With safe, hydraulic-powered dock leveling, a job shop can focus on its metalwork
April 2012 - Consider the dock. For all practical purposes, it’s a shop’s entry where a truck backs up, the door opens and pallets of parts are loaded. Through that threshold between shop floor and semi-trailer is where shipment occurs, the last, crucial step of production. Because any job shop’s attention is directed at getting perfect orders out on time, all transitions of material handling must be reliable—from the forklift driver to the dock platform below.
In 2005, Pro Metal Works Inc., DeForest, Wis., broke ground on a 42,000-square-foot facility to accommodate growth its previous 13,000-square-foot shop could not. The company needed loading docks as well as space for its lasers, turret punch presses, press brakes and welding capabilities.
With multiple truckloads of mild steel, stainless steel and aluminum fabricated parts shipping out daily, Pro Metal Works designed its new building with two docks, a necessity its previous building lacked, says Tom Carroll, president.
“We always had to have two guys loading a truck. One guy up on the truck with a pallet jack and the other guy with a forklift,” he says.
Pro Metal Works paired its docks with RHH hydraulic-powered dock levelers, manufactured by Rite-Hite Co. LLC, to eliminate two sets of hands required for loading shipments and create an adjustable plane across which forklifts could safely drive onto truck beds, Milwaukee-based Rite-Hite specializes in loading dock equipment, safety barriers and industrial doors. Its production facilities are located in Horn Lake, Miss., and Dubuque, Iowa.
The customized dock levelers have made Pro Metal Works’ loading process safer and more efficient. Without the need for multiple workers to load a truck, the potential for injuries and accidents is low. “We’ve eliminated that possibility,” Carroll says.
Aside from curtailing potential accidents involving multiple workers, the dock levelers make operating forklifts safer, too, says Walt Swietlik, director of customer relations and sales support at Rite-Hite. The dock leveler platforms, referred to as the deck, have a beveled Safe-T-Lip that smoothes the transition between truck bed and deck so forklifts can drive safely across. When the leveler is in the stored position, the lip doubles as a fail-safe barrier.
“Unfortunately, you’d be shocked at how many times somebody will have a dock door open. [It] might not be a forklift driving off the end of a dock, but it might be some wheeled cart that gets too close and rolls off the end,” he says. “It might be filled with all kinds of finished product.”
Follow the height
Pro Metal Works, now with 22 employees at its Madison-area shop, bends, cuts and punches parts for a multitude of industries, such as agriculture, defense and transportation. “We work for people with their product line,” Carroll says.
The loading docks primarily are used for outgoing product because raw material sheet up to 60 inches wide by 120 feet long wouldn’t easily fit. In that case, it’s brought in through separate, larger bay doors. However, when tooling or hardware comes in on a truck, it will come in through the docks.
“We probably have at least four or five different truckloads that go out a day,” he says. “The majority of the time we’re using the docks for materials shipping out.”
When a truck backs up to the dock, an operator pushes a button, activating the hydraulic lift arm beneath the leveler. It raises the 7-foot-wide, 50,000-psi minimum-yield, diamond-tread steel deck plate. Once the truck is parked, the operator releases the button. The lip extends when the deck is fully raised then descends on the trailer bed.
“Once we’ve loaded the truck, we hit the button again, and the leveler comes up to a certain point,” Carroll says. “That lip that rests on top of the truck will fold in, and we let the button go and it goes right back to level. Pretty simple.”
A dock’s typical height is 48 inches. But no two trailer beds are identical. Most of them also are 48 inches high, give or take, says Swietlik. The inevitable factor, which the leveler accounts for, is trailer height fluctuation caused by heavy payload.
“You could easily have a trailer come in that’s 50 inches high, come in empty, and then you put 40,000 pounds of steel on it. The next thing you know that truck is sitting down 44 inches,” he says.
For the last 10 to 15 years, trailer manufacturers increasingly have opted for air suspensions, often indicated by “air-ride equipped” written on a truck’s side, instead of springs or shocks. Although it provides a cushioned ride for cargo, it presents a challenge for dock leveling.
Rite-Hite’s leveler design features a constant radius pivot hinge at the back of the deck, a simple yet key consideration for the dock leveler to follow the trailer as it’s weighed down. The concrete floor area inside the dock is recessed, accommodating the hydraulic arm and motor components under the leveler structure. The pit lets the deck slope down when a trailer is lower than the dock.
According to Swietlik, the hydraulic leveler incorporates a check valve intended to arrest leveler free fall should a truck unexpectedly pull away.
The added safety benefit of the check valve eliminates what is called stump out, which occurs when a leveler bottoms out on safety legs intended to keep the deck level when trailer height shifts under the weight of forklifts and payload. Non-hydraulic levelers include these safety legs.
Before the truck pulls away, the chamfered lip is folded up from the truck. This keeps the lip from “flopping down,” Carroll says.
Seals and service
Rite-Hite manufactures its dock levelers in air-powered and mechanical versions in addition to the hydraulic, depending on the deck-control needs of the end-user. For Pro Metal Works, the hydraulic version has proven to be the perfect fit.
For maintenance, the dock can be raised and held in place with the Safe-T-Strut, a lockout prop that gives access to the pit to clean or inspect the leveler’s mechanisms. The strut protrudes from the lip, alerting nearby workers that someone may be underneath the deck.
As it is, the leveler’s design and absence of complicated components has minimized maintenance. “We don’t really run into having to get underneath it. That’s because we’re never really having to run maintenance on it,” Carroll says. “It’s like a Maytag machine. Since we put in those levelers, we’ve never had to have service come over to fix them.”
To keep out the elements that come with a Wisconsin winter when loading a trailer, Pro Metal Works installed Rite-Hite dock seals along with its dock levelers.
“It kind of locks off the dock to prevent cold winter air from getting inside,” Carroll says. “Those have been great.”
The foam and fabric pads are affixed to the dock’s exterior to prevent both precipitation from contaminating metal parts as well as air from escaping when a truck is being loaded. A curtain above the dock door covers the entrance. “The goal there is to conserve energy, which is a huge topic for many of our customers these days,” Swietlik says.
As Pro Metal Works’ business picks up, it can focus on perfecting the metalworking for its diversified client base. When it can rely on safe, simple and strong dock leveling, it can devote energy and attention to its delivering product.
“I’ve eliminated an extra guy having to unload and load a truck,” Carroll says. “When we’ve got product going out, it’s definitely made us more efficient.” MM