+2 votes

Do cut-outs and rat holes and welds be rounded to a radius of 2mm?

asked Aug 18, 2014 in Material by belmoreno (2,190 points)
Does ISO 8501-3 apply to all surfaces in the ballast tank that includes cut-outs and rat holes and welds that should be rounded to a radius of at least 2mm prior to Blasting and Coating?

3 Answers

+1 vote
answered Aug 18, 2014 by Normandy (21,040 points)

Yes, all surfaces should be finished to ISO 8501-3, preparation grade P2. This means that all edges, including cut-outs, rat holes and welds should be rounded to a radius of at least 2mm by three pass grinding in immersion area and 1C for dry spaces.

+1 vote
answered Aug 18, 2014 by josvanden (3,240 points)
For a tank coating area (water ballast, potable water, drill water, diesel oil, sump tank), all sharp edges including edges of hole cutouts, should be grounded to a profile of approximately 2mm radius. Three pass edge grinding is considered to satisfactory. Free edges of rolled structural members such as steel angles, built-up sections, need not be ground, provided those edges are sufficiently round with a radius of approximately 2mm.

For all other coated steel areas, one pass edge grinding is required to remove steel to a minimum right triangular shape of 2mm x 2mm. Any burrs caused by grinding should be removed.
0 votes
answered Aug 19, 2014 by Normandy (21,040 points)
Regarding the Blasting and Coating activities, all welded areas and appurtenances should be given special attention for removal of welding flux in crevices. Welding splatter, slivers and underlying mill scale exposed during blasting should be removed or repaired. Before any primer is applied, all areas should be checked and all welding and cleaning pickups completed.

After blasting, all blast grit and dust should be cleaned from both internal and external surfaces, including removal from crevices, recesses, etc. All exposed laminations on structural items, shapes, girder beams, etc., should be grounded smooth and surface treated before the primer is applied. Any areas of lamination requiring NDE should be checked, remedial repairs made, re-blasted and re-primed.