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CHUUK, The Federated States of Micronesia (NNS) -- Seabee Divers from the Naval Facilities Engineering and Expeditionary Warfare Center (NAVFAC EXWC) Dive Locker conducted testing and evaluation of the Husqvarna Diamond Wire Saw (DWS) in support of Mobile Diving Salvage Unit (MDSU) ONE salvage efforts of the MICRO DAWN this past December.
The MICRO DAWN is a 185-foot steel hull cargo vessel weighing approximately 900 tons that sank pier-side in Weno Harbor, Chuuk State, FSM during a 2006 typhoon. In 2017, FSM requested U.S. Department of Defense assistance in removing the wreck, and MDSU ONE was tasked to begin salvage operations in July 2019. After initial evaluation, it was determined that the most feasible salvage plan would include cutting the ship into multiple pieces, and subsequently dragging, floating or heavy-lifting the individual pieces to a location where they would no longer be a hazard for navigation.
Typical cutting methods employed during similar efforts have included steel-tubular, Broco, oxygen-acetylene, and Kerie cable cutting. However, in an effort to investigate new tools and technologies that can increase efficiency of port clearance and salvage operations, MDSU ONE requested support from the EXWC Dive Locker in evaluating the Husqvarna Diamond Wire Saw.
The EXWC Dive Locker has been developing the Diamond Wire Saw (DWS) for military use since 2016 with the primary mission of developing a highly portable, effective means to execute surface and subsea demolition and salvage cutting. Previous efforts by EXWC have focused on waterfront structure demolition in support of Underwater Construction Team (UCT) missions; however, in an effort to expand development and support to all Navy Expeditionary Combat Command (NECC) units, EXWC initiated ship salvage testing and evaluation as well.
The EXWC team traveled to Chuuk and joined MDSU ONE in early December, where they completed two major cuts during their stay. The first section of the Micro Dawn cut was the forward superstructure. The cut cross-section was approximately 8-feet by 22-feet, and weighed 25 tons. The section took 10 hours to cut and contained multiple compartments and hatches, with dozens of fuel and hydraulic pipes, valves and wire looms. There were also sections that were inaccessible by divers of which the contents were previously unknown. While cutting through an inaccessible section, the team discovered a hydraulic accumulator corroded to the bulkhead that was still pressurized with high-pressure gas, a surprising fact given that the ship had sank more than a decade previously. If a diver had inadvertently cut into this by hand, he or she could have been seriously injured, but since the team was utilizing the DWS, the cylinder wall was breached and the gas was released in a safe and controlled manner.
The second and largest cut made took place over a five-day period and was designed to cut the Micro Dawn through its entire beam, including the deck and keel. The cross section of the cut was 15-feet by 35-feet and weighed over 90 tons. The keel was comprised of double walled steel and contained many pipes and compartments. The total cutting time over the five-day period was 14 hours. A relatively similar cut made months earlier took the MDSU company seventeen days to complete utilizing conventional cutting methods. The use of DWS resulted in approximately 340 percent gain in operational efficiency, despite the inherent trial and error involved in the initial testing of new technology.
The testing and evaluation of the Diamond Wire Saw on Chuuk proved that the technology has the capability to significantly increase the speed of ship breaking while also reducing potential risks to divers. However, there is still a lot of work to be done in developing the tactics, techniques and procedures for diamond wire saw cutting in salvage operations. There may be more capable saws and better techniques that can be utilized, but this first proof of concept evaluation was extremely successful, showing a lot of promise for utilizing this technology to increase the speed and agility of our warfighters in the future.