Shell Head

Module from the Pressure Vessel Engineering Curriculum curriculum.

Module 2 - Shell and Head Design for Internal Pressure · Learning Objectives · 1. Apply UG-27(c)(1) circumferential stress equation for cylindrical shells · 2. Apply UG-27(c)(2) longitudinal stress equation (usually not controlling) · 3. Select head type and compute thickness per UG-32 (ellipsoidal, hemi, F&D, conical) · 4. Understand t/R limits beyond which the thin-shell equations do not apply · 5. Include corrosion allowance, forming thickness loss, and undertolerance · Pressure Design Equations (UG-27 and UG-32) · Shell circumferential: t = P*R / (S*E - 0.6*P) valid for P <= 0.385 S*E and t <= R/2. Shell longitudinal: t = P*R / (2*S*E + 0.4*P). 2:1 Ellipsoidal head: t = P*D / (2*S*E - 0.2*P). Hemi head: t = P*R / (2*S*E - 0.2*P). F&D head (ASME standard): t = 0.885*P*L / (S*E - 0.1*P) where L = crown radius. Variables: P=design P (psi), R=inside radius (in), D=inside diameter (in), S=allowable (psi), E=joint efficiency, t=required thickness (in, exclusive of CA). · Head Type Comparison

Head Type	K Factor	Vol (ft3 for 60in ID)	Cost Index	Depth	Typical Use
2:1 Ellipsoidal	1.0 ref	54.5	1.0	D/4	Most process drums
Hemispherical	0.5 (thinner)	86.3	1.8-2.5	D/2	High P or large D
Flanged & Dished	~1.77 (thicker)	40.8	0.8	0.17D	Low P, utility
Conical (30-60 deg half-angle)	Varies	Depends	0.9-1.2	Cone length	Reducers, bottoms
Flat (stayed)	Very thick	~flat	0.6	0	Small manways
Joint Efficiency E (UW-12)
Joint Type	Full RT	Spot RT	No RT	Notes	UW Ref
Category A (long seam butt)	1.00	0.85	0.70	Most critical	UW-11
Category B (circ seam butt)	1.00	0.85	0.70	Both heads	UW-11
Category C (nozzle to shell butt)	1.00	0.85	0.70	Per reinforcement	UW-11
Category D (nozzle to head)	1.00	0.85	0.70	Reinforcement rules	UW-16
Double fillet lap (not common)	-	-	0.55	Limited to low P	UW-12(c)

Source: Pressure_Vessel_Engineering_Curriculum_v1.xlsx · Sheet: Shell Head

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