Internal structural members of API 650 tanks

When the API 650 tanks top shell course is the minimum thickness indicated in 5.10.4, Table 5-6 and Figure 5-6, details a – e, h and i, the minimum anchorage shall be designed for normal loads as specified by the Purchaser and by this standard. See 5.11.2.3 for the allowable stress. When the top shell course is thickened beyond the minimum thickness provided in Table 5-6 or as in Figure 5-6, details f and g, or a knuckle is used, the minimum anchorage shall be designed for three times the internal design pressure. The allowable stress for this loading is 90% of the minimum specified yield strength of anchorage material.

API 650 tanks in which liquid fluids are stored and designed to withstand atmospheric pressure operation, less than 18 kPa, or internal pressures not exceeding the weight of the API 650 tanks roof, with temperatures no higher than 93, 3 C are included in the scope of this design code.

Generally, external environment corrosion should be considered before design and construction of API 650 tanks and so on storage tanks. The corrosion on the outer surface of storage tank is often worse than that on the inner surface. Especially in the chemical industry area, there are often acid fog, alkali or salt dust in the atmosphere. These impurities form an active corrosive medium with dew or steam and oxygen in the atmosphere. The corrosion of the external environment of the storage tank shortens the maintenance period of the storage tank, even causes the storage tank to be scrapped in advance, which affects the normal operation of the storage and transportation.