There are so many options for handling heavy loads today that it requires quite a bit of study to even explore the options. And, of course, application rules the day with some loads being handled outdoors, indoors, in harsh environments or in tight locations. The key is flexibility and not getting yourself trapped in one-technology-is-the-only-technology thinking.
Users and buyers tend to get locked into inflexibility when it comes to heavy-duty conveyor systems. “We’re coming up with new ways of engineering heavy-duty conveyor that allows for modular conveyor assembly and distributed control. Using today’s network architecture for controls and communications with modular electrical systems, we can ship out assemblies that can be installed quickly on site to eliminate downtime,” says Greg Pate, product engineer for Control Engineering, a division of Jervis B. Webb.
Today, heavy-duty conveyors are preassembled in the shop and tested fully before shipment. This means the conveyor is far simpler to relocate and reuse with modular pieces in the field. “With old conveyor designs, when you took them apart, you had nothing left,” says Pate.
Two areas where there has been growth in heavy-duty roller conveyor are air cargo and container screening. These can be everything from semi-truck trailers to ULD cargo containers for air transport to loading and unloading cargo ships. The conveyor is used to transport the container through an X-ray or other scanning technology. “The attack on September 11 increased the need for this heavy-duty screening,” says Earl Raynal Jr., sales manager for Control Engineering.
Another application is at border crossings with inspection of semi-trucks. There has to be some means of moving the containers in the truck through the screening system at a controlled speed. An overhead crane takes the containers off a flatbed truck or off a railcar.
The military uses heavy-duty conveyor in handling armaments for weapons decommissioning. The armaments are taken out of storage, broken into smaller components and then are destroyed. The conveyors move rocket shells or containers through various stations for deassembly and decontamination.
Integrating guided vehicles or shuttles on rails is often common with heavy-duty conveyor. Common applications include exiting stretchwrapping or palletizing onto shipping conveyor.
At the Ball Foster Glass Container Company, the Webb Heavy-Duty Roller Conveyor Systems, a division of Control Engineering Company, installed two, high-speed transfer cars to integrate conveyor lines handling fragile glass bottles using palletizers and a system controller. The conveyor is mated with a Smart T-Car, an automatic vehicle that shuttles quickly between roller conveyor lines to help keep the amount of conveyor to a minimum. The control system communicates to the Smart T-Cars using a spread-spectrum radio modem; a touch-screen panel is mounted on the enclosure door for easy operator interface when programming and diagnostics are performed. The vehicle capacity is a heavy-duty 10,000 pounds with variable-speed motion of 20 to 350 feet per minute (fpm).
Each Smart T-Car is equipped with two chain-driven, live-roller conveyors. The conveyors are arranged end-to-end so that the Smart T-Car transports two palletloads at a time. The cars are integrated with up to nine palletizers for receiving two pallets side-by-side of strapped, cartoned or uncartoned glass bottles.
The automated system eliminates damage to the glass bottles. Ball Foster plans to add two new palletizer lines.
Making the most of skid conveyor
For loads more than 3,000 pounds, Eisenmann uses a dual-strand, skid conveyor. It incorporates two chains that move pallets or skids that sit on top of the chains. The system allows for 90-degree transfers and is flexible for transporting heavy loads. To make a turn you can either use a cam lift where a conveyor lifts the pallets and transfers it at a 90-degree angle, or a turntable can move the skid 90 degrees and move it onto a conveyor.
Eisenmann uses these conveyors to transport five or six truck frames to a hoist that lifts the skid and drops it into an electro-painting tank.
Assembly lines are another application for moving refrigerator frames easily down the line. The chain conveyor moves the heavy load.
Power & free conveyors
Overhead power & free conveyors have capacities to 3,000 pounds. Eisenmann conveyors feature silent accumulation, which is contrary to the typical noisy design of these conveyors. The system disengages the carrier from the chain and makes for silent accumulation. Power & free allows multiple paths or spurs for automatically routing product through different processes at different speeds. In a paint finishing system, you want to move items through painting at slow speeds and then transport the product to assembly and shipping areas at a faster speed. And then accumulation areas are needed. Power & free allows for all these needs.
Power & free carriers can be fitted with an automatic ID tag, which allows automatic routing and the tracking of statistical information in reference to those parts as they pass through an assembly line. The tags are made of slotted metal on a metal plate and look like a bar code.
Rich Goelz, sales manager, general industrial systems for Eisenmann, says cost justification for power & free conveyor comes from two factors: cost of ergonomics in injury to workers and cost of re-handling in damage to product. If you’re not using power & free conveyor, there is more possibility of hitting and damaging product.
