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Bridge Saddles Cast in a Blaze at
Japan Steel Works

Photos by Torin Boyd

Workers are preparing the molding for the W-line component of the East Saddle in the foundry shop of Japan Steel Works (JSW). Two days later tons of hot molten steel was poured into this mold to make the cast.

The pouring of hot molten steel into a casting mold at the foundry shop of JSW. This was to make the W-line component of the East Saddle of the bridge.

The “West Jacking Saddle” is being hoisted from the location where it was cast, moved by crane to the opposite end of the foundry shop, and torch-cut and hammered to remove the sand casting mold.

Seen here is the completion of the casting phase in which the 150 ton “West Jacking Saddle” was made in the foundry shop of JSW. It was then moved by rail to an adjacent building to undergo the heat treatment phase.

Welders are working on W2E1 component of the West Deviation Saddle in the fabrication shop of JSW.

The rough machining of the W2W3 component of the West Deviation Saddle

Ultrasonic testing on the W2E3 component of the West Deviation Saddle


The island of Hokkaido in northern Japan is home to wild lands, icy winters and snow monkeys, hot springs and volcanic plateaus. And in its industrial port city of Muroran, within the immense workshops of the hundred-year-old Japan Steel Works (JSW) plant, an equally striking scene unfolded in late 2008 as molten steel was cast into a 165- ton “saddle” that will eventually be one of six saddles to hold and guide the new East Span’s main suspension cable.

“JSW specializes in large, heavy products, not in small items,” explained Iga Hiroshi, senior advisor to the company’s Steel Products Department. A stroll through any of the plant’s dozen sports-field-sized buildings, which are filled with mammoth steel components and the substantial equipment needed to manufacture them, makes you feel as if you’ve shrunk to the size of an ant and are lost in a tool box.

Cast steel components of this gargantuan size are in high demand for use in turbines, thermal and hydroelectric power plants, nuclear reactors and oil refineries – as well as suspension bridges – and JSW is rapidly expanding their Muroran facilities to meet global demand (and their two-year waitlist for new orders). The company is a leader in bridge component manufacture, having fabricated over 70 saddles for bridges worldwide.

JSW started work on the six saddles they fabricated for the new San Francisco-Oakland Bay Bridge East Span in September 2007, and shipped them to California in spring of 2010.

On the October, 2008, day of the steel pour for the Bay Bridge’s east saddle, the foundry was abuzz with ironworkers clad in firemen suits and draped in asbestos protective gear. They stood mere inches from the action as molten steel – which at nearly 3,000 degrees Fahrenheit looked more like pure light than liquid – shot from an overhead ladle through feeders and into the hollow cavity of the sand mold. Sparks flew and the ambient temperature in the warehouse rose, and, in less than 15 minutes, 165 metric tons of molten steel worked its fiery way into each corner and crevice of the mold.

After a pour, it takes nearly two weeks for a red-hot saddle to cool to room temperature, at which point it is broken out of its mold. In a loud and brutal process known as fettling, excess sand and unneeded parts are air-blasted and hammered off the truck-sized saddle before the piece is moved to the machine shop for milling and shaping.

In the many months at JSW before each saddle was finished, it moved from foundry to machine shop to fabrication shop and back again as it was shaped, tested, refined, fitted with additional steel plate parts, further tested and finally prepared for shipment.

When the new East Span is fully constructed, these six saddles will cradle and guide the single main cable from its eastern anchorage to the top of the tower, down to the western side of the span where it will wrap under both decks before returning to the tower top and back to the eastern end of the span. The cable anchors into the bridge deck, and the counterbalanced weight of the span is transferred to the tower, making it a self-anchored suspension (SAS) span.

Each of the six saddles is uniquely shaped for its individual use and location. The cable will anchor into two “splay” saddles – which allow the cable to spread into separate strands and distribute the load evenly and safely – in the span’s eastern deck section. At the top of the tower, a single 450-ton tower saddle will smoothly transfer the load from the cable down through the tower, and allow the cable to slide as loads pull from one side or the other. Two immense “deviation” saddles will guide the cable in its loop under and around the parallel bridge decks at the western end of the span. The sixth saddle is a 60-ton jacking saddle that will be hydraulically adjusted to tighten and loosen tension on the cable during construction and load transfer.

But in 2008, these massive steel saddles were still under Hiroshi’s watchful eye. As a technician used an ultrasonic testing device to do a typical pulse-echo integrity inspection on one of the saddles, Hiroshi observed and mused aloud that he would like to visit the Bay Area once the new East Span is complete. “It’s like having a child,” he said with a smile, “You want to see it grow up.”
— Karin Betts


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