SC&RA Job of the Year: Transporting a mammoth stator through the Carolinas

Transporting a mammoth stator through the Carolinas proved to be a long, drawn out project. Terry White reports.

The challenges faced by Houston-based Mammoet USA when it transported an important power plant component 310 miles through the Carolinas turned out to be every bit as mammoth as the load itself. Weighing in at 879,635 pounds, the stator stood 35 feet long by 19 feet wide by 18 feet high. A stator is a mechanical device consisting of the stationary part of a motor or generator in or around which the rotor revolves.

Mammoet personnel and equipment first came into direct contact with the stator on May 15, 2009, when the company loaded it onto a deck barge measuring 180 feet long by 54 feet wide by 12 feet high at the Port of Charleston, SC. The stator went directly onto a double wide 18-line Goldhofer that had been positioned on the barge for receipt of the cargo. The load was then secured for transport.

The barge traveled to Hardeeville, SC for offloading. Because of the strong river currents in the area, Mammoet employed a spud barge to steady the deck barge during offloading. After docking, the Goldhofer transporter was rolled off the barge to an awaiting Mammoet 500-ton gantry lift system, which lifted the stator from the transporter and placed it onto cradle mats.

The mats were secured with Williams rods to the 500-ton suspension transport frame assembled around the stator. Mammoet's jack stands supported the ends of the transport frame until final positioning on the transporters.

To transport the stator and insure proper load spreading during the move, the transport frame rested on 72 axle lines of modular transporters, driven by five prime movers. Add in the transport equipment, and the load that left Hardeeville stretched to 300 feet long by 25 feet wide by 20 feet high. The gross weight of cargo and equipment totaled 2,055,912 pounds, the heaviest load ever permitted for over the road transport in the state of South Carolina.

Third-party civil engineers, secured by Mammoet, conducted extensive bridge analyses to determine the stability of all 21 bridges along the route. Twelve bridges in the second half of the route required additional load spreading through the use of a specially designed hydraulic dolly system. When necessary, Mammoet increased the number of dollies for each 18-axle transporter from 8 to 10.

Six bridges required the positioning of 80-foot steel ramps to support the weight of the cargo. Four bridges required additional supports, made by both the Mammoet and third-party fabricators. At one point, the original route had to be changed to avoid a bridge found unacceptable for the cargo's transit per a third party bridge study.

On two occasions, conditions necessitated a crossing of the median. Up to 112 laminated mats were used in these instances. When the cargo arrived near Chesnee, SC, Mammoet personnel dismantled the transport frame and used a 1,100-ton gantry to place the stator onto doublewide 18-line truck-pulled conventional trailers due to the limited clearances on the project site.

Mammoet's project management team worked closely with the Department of Transportation (DOT) in South Carolina and North Carolina to obtain all necessary permits. Permits were issued in three separate phases, each requiring a separate detailed traffic plan that included details such as detours and specific location of utility line raising/removal.

As dictated by the transport permit, Mammoet provided ample advance notice to county and city law enforcement, county DOT engineers, county emergency coordinators and managers, and local school districts. To comply with state regulations concerning vegetation, arborists and tree trimmers approved by the state DOTs were commissioned by Mammoet for study and removal of any foliage that presented obstacles.

Additionally contractors approved by the state DOTs were required to set detours and manage lane closures. About 70 percent of the route was along two-lane secondary roadways.

The last portion of the route to the site, passed through the Appalachian Mountain foothills, with grades reaching 12 percent. An additional prime mover assisted with negotiation of the steep terrain. Three units were positioned in front of the cargo to pull while three units pushed from the rear of the transport configuration.

A final configuration change was made in order to navigate the limited clearances on site. Two 18-axle line transporters and 26 dollies made up the 14'6" wide configuration.

Mammoet dedicated 21,279 man-hours, including engineering, to this job. The 18 Mammoet employees in the transport crew were joined by representatives from the South Carolina Department of Transportation, police escorts and 15 support trucks.

Mammoet totaled nearly 500 hours of in-house engineering, and the third-party engineers that undertook the bridge analysis required nearly 10 times that amount. Before selecting a suitable route, the Mammoet team studied 2,000 miles of roadway.

After nearly seven months in transport, the job ended on December 10, 2009. At times, movement was slowed by factors such as weather and the need for configuration changes. Additionally, crews were severely limited by particular hours they are allowed to transport by the state DOTs.

Despite the complexity and special challenges of the project, Mammoet experienced no lost time incidents or injuries. Moreover, inspections by the permitting office on all bridges and roadways immediately after crossing revealed no infrastructure damage.