Bay Crane overcomes constraints

Expert rigging was imperative in the lifting and placement of a prefabricated main electrical building at an industrial site in the USA.

Prefabrication and assembly on the ground prior to lifting are common features of today's rigging and transportation business. Valuable time and space can often be saved when project and shipping constraints allow massive prefabrication.

A recent job illustrating this was done by New York-based Bay Crane in the USA. It handled the lifting and placement of a large prefabricated building at an industrial site. The feasibility of constructing, shipping and erecting the Main Electrical Building (MEB) in one piece was carefully studied, and detailed rigging and crane placement studies were produced to ensure that the building could be handled on the confined site without undue impact on the work of other contractors.

Since the project had direct access to the water, the final dimensions of the MEB were not constrained by normal over-the-road hauling restrictions. The unit could be fully assembled in Houston, Texas prior to shipping. The MEB's final details were impressive: 150 feet (46 m) long, 30 feet (9 m) wide and a weight of 369,000 pounds (167 tonnes). Total lift weight with rigging tackle was 410,489 pounds (186 tonnes). The rigging tackle alone weighed just under 42,000 pounds (19 tonnes).

The MEB was delivered to the project on a 200 by 48 foot (61 x 15 m) flat deck barge, and offloaded by a barge-mounted 500 US ton (450 tonne) capacity Clyde 52 revolver supplied by Weeks Marine. The rigging tackle layout was necessarily complex to accommodate the 12 non-symmetrical lift points on the base of the building, and the offset centre of gravity.

To comply with the manufacturer's requirements, the MEB was loaded onto a Goldhofer trailer set up in a double-wide, 6-deck-6 configuration for the short haul to the installation point. This ensured the building was fully supported along its length, and that there was no overhang at either end of the trailer deck.

Towed by a Kenworth C500 prime mover, the MEB was brought under the hook of two of Bay Cranes' 500 tonne capacity Liebherr LTM 1500 8.1 telescopic boom wheeled mobile cranes. Due to the offset centre of gravity, one end of the building was 20% heavier than the other. For greater capacity, one LTM 1500 8.1 was fitted with 92 feet (28 m) of luffing fly jib, while the lighter end was lifted by the other crane on main boom only for greater manoeuvrability.