Pressure Vessel Roundness Tolerance
Maximum Allowed Out of Circular Form (Roundness) for Pressure Vessel Under External Pressure - Designation e.
External Pressure applied to pressure vessel. The shell of a completed vessel to operate under external pressure shall meet the following requirements at any cross section.
The maximum plus-or-minus deviation from the true circular form, measured radially on the outside or inside of the vessel, shall not exceed the maximum permissible deviation e obtained from
e = 1.0 t
e = 0.2 t for points falling above or below these curves. Measurements shall be made from a segmental circular template having the design inside or outside radius (depending upon where the measurements are taken) and a chord length equal to twice the arc length.