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DAVID J. DUNN <br />Metallurgy/Materials Consulting <br />930 Mtn View Dr, Leadville, CO 80461 <br />719-486-838 email alendavedunoCa~aol.com <br />Mr. Tavis Rogers <br />Climax Mine, <br />Climaa Molybdenum Company <br />Climaa, CO 80461 23 December 2004 <br />SUBJECT:CLIMAX MAYFLOWER WATER TREATMENT H2SO4TANK THICKNESS, 15Nov04 <br />21Dec04 Addendum <br />SUMMARY <br />Ultrasonic thickness tests on upper and lower domed heads and cylindrical side plates in the <br />Mayflower Water Treatment Sulfuric Acid Tank #18-4240, done IS November 2004, show minimal loss <br />except for a narrow band presumed to correlate with the upper liquid level wetted/dried interface where a <br />loss of about 0.10" has occurred in the origina10.500" steel side wall plate. <br />Tests were made through paint to avoid grind off and damaging the protective coating, presently <br />intact and preventing exterior corrosion, on the resulting bazed test area. Since thickness variations are <br />apparently modest considering inaccuracy caused by paint thickness variation. Variations in paint thickness, <br />comprised of two coats, constitute about 0.005-0.025" of thickness readings taken through exterior paint. <br />Side plate thickness measurements vary from 0.472" min. to 0.527". Thickness readings below the <br />assumed upper liquid level vary between 0.472-0.501" on side plates, excluding the narrow band of loss at <br />the liquid level. Thickness readings above the liquid level line vary from 0.512-0.527". This suggests that <br />loss due to corrosion below liquid level has been 0.040" max. On side plate including paint variations. <br />Thickness on bottom head varies from 0.0.465" to 0.524 so losses by corrosion is at most 0.059" <br />including paint variations. Net steel loss is probably closer to 0.040" on the bottom head, less than 10% or <br />original 1/2" steel head thickness. Thickness loss on the upper head, excluding the sharp radius aY the <br />dome/cylinder deformation azea, is nil. <br />21 December 2004 Additional Testing <br />Following cleaning of the tank, additional thickness tests were made on 1) the lower head interior <br />surface, on clean, bare steel. Thicknesses are predictably lower since paint thickness is not included in the <br />total ultrasonic thickness test readings. Readings vary uniformly from 0.451" near bottom centerline to <br />0.494" at the start of the hemisphere/cylinder transition where the bottom head is welded to the tank wall. <br />Minor localized pitting perhaps O.OIO-0.015" deep was noted at about 20" out radially from tank bottom <br />center. <br />Arc or acetylene torch gouges were noted on the tank bottom exterior in an area about 4"x6". The <br />suspected origin of these gouges is removal of a nut or lifting eye welded to the tank bottom for attachment <br />of a tag line during lifting and removal from Mill Area to Mayflower site. These gouges appear to be about <br />1/16" deep. Metal immediately adjacent to gouges is 0.452-0.466" thick measured through I coat of clear <br />primer. (see attached photos). Since internal corrosion rate appears to very slow, these gouges probably will <br />not develop into leaks for many yeazs. <br />A patch could be welded over the goughed area to insure that leakage will not develop if the <br />than should hole through at this site. Ideally, this should be done while the tank remains empty. <br />This tank appears to be in good condition with ample remaining thickness to serve its current use. <br />David J. Dunn <br />