New products and attitudes can cure what’s ailing your dock and add years to your company’s well being.
by Clyde E. Witt, executive editor
Imagine your manufacturing plant or distribution center as a heart with valves at specific locations. You call those valves receiving and shipping docks. Now, think of those valves in more accurate terms as material transfer zones. You’ve expended a lot of time and money keeping your heart functioning at peak levels, but have you paid as much attention to those valves that regulate the flow of material in and finished goods out?
Many factors impact and impede the functioning of those valves. How smoothly they operate can change more quickly than you might imagine. Ten years ago, for instance, you planned 50 feet of space from your dock door to your first row of racks because you could easily get a full slug of material off a trailer and into that space. Have you noticed that recently nearly all trailers arriving at your dock are 53 feet long? Might that be why you’re having lift truck traffic jams and near-hits with pedestrians?
Another recurring problem is when a truck driver, focused on just-in-time deliveries, pulls away from the dock only a fraction of a second too soon. The result can be a major catastrophe.
Or the painful experience of a dock door, your shutter on the world, failing to open, close or sticking someplace in between. Two choices: You can forget about on-time deliveries or call the door repairman because a lift truck fork just skewered the lower door panel.
Focusing on the problem
According to the Unsaleable Products: 2000 Industry Benchmark Report released by Food Distributors International, Food Marketing Institute and the Grocery Manufacturers of America, damaged products cost the food industry one percent of annual sales, or $2.4 billion. That’s enough to make anyone sick. “Fortunately,” says Ken Bowman, a distribution specialist for Rite-Hite Corporation, much of the damage can be traced back to distribution procedures and environment.”
Fortunately? Well, if you know what’s causing the problem, you can work to prevent recurrences. No matter how far a product travels, the most treacherous part of its journey is the short span from the trailer to the racks — the material transfer zone.
Assuming your goods have not suffered damage from the pallets they were loaded onto (a serious culprit in the damaged-products mystery), the next-best place for damage comes at loading and unloading time. Today, basic dock design must take much into account. For example, changes in trailer design account for many mismatches at the dock.
The common trailer length used to be 48 feet, with interior dimensions of about 96 inches wide and 107 inches high. Today’s load haulers are 53 feet long and up to 101 inches wide. For trailer loaders, that means 40" x 48" pallets can be loaded with the long edge leading (double pinwheeling as it’s termed) two across, to use the full width of the trailer. Couple this fully loaded trailer with a now lower trailer bed profile, frequently less than the 48-inch “standard” dock height, and you have the ingredients for product damage.
The obvious indication of a problem is the simple fact that the trailer is too wide for the door opening.
“What we see [if a trailer door opening is wider than a dock opening],” explains Walt Swietlik, customer relations manager at Rite-Hite, “is those first few pallets are difficult for the lift truck operator to reach because of interference with bumpers or pit walls surrounding standard six- or seven-foot-wide levelers.” Doors get damaged, product gets damaged and trailers get damaged.
Even after the first few rows of pallets have been removed, product can still be damaged if the lift truck hits the interfering pit wall as it’s backing out of the trailer. There are many safety issues arising from unloading or loading trailers, especially if a pallet edge comes into contact with anything. Lift truck operators are in jeopardy of being knocked from a truck. Damaged pallets can harm people removing goods.
New approaches
Dock equipment manufacturers today realize they are no longer in the compo-nent equipment business. They are in the business of creating a new approach, or methodology, for handling material at the most critical points of the supply chain process.
“One of the important trends we’re seeing,” says Shawn Ward, director of sales for Kelley, “is the benefit of [electronically] interlocking the dock leveler, trailer restraint and overhead door.” Interlocking ensures that the attendant will operate all the dock equipment in the proper sequence, providing a safer, more efficient operation. Additionally, all these control buttons can be combined into one control panel utilizing a single electrical input line, reducing wiring costs and providing a cleaner building wall.
There are numerous benefits to having a system that uses a single electrical input line, as well as having all the controls for the door, dock leveler and trailer restraint in a single panel. Another safety feature during maintenance is the ability to lockout and tag the entire system at a single point.
