3.3.5 Required Minimum Wall Thicknesses for Pipes
For pipes in the gravity drain systems covered by 4-6-4/3.3, the wall thickness of steel piping is not to be less than given below: 3.3.5(a) Piping where Substantial Thickness is Required. For scupper and discharge pipes between hull plating and the closeable or non-return valve, where substantial thickness is required: i) External diameter of pipes equal to or less than 80 mm (3.15 in.): thickness not less than 7.0 mm (0.276 in.) ii) External diameter of pipes 180 mm (7.1 in): thickness not less than 10.0 mm (0.394 in.) iii) External diameter of pipes equal to or more than 220 mm (8.7 in.): thickness not less than 12.5 mm (0.5 in.) Intermediate sizes are to be determined by linear interpolation. 3.3.5(b) Piping where Substantial Thickness is not Required. For scupper and discharge pipes inboard of a closeable or non-return valve, where substantial thickness is not required: i) External diameter of pipes equal to or less than 155 mm (6.1 in.): thickness not less than 4.5 mm (0.177 in.) ii) External diameter of pipes equal to or more than 230 mm (9.1 in.): thickness not less than 6.0 mm (0.236 in.) Intermediate sizes are to be determined by linear interpolation.