Anything, anywhere

Power contractor Shaw Group is using the first two models of Bigge's giant derrick to build two nuclear power plants in the eastern US.

The two Bigge125D AFRD's went into service this summer on the Vogtle Electric Generating Plant in Waynesboro, Georgia and VC Summer Nuclear Station in Jenkinsville, South Carolina.

Both cranes are building the same kind of reactor, a newly-designed, two unit site, using Westinghouse Electric Company two-loop pressurized water reactor, AP1000.

The Shaw Group positioned the AFRD between two reactor units in order to build both units at once.

Pete Ashton, vice president of Bigge, explains how this method differs from the way reactors are usually built. "At these sites, there are two different reactor units being built side by side at the same time. No other crane in the world has the capacity to service two concurrent build locations at one time and the module assembly yard including rail deliveries. The Bigge125D services approximately 28 acres with high capacity hook coverage."

"Any other crane could only serve portions of one unit at a time, and the loads would have to be brought to the crane from the storage yard at great expense. The cranes would need to be located closer to the load setting location, causing delays and excavation rework. The second unit would either require a second crane or a relocation of the first crane with either option resulting in significant additional cost and schedule delay. If a crane has to be relocated, you not only have downtime, but you have significant added cost and risk to relocate and you have to incorporate out of service time into your construction schedule while the relocation happens." says Ashton.

Bigge's client completed load testing on the AFRD in July at the VC Summer site per US federal OSHA requirements.

Ashton says, "The Federal OSHA requirement is load testing to 110% of the maximum capacity that will be lifted. So, even though these are 4,000t rated capacity machines, the customer load tested to a little more than 1500 tons which exceed his maximum lift and tested the machine to its maximum load moment."

With a reach covering approximately 28 acres (113,000sq m), the AFRD can lift loads from the storage and module assembly yards to either reactor unit in minutes.

This allows for more flexible schedules, Ashton says, "For the builder using smaller cranes, he is always restricted by the location of the crane and what the crane can lift within its reach. He has to add it into his planning. The Bigge125D eliminates this consideration."

"Every construction project revises the construction schedule and sequence based on real time performance, and the Bigge125D allows the builder to adjust his planning in real time without having to incorporate limitations of the project crane support. By our crane being so big and having so much capacity, he is free to lift anytime, anywhere, anything on the jobsite and can focus on other things rather than accommodating crane constraints. As an example, if a lift is delayed on unit 1, the machine can swing to unit 2 in minutes and service those lift requirements, promoting the overall project progress. We can support any change that's asked for."

One key to the AFRD's long reach is its innovative counterweight design; a 5,000 USt concrete counterweight, cast onsite and in place, maximizing the crane's heft.

"The concept is significantly different than a ring or crawler crane in that the machine rotates around a static counterweight. A traditional crane moves the counterweight opposite load, which requires significant machinery and structural support. We leave the counterweight in one location allowing it to be larger and supported by the ground, rather than manufactured structural steel and rotating machinery. We've enhanced capacity at minimal cost." says Ashton.

"On a nuclear project they have a significant amount of concrete and excavation, so the cost for the counterweight is relatively small. Additionally, at the completion of the job, the counterweight can be left in place and covered over, saving significant demobilization costs."

Bigge sees potential for the derrick not only in nuclear modular construction, but also for oil platform fabrication, shipyards, and other long duration projects requiring heavy, repetitive lifts. "Modular construction is now being adopted in the nuclear industry but it's been a part of other construction industry methods for many years."

Ashton says, "Typically where it's going to provide the most value is working on a project or in a facility that is doing lots of very large lifts over longer periods of time as opposed to being set up for a single or small quantity of lifts and then tearing it down and going away. "While transportation costs are important, the ultimate value of this machine is its ability to lift loads at production speeds like nothing else and therefore we choose to optimize lifting capacities and performance speeds." Ashton says that the machine transports in approximately 150 common type truck loads and the machine assembles and disassembles typical of modern cranes and in the same relative time frames. "Hoisting, booming and slewing speeds are all very fast for a machine of this magnitude and compare with smaller classes of modern heavy lift cranes." says Ashton

At Vogtle, work on the new nuclear reactors is expected to wrap up by 2017, and works at VC Summer will conclude in 2019, says Shaw. Shaw has credited the Bigge125D as a key factor in being able to maintain their schedule.

Looking to the future, Bigge says it is designing a number of larger machines.