Heavy-duty power & free conveyors are used today for painting truck bodies and components for one of Eisenmann’s manufacturing customers. Eisenmann uses these conveyors for a programmable hoist dip system. Parts are racked on individual power & free carriers and are transported to the programmable hoist pretreatment and electrocoat lines. At this point, racks are automatically transferred from the power & free conveyor to the hoist system load station. One rack of large parts, two racks of medium parts or three racks of small parts can be loaded into the electrocoat system and be processed concurrently using the programmable hoists.
After coating, the parts racks are automatically transferred back to the power & free conveyor. With these automated conveyors, worker staffing is minimal, which reduces the chances for injuries when handling these heavy parts.
Goelz advises you not to limit yourself to one specific type of conveyor until you’ve explored all options. That can include overhead conveyors, power & free, skid and slat floor conveyors, and tow-line conveyors. He offers that, for example, in truck manufacturing tow-line conveyors were the standard for moving large cabs through painting and assembly. Now skid conveyors are an ergo-nomic option and can be a cost-effective alternative.
Heavy-handling lift trucks
The Raymond Corporation has done some new things with the Swing-Reach turret truck product line by offering extended load handlers that allow operators to take longer loads but still utilize narrow aisles. Loads up to 108 inches wide can now be handled up to 42 feet in the air while still using very narrow aisles of about 74 inches. The load capacity at that height is 1,600 pounds.
Sideloader truck capacities range from 6,000 to 10,000 pounds. They are for handling loads of steel or lumber, or rolls of floor tile.
Applications include coil steel handling, but the largest use is handling steel bar or sheet stock, loads up to 10,000 pounds with lift heights up to 30 feet in the air and loads as long as 26 feet.
There are options for hydraulic fork positioners. With long loads, Raymond utilizes auxiliary carriers allowing for four forks under the load to support it. Fork positioning is needed when loads run shorter than 26 feet, let’s say 15 or 25 feet.
“When specifying these heavy-duty sideloaders, keep in mind they can reduce your storage requirements by 50 percent to 60 percent so you can make use of very narrow aisles,” says Mike Gay, product advocate for VNA products for Raymond. Carrying a 26-foot-wide load with a conventional counterbalanced lift truck makes for 26-plus-foot-wide aisles. These trucks work in aisles just five feet wide with the load parallel to the aisle.
Gay’s top buying tip is to make sure the dealership network is strong and knows lift truck maintenance.
Crown chose a more traditional, SCR electrical control system for its FC 4000, four-wheel sit-down trucks with 6,000-lb capacity. Joe Ritter, director of marketing and product management for Crown Equipment Corporation, says the SCR controller allows for a more robust motor and electrical system to handle tough applications like severe angle ramps at indoor loading docks or ramps leading from one building to another.
Specialty handling with paper
Paper roll handling comprises the large part of cushion tire, large lift truck applications. These trucks typically need excellent cooling systems because they’re used on short runs from the inside of a rail car to inside a warehouse or to the back of a trailer. Short runs put a strain on the transmission and the cooling system given the heavy, 8,000-pound paper rolls being moved.
There are a lot of specifications for paper roll handling. It’s almost a class in itself. Trends are to stack 90-inch-tall paper rolls three high, and there are various sizes in width and height for paper rolls. But the industry tends to be going with heavier and taller paper rolls.
“Buyers are looking for trucks that will allow for both stacking three high and trucks that are sized right to drive into the back of a trailer truck or rail cars. If the truck is sized too heavy though, there’s the possibility of falling through the floor of the truck, or, if too big, not being able to maneuver within the trailer,” says Martin Boyd, manager for I.C. product planning for Toyota.
Today, paper roll trucks are designed right to the edge with a 12,000-pound capacity. If you go to a 15,000-pound-capacity truck, you’ll probably fall through the floor, unless the trailer is structurally upgraded.
Offered with Toyota’s larger 8,000- to 12,000-pound lift trucks, is a planetary drive axle, which makes the trucks more reliable and rugged. It distributes stresses from the drive train more evenly than just a conventional, ring-and-pinion setup. “Typically, smaller trucks have the ring-and-pinion drive train. You typically see a planetary drive axle on trucks with 16,000-pound capacity and higher, but Toyota puts it on 8,000-pound trucks and higher,” says Boyd.
Heavier-duty means fewer, more costly trucks
Some users are trying to handle larger loads to reduce the number of lift trucks in their fleet. Doubling up loads and doubling capacity on the lift truck is one example. You don’t find it so much in warehousing, but more in lumber handling, concrete block and pavers.
The cost of ownership is greater for heavy-duty trucks than for light-duty trucks, and the productivity factor is greater, says John Piccolo, manager of big truck sales for Yale Materials Handling Corporation. If you’ve got 50, 5,000-pound cushion tire trucks and one breaks down, that isn’t nearly as much a productivity problem as having a yard with just four heavy-duty, 15,000-pound pneumatic trucks and one breaks down. A quarter of your productivity is harmed.
