4　Design Basis

4.1　Design Pressure

4.1.1　The design pressure for columns shall be determined according to those specially required by process systems or those specially defined in project design documents,but shall not be less than the values specified in Articles 4.1.2 and 4.1.3 of this Specification.

4.1.2　The principles for determining the design pressure of columns shall conform to the requirements indicated in Table 1.

Table 1　Principles for Determining Design Pressures

4.1.3　For a column comprising multiple chambers,the design pressure for each chamber shall be determined according to its working pressure,while the maximum differential pressure between chambers shall be considered.