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Efficient, Cost-Effective, Low-Emissions Method to Cutting Nuclear Submarine and Aircraft Carrier Hulls


OBJECTIVE: The objective is to develop an innovative metal cutting system for submarine and aircraft carrier hull disposal that achieves competing requirements for environmental compliance; safety and health requirements; scheduling, manpower and time constraints; while achieving increased cost efficiencies to translate into life cycle cost reductions. DESCRIPTION: The primary metal cutting technology used today for shipbreaking is Oxy-fuel torches. This is also the main generator of visible particulate matter (PM), which is measured by"opacity". Opacity is the smoke generated by burning of the torch gas, the iron and carbon in the steel, and the steel surface coatings at/near the kerf (including paint and a rubber-like special hull treatment and its adhesive). The PM emissions linger in the air long enough to be detected and reported by observers using the Ringelmann Method. The fuel that causes 90% of the dark smoke is the surface coatings. A minimum of 9"of each side of the torch path must be cleared to bare steelinside and outto avoid these substrates from burning and contributing to opacity). Reducing the opacity emissions will have added safety and health benefits. On November 4, 2010, Occupational Health and Safety Association Instruction CPL 02-00-136 was replaced by CPL 03-00-012 with significant changes to increase the overall worker safety during shipbreaking operations. The Navy has been searching for alternative or modification technologies to achieve the competing requirements listed above, with a focus toward faster cold-cutting methods to avoid the cost and time associated with preparing the steel to a bare surface inside and out. For in-service submarines, the latest technology is a much slower but safer method of using a"Super-Saw", as shown in Reference 1, which is being used by several shipyards. The current problem with the Super-Saw for shipbreaking is that it is prohibitively slow, does not have a wide enough kerf, and is cumbersome for access in shipbreaking applications, particularly for surface ships. Currently, the Navy is taking a short-term, preventative approach to reduce opacity in order to continue its mission in shipbreaking: Oxy-propane torches are used to dismantle submarines inside tensile fabric tents equipped with fans to capture fugitive PM emissions. This method is very costly with respect to support functions, because as each hull section has been completed, the containment needs moved, the hull section craned out of the dock, and the containment reset for the next cut. Due to size and the fact that submarines sit below the dry dock wingwall, whereas a cruiser is far larger and sits above the wingwall, the containment method would be at least ten times as complex, thus prohibitively expensive. Further, an aircraft carrier, using the same methodology would be at least one hundred times as complex, and entirely infeasible. So far, a variety of cutting technologies have been demonstrated for the Navy, each of unique design, and therefore, its own set of pros and cons, many addressed in Reference 2. In general, technologies included both cold and hot cutting; including slurry jet, diamond wire, plasma arc, and different torch fuel gases. Over the years, many methods have been attempted and studied for shipbreaking by several countries, and they are collected in References 3 and 4. The Navy has not yet seen a single technology with all its desired advantages. This effort is looking for an innovative, revolutionary solution that will meet or exceed federal, state and local environmental and safety standards while meeting the scheduling constraints (as measured in distance cut per unit time), and efficiency/cost/manpower constraints (as measured by distance cut per man day--accounting for all operating and support personnel required, including setup and teardown between cuts). Constraints are discussed below. Innovative research is needed to develop and construct a cold cutting method such as a circular or reciprocating saw or milling head system, preferably with at least a semi-robotic control, that meets the following additional requirements: - Able to cut high-tensile steel - Portability: preferably in"man-handle-able"modules sized to be brought into inside ship spaces, with the ship within a drydock. - Power: hydraulic/electric/pneumatic - Control: hydraulic/electronic at cutter, man drivable, preferably not requiring programming for each cut - Cut: Quality of cut and accuracy of cut are NOT an issue. This is scrap. Speed must be high to compensate for setup and removal time (minimal accepted lineal cutting speed of 10 inches per minute on 2"thick steel sheet, with the same speed or better on thinner work pieces). Considerations must be taken that submarine and ship hulls are not flat plate and have a radius of curvature. Ideally the cutter would be flexible in its cutting path so that it could be steerable around obstructions. Cut kerfs (width) is required to be 1/2"minimum 