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.