Because there is a difference in shipping and receiving docks, as well as differences within those categories, having a single point of control allows you to customize the operation of the dock to fit your needs. Basic indicators on a control panel should include lights to signal the interlocking of the leveler and give indication that the restraint is engaged as well as the overhead door in position. There should be indicators to make the operator aware that the leveler has been stored safely before the restraint is able to release the trailer. There should also be some indication that the restraint has automatically engaged the trailer on activation of the dock leveler.
A well designed panel also has pushbuttons to operate the overhead door and a switch for the dock lights.
Based on the client’s requirements, the dock system consists of an enclosure surrounding an overhead door that can service a wide variety of vehicles arriving at the dock. And the dock leveler has to be specific to the client’s applications, which might require segregating the differences between shipping and receiving operations. Safety is not abandoned in any way. The vehicle restraint ties into the system in such a way that a dock attendant is almost forced to use it to ensure his or her safety as the trailer is being unloaded.
It might seem obvious, but one thing to keep in mind if you’re planning a new dock or retrofitting an existing facility — make the doors wide and tall enough. Current recommendations for non-refrigerated operations are for door spaces nine feet wide and 10 feet tall. To add flexibility that will accommodate various size trailers, you can add shelters and seals. These essential products can be adjusted to give lift truck operators unobstructed access to loads.
To handle the newer trailers, dock levelers are now available in lengths to 12 feet and widths up to 102 inches. While air-bag-controlled levelers are the latest innovation for controlling the height and speed of levelers, hydraulic levelers continue to be the best sellers.
A smooth transition from trailer to dock in the material transfer zone is important to the product, but probably more important to the lift truck operator. That all trailers are not of equal height and that dock heights vary, is well known — thus the need for dock levelers. What is now being discovered is that because of air-ride suspension in many new trailers, the level of the trailer changes as the trailer load increases or decreases.
Bowman says, “We’ve found that bed height can drop four inches to eight inches by the time loading is finished.” Ideally, the dock leveler descends with the trailer bed as each load adds weight to the trailer. However, if the bed height lowers significantly, the dock leveler adopts a steep slope that the lift truck operator must negotiate.
The load can be damaged if the lift truck hits bottom on its way into the trailer. What can also happen is what experts call “stump-out.” When the mechanical safety legs on levelers interfere with the platform’s ability to follow the trailer bed down below deck height, a steep slope is created. The lift truck can contact this slope on the way out of the trailer, creating the potential for load spills or, worse, injuries to the operator.
What’s the cure? Stump-out can be eliminated with hydraulic or air-bag levelers that do not incorporate mechanical safety legs. Levelers providing a full-range free float eliminate the potential for stump-out. The best way to smooth the transition in the material transfer zone is the use of extra-long levelers or ground-level hydraulic truck leveling systems. The longer levelers will decrease the angle of the bridge into the trailer by extending the transition area. Truck levelers eliminate the slope altogether by adjusting the height and angle of the trailer bed to match that of the dock.
Doors and seals
The principal concern with dock doors and seals continues to be damage. While it’s obvious that training operators is the best way to prevent damage, the fact remains that doors get hit and seals get rubbed and mashed.
The latest devices to improve door operations are new approaches to the challenge of counterbalancing. It’s estimated that 98 percent of the doors operating today have springs as the counterbalance. The inherent problem with springs is that from the day the door is instal-led it’s in the process of going out of adjustment.
You can have the door adjusted on a regular basis or let it wear to the point of failure, then get it fixed. As the door creeps out of adjustment, the bottom panel sinks lower (when the door is open) and eventually a lift truck operator hits it with a load. A secondary problem involves ergonomics and safety. The out-of-adjustment door gets heavier as the counter-balance gets out of adjustment.
Now, several manufacturers are moving away from the spring and turning to an older, simpler technology, a counterweight similar to the type found in old window sashes. The weights don’t go out of adjustment, and the use of aircraft cable has eliminated the problem of the door losing its counterbalance and falling.
There have also been improvements in designing doors with breakaway panels, improved locking systems and better insulating material.
