Consider a 102-inch-wide trailer in position at a traditionally designed dock, filled to the rear sill with double-pinwheeled, 48-inch-wide pallets. Also factor in a foam dock seal with a 96-inch-wide overhead door, which is common at many loading docks. Pallet loads fill the width of the trailer, leaving virtually no maneuvering space.
A lift truck can remove the first loads (end loads) only by pulling them straight off. But this is difficult at best because the foam dock seal and door jam obstruct the load on each side.
Even with no dock seal, the building wall may interfere on one side or the other, unless the truck has backed in perfectly on center. If the forklifts can't remove the end loads, employees must unload those pallets by hand, wasting time and money.
More complications come into play when the same truck rides on low-profile tires because the trailer bed rests four to six inches below the typical 48- to 50-inch dock height. Lift trucks are now constrained by the walls of the six-foot-wide leveler pit, which doesn't allow for straight-in access to end pallets. As such, the lift truck must spend a great deal of time to carefully extract end loads.
The situation becomes even more difficult when double-pinwheeled and double-stacked pallets are involved. Now the upper loads cannot pass through the door opening and hand unloading is virtually unavoidable.
Other Pitfalls Lurk
Many additional pitfalls exist when servicing modern trailers with conventional dock designs. Drivers may violently strike the corner of the building wall when backing out of a trailer. Another example involves lift trucks servicing trailers with low beds (six to 12 inches below dock) by way of six- or eight-foot-long levelers. Drivers may face excessive platform slopes. As such, they must accelerate sharply when backing out with loads in order to make the incline, which causes load instability.
Other key concerns include dock shock and trailer drop, two safety issues that also slow productivity and create potential for product damage.
Dock shock describes jarring that occurs when a lift truck (stand-up walkie or forklift) crosses between the warehouse floor and the trailer bed due to the bumps and gaps that exist on traditional dock levelers. Trailer drop describes vertical trailer bed movement or "drop" that occurs with the weight of lift trucks traveling in and out of unstable trailers. The situation is compounded when trailers with air-ride suspension systems are involved.
Mismatched dock designs often present a number of significant problems. Unfor-tunately, these problems are magnified in a finely tuned supply chain that depends on the smooth flow of materials at all points.
Don't Abandon Safety
In any plant, safety must be a given and it's important not to put employees at risk for the sake of speed-to-market. It's also important to think ahead.
Safety and productivity are inexorably linked. If pallets are easily accessible with forklifts, manual work—as well as possible injuries— reduced. If forklifts can back out of a trailer without fear of crashing into a pit wall or running into trailer drop, driver confidence is gained.
If proper dock seals/shelters are in place, employees are protected from the elements and able to work efficiently. If dock levelers float to meet the bed of a trailer with air-ride suspension, product slippage and accidents related to steep grades are avoided. Additionally, the comfort level that a forklift driver has knowing a trailer is properly restrained cannot be overstated.
Facilities simply cannot afford to overlook the Material Transfer Zone when developing plans for an efficient and high-performance supply chain. The prudent strategy is to make wise choices in dock design and equipment today. Doing so provides relatively quick payback and a long-lasting solid return on investment.