Nozzle in Ellipsoidal head designed to Code Case 2286-4

[MrPDes]

Code Case 2286-4 provides alternative rules for designing cylinders, cones, spheres and heads for external pressure.

The design for an ellipsoidal head has reduced the thickness of a convensionally designed VIII-1 head from 53mm to 41mm.

The code case provides rules for locations and sizes of openings in cylinders, but no rules for openings in spheres or ellipsoidal heads. There are general rules for openings but they are contained in a paragraph that only refers to cylinders, so they may not actually be general rules after all.

Does anyone out there have any experience for this code case?

For reference the minimum thickness of this head would be 36mm for PD5500 which does not allow any nozzles to be located in the knuckle of the head. Another words, conventional VIII-1 heads are very sturdy beasts.

 

[pdiculous963]

Based on a quick scan of the code case, I would say you should just use UG-37(d)(1) for the heads.

It may be worth using CC2965, which allows you to use Div. 2 rules with Div. 1 allowable stresses. Div. 2 uses the rules of CC2286 for external pressure design and is clear regarding the reinforcement rules for openings under external pressure (paragraph 4.5).

 

[TGS4]

I second applying Code Case 2965.

 

[MrPDes]

Yeah, CC2965 gets me about 48mm. Still quite allot.

This is a simple head without pressure or temperature cyling or corrossion and has a single opening that has no applied loads. Code Case 2286-4 is ideal if it could only be more specific on the opening requirements.

Whats more, the design is for multiple vessels so the cost of extra thickness adds up with each head.

 

[pdiculous963]

I believe the rules are identical between CC2286 and Sec. VIII Div. 2. You should be getting the same result for t-min as the calculations use yield strength and elastic modulus, not allowable stress.

 

[Duwe6]

Fully reinforce the hole with a repad, not using the nozz pipe or excess thickness of the head [if any]. Now, structurally, that hole no longer exists.

 

[MrPDes]

Golly gosh, CC2286 is just the same as Sec. VIII Div. 2. I was incorrectly using UTS instead of Syield.

Both VIII-1 and VIII-2 are sturdy beasts relative to PD 5500.