March/April 2009
With the help of a large counterweight, equilibrium cranes can lift more weight, with a longer and higher reach, than their conventional counterparts—and use less energy while doing so, their manufacturers say. By Diana Mota Morgan
Equilibrium cranes are a rare sight in North American scrapyards, but they're more common in Europe. Perhaps Europeans tend to tackle higher scrap piles in smaller yards. Perhaps they prefer the cranes' quiet, clean electrical power. Or perhaps they like the idea of using one crane that can reach the equivalent distance of several conventional cranes. The companies that manufacture equilibrium cranes—also called equilibrated cranes or EQ cranes—say U.S. yards can just as easily avail themselves of these benefits. For a high-volume yard with the right layout and needs, an equilibrium crane might be worth a look.
Explaining Equilibrium
Equilibrium—or balance—is the key to how these cranes work. "In a conventional hydraulic excavator converted to a material handler, the counterweight only helps to balance the entire machine weight on the rotating bearing," says Mark Osborne, president of E-Crane International USA (Galion, Ohio). "The hydraulic system [must] raise the entire weight of the boom, stick, grab, and full load each and every cycle." That consumes as much as 80 percent of the energy such cranes require, these manufacturers say.
In an equilibrium crane, the hydraulic cylinders only lift half of the payload. The counterweight lifts the other half as well as the boom, stick, and grab, making it more energy efficient. When building such a crane, "we set the crane in a specific position to fill the counterweight," says Dennis Manley, senior project manager for Metso Minerals (Pittsburgh), which acquired certain assets of Sobemai International (Maldegem, Belgium) to market and sell its equilibrium cranes. Then the company fills the counterweight with concrete until balance is achieved between the counterweight and the lifting tools (such as the bucket, boom suspension, and quick disconnect) and half the payload. Similarly, "with an E-Crane system, the crane remains within 20 percent of a true balanced condition throughout its entire working range," Osborne says.
The primary benefit of this design is that the crane can lift more—and lift it higher—using less power. Energy savings can be as high as 50 percent when compared with a conventional cable crane and as high as 80 percent when compared with hydraulic excavators, Osborne says. "E-Cranes use about 25 percent of the horsepower a conventional hydraulic crane uses doing the same job." The manufacturers also tout the cranes' environmental benefits. "Electric power is normal on an equilibrium crane," Osborne says, "whereas most converted excavators are powered by diesel engines. And diesel is expensive, dirty, messy, and noisy."
The equilibrium design means more stability and less stress on the machine, the manufacturers say. Further, "because of the balancing counterweight, equilibrated systems can be equipped with much longer reaches than conventional material handlers," says Andreas Ernst, marketing manager with Sennebogen (Charlotte, N.C.). The cranes "provide a real advantage whenever long reaches—of at least 85 feet—are needed or more lifting capacity is required." Because of this reach, "one equilibrium crane can do the job of three tactical cranes in a more compact area," says Kilian DeLille, general manager of Sobemai. Osborne concurs. "Our last scrap-handling customer replaced three large wheel-based material handlers with one rail-mounted 1000 series E-Crane."
Because they don't need the weight in their base to remain stable, equilibrium cranes come with several different mounting options, such as a fixed pedestal, a free-standing pedestal, rail, crawler, and a gantry—even one high enough so that fully loaded trucks can drive underneath it. Like other cranes, equilibrium cranes can use a variety of attachments.
Design Differences
Starting with the general principle of equilibrium, manufacturers have taken a few different design approaches to their cranes. At Sennebogen, "we use a fixed counterweight," Ernst explains. "The others use a moveable counterweight." A fixed counterweight simplifies the crane and maintains the balancing advantage, he says.
The equilibrium cranes from Seram Group (Perpignan, France) use hydraulics to tilt the counterweight in relation to the stick movement, explains Project Manager Pauline Julia, keeping the loading equipment in permanent balance. "The boom cylinder only requires the power to lift the load, not the boom and stick," she says. "For this reason, the average working pressure of a Seram equilibrium crane is only 2,610 psi."
E-Crane and Metso offer cranes with moveable counterweights, but with a different design: Their parallelogram-style boom provides a direct mechanical connection between the counterweight and the load. "That connection between the stick, the boom, the push-pull rod, and the counterweight is what creates a parallelogram so that at any moment in time that crane is balanced," Manley says. The Metso/Sobemai design uses two horizontally mounted counterweight cylinders, which provide added safety and speed, the company says. "Shifting the position of the counterweight allows the counterweight to help lift the load while moving the stick in and out. You're using the structure to help lift the load." This parallelogram system ensures near-perfect balance throughout the boom's full working range, Osborne says. "This allows for lower installed power, increased reliability, and lower long-term operating costs."
Equilibrium crane manufacturers tout some standard features: safety-check valves for cylinders, better all-around visibility because the cab is higher than it would be on a conventional material handler, UL-certified electrical components, overload protection systems, and maintenance areas that are easy and safe to access. Beyond those, the cranes vary in their capacity, reach, and other attributes—and price. "It all depends on what you want to put in those machines," Ernst says.
- E-Crane can build its machines with up to 150-foot outreach and up to 200-foot vertical reach capabilities and 5-ton to 50-ton duty-cycle capacities. "The smallest E-Crane series has a duty-cycle rating of 6 [short] tons and outreach to 105 feet," Osborne says. "For scrap, the largest series would have a duty cycle of 35 [short] tons and an outreach to 145 feet."
