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Overhead Handling: Handling Up High

Using the overhead space in your facility not only frees up floor space, but also leads to more efficient product movement
By Sara Pearson Specter, Editor at Large
April 01, 2010

Using space overhead frees up the floor for safer, more efficient movement of products, work-in-process and associated tooling. In addition to decluttering the work zone, these systems offer enhanced ergonomics, plus a means to move items too large to be transported with a fork-based vehicle.

Track-based conveyance

For moving products weighing 5 pounds to 1,500 pounds, overhead chain systems are the most common type of overhead handing. Evenly spaced pendants hanging along a single chain are pulled through a single enclosed track, or I-beam track, to carry the loads.

The next level of conveyance is dual-track power-and-free systems. These systems are comprised of a chain track on top, which provides the power, and the free track below, which contains the trolleys that move loads through the system.

Capable of carrying 25 pounds to 25,000 pound loads, power-and-free conveyors are used extensively in conveying materials to and from automation, manual workcells, and hostile environments like industrial washers, paint equipment and ovens, according to Brent Brosch, director of product sales for Jervis B. Webb (248-553-1000, http://www.jervisbwebb.com). “Power-and-free conveyors are extremely flexible, versatile and can be programmed to service a few work cells or an entire plant with proven reliability,” he says.

“From a new development perspective, lately there's been more emphasis put on noise reduction in chain and power-and-free conveyors, with use of non-metallic wheels to reduce the noise in a workplace,” says Brosch. And, to further reduce noise, other components are also being made of non-metallic materials, he adds.

Ideal for carrying a load from Point A to Point B, electrified monorail systems are best suited for moving high-value products across long distances with fewer stops. The system consists of a single rail or I-beam from which a hook or hoist hangs, providing lateral and vertical movements of loads weighing up to 30,000 pounds.

“Monorails have remained very similar in appearance over the past 30 years, but a lot of subtle improvements have been made,” Brosch says. “Previously, most I-beam systems were built for very heavy-duty cycle use, particularly in automotive manufacturing. Today, other industries with light- to medium-duty manufacturing applications, like appliances and warehousing, are installing lighter duty monorail systems appropriate for their needs.”

Workstation and overhead cranes

Offered in multiple types and load capacities, cranes are comprised of three components:

  • a stationary or mobile bridge made of rails and carrying one or more trolleys,
  • the unit that travels side to side and carries the hoist, and
  • a lifting device that hooks onto and manipulates a load.

Cranes can be manual or power driven, depending on the application and the size of the load that has to be moved.

On the smaller scale, workstation cranes enable operators in a work cell to safely manipulate relatively light loads. These free-standing units handle product in a relatively limited area, like in production environments.

More workstation cranes are being installed as part of lean-driven manufacturing process changes, says Jeff McNeil, marketing manager for Gorbel (800-821-0086, http://www.gorbel.com). “To enhance the ability to produce multiple products in a single assembly area, companies are turning to flexible systems that maximize the productivity of their operators—installing more ergonomic workstation cranes and lifting devices to help users work smarter,” he says.

Some of the newest workstation cranes are intelligent devices that combine manual and servo-driven operations, McNeil says. The manual function allows workers to move at their own pace as they walk to a bin, select a part and guide the crane to a machining center process. The servo-driven function controls the positioning of the part on the machine, preventing damage to either, by slowing down for part placement and release.

Massive overhead cranes move heavy loads that are not practical to transport with a lift truck over long distances. Ceiling-mounted bridge cranes are often part of the building structure. Top-running, double-girder cranes mount the bridge on top of the runway and have two girders for the bridge. Always powered, these bridge cranes offer capacities up to 600 tons. Alternately, under-hung cranes have a trolley that runs on the bottom of the support I-beams. They're ideal for loads of 15 tons or less.

Gantry cranes look similar to overhead bridge cranes but are not part of the structure of a building. Instead, a gantry consists of two uprights connected by an I-beam that serves as a bridge for the trolley. They can be either powered or manually manipulated and handle capacities up to 5 tons.

Speed control continues to be refined in overhead cranes for better load handling, says John Paxton, president of Demag Cranes & Components North America (440-248-2400, http://www.demagcranes.us).

