Toriconical tank heads are different from conical heads in that they have a radius at the flanged head. They can also be formed from flat plates. While more expensive than conical heads, toriconical heads uniformly distribute localized stresses and reduces them in the area near where the cone and the shell join together. Toriconical tank heads are often used in hoppers and towers.
Inside Knuckle Radius: At least 6% of diameter if code (See ASME Section VIII, Division I, UG-32 for clarification). Typically 3 X the material thickness if not code.
Typical Thin Out Allowance: 1/2” and Under – Add .03125” to the minimum. Over 1/2” – Add .0625” to the minimum