4.5 Minimum Thickness
4.5.1 After the columns are fabricated and formed,the minimum thickness of the column shells,excluding corrosion allowance,shall comply with the following requirements:
a)For the column shells fabricated with carbon steel or low alloy steel,the minimum thickness shall be 2D/1000,but not less than 3mm;
b)For the column shells fabricated by high alloy steel,the minimum thickness shall notbe less than 2mm;
4.5.2 The minimum thickness of the cladding of clad steel plates shall comply with the following requirements:
a)For clad steel plates used to ensure the operating fluid in a clean state(without contamination by iron ion),the minimum thickness of the cladding shall not be less than 2mm;
b)For clad steel plates used to prevent corrosion from operating fluid,the minimum thickness of the cladding shall not be less than 3mm(including the undertolerance).
4.5.3 The minimum thickness of stainless steel weld overlay on the inner surface of column shell shall not be less than 3mm.
4.5.4 The minimum thickness of the finished stainless steel weld overlay of any components(e.g.,flanges,cover plates,etc.)shall be 2mm.