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C.1.4.1 Deck Plate Internal Corrosion a. _X_ For safety, before accessing the roof, check with ultrasonic instrument or lightly use a ball peen hammer to test the deck plate near the edge of the roof for thinning. (Corrosion normally attacks the deck plate at the edge of a fixed roof and at the rafters in the center of the roof first.) C.1.4.2 Deck Plate External Corrosion a. ___ Visually inspect for paint failure, holes, pitting, and corrosion product on the roof deck. C.1.4.3 Roof Deck Drainage a. _X_ Look for indication of standing water. (Significant sagging of fixed roof deck indicates potential rafter failure. Large standing water areas on a floating roof indicate inadequate drainage design or, if to one side, an unlevel roof with possible leaking pontoons.) C.1.4.4 Level of Floating Roof a. ___ At several locations, measure distance from roof rim to a horizontal weld seam above the roof. A variance in the readings indicates a nonlevel roof with possible shell out-of-round, out-of-plumb, leaking pontoons or hangup. On small diameter tanks, an unlevel condition can indicate unequal loading at that level. C.1.4.5 Gas Test Internal Floating Roof a. ___ Test for explosive gas on top of the internal floating roof. Readings could indicate a leaking roof, leaking seal system or inadequate ventilation of the area above the internal floating roof. C.1.4.6 Roof Insulation a. ___ Visually inspect for cracks or leaks in the insulation weather coat where runoff rain water could penetrate the insulation. b. ___ Inspect for wet insulation under the weathercoat. c. ___ Remove small test sections of insulation and check roof deck for corrosion and holes near the edge of the insulated area. C.1.4.7 Floating Roof Seal Systems a. ___ Measure and record maximum seal-to-shell gaps: b. ___ Low pump out ___ Mid-shell ___ High liquid level b. ___ Measure and record annular space at 30 foot spacing (minimum of 4 quadrants) around roof and record. Measurements should be taken in directly opposite pairs. 1. ________ _______ Opposite pair 1. 2. ________ _______ Opposite pair 2. c. ___ Check if seal fabric on primary shoe seals is pulling shoes away from shell (fabric not wide enough). d. ___ Inspect fabric for deterioration, holes, tears, and cracks. e. ___ Inspect visible metallic parts for corrosion and wear. f. ___ Inspect for openings in seals that would permit vapor emissions. g.___ Inspect for protruding bolt or rivet heads against the shell. h.___ Pull both primary and secondary seal systems back all around the shell to check their operation. i.___ Inspect secondary seals for signs of buckling or indications that their angle with the