- E-Crane's integrated digital control system, the electronic machine manager, "integrates control of the main pump, distribution valve, and joysticks without the use of external pilot lines or electrical relays," Osborne says. "Deployment of this system also allows remote diagnosis and troubleshooting from our headquarters." As for price, "the basic 700 series E-Crane that is ideal for scrap handling is available—delivered, and installed, including training—for under $1 million," Osborne says. He estimates operational costs at about 1.5 percent of the selling price per 2,000 operating hours.
- Sennebogen's series of cranes provides ranges from 65 feet up to 115 feet. Sennebogen also boasts the only machines that can use either diesel power or a variety of electrical packages. Operators can use the electric motor for daily operations, Ernst says, and diesel power to move the machine around the yard. The cranes also operate without electronic controls, which simplifies maintenance and increases reliability, he says. They come standard with automatic lubrication systems. Most machines start around $1.5 million and can go up to $3 million.
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Metso's series has a reach range of roughly 50 feet to 150 feet and a lifting capacity of 2 mt to 55 mt. The company developed an 85-foot crane with a 6 mt lifting capacity "because it's a standard size for scrapyards," DeLille says. Metso uses programmable logic control to continually optimize the operation of its cranes. It also offers online remote troubleshooting and maintenance services.
- Seram's machines have ranges from about 50 feet to about 130 feet and can lift up to 10 mt. The units have 480-volt motors starting at 150 hp and going up to 800 hp. Seram's equipment also collects information and sends alerts and data to the customer and to Seram engineers.
Training, Operation, and Maintenance
"Due to the material-handling design and operation, most [workers] can operate the machine with little training," Ernst says of Sennebogen's equilibrium cranes. Training "is more to get the feeling for the size of the machine than learning the functions of the operating instruments." The company fully assembles and tests every machine at the factory, at which time it offers customers and maintenance people training on it. In contrast, Metso provides two days of classroom training and three to five days of on-site training.
Maintenance for the cranes is minimal, the manufacturers say. "It's really all preventive maintenance," DeLille says. They require the usual hourly, daily, and weekly maintenance—such as hydraulic oil changes and lubrication—as other material handlers, Ernst says. Owners should complete the first major overhaul at around 25,000 to 30,000 operating hours, he adds.
When something does go wrong, the availability of parts and service can be crucial. It's important to keep maintenance-related downtime to a minimum. "Operating costs as well as service parts availability are key [considerations]," Ernst says. "The best machine in the world won't work if spare parts are not easily available." The absence of electronics in his machines helps reduce downtime, he says. Sennebogen operates a warehouse in Charlotte, N.C., and provides more than 180 service and parts locations in North America, it says. E-Crane operates a parts warehouse at its headquarters in Ohio. Further, "the majority of parts on an E-Crane are from large global suppliers such as Caterpillar, Rexroth, and Square D," Osborne says. Metso offers a service team available 24/7 and parts and service locations throughout the United States. It is developing lifecycle services, which might include anything from periodic inspections to the complete operation and maintenance of the crane. Seram is in the process of bringing technical support to the United States, Julia says.
How long a crane will last depends on the preventive maintenance the customer provides. E-Crane puts the life of its cranes at 40,000 operating hours, Osborne says. "This is a big difference compared with a conventional hydraulic material handler," which lasts about 15,000 hours, he adds.
Is It Right for Your Yard?
Equilibrium crane manufacturers are quick to point out that these machines are not suited to every scrapyard. They can be slower and less flexible than some material handlers, though their greater lifting capacity and reach could potentially compensate for their slower speed. If speed and flexibility are paramount, "it may make more sense to invest in a standard material handler with the shorter reach, as they are much faster in their cycle times," Ernst says. Also, an equilibrium crane isn't a good fit for a scrapyard that processes smaller amounts of scrap. "Its best application is to process moderate to large amounts of scrap," Osborne says. "Many times you will be limited by the production requirements of the yard, such as shredder and truck size," Ernst adds.
These machines' horizontal and vertical reach and substantial load capacity make them a good choice for working larger stockpiles or high-volume yards and feeding a shredder or a large shear, these companies say. Potential buyers should ask themselves what capacity they need, DeLille says. "For feeding a shredder, how many car bodies per minute do they want to get into the shredder? Or how many tons per cycle need to go into the shear?"
Yard size and design in terms of material flow are other important factors. Buyers should consider the logistics for bringing in the scrap, DeLille says. "How is it organized? Does the crane have to stockpile and feed [the shredder] at the same time?"—which is something an equilibrium crane can do, he says. The machines' high vertical reach and long outreach capabilities allow yard owners to maximize space, Osborne points out. If yard space is a concern and you "need extensive reach and scrap-pile height, an equilibrium crane probably makes the most sense," Ernst says.
Depending on the type and volume of work, and factoring in the projected fuel savings and the cost of new equipment, "the company should look carefully at what it really wants to accomplish regarding fuel savings, reach, lifting capacity, maintenance savings, and other performance categories," Ernst says. •
Diana Mota Morgan is associate editor of Scrap. Mark Crawford, a writer based in Madison, Wis., contributed to this story.
With the help of a large counterweight, equilibrium cranes can lift more weight, with a longer and higher reach, than their conventional counterparts—and use less energy while doing so, their manufacturers say.