Working under a pressure not exceeding the static head corresponding to the depth of the tank, built up from pressed steel plates 1220 mm square. The sectional dimensions are interchangeable with the imperial dimensions of the 1949 edition of the standard.
BS 1564:1975 history
0000 BS 1564:1975(1999)
1975BS 1564:1975 Specification for pressed steel sectional rectangular tanks