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You may have heard rumors that Bigge Crane and Rigging Co. is bulding a 7,500-ton super crane, but not until now has the company talked openly about this monster machine.

ENR is proud to bring you this exclusive report from Las Vegas.

You won't find this beast at CONEXPO—it would cover an area nearly ten times larger than the largest outdoor booth here—but on March 24 while at the show, we caught up with Pete Ashton, Bigge's vice president of major projects, who sat down with us to discuss some details about Bigge's big one.

"We are supplying two machines for new modularized construction at two, two-unit nuclear reactor power plants," he said.

Right off the bat, Ashton was choosing his words carefully. Nukes are sensitive projects in general, but the situation in Japan has put a big question mark on the future of nuclear-power construction in the U.S. He remained optimistic.

"The reality is this country needs more baseload power," said Ashton. "It's a tough choice, but if it can be done safety nuclear is an important part of our baseload energy."

According to Ashton, the Bigge 125D AFRD, or A-Frame Ring Derrick, was designed about three years ago for a general contractor that is building the first two new reactor sites in the U.S. since the mid-1980s. Ashton declined to name the client, citing the terms of a confidentiality agreement.

Based on public information, though, we think it is highly likely that the machine is destined for the V.C. Summer Nuclear Station in Jenkinsville, S.C., and the Vogtle Electric Generating Plant near Waynesboro, Ga.

For both those projects, Shaw Group Inc. is building the plants, consisting of Westinghouse AP1000 power units, using the modular construction method. As we've seen on these and other projects, modular construction requires super-heavy-lift machineryAn attempt to reach a Shaw official for comment was not successful.

In basic form, the AFRD looks similar to the huge ring-type, A-frame cranes produced by international heavy-lift firms like Mammoet, Sarens and ALE. However, the Bigge truly is a unique animal.

The idea here is to offer a broad lifting footprint, high capacity and fast production without ever needing to relocate the machine during the life of the project. That's really the ideal scenario in the modular world, where construction is all about assembling pre-fabricated structures rather than fabricating and assembling at the same time.

In that sense, the AFRD serves the jobsite much like a tower crane: It stays in one place, covering a wide swath of land that is shared among trades.

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Technically speaking, though, this is a derrick—it is even designed under the ANSI B30.6 industry standard for derricks.

If you think derricks are old-school, think again. Ashton explained that the AFRD is more versatile than a traditional derrick in that it moves faster, can rotate a full 360° and serves the entire jobsite—covering both reactor units—without needing to be repositioned.

Simply put, think of this as a modern spin on a derrick and ring-type crane, both of which have limited working envelopes. "It's a subtle technical difference," Ashton said.

The AFRD is incredibly muscular. In its current configuration, it is designed to carry 560 feet of boom for a maximum load moment of 125,000 tonne-meters. With that much boom, the machine can lift up to 4,000 tons, Ashton said.

When fitted with 300 ft of boom, it can lift 7,500 tons. That would make it the highest-capacity ring-type crane on the planet, according to Bigge.

"Bigge's design will revolutionize the way nuclear power plants are constructed," says Weston J. Settlemier, president and CEO of Bigge, on the company's website. There, Bigge also provides an animation showing how the crane works.

Since maximum capacity means nothing without radius—cranes need to lift up and away—San Leandro, Calif.-based Bigge is building the AFRDs to be good for over 1,500 tons at a 440-ft radius. That is a typical heavy lift in the world of modular powerplants.

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Designed to maximize usable space around the rig, the machine rotates on a 5,000-ton, cast-in-place, reinforced concrete counterweight poured no higher than at-grade. The rotating upperstructure travels on twin, parallel bogeys riding on steel rails. The rails rest on spread footings and are also installed flush with grade.

On the ground, the rig stretches over a 300-foot diameter to the outside of the outer rail. However, the space not occupied by the bogeys remains usable. Trucks and other jobsite vehicles can drive across the rails, and materials can be stored inside the ring.

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Having the rails and counterweight installed at grade is one feature that sets the AFRD apart from other ring-type machines, which lock up land due to their above-grade traveling systems.

"You've returned real estate back to the job," Ashton said. "With a traditional ring-type design—you go plop—and you've taken up all that real estate."

Another differentiator is the counterweight design. With other ring-type cranes, the mass typically rides on a wagon that travels opposite the upperstructure.

In Bigge's case, the counterweight is buried underground, at the ring's core. The company invented a special universal joint that accommodates multi-axis rotation. Swiveling laterally protects the derrick in case the foundations experience differential settlement.

Speaking of that, Bigge designed an electrohydraulic self-leveling system to ensure that the machine is always lifting on a level surface.

"The machine is truly state-of-the-art," said Ashton, adding that the machine rotates 360° in under 20 minutes.

Other features include four hoist drums that are independently reeved into a 1,500-ton load block. Total wire rope on the machine spans 12 miles, and its five diesel engines together generate more than 3,000 horsepower.

Made in the U.S., the first unit is being shipped now. The second is being built and is due to be delivered in the second quarter of this year. Each takes about 200 truckloads to ship and assembles in about two months.

The two AFRDs are just the first in a family of new supercranes.

"We have designed both larger and smaller models," said Ashton. "This machine is very scalable."