Ellipsiodal Head: external Pressure

[Water_Guy]

Section UG33 (a) (1) provides to use Section UG32 (d), along with UG33 (d) for external pressure on ellipsoidal heads.

Section UG32 (d) formula (1) is applicable for 2:1 elliptical heads (manufacture's standard). What if the head is fabricated for a large vessel, where say the inside diameter is 77' and 1 minor axis is 31', a 2.48:1 ratio and the other head minor axis is 26', a 2.96:1 ratio ? I don't see where the Code provides for such a scenario.

 

[TGS4]

See Appendix 1-4.

 

[Jano6924]

On UG-33(d) take a look into Table UG-33.1, this table is in terms of outside dimensions, skirt outside diameter Do, outside axis ho, then you get factor ko and then Ro = ko*Do. This table covers a range from 1.0 to 3.0 but since you mention inside dimensions you must check if outside dimensions fall within this range.

You shall follow steps 1 to 6 of UG-33(d) to get the external pressure for each head. Don’t’ forget to check against UG-33(a)(1)(a).

Hope this helps.