The requirements of ASME pressure vessel opening reinforcement

　　The shape of the hole

　　The openings on the round cylinder or conical shell and the head are preferably round, elliptical or oblong, but the specification does not restrict the use of other shapes of heads.

　　When the ratio of the long and short diameters of the openings of the elliptical head is not greater than 2: 1, the reinforcing area across the short diameter should be increased to prevent deformation due to torque.

　　Ug-36 (b) dimensions of openings

　　For the inner diameter of the shell ≤60 ’’ (1250mm), the size of the opening shall not be greater than 1/2 of the diameter, and the maximum size shall not exceed 20 ’’ (508mm).

　　For the inner diameter of the shell > 60 ’’ (1250mm), the size of the opening shall not be greater than 1/3 of the diameter and the maximum size shall not exceed 40 ’’ (1000mm).

　　For threaded connections or expansion joints, the diameter of the openings on the shell and head should not exceed 2-3 / 8in. (60mm).

　　The center distance of any two unreinforced openings shall not be less than the sum of the diameters of the two holes.

　　The center distance of any two unreinforced openings in three or more opening groups shall not be less than:

　　(1+1.5Cosθ)( d1+d2)——For the cylindrical shell and conical shell

　　2.5( d1+d2)——For shells and heads with double curvature