“Spot-And-Sweep” Blasting As a Cost Effective Method of Underwater and Outer Hull Surface Preparation
Evaluation of “Spot-and-Sweep” Blasting as a Cost Effective method of Underwater and Outer Hull Surface Preparation Prepared for: National Shipbuilding Research Program Surface Preparation and Coatings Panel (SPC) Submitted by: Gordon Kuljian, Consultant Stephen Cogswell, BAE Systems Southeast Shipyards John Odwazny, Chariot Robotics J. Peter Ault, P.E., Elzly Technology Corporation May 2012 Approved for public release; distribution is unlimited. Category B Data – Government Purpose Rights. EXECUTIVE SUMMARY The current U.S. Navy underwater hull surface preparation strategy is to completely remove the coating systems after an 8-year service life. This is accomplished through abrasive blasting or ultra-high water- jetting (UHPWJ) and is the only strategy approved under NAVSEA Standard Item 009-32 (preservation). Surface preparation in the commercial arena (general cargo fleet, tankers, bulkers, and cruise liners) generally consists of repairing the system at 36-60 month intervals by removing only loose or delaminated coating, applying primer to exposed steel, adding additional anti-corrosive as needed and applying full antifouling coats. Such a practice is termed “spot-and-sweep blasting”. This project examined using commercially available high speed semi-automated robots in conjunction with ultra-high pressure water-jetting (UHPWJ). This process of high speed spot-and-sweep surface preparation is being used now and for the past several years in yards throughout Europe, the Middle East, Japan, Singapore, and the Caribbean. The concept is approximately 5%-10% of the anti-corrosive coating breaks down periodically and therefore it is redundant and unnecessary to completely remove 90%-95% of intact coating to bare metal, as is the current requirement in Standard Item 009-32, each time the coating system is renewed.
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