Piccolo says that, typically, you don’t have as many of these heavy-duty trucks around. That makes paying more for a better-quality truck at time of purchase a smarter idea. The trucks aren’t commodity machines. When some parts fail on a truck, the truck may be taken back to a shop so a crane can lift out the heavy-duty part. The mast on a 36,000-pound truck weighs up to 12,000 pounds as opposed to a 5,000-pound truck with a mast that weighs 2,000 pounds.
Meeting the demand of 24-hour turnaround for heavy steel products in a Just-In-Time environment led Southwestern Ohio Steel to rethink its handling on three shifts a day. The company stores up to 80,000 tons of raw steel material and ships about 1,500 tons per day. Challenges to the company included increasing its capacity, optimizing space and maintaining a grip on labor cost and waste.
Southwestern used to store all its product on the floor, leading to problems with rust, skids and product damage. The company turned to a local material handling equipment dealer, Storage Concepts Inc. in Ohio. The goal was to treat dense, bulky coils of steel like any other off-the-shelf product. A plan was devised to get the product off the floor and reduce handling to just two steps. A Raymond Corporation sideloader handles the firm’s steel coils in very narrow aisles at heights to 208 inches, allowing the firm to store coils horizontally four levels high and coils on skids 11 levels high.
Bar codes are fixed to each pick location on the racks, so Southwestern operators aboard the Raymond sideloaders use scanners to speed their pick rates and report inventory movement. With this system, Southwestern has greatly reduced dings and rust.
Containers are an important element when it comes to heavy-duty product protection and motion, especially with oddly shaped parts. At the Dodge Ram truck chassis operation at Tower Automotive Plant in Milwaukee, Wisconsin, Topper Industrial worked carefully on containers used to transport truck box frames from the forming area to the weld area. A new hydro-form process of making truck parts meant that keeping the 3,000-pound load of 77 parts in place in any standard crate would require metal strapping. That would be expensive and time consuming.
Topper developed a container that would interface with the robots that operate on the manufacturing line as well as trap parts safely in a crate without banding them or requiring manual intervention. The crates had to not only hold the parts but also allow for easy access for later assembly line work.
Topper designed a crate with an inner frame that actuates a vertical clamping bar. During crate loading or unloading, a floor-mounted pedestal holds up the inner frame. When the container is being moved by lift truck, the inner frame tips down, clamping the frames against the outside frame posts. This holds parts securely in place during storage and when moved across the plant floor.
Air casters defeat friction
Air casters ride a thin film of compressed air to lift and move the heaviest loads you can imagine. All they need is a non-porous, fairly level floor surface in pretty good repair to do the trick. Steven Reining, sales manager for Air Caster Corporation, provides these applications.
• Kawasaki and Transportation Transfer Authority are firms that manufacture as well as rebuild subway cars nationwide as well as two-story Pullman railroad cars with observation decks that weigh 120,000 pounds. The cars are moved from one assembly station to another, starting with the interior truck, then adding frames and other components. The firms may have two railroad tracks coming into and out of their plant and seven or so tracks inside the plant for different assembly lines. The air caster shuttle allows movement of rail cars from one track to another and also allows a truck to be floated off the line for additional special assembly and allows other trucks to pass by. This is a major advantage over conventional track-type assembly lines.
• In agricultural, air casters are used at Caterpillar Clauss manufacturing plants out West to build 60,000-lb combines on top of platforms.
• Air Caster is building a 14-foot turntable for a BMW facility in Greenville, North Carolina, to build sports cars and SUVs. The turntable is used for rack loading and unloading. Workers pull parts from one rack until the rack is empty, then rotate the turntable to access the rack full of parts off the other side.
• With the flexibility of air casters, mobile homes can be moved sideways down an assembly line, which doubles the assembly line density and doubles capacity.
• In the military, air casters are used in the manufacture of cruise missile launch tubes.
Other ergonomic aids include air casters fitted to lift and tilt tables. These are used in foundries for moving heavy loads around the facility. Conventional pneumatic lift-and-tilt devices are installed over a turntable or over a mobile platform fitted with air casters.
The most important thing to keep in mind about air casters is that they make moving heavy loads more ergonomically feasible.
“It takes just a pound of push for every 1,000 pounds of weight you’re moving. You still have some issues due to gravity if you’re pushing up hill, as finding a floor that’s perfectly flat is unusual, but a single person can easily move 15,000 pounds,” says Reining. To prevent drift on floors that aren’t flat, a single, air-actuated guide wheel is installed under the center of the load. This wheel also permits steering.
