to make it more sustainable. When they looked at loading dock areas, they noticed that each truck that pulls up to a dock position creates an opportunity for energy to escape the building. Trucks can be parked at the dock for hours throughout the course of a day, creating significant energy loss if the doorway is not properly sealed. If the gap between the trailer and the dock is not tightly enclosed, the HVAC system works overtime.
Even though the door is closed, the building envelope may not be sealed. On busy docks, lift trucks often impact and damage the door or the door track. Though a damaged door requires immediate attention, a partially damaged door may still function but can allow continual energy loss. Even a slight bump can cause the door to be misaligned, and the resulting gap, however slight, can lead to hundreds of dollars of lost energy annually.
Impactable dock doors are the first line of defense. These doors are built to stand up to the occasional bump or a severe collision. Rather than becoming damaged from the force of a major impact, the door panels release and can be easily set back in place. Fully impactable models have the door seal attached to the door panel rather than the doorframe. The door can roll up and be out of harm's way, maintaining a consistent seal.
Standard pit-mounted dock levelers provide safe trailer access for lift trucks, but the pit cut into the concrete dock floor presents a challenge in sealing the dock. As an alternative to pit-style dock levelers, vertical-storing powered levelers store upright when not in use. This design allows the dock door to close tightly against the concrete floor to seal in energy and lock out the elements. These levelers and dock bridges provide the added benefit of a full perimeter seal. They also act as a steel barrier when stored to protect overhead doors from lift truck assaults.
For facilities that use standard pit-style levers, one solution is pit-style dock levelers with seals. Dock levelers are typically mounted in concrete pits; however, that configuration creates small gaps between the edge of the dock leveler and the pit wall, which exposes the facility to interior and exterior airflow exchange.
With a pit-style leveler, any breeze outside can be detected by simply standing over the gap between the floor and leveler platform. Tightly closing the dock door and installing standard neoprene or brush weatherseal does not completely cut off the airflow.
Both new and existing pit-style dock levelers can be outfitted with an advanced weatherseal system comprised of open-cell foam and heavy-duty vinyl that effectively fills gaps around the sides and rear of the dock leveler and provides a superior seal around the dock leveler perimeter.
Seals and Shelters
Even when a lift truck is working as fast as it can to load or unload a trailer, there is a period of time when the door is fully open. Dock seals are critically important to containing conditioned air in the dock areas. As with damaged dock doors, a poorly specified seal or shelter also permits 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 sealing off the gaps between the trailer's door hinges. Dock shelters consist of fabric attached to side/head frames to create a canopy around the full perimeter of the trailer; they allow full, unimpeded access to the interior of the trailer.
Galvanized steel backing offers many advantages over wood backing. Wood backing has a solid mass that does not yield when the seal is compressed. This often results in damage to the building. On steel backing, the solid mass is replaced with compressible foam on a steel frame. Steel backing does not rot, split, crack or warp. It uses plated screws with load-spreading washers in the steel to provide a strong hold on the fabric.
Other Energy Savers
Though largely regarded as safety devices, vehicle restraints also play a role in helping seal off dock doorways. Many docks use rubber wheel chocks to hold trucks in place during loading/unloading. However, rubber chocks are no match for the forces exerted by lift trucks driving in and out of trailers.
This force can gradually cause a trailer to “walk” away from the dock, forming a doorway gap. A powered truck restraint can help ensure the trailer is held snuggly to the dock, with the back end of the trailer fully enveloped by the dock seal.
And, LED dock lights provide thousands of hours of illumination and save considerable time and money spent on replacing bulbs. Because dock activity can be rough on lights, light housings should be designed for lift truck impact. Units with acrylic covers offer protection for food and packaging operations.
Finally, master control panels can tie all of this equipment together. Programming ensures that dock doors are not opened until trailers are parked and gripped by restraints. Restraints will not release trailers until the door is fully closed.
When it comes to going green, the loading dock can be the first line of defense against energy loss and an effective offense toward a more sustainable operation.
Michael Brittingham is manager of marketing communications at 4Front Engineered Solutions Inc., a manufacturer of loading dock equipment.