25-REHABILITATION OF THE EAST ELEVATED STORAGE TANK

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SSPC-Guide 6 October 1, 2004 3.9 AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI):9 be noted that the abrasive used for abrasive blast cleaning may contain toxic components. * ANSI 29.2 (1979) Fundamentals Governing the Design and Operation of Local Exhaust Systems *ANSI Z9.2 (2001) Fundamentals Governing the Design and Operation of Exhaust Systems * ANSUASC Z9.4 (1997) Exhaust Systems - Abrasive Biasting Operations - Ventila- tion and Safe Practice 3.10 NATIONAL FIRE PREVENTION ASSOCIATIONtO NFPA 701 Standard Methods of Fire Tests for Flame Propagation of Textiles and Films 4. Procedures 4.1 SELECTING METHODS OF SURFACE PREPARA- TION AND DEBRIS COLLECTION 4.1.1 SurfacePreparation Method: Prior to selecting and specifying a containment system, it is necessary to determine the method to be used for surface preparation of the steel. Considerations for selecting surface preparation follow. 4.1.1.1 Coatings can be removed from the surface by a variety of techniques. These include: Abrasive blasting (e.g. open blasting with expendabie abrasives, open blasting with reusable abrasives, vacuum [closed] blasting with reusable abrasives, nonrecirculating closed blast systems). Water blasting and pressurized water jetting (with or without abrasives). Chemical stripping. Hand and power tool cleaning (with and without local- ized exhaust). 4.1.1.2 Methods vary significantly in their productivity, degree of cleanliness and surface profile achieved, utility and support requirements, dust and waste produced, clean-up required, and costs. For example, open abrasive blasting with expendable abrasives requires the greatest quantity of abrasive and produces the greatest quantity of dust and debris. Methods which do not utilize abrasive generally produce the least amount of dust and debris. NOTE: The toxicity characteristic of the waste is indepen- dent of the volume of the waste generated (e.g., paint chips alone or paint chips combined with abrasive). It should also 4.1.1.3 Before specifying a method of surface prepara- tion, the manufacturer of the coating to be applied should be consulted to assure that the degree of cleaning and surface profile produced will be satisfactory for coating system per- formance. 4.1.2 Methods for Collecting Debris: Debris may be collected from the surface at the point of cleaning (e.g., with vacuum) or from the general work area. The collection method should be selected in conjunction withthe paint removal method and the containment system design to assure a completely integrated operation. The debris should be collected on a regu- lar basis and not left to accumulate over the course of a job. Methods of collecting debris are described in Section 5.2. In addition to collecting debris within containment, debris that escapes the contained area should be removed on a rou- tine basis (e.g., end of work day, or as specified) to prevent winds or rain from carrying it onto surrounding property, into soil, ground, or storm sewers, or into bodies of water. 4.2 SPECIFYING CONTAINMENT SYSTEMS 4.2.1 The facility owner or representative should specify the class of containment required and/or the environmental monitoring criteria that will be used to verify the containment's effectiveness. The specified containment should be main- tained in accordance with the approved design throughout the course of surface preparation. Because of uncertainties in the measurement and significance of containment efficiencies, it is not a good practice to simply specify a level or percent of containment. Methods for specifyi ng containment systems and items that should be considered are found in Sections 4.2.2, 42.3, and 4.2.4. Containment for paint application is beyond the scope of this guide. 4.2.2 Containment System Classes: The classifications described below vary in the degree to which the containment design can be effective in controlling emissions of dust and debris into the environment. Note that emissions requiring control include spills and leaks of material in addition to plumes of airborne dust and debris. The degree of emissions control is greatest for Class 1 and least for Class 4. Selection of a containment system with greater emission control capability is required for surface preparation methods which produce the greatest quantity of dust and debris. Containments with lesser emissions control capability are required for surFace preparation methods which produce the least quantity of dust and debris. For example, a Class 1 containment for abrasive blastcleaning (designated 1 A) 9 American National Standards Institute, 1819 L Street, NW, Suite 600, Washington, DC 20036. Standards downloadable from www.ansi.org. 10 NFPA (National Fire Protection Association), 1 Batterymarch Park, Quincy, MA 02169-7471 Telephone: +1 617 770-3000 Fax: +1 617 770- 07 or www.nfpa.org. ~-3 511