For 100 years the Hiram M. Chittenden Lock's trunnions, gears and gates maintained the levels of Lake Washington's and Lake Union's waters.
Obviously, these parts performed well for more than 100 years of nearly constant use, but as you might imagine, the Ballard Locks, as they're locally known, were due for an upgrade. For this project, Redside Construction partnered with Machinists Inc. Redside Construction, which does a lot of barge work with cranes and other equipment mostly on the water, was contracted by the U.S. Army Corps of Engineers to remove the old gates and install new ones. Machinist Inc. performed machining and fabrication on the gate trunnions, pins and arms.
"The gates, arms and trunnions were manufactured by somebody else," said Jeff Tomson, Machinist Inc., director of marketing. "We ended up fine tuning all of them and manufactured all the pins, associated hardware, bearings and bushings. It was a challenging assembly and installation process on this historic landmark."
The trunnions were welded, machined and bored to size within very tight tolerances. The pins had a slip-fit, tight tolerance to go inside the trunnion bracket. The very high-end bushings are self lubricating, with high wear and load characteristics, and support enough load to hold back the entire Lake Washington and Lake Union.
The project objectives were:
• Remove and dispose of the old gates and bushings
• Fabricate new trunnions, shafts, bushings, wire ropes and other components
• Repair pier concrete per plan and as necessary
• Install new anchor bolts
• Install new trunnions (using newly mounted anchor bolts)
• Install six new gates, including new wire ropes
Tomson said they were very worried about the alignment while swapping out the old parts for new ones.
"Each of those mounting places had to be aligned with within very tight tolerances to allow the gates to pivot," he said. "We were quite worried about that, the fit between the gate arms and trunnions, the gate arm centerline pivot, and the outer radius of the gate itself. All of this had to be spot-on so the gates interface and seal against the concrete spillway."
Most of the challenges actually came at the end, just before installation, Tomson said. There were a lot of concerns about the fit. Machinists Inc. did a lot of testing on the ground beforehand, working with Redside Construction on a test fixture.
All the gates were pre-assembled and run through a series of tests, so that when they are installed, everything is going to fit and run correctly.
"You can't afford a delay once you start installing. If it doesn't fit or doesn't work, you have a big problem. You really need to iron out the issues ahead of time, to the best of your ability. Really pay attention to what the possible problems could be," Tomson said.
Once Machinists Inc. and Redside Construction had access to the gates, Tomson said it was about a two month process. The actual gate installation took less than two weeks.
And once the job was complete, there were smiles all the way around.
"Yeah, I've been told everything functions fabulous. The primary contractor, Redside, is very happy as well as the Corps of Engineers," he said.
For more information contact Jeff Tomson, Machinists Inc., 206.763.0990 - www.machinistsinc.com