Air Caster Corporation solved the problem of moving 120,000-pound generator rotors around a storage warehouse that had no overhead cranes. The Illinois Power Plant, a division of Dynegy, decided to use friction-free air casters to float a large load from the receiving dock to its storage location, awaiting use as a spare rotor in a power plant. The rotor was four to five feet in diameter by 40 feet long and was supported by two cradles. The floor at the warehouse was in good condition but had a number of construction joints that had to be crossed. To eliminate these gaps in the floor surface, sheet metal was used to form a pathway. To provide needed support for the rotor cradles, structural frames were made and two Air Caster Loadmovers were mounted under each frame. A portable air compressor was all that was needed to lift the 120,000-pound load — supported on only a thin film of air.
Hoists for heavy-duty lifting
When it comes to hoists, there are a host of things to get right in terms of specifications for safety and long life. Heavy-duty chain hoists can be found in power plants picking up large generators, and also in steel handling, maintaining pumps and motors. Columbus McKinnon offers a new Lodestar XL, a higher capacity chain hoist that takes up to 7.5 tons. Wire rope hoists are also available from the firm including the Shaw-Box World Series and Yale Global King hoists, which lift up to 10 tons.
Art Zobal, package hoist product manager for Columbus McKinnon Corporation, offers some tips on specifying heavy-duty chain hoists:
1. Duty cycle. There are standards to help you size a hoist. The standard takes into consideration the capacity and how many starts per hour will be made. Most hoists are rated for H4, which is heavy-duty at 300 starts per hour.
2. Attachments. Any below-the-hook attachment must have its weight factored with the load, including spreader beams.
3. Load weight. A lot of users underestimate load weight. You can pick up the load with a scale-mounted hoist. As weights may increase at some time in the future, consider oversizing the hoist.
4. Support structure. If you already have an existing beam or if you’re going to add on to a building with a beam or monorail, you need to check with a structural engineer or the building’s manufacturer to check weight capacity.
5. Lift speed. Most hoists are available in three-speed, two-speed or single-speed, 12 foot per minute or 16 foot per minute, etc. In high-production applications for offloading trucks, you need a faster speed. If you’re setting some heavy dies into a plastic injection molding machine, a slower speed or a two-speed machine may be needed to set the item down softly.
6. Chain travel. How much distance is between the bottom of the floor and the hoist? With chains, you can vary the length of travel.
7. Voltage. If there is only 115 volt single-phase you probably can’t pick up a high-capacity load; 230 volts or 460 volts are needed for higher-capacity, two- or three-phase hoists.
8. Headroom requirements. Headroom is measured from the saddle of the hook or any attachment to the bottom of the beam the hoist rests on. Bigger hoists may have a 3-foot headroom requirement. This is a critical factor where the ceiling or beam is low and the load or truckbed is high.
9. Type of suspension. Some hoists can be suspended or be fitted to a motorized trolley or a hand-geared trolley. If the hoist moves just a few feet, then an endless chain can move the hoist. But if you’re frequently moving it 100 feet, then a motorized trolley is called for.
10. Indoors or out. Most hoists can handle some weather, but they can be protected well from outdoor weather if the manufacturer is alerted.
Keep in mind that sizing the hoist right for the application is critical. If it’s not sized right, the application may have problems that are not the fault of the hoist. Frequent use must be communicated, as well as information about whether you’ll be maxing out the hoist every time it’s used or only occasionally.
“This affects overall life of the hoist, as it can with proper sizing last 30 to 40 years. There are safety issues when hoists are not installed or maintained properly, so a competent distributor is important,” says Zobal. MHM
Lift Truck Advice
Here are some rules of thumb for heavy-duty lift trucks:
• Look for proven strength and reliability;
• Demand speed with precise control for increased productivity;
• Select a compact and highly maneuverable truck;
• Make sure operators appreciate all aspects of their site;
• Check on product support because you can’t afford downtime.
Courtesy, Rick E. Witing, product manager for Komatsu Forklift USA Inc.
Contact these sources for more information on heavy-duty handling.
Air Caster Corporation, (217) 877-1237, [email protected]
Columbus McKinnon Corporation, [email protected], www.cmworks.com
Control Engineering, a division of Jervis B. Webb, [email protected]
Crown Equipment Corporation, [email protected]
Eisenmann Corporation, [email protected], www.eisenmann.com
Komatsu Forklift U.S.A. Inc., 800 821-9365, www.komatsuforkliftusa.com
The Raymond Corporation, [email protected] or www.raymondcorp.com
Topper Industrial, [email protected], www.topperindustrial.com
Toyota Material Handling USA, contact the dealer in your area by going to www.toyotaforklift.com
Webb Heavy-Duty Roller Conveyor Systems, Control Engineering Company, Jervis B. Webb, www.heavydutyconveyors.com
Yale Materials Handling Corporation, 800-233-YALE or www.yale.com, [email protected]