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NEWS | April 29, 2024

Employees from Shops 11, 17 and 75 use 'cold-cutting' method to cut up old Dry Dock 3 caisson for recycling

By Max Maxfield, PSNS & IMF Public Affairs

A team of Puget Sound Naval Shipyard & Intermediate Maintenance Facility workers is using a wire saw to recycle one of the original caissons for Dry Dock 3.

Workers from Shop 75, Dismantlers; Shop 11, Shipfitter; and Shop 17, Sheet Metal; developed a method of using a commercially available wire saw from Husqvarna, which uses a 3/16 inch wire cable with industrial diamond ferrules approximately 1 inch apart, to cut through both the steel and the 760,815 pounds of concrete ballast at the bottom of the caisson. The bottom portion of the concrete-filled caisson is being sliced up in even cross-cut sections like pieces of a gigantic cake.

“Old caisson 3,” which everyone’s best guess is more than 100 years old based on when Dry Dock 3 was built, became obsolete after the dry dock was retrofitted and equipped with a new caisson. Since caissons are custom built to precisely fit specific dry docks there was no other potential use for the old caisson at PSNS & IMF, and it needed to be recycled.

This method of cutting is commonly referred to as a rope saw, even though this particular setup uses wire cable.

According to Alan Nelson, off-hull zone manager with Code 350, Inactive Fleet, Reactor Compartment Disposal and Recycling, the steel above the concrete ballast was cut away using cutting torches, as the IRR team does with submarines. However, the concrete ballast is not something the IRR team are used to dealing with.

“The concrete has been the unique challenge,” Nelson said. “Cutting metal is what we have done for years, but the concrete aspect is new. Several methods were looked at, and the rope saws were decided on due to the non-destructive nature to the dry dock and our existing knowledge of the rope saws.”

Gary Schmitz, swing shift general foreman, Shop 75, said he has been using this wire saw for the past five or six years. For this caisson job, Shop 75 trained a few Shop 11 workers from the cold cutting crew how to operate the saw.

Schmitz said teams or two or three workers per shift are needed to get the work done safely and effectively

“At a minimum we need two people, but it’s best to have three working the cut,” Schmitz said. “You should have one with hands-on control of the saw while it is running. Another worker should be on the opposite side of the cut, where the operator is unable to visually see the cut taking place. Finally, you should have one person as a go-between ensuring the pulleys are in the correct location and the rope is tracking as required through the cut.”

The entire project will take about four years — including work stoppage because of the COVID-19 pandemic — from planning to completion. The actual cutting up of the caisson should take about two years.

“When I was assigned this work late November last year, I started with a crew of eight people,” said Gordon Simmons, supervisor, Shop 11. “One who had rope experience taught the team how to safely operate and maintain the set-up. He has since moved on, and I have had six mechanics working as a team since the middle of January.”

“Originally, the caisson was to be cut into 13 eight-foot-long sections,” Simmons said. “The disposal contractor requested four-foot sections, so the amount of cuts doubled to 26. Code 715 rigging engineers were instrumental in the layout out of the cut lines. They took into effect the size and weight of each piece and laying out the pick holes for a safe and smooth pick of each cut section.”

The project have proven how effective a commercial-off-the-shelf wire saw can be, and it has potentially added another tool for the IRR team to use on other projects.

Jack A. Tappe, IRR project superintendent, Code 350, said his team are looking at the wire saw technology and the method used for this project for future use within the IRR program.

“The diamond wire saw is another form of ‘cold-cutting,’ which is used extensively on the recycling of Los Angeles-class submarines,” Tappe explained “Cold-cutting is a game changer because it removes or greatly reduces the amount of hot work — also known as burning — that we do. By getting away from burning we can greatly reduce the probability of fires. We also can use these technologies in addition to hot work, which allows us to recycle more efficiently and far more safely than on previous projects.”