“The enhancements include smooth acceleration and deceleration of the hoist and even step-less control, similar to the gas pedal on a car,” Paxton says. “The more you push on the button, the faster you go, and as you let up, the slower you go. That gives the operator improved control for spotting and positioning.” This functionality results in improved productivity.

A bigger trend in 5-ton and above cranes, says Paxton, is the integration of smart controls to enhance safety and reduce downtime. “These controls monitor the hoist, store information including warnings and error codes, and allow the data to be retrieved. By monitoring the load spectrum, users know how the hoist is being used and can schedule maintenance as needed, both predictive and preventive.” This also improves safety and reduces downtime due to unexpected repairs, Paxton adds.

Crane controls

Driven by safety concerns, more and more overhead systems are being controlled by wireless radio remotes instead of wired pendant control. The wireless method permits the operator to run the crane from a safe distance, while pendants require the operator to be near the load as it moves.

Wireless systems include a radio receiver mounted on the crane and wired into the programmable logic controller (PLC) and motors that are turned on and off by the system. They also include a handheld transmitter that the operator uses to send a signal to the receiver.

“One of the emerging trends we see in crane controls is remote diagnostics,” says Haroon Inam, vice president of global engineering for Cattron Group International (724-962-3571, http://www.cattrongroup.com). “This and a multitude of other reports—including productivity monitoring and safety conformance—can be custom-created to examine crane behavior, as well as operator behavior.”

Reports are generated from the data collected by the machine control unit. “The information can be conveyed to a global help desk not only for condition-based monitoring, but also to enable remote upgrades of software without the need for a technician to visit each site individually,” says Inam.


Power-and-free conveyor supports powder coat line

For Gradall Industries, manufacturer of excavating equipment for highway, industrial, railroad and mining industries, a small part can weigh as much as 2,500 pounds—and large parts range up to 9,000 pounds. This size and mass presented a challenge for handling through their paint system.

To shepherd the small parts through their powder coating line, the company selected an enclosed track power-and-free conveyor system (Jervis B. Webb, 248-553-1000, http://www.jervisbwebb.com) with two-speed transport conveyors in the line that process up to six carriers per hour.

The three-trolley carrier system uses a lowerator to improve ergonomics in the load/unload process. Carriers travel on the slower (3 feet per minute) process line through washer, dry-off and powder booths. The 40-feet-per-minute transport conveyor delivers the carriers to the dry-off oven, cure oven and cooling tunnel. Oven and tunnel times are adjusted at a control panel, opening when a carrier's time is up. Control logic ensures that only one set of doors is opened at a time to prevent heat loss.

The system permits Gradall to powder coat all of the parts necessary for three shifts of assembly in a single shift of powder-coating, while improving product flow and reducing the level of rework significantly.

Free-standing workstation crane gives machine shop flexibility

After relocating to a new facility, Just In Time CNC Machining (JIT) needed a flexible lifting system to meet growing production needs. The company handles parts in a range of sizes and weights, from large production runs to smaller runs or prototypes.

The facility, which the company leased, provided multiple challenges: high ceilings, multiple columns, CNC machines and loading bays. Due to the layout of the facility, the goal was to install one crane system to service several CNC machines.

Ultimately the company purchased a free-standing workstation crane with three, 23-foot long, 1,000 pound aluminum bridges (Gorbel, 800-821-0086, http://www.gorbel.com). System supports were staggered to allow 124-foot runways to cover the length of the building and remain centered over each of the machines and work bays. Extra long headers help the positioning of the support columns.

“It's great having the multiple bridges, because if one is busy, we've still got two available, and you're not waiting on someone to finish,” says Jim Alexander, owner of JIT. “The workers really liked the system since day one. Productivity is very good, and we haven't had any lifting injuries.”

About the Author

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Sara Pearson Specter
Editor at Large

Sara Pearson Specter has written articles and supplements for Modern Materials Handling and Logistics Management as an Editor at Large since 2001. Based in Cincinnati, Specter has worked in the fields of journalism, graphic design, advertising, marketing, and public relations for 15 years, with a special emphasis on helping business-to-business industrial and manufacturing companies. Specter graduated from Centre College in Danville, Ky., with a bachelor’s degree in French and history.


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