To add life to dock seals, manufacturers are now constructing frames with steel or other components that can withstand impacts and weather. Using head pads that slide up and down as the trailer moves reduces the potential for wear and tear at the top of the seal. Along the sides, wear pleats are still popular, as well as new material that is abrasion resistant. Another improvement to seal material has been the use of fire-retardant foam in the header, along with layers of foil to dissipate the heat generated by trailer lights pushing against the pads.
Trailer restraints
Trailer restraints are not new. They’ve been around the dock for more than 20 years and acceptance of the product seems to be on the increase. The function of the restraint is to control trailer/dock separation. The hook prevents aggressive, early trailer departure, trailer creep caused by lift truck traffic and trailer tipover should the landing gear of the trailer fail.
Programmable control of the leveler is now available from many manufacturers to improve the communication between the truck driver and the dock attendant. Interior and exterior panel lights keep both parties informed of the status of the trailer and restraint as the trailer approaches the lip of the dock.
Tough medicine
The dock doctors have plenty of recommendations for keeping your dock healthy. For starters, if you’re building a new facility or retrofitting your current building, you have to think of the trailer as part of the building’s basic design. The trailer is just an extension of the material transfer zone.
Another solution, and this is a bitter pill for some clients to swallow, says Swietlik, is to cut back on the number of dock positions you’re planning. This might seem to be counterproductive, but it opens the flow of material and reduces the potential for logjams.
Designers recommend you keep in mind how you will use the entire cube of the trailer, dock area and building. Try to imagine it as a single space, not separate entities. The combination of the right equipment can make or break your operation, says Mary Blaser, marketing manager, dock products group, Rite-Hite. “The concern for dock efficiency and safety extends 200 feet outside the building and 60 feet inside the building,” she adds.
You have to look at dock design as more than what kind of lift truck will be bringing the loads to the trailer. There might be no lift trucks if you chose to floor-load the trailer with extendable conveyors.
Getting a clean bill of health
It is easy to come to the conclusion that the loading dock area is likely to be the most hazardous part of your operation. Consider the combinations of hazards and the volume of activities that occur in this area.
As Dave Piasecki, consultant with Inventory Operations Consulting LLC, says, “For the lift truck operator, ramps and inclines, overhead obstructions, dissimilar surfaces often wet and slippery, poor lighting in trailers, other vehicular traffic, pedestrian traffic, restricted views, sheer drops, trailer creep, congested staging areas, and accumulations of empty containers, pallets and debris are hazards that can all be present at the same time within a confined area.”
While OSHA does require training of lift truck operators on these types of hazards, many operations often fail in providing detailed hazard assessment, operational procedures, and day-to-day enforcement of safety issues. In addition, employees who do not operate lift trucks are rarely trained on dock safety issues even though they share many of the same risks.
The biggest reason to put a priority on dock safety is not so much related to the frequency of accidents in dock areas as it is to the potential severity of injuries that can occur in these types of accidents.
For nearly all industries, the dock has changed drastically in the past couple of years, and can change quickly in a matter of months. If your company opts to install a returnable container program, suddenly you are not only shipping products, you’re shipping empty containers or specialized racks and dunnage back to your suppliers. We talk about the supply chain all the time, but when you get down to defining what the supply chain is, you discover it’s not made of electrons, nanoseconds or fancy buzzwords. It’s still forged from steel and cement as well as flesh and blood. The supply chain begins and ends at someone’s receiving or shipping dock. It’s people who load the trucks and scan the bar codes. The whole supply chain process does not begin until the product leaves the building. And it’s not out the door until it’s out the door. MHM
Help Is Available
For more information on dock components and systems, visit the following Web sites and sources:
Material Handling Management, mhmanagement.com;
Aleco, aleco.com;
ASI Technologies, asidoors.com;
APS Resource, apsource.com
Autoquip, autoquip.com
Beacon Industries, beacontechnology.com;
Bishamon Industries, bishamon.com;
Blue Giant, bluegiant.com;
D.L. Manufacturing, dlmanufacturing.com;
Dynaco USA, dynacodoor.com;
Flexon, 800 365-3667;
Georgia Boot, georgiaboot.com;
Inventory Operations Consulting, inventoryops.com;
Kelley, kelleycompany.com;
