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F. Spot Repairs At Areas of Weld Removal or Welding: <br />1. Prior to welding, remove existing tank coating from the interior and <br />exterior tank surface within a one foot diameter area centered on the <br />welding location. Remove grease and oil in accordance with SSPC-SP 1 <br />and then abrasive blast surfaces to near white metal in accordance with <br />SSPC-SP 10 or power tool clean to bare metal in accordance with <br />SSPC-SP 11, as appropriate or as directed by the Engineer. <br />2. Feather edge of surrounding sound coating around perimeter of the one <br />foot diameter area where the existing coating was removed. <br />3. Remove grease and oil in accordance with SSPC-SP 1. <br />4. Coat surfaces within 8 hours of abrasive blasting or power tool cleaning, <br />unless environmental conditions are maintained. Do not coat surfaces <br />before power tool cleaning. <br />5. When abrasive blasted or power tool cleaned surfaces rust or discolor <br />before coating, clean surfaces again to remove rust and discoloration. <br />6. When metal surfaces are exposed because of coating damage, power <br />tool clean surfaces before touching -up. <br />7. Spray, brush or roller apply new primer and finish coatings to the welding <br />area. The new coating shall overlap the feathered edge of the existing <br />coating by two inches. <br />G. Abrasive Blast -Cleaned Surfaces: Coat abrasive blast -cleaned surfaces with <br />primer before visible rust forms on surface. Do not leave blast -cleaned surfaces <br />uncoated for more than 8 hours, unless environmental conditions permit and are <br />approved by the Engineer. <br />H. All compressed air supply shall be properly equipped with suitable after coolers, <br />oil and moisture separators to prevent contamination of abrasives and/or blasted <br />surfaces. These separators shall be of the continuous bleeding or automatic <br />dumping type. In order to prevent contamination of abrasives and/or blasted <br />surfaces, it is recommended that the separators be installed between the <br />compressor air outlet and the blasting pot compressed air inlet. <br />Stop abrasive blast cleaning in sufficient time to remove all dust, spent abrasive <br />and other foreign matter from and around all blasted surfaces (including rigging <br />and equipment) and to allow the atmosphere to clear before any coating is done. <br />Removal of these materials shall be by clean brush or suitable industrial vacuum <br />with particular attention given to welds, pockets, poorly accessible areas or any <br />overhead areas. <br />Apply the first coat to all prepared surfaces, except that there shall remain <br />uncoated a 3 inch to 4 inch border of blasted steel at the end of each workday. <br />When blast cleaning resumes the following workday, this border shall be <br />reblasted up to and including 1 inch to 3 inch of the previous primer coating. <br />K. Take extra care during all blasting operations, to prevent damage or abrasive <br />impingement upon previously applied -coated areas. <br />L. A prime coat shall be applied within eight (8) hours after sandblasting. When the <br />humidity exceeds 80%, the prime coat shall be applied within four (4) hours after <br />sandblasting. If conditions are questionable, the Engineer shall make the <br />P05367-2016-000 / Mounds View 09 96 20 - 10 PRESSURE VESSEL COATING <br />2019 WTP Rehabilitation SYSTEMS <br />