5　Design of Metallic Components

5.1　General Requirements

5.1.1　The low temperature steel storage tanks for petrochemical services shall be designed based on various combinations of loads.

5.1.2　The maximum allowable tensile stress of any plate or weld metal shall be in accordance with Table 5.1.2.

5.1.3　For seismic design，the allowable stress may be taken as following：

1　The allowable stress for precautionary earthquake may be 1.33times the allowable stress under operating conditions.

2　For seldom occurred earthquake，the allowable stress in tension may be 1.00Rel，and the critical yield stress may be taken for allowable compression stress.

5.1.4　The allowable tensile stress in the tank anchorage shall comply with the following requirements：

1　Normal operation：0.50Rel.

2　Test：0.85Rel.

3　Precautionary earthquake：0.67Rel.

4　Seldom occurred earthquake：1.00Rel.

5.1.5　Shell attachments and embedments shall be designed for a load corresponding to the full yield capacity of the uncorroded anchor bolts or anchor straps.

5.1.6　For LNG service，anchors made from 9% Ni steel or austenitic steel shall apply the anchor material yield stress at the boiling point temperature specified in the current national standard General characteristics of liquefied natural gas GB/T 19204 or colder.

5.1.7　The allowable compressive stress of the compression area at roof-to-shell junction shall not be greater than 120MPa.

5.1.8　For butt welds，where the load is perpendicular to the weld and in the plane of the plates，the allowable stress shall be limited to the value given in Table 5.1.2，and where the load is parallel to the weld，the allowable shear stress shall be limited to 75% of the value given in Table 5.1.2.

5.1.9　For fillet welds，where the load is perpendicular to the weld，the allowable shear stress shall be limited to 70% of the value given in Table 5.1.2，and where the load is parallel to the weld，the allowable shear stress shall be limited to 50% of the value given in Table 5.1.2.