25-REHABILITATION OF THE EAST ELEVATED STORAGE TANK

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Blast cleaning operations shall be done in such manner that no damage is done to partially or entirely completed portions of the work. Dry blast cleaning operations shall not be conducted on surfaces that will be wet after blasting and before painting, or when ambient conditions are such that any visible rusting occurs before painting or coating. If any rust forms after blast cleaning, the surface shall be re-blasted before painting. The blast cleaned surface shall be examined for any traces of oil, grease, or smudges. If present, they shall be removed as outlined in Specification SSPC-SP 1-63, "Solvent Cleaning". The height of profile of the anchor pattern produced on the surface shall be limited to a maximum height that will not be detrimental to the life of the paint film. The maximum particle sizes specified in paragraphs 1 to 7 may produce an anchor pattern that is too high or too rough for the paint system to be used. In such cases the abrasive sizes should be reduced. If the application of the second coat of paint is deferred, an adequate reduction in anchor pattern depth shall be made. The blast cleaned surface should be further treated or primed, as specified in the agreement covering the work, preferable within 24 hours after blast cleaning when practicable, but in any event before any visible or detrimental rusting occurs. Where chemical contamination of the surface may occur, the steel should be painted as soon as possible after blast cleaning. 2.04 SAFETY PRECAUTIONS If fire or explosion hazards are present, proper precautions shall be taken before any work is done. If the structure previously contained flammable materials, it shall be purged of dangerous concentrations. Nozzle blast operators exposed to blast dust shall wear a U. S. Bureau of Mines approved helmet connected to a source of clean, compressed air. Ts2-3.. 44'7