3/4-1"preferred. Depth of cut from 1/2"to 4"This can be accommodated by changing cutting tool. Cutter should not require access to both sides of panel. - Cutter: If a cutter is used, cutter should be designed for dry or very minimal coolant/lubrication. - Cutter system must be suitable for use in year-round, open-weather, salt waterfront environment. - Resultant opacity below the limit set by Puget Sound Clean Air Act (PSCAA) and also lower than the norm of oxy-propane torch cutting - With respect to safety, designing a cutter to cut large sheets of plate at high speed within OSH noise limits will pose a challenge. Other safety challenges, as discussed in Reference 2, involve repetitive motion and fatigue injuries and ergonomics which need to also be taken into consideration for a successful product. Since Oxy-fuel torches are also the globally dominant technology for large-scale metal-cutting, more organizations, including private entities will likely be affected by more stringent environmental regulations, enforcement and good environmental stewardship, making the tool developed good potential for commercial use. PHASE I: Develop concepts for an improved ship cutting operation/system that meet the requirements described above. Demonstrate the feasibility of the concepts in meeting Navy needs and will establish that the concepts can be feasibly developed into a useful product for the Navy. Provide data on expected cutting rates on 2"and 1/2"thick HY-80 plates, including kerf width and feasibility of performance in a realistic environment with curved hulls that are sitting in a dry dock. Data, if applicable, should be included with respect to portability, the expected power requirements, the identification and quantity of lubricant required, the expected quantity and identification of byproducts entering the environment (to include expected opacity levels), and expected life/replacement frequency of the cutter blade or bit for both 2"and 1/2"thick specimens. Finally, the expected number of workers and the skill sets needed for a cut from setup though completion should be included. Document optimum parameters, approach, tradeoffs, benefits and risks. Provide a Phase II development plan with performance goals and key technical milestones, and that will address technical risk reduction. PHASE II: Based on the results of Phase I and the Phase II development plan, develop a working prototype of the selected concept. The prototype will be evaluated to determine its capability in meeting the performance goals defined in Phase II development plan and the Navy requirements for the Improved Hull Cutting Operation System. Demonstrate that the system will work in a simulated shipyard operating environment, which could also include paint or residual special hull treatment coatings. Evaluation results will be used to refine the prototype into an initial design that will meet the described Navy requirements. The company will prepare a Phase III development plan to transition the technology to Navy use. PHASE III: The Company will be expected to support the Navy in transitioning the technology for Navy use. The company will finalize an Improved Hull Cutting Operation System solution, including any refinements identified and lessons learned in Phase II. The company will support the Navy for test and validation to certify and qualify the system for Navy use. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Since Oxy-fuel torches are also the globally dominant technology for large-scale metal-cutting for public and private companies alike, more organizations will likely be affected by more stringent environmental regulations, enforcement and good environmental stewardship, making the tool developed good potential for commercial use. As submarines are among the toughest structures to dismantle due to type of material and thicknesses, any system designed to efficiently cut a submarine hull will, in turn, work on any other Navy hull or commercial ship application. With the growing popularity in recycling and conscientious environmental stewardship, metal cutting work is expected to increase. Further, commercial potential can be realized in similar type metal cutting operations that go beyond shipbreaking. As air quality regulations become stricter, any large-scale metal cutting facility or installation may become potential customers for alternative metal cutting techniques. REFERENCES: 1. Naval Safety Center Success Stories: Super-Saw. 11 April 2011. Accessed 16 March, 2012.2. Paulson, Kathleen, et al."Initiation Decision Report: Innovative Technologies to Control/Reduce Emissions from Metal Cutting Operations."NAVFAC Technical Report TR-2368-EV. Naval Facilities Engineering Service Center (NAVFAC ESC), October 2011. 3. Nijkerk, Alfred A. & W.L. Dalmijn. Handbook of Recycling Techniques. The Hague, Netherlands: Nijkerk Consultancy, 1998. 4. Sarkisov, Ashot A. & A.T. Du Clos. Analysis of Risks Associated with Nuclear Hull Decommissioning. Disarmament Technologies, Vol. 24. Dordrect, Netherlands: Kluwer Academic Publishers, 1999.
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