Sheedy recently performed a complete change-out of three cooling towers on the Providian Financial Building located at 201 Mission Street, San Francisco, CA. The rooftop cooling systems could not be reached by means of a crane due to the height of the 30-story, 416-ft tall structure. Instead, Sheedy used a roof-mounted derrick that was brought up through the building’s freight elevator by hand and then erected on a specially designed platform that tied into the rails of an existing window washing machine thereby eliminating the need to penetrate the roof for tie-down points. The derrick, unique to the crane industry, was designed and built by Sheedy for just such applications.

In order to gain access to the equipment loading area, the derrick had to be placed on the side of the building facing an off-street parking area. However, the cooling towers were positioned on another side of the structure and thus out of reach of the derrick’s boom. To overcome this obstacle, Sheedy used the derrick to hoist the legs and beams of a 100-ton hydraulic gantry to the roof then jack and rolled the components across the building where they were erected by hand over the cooling towers.

The hydraulic gantry lifted each cooling tower off a 4-ft high frame where it was then split in half with each section weighing approximately 7,000 lbs. The lower section of the cooling tower was jack and rolled back across the building and lowered down to the ground by the derrick. The top section of the cooling tower was removed in the same fashion. After the old components were removed the new 2-piece cooling system was lifted and placed into position. It took one week to remove and replace each tower and required the hydraulic gantry to be erected and disassembled six times. Hoisting was performed on the weekend with minimal impact on the building’s tenants. Sheedy completed the entire change-out on time and within budget.