Swift Dam Penstock and Bifurcation Project

Overview of the Penstock and Bifurcation Project

Name: Swift Hydroelectric Project Surge Arresting Structure
Category: Shop Fabrication

At the time of construction, the Swift Dam project was one of the most ambitious contracts that T BAILEY, INC. had completed.

The penstock pipe was 400’ long and 15’ 10” in diameter, but what made it even more complex was that it had several elbows and split into two 11’ 4” diameter pipes (the bifurcation). The hydroelectric penstock shafts had very stringent tolerances and required precise, defect-free welds.

The fully assembled penstock and bifurcation were too large to transport to the job site and were also too difficult to fabricate in place. This forced T BAILEY, INC. to get creative with our fabrication and construction process — to learn how we solved this challenge, read on.

4 Challenges We Solved While Fabricating Penstock for the Swift Dam

Due to the scope of the Swift Dam project and the complex geometry of the penstock, there were a number of challenges that we encountered during the manufacturing process. This section of the case study is dedicated to analyzing these challenges and the innovative solutions produced by T BAILEY, INC.’s professionals.

Challenge #1: Setting up a Fully-Functional Fabrication Shop in the Wilderness

The first challenge we encountered was figuring out how to get the penstock fabricated and delivered to the job site.

Ideally, we would have built the large fabricated sections at our fabrication shop in Anacortes, WA, inside a dry facility with easy access to cranes and tools. However, the freight costs required to move the oversized sections of penstock the hundreds of miles from our shop to the job site would have sunk the project’s budget.

To solve this problem, we decided to find a location near the job site where we could set up a mobile fabrication shop.

This search led us to Beaver Bay State Park. The park had shut down for the winter and had a flat parking area that would be suitable for fabricating the large diameter penstock and bifurcation. What made this location even more enticing was that the parking lot was only 2 miles away from the project site — far better than the 250-mile drive from our Anacortes shop.

Once the park was secured for use, we had to set up a “shop” to build the large pieces of pipe. We covered our work section with 100’ x 100’ tarps to protect our fabricators from the adverse weather conditions present during Pacific Northwest winters. The tarps were supported at the midpoint with 20’ long pipe and supported vertically with either a crane or 60’ manlift.

We equipped the mobile fab shop with welding machines and cranes. Thankfully, our crew was used to working in field conditions like this due to T BAILEY, INC.’s extensive experience with field-constructed tanks.

Challenge #2: Assembling the Penstock in Adverse Weather

The next series of challenges came from having to assemble penstock deep in the forests of southern Washington.

We would fabricate and assemble small pieces of the penstock at our Anacortes shop and ship these south to our mobile fab shop. T BAILEY, INC.’s mobile team would then assemble these pieces into larger sections of pipe.

The fastest and most accurate method of welding the pipe sections together was to use the submerged arc process. This process is weather dependent and cannot be performed in windy rainy weather. As you can imagine, this being the PNW, almost every day came with windy and rainy weather.

Since we couldn’t wait for summer to roll around, our team fabricated a mobile platform that would surround the pipe being worked on. This platform sheltered our welders and allowed them to use the sub-arc in spite of the wind and rain.

Challenge #3: Transporting the Completed Penstock to the Job Site

As each 40’ section of the penstock was completed, they needed to be moved to the job site. Unfortunately, due to the size of the pipe, we couldn’t use any standard semi-trailer.

To overcome this challenge, our team fabricated a “super-sized” trailer specifically for this project. The custom trailer consisted of a deck of I-beams and Schnabel ends, mounted on semi axles. We attached this to a standard semi-tractor and used this setup to haul the penstock the remaining 2 miles to the job site.

Challenge #4: Fabricating the Bifurcation Section

By far the largest challenge was the fabrication of the bifurcation section. This section was assembled in four large sections at the campground site. These four sections were then transported to a staging ground adjacent to the project site for final assembly.

Once assembled, the bifurcation unit was 26’ tall, by 33’ wide, by 33’ long, and weighed approximately 120,000 pounds — an almost impossible size to move. To ensure that we’d be able to transport the completed section, we assembled the final unit on the bed of our custom trailer. Then the trailer transported the entire unit the last several hundred yards to the job site.

At the job site, the client hung the bifurcation from a crane and lowered it into the ditch.

In addition to the bifurcation section, there were several 15’ 10”-diameter elbows that needed to be fabricated. This process was much different in the field since our fabricators were forced to go without the use of our Anacortes shop’s concrete floor and overhead cranes.

To overcome this obstacle, a level steel base jig was built to fabricate the elbows on. The elbow gore sections were stacked vertically on each other with the mobile crane. Once completely fabricated, the elbow was laid flat on the jig/custom-trailer, along with our 40-ton and 28-ton mobile cranes, for transportation to the site.

The Northwest’s Leading Penstock Fabricator

The ability of our team members to set up and operate a mobile fabrication shop is just one of the many reasons why T BAILEY, INC. stands as an industry leader in the Northwest. Our decades-long history with field-erected construction has given us the flexibility and versatility to complete difficult projects on schedule.

Another advantage of partnering with T BAILEY, INC. is our advanced fabrication capabilities. As demonstrated in this case study, our expert fabricators are able to cut and assemble complex geometries and intersections. When you work with us, every cut and intersection is done right the first time, every time.

To learn more about how we can help you save time and money on your next penstock or bifurcation project, contact T BAILEY, INC. today.

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