Single-deck pontoon floating roof API 650 mechanically-anchored tanks

Allowable compressive stresses shall be in accordance with 5.5.4 except that for aluminum alloy plate the allowable compressive stresses shall be reduced by the ratio of the modulus of compressive elasticity to 29,000 for values of (t – c)/R less than 0.0175 and by the ratio of the minimum yield strength for the aluminum alloy in question to 30,000 for values of (t – c)/R equal to or greater than 0.0175 (see 5.5.2 for definitions). In all other equations in this standard API 650 mechanically-anchored tanks where yield strength or modulus of elasticity is used, such as Equations 27 and 28, similar corrections shall be made for aluminum alloys.

For floating roof API 650 tanks, the net working capacity is the liquid volume contained between the API 650 mechanically-anchored tanks maximum operating level (300 mm below rim for metallic type seals and 600 mm below rim for fabric type seals) and the minimum operating level (API 650 tanks roof supports clearing the tank bottom by 25 mm while set at the operating position).

Crack treatment of API 650 mechanically-anchored tanks weld area: find out the crack tip with ray or ultrasonic flaw detection, drill cut-off holes at both ends of the crack with the cut-off method, the hole depth is slightly greater than the crack depth, or groove (crack stop groove) is made by angle grinder at both ends of the crack, shovel and grind the whole crack, and grind it into a suitable groove; use radiographic inspection and dye detection to verify that the crack has been completely excavated, and finally repair welding.