Painters prepare to inspect a recently painted section of the main cable.
©Golden Gate Bridge, used with permission,
www.goldengate.org
Spanning the Golden Gate Strait, the bridge, once the longest suspension ever built, is now ranked 9th in the world.
construction. Tis material consists of manila rope impregnated with beeswax over which lead wool was pounded to result in a solid watertight seal. Many of these joints have shown signs of deterioration so the material is being removed by hand and replaced with a modern polyurethane sealant. “Te cleaning and resealing of the cable bands is detailed work requiring hand tools and patience. We found we were pioneering the techniques as we got into it and were fine-tuning them as we went along,” shared bridge paint foreman Herbert Gabriel. Next, the repainting process could begin. Te first step is handwashing the cable with clean water and mildicide to remove any organic growth. Te cable is then power tool cleaned using synthetic pads to remove existing coatings that are poorly adhered. Debris from this operation is captured by vacuum shrouds on the power tools. Bare metal areas are then touched up with a zinc rich primer. Te entire cable assembly including the cable bands, portions of the suspender ropes and the hand rope system (installed on the top surface of each of the main cables) are overcoated with a three coat high performance elastomeric paint system followed by a high performance finish coat in the distinctive International Orange color for which the bridge is known. Bridge painter Mark Dahlund added, “Tis is a labor intensive job; we take pride out there every day knowing the cables are really the backbone of the Bridge.” Te idea was that the first 400-foot-long section would be the laboratory where
workers and engineers would problem solve, validate selection of materials and methods and find ways to be the most efficient in a tight space with an elaborate scaffolding system. A single crew of 6 workers, battling one of the foggiest summers in recent years, completed the first section in 5 months. Bridge painter Ron Chatham observed, “Tis project is all about team work, figuring out the right steps together and sticking to them. Te fog this summer was one of the biggest challenges.” In early October 2011, crews began the disassembly and reassembly of the scaffolding along a 400-foot-long segment heading north from midspan where crews will then renovate this segment of the west side main cable over the next five months. Next, and possibly concurrently, the midspan sections of the east side main cable will be encircled in scaffolding and an additional crew will take on that section. With the midspan section completed, workers will then move to the upper
reaches of the cables using an entirely different hoisted or traveling stage system. With 15,300 feet of main cable, it is estimated that bridge crews will complete the repainting in about six years. Weather and crew availability will play a dominant role in the speed toward completion. Once completed, the main cables will continue to be maintained through spot painting as needed. y
22 NOVEMBER-DECEMBER 2011 WIRE ROPE EXCHANGE
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