Monster Machines Doing Heavy Duty in California
Construction pros are no strangers to heavy equipment, but two new machines working on the eastern span of the $5.5-billion San Francisco-Oakland Bay Bridge make most ordinary tools look like children’s toys.
Mike Flowers, project director for American Bridge/Fluor Enterprises Inc. joint venture, says he knew very early that standard construction cranes just were not up to the job, which is to build the bridge’s unique self-anchored suspension span. “When we started looking at it, we could not find anything here in the U.S. that was even remotely capable of doing what was required,” says Flowers. “The cranes on most bridge jobs might be able to pick 150 tons, and on this project we need to pick pieces that go as high as 1,300 tons.”
The solution was a custom-designed, barge-mounted, shear-leg crane with an impressive 1,700-tonne capacity. But just getting this massive machine—dubbed the Left Coast Lifter—to the jobsite proved to be a major undertaking.
After having the specially reinforced, 100-ft-by-400-ft barge built in Portland, Ore., ocean-going tugs towed it to Shanghai in April 2008, where the Zhenhua Port Machinery Co. built, installed and tested the crane with loads up to 2,000 tonnes. The finished product, with twin 328-ft-long, self-erecting booms, was loaded aboard a 750-ft, semi-submersible cargo ship that sailed under the Golden Gate Bridge in mid-March. The deck had to drop nearly 21 ft to release the barge.
The scale of the $50-million machine boggles the mind. Weighing in at 3,920 tonnes, the crane sports twin 850-tonne hooks along with a single 100-tonne hook and a 10-tonne utility hook. Raising the boom from its minimum to its maximum lifting angle takes more than an hour.
Despite its enormous dimensions, Flowers says the Left Coast Lifter only requires a crew of four. “With its LCD touch-screen displays, video monitors and joystick controls, it has actually proven to be fairly simple to operate,” he says.
As for what happens to the Left Coast Lifter after it has completed its 18-month assignment, Flowers says the joint venture will have to weigh the business implications of keeping the crane and finding more work versus selling it. “Who knows, maybe it will end up on eBay,” he says.
Pump It Up
In addition to 67,000 tons of steel, the Bay Bridge project requires concrete—lots of it. Much of that will be put into place by a Putzmeister 70Z-Meter, the world’s largest truck-mounted concrete pumper.
The truck was the brainchild of Mike Paragini, owner of Associated Concrete Pumping, Sacramento, who approached Putzmeister about building the rig several years ago. He took delivery of the German-built machine last August and has been using it on construction projects throughout northern California and Nevada.
Even by the standards of so-called super-boom concrete pumpers, the 70Z-Meter’s statistics are impressive. The five-section Z-fold boom offers 227 ft of vertical and 213 ft of horizontal reach. The 200-cu-yd-per-hour pump is...
...mounted on a five-axle trailer, which is pulled by a Kenworth C500 tractor with a hydraulic drive system on its twin front axles that give it all-wheel-drive capability in low-speed situations.
While owning the world’s largest concrete pumper comes with undeniable bragging rights, Paragini believes it also gives him a distinct competitive advantage. “What I sell is placement capabilities,” he explains, “and when you set this truck in the same spot as a typical 58-meter truck, the 70Z-Meter can cover 41% more square feet.”
Knowing that extra reach would come at a price, Paragini and Putzmeister engineers spent hours looking for ways to reduce weight and consulting with California Dept. of Transportation officials to optimize specs like axle loads. That up-front work has made the 70Z-Meter as easy to schedule as his smaller rigs, which he says gives him greater flexibility when responding to customers’ needs.
“This truck is just over 70 ft long and weighs 175,000 lb, but it is totally roadable,” Paragini explains. “If a client calls us at 4 p.m. to change the location of tomorrow morning’s job, we can just go where we need to go without having to scramble to get a lot of complicated special permits.”
One might think the 70Z-Meter’s size would present other mobility problems on the road and at the jobsite, but Paragini says that is not the case. “This thing has a turning radius of just 59 ft, which actually makes it the most maneuverable of all the large booms I have,” he explains. “With two steerable axles on the tractor and three computer-controlled steerable axles on the trailer, it tracks very nicely, even in tight spots where you are not able to swing wide turning a corner.”
While he has been pleased with the 70Z-Meter’s performance, Paragini admits the design process was every bit as much fun for him as seeing the finished product. “I have been in this business for 30 years, and pioneering these new concepts is what keeps it exciting.”
