Vertical Steel Shot Blasting Systems: Ship Hull © 2002 Blastrac, NA. All rights reserved. No portion of this article may be reproduced without the express written consent of Blastrac. Introduction What process can enhance your coating adhesion, reduce your costs, while gaining control and consistency of your surface preparation process? The fact is, there are several technologies in today’s marketplace that are vying for your attention to accomplish all of these tasks. They include: - Abrasive air blasting - Vacuum recycling abrasive blast cleaning - Power tool cleaning - Wet abrasive blast cleaning - Ultrahigh-pressure water jetting - Steel shot blasting systems Steel Shot Blasting Systems These systems are used to prepare the steel surfaces of storage tanks and ship hulls, undersides and decks prior to the application of coatings. Environmental and safety concerns are facilitating changes in the way these surfaces are cleaned and prepared. Other factors encouraging change are escalating liability and job site costs. These recycling abrasive blast machines that run steel grit have been shown to reduce environmental hazards and improve the quality of finish while reducing job turnaround time and cutting costs by as much as 50%. Dramatic improvements in centrifugal wheel blast technology have allowed the Blastrac steel shot blasting systems to be used in areas that previously had been unreachable. Environmental concerns and the new capabilities of these machines provide a powerful incentive for their use in the shipbuilding, storage tank and petrochemical industries. Reduction of Environmental Hazards Let’s take a look at why Blastrac systems reduce these hazards. 1. A mouth seal is used to contact the surface being cleaned to form a tight seal. 2. Enhancing the seal arrangement is a dust collector, which provides a negative air vacuum at the work area. Any particulate generated in the blasting process will be captured and contained. 3. Job site containment is reduced considerably to eliminate full containment. 4. Reduction in noise emissions makes for a safer work environment. 5. The systems significantly reduce clean-up. Disposal of spent abrasive is reduced to pounds, not tons. Reduced Liability and Job Site Costs Blastrac systems can reduce liability and job site costs. Some of the factors contributing to this include 1. Allows other trades to work in surrounding areas simultaneously. 2. Manpower requirements reduced to 1-2 persons per machine to run. 3. Reduced workman’s compensation exposure. 4. Containment tents not needed for the blasting area where the system is used. 5. Reduced clean-up and disposal costs. 6. Less time spent on the job site for faster turnaround times Improved Quality of Finish 1. By using a system that can use steel grit, steel shot, or both, Blastrac systems can be customized to job conditions or requirements. 2. The system works with a consistent intensity, thus reducing inconsistent results.

3. Consistent surface preparation enables a more consistent amount of paint to be applied. There are far fewer surprises to deal with. Reduced Job Costs 1. Reduction in manpower needs. 2. Less manpower needs = lower workman’s compensation. 3. Jobsite containment reduced, if not eliminated. 4. Reduced disposal costs. 5. Consistent surface preparation means better paint cost control. 6. Less time on the jobsite allows for easier scheduling of more jobs per a given amount of time. 7. Far fewer surprises to overcome and a predictable cost factor to use when bidding future work. Steel Shot Blasting System Technology The steel shot blasting technology works by throwing an abrasive mixture of steel shot and grit at a high velocity onto the surface being cleaned. This is achieved through centrifugal force by a wheel with removable paddle type blades that revolve at a high speed. Abrasive travels along the radial length of the blade and is thrown at a high velocity in a predetermined and adjustable direction. Once the abrasive impacts the surface, thereby cleaning it, the abrasive rebounds into a reclaim chamber where it is recycled. The reusable abrasive is separated from the dust and debris and is transported into a storage hopper for recirculation. Airflow transports the dust and debris through a hose to the dust collector where it can be disposed of later. The vertical system uses a resilient mouth seal to compensate for any variations in the contacted surface. Blastrac Vertical Ship Hull Application The following Blastrac system application details the removal of chlorinated rubber from a natural gas tanker. There were approximately 110,000 square feet to be blasted and the specifications required an SP-10 finish. Equipment Used (1) Blastrac System with companion dust collector and 300 feet of duct hose 2,500 lbs. #16 steel grit 1,000 lbs. #25 steel grit 1,000 lbs. #12 steel grit Costs of Blastrac System for Vertical Ship Hull Application Item Cost Price Per Square Foot Abrasive $1,251.00 1 cent Spare Parts $4,760.00 4 cents Crane $24,200.00 14 cents Labor- $35.00/hour-230 hrs (2 people- 1 operator, 1 support)

$24,200.00

22 cents

Summary for Vertical Ship Hull Application Work was completed on a round-the-clock basis. Due to the severe angles of the ship hull, a true time summary was not recorded. Square foot per hour recordings ranged from between 450 square feet per hour to 625 square feet per hour. Disposal was reduced by more than 500,000 pounds. The price per square foot using the Blastrac system was 41 cents. Measurable Results Relating to the Blastrac Process Principal benefits of using the Blastrac system technology are the significant reduction in air, water and noise pollution resulting from its use. Capital equipment costs can be amortized over a large surface area and the high productivity of the equipment reduces the cost of labor.

Less equipment is required to complete a job resulting in quicker mobilization. No containment or significant safety equipment is necessary. Airborne dust and particulate emissions are eliminated, protecting the environment and workers in the area. Disposal costs are minimal while liability and workman’s compensation costs are greatly reduced when the Blastrac system is used. A high quality, even surface finish, that is immediately ready for coatings, is produced: no blow down is necessary. There is a large reduction in turnaround time for the job to be completed because the cleaned steel can be coated at the end of each shift. SUMMARY: ISSUES TO CONSIDER While there are many factors to consider when choosing a method of surface preparation for steel surfaces, cost, turnaround time, environmental safety and flexibility have become important ones. In some cases disposal and material costs are not as much of an issue, particularly in areas where environmental regulations have not gone into effect. In a growing number of regions however, environmental issues can no longer be ignored. Blastrac Systems have been shown to be a highly effective method of surface preparation while protecting the environment and the safety of workers in the area. Costs have been shown to be less than that of other methods and the time taken to complete projects had been drastically reduced.