API 650 low-alloy steel tanks maximum slenderness ratios

Material for the outer tank API 650 low-alloy steel tanks and for the roof that contains the vaporized liquefied gas but is primarily subjected to atmospheric temperatures may conform to one of the following:
a)Table 4-1 for design metal temperatures down to –35°F (lowest 1-day mean ambient temperature of–35°F) without impact test unless they are required by Table 4-1 or by the Purchaser.
b)Table R-3 for design metal temperatures down to –60°F without impact tests unless they are required by Table R-4 or by the Purchaser.

Prevent the storage liquid from impacting the inner wall of the API 650 petroleum storage tank or increase the internal pressure, reduce the corrosion of the tank top and the tank wall, and extend the service life of the API 650 low-alloy steel tanks storage tank.

The most popular standards for API 650 low-alloy steel tanks are API Std 650, JIS B8501, BS2654, GB50341, etc. The formulas used in each standard are derived from the hoop stress calculation formula of membrane theory. Combined with the stress characteristics of API 650 low-alloy steel tanks, plus the allowable stress, weld coefficient and additional wall thickness, the wall thickness calculation formula is complete. The allowable stress and weld coefficient are determined according to the material performance characteristics and construction technology level of each country. According to different API 650 low-alloy steel tanks standards, the calculation results of tank wall thickness are sometimes quite different.