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 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
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
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
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
— Karin Betts