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ASME Pressure Vessel Head Thickness (UG-32) Calculator mechanical
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ASME Pressure Vessel Head Thickness (UG-32) Calculator

Calculate minimum required wall thickness, corroded MAWP, and knuckle stresses for 2:1 semi-ellipsoidal, torispherical F&D, and hemispherical heads per ASME Section VIII Div 1.

Head Geometry & Operating Conditions

Typical: 1/16" to 1/8"

Material & Joint Efficiency

SA-516 Gr 70: 20,000 psi (-20 to 500°F)

Thickness & MAWP Results

Required Minimum Thickness (with CA)
-- in
-- mm nominal fabricated thickness
Calculated Uncorroded t
-- in
-- mm pressure boundary
Corroded MAWP
-- psi
-- bar gauge
Inside Crown Radius L: -- in
Knuckle Radius r (6% min): -- in
UG-32 Formula Employed: --
Commercial Plate Recommendation: --
--

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Frequently Asked Questions

Why are 2:1 Semi-Ellipsoidal heads widely favored over ASME Torispherical (F&D) heads?

A 2:1 Semi-Ellipsoidal head has an aspect ratio of depth to diameter of 1:4, resulting in a membrane hoop stress that virtually matches the cylindrical shell itself. Standard Torispherical heads (6% knuckle radius, 100% crown radius) suffer severe bending stress concentrations at the knuckle transition, requiring roughly 30% to 50% greater metal thickness.

What is the significance of Joint Efficiency E (UW-12)?

Joint efficiency E accounts for the structural reliability and weld inspection level of the seams. Type 1 fully radiographed butt welds receive E = 1.00. Spot radiographed welds receive E = 0.85, requiring 17% thicker plate. Uninspected welds receive E = 0.70, forcing a 43% thickness penalty.

Why must corrosion allowