Massive Kroll Tower Crane Supports Seattle Tunnel Job
Krøll is known for making the heftiest tower cranes in the world, but its rigs are rarely seen in the wild. A contractor is using one to help build out a tunnel that will house new light-rail lines in downtown Seattle.
As a portion of a larger $1.8-billion U-Link project that adds 3.15 miles of light-rail track in twin-bored tunnels from downtown Seattle north to the University of Washington, JCM—a joint venture of Jay Dee, Frank Coluccio and Michels Pipeline—had to stage its tunneling work on the same site as the program's Capitol Hill Station project. That job takes up about a third of the site and creates a gulf between the east and west areas, says Michael DiPonio, JCM project manager.
Instead of bringing in two or more crawler cranes to get hoisting capability throughout the area, JCM opted for a Krøll 1800, which reaches about 80% of the entire site with one machine.
Krøll distributor Terry McGettigan, Tower Crane Support, San Diego, helped JCM find a crane large enough to handle the job. Due to the limited availability of large cranes for sale in North America, JCM opted to buy new from Krøll.
JCM bought the model K1800, manufactured in Denmark, for $2.2 million, spent another $280,000 on shipping and erection—it arrived this past January and should work on the job for nearly three years—and $250,000 on the crane's foundation. Under Washington code, the foundation required costly design reviews even though it takes up just 13 sq ft.
Also known as a horizontal-jib crane, the hammerhead is a monster. It is rigged with 250 ft of jib and has a hook height of 112 ft. The beast is fitted with 176,000 lb of counterweight and has a maximum capacity of 132,000 lb out to 80 ft. At its farthest radius, it can lift 33,000 lb at its jib tip of 246 ft—a working diameter of nearly 500 ft. The hoist reeving can be changed in minutes from a two-part line, which has a capacity of up to 44,000 lb, to a six-part line, which has a capacity of up to 132,000 lb.
“It would take the equivalent of a 700-ton mobile crane with over 300 feet of boom to match that of the K1800's maximum load radius,” says McGettigan.
Even with such a large rating at 1,800 meter-tonnes, the tower crane has doubled as a general hook crane, too. The Krøll helped excavate the site, and it has assisted in putting together the tunnel- boring machine and hoisting muck cars weighing 56,000 lb each. Today, it is delivering precast tunnel liner segments to help finish out the tunnel.
The working range allows JCM to unload, for example, 25,000-lb stacks of precast-concrete tunnel segments from a single unloading station and place the stack into inventory nearly anywhere on the site, according to DiPonio.
Having one operator overseeing the entire site—which is hedged in by trolley lines, high-powered lines and telephone lines on three sides in a tight neighborhood—improves sight lines and safety. JCM also voluntarily installed an electronic sensing system that shuts down the crane before it nears utility lines.
The city of Seattle has strict noise requirements, and the electric-powered crane makes minimal noise, users add.
“The speed of accomplishing the hoisting operations across the project has been surprising for us and contributes to our productivity,” DiPonio says. “We knew we were getting astounding reach and with good capacity, but we didn't realize the speed and precision that would be coming along with it.”
Even so, the K1800 is something of a lightweight for Krøll, whose biggest model, the K10000, can lift about 100 tons at 300 ft. The company has designed the K25000, capable of 400 tons at 187 ft. McGettigan says Krøll awaits an order for the roughly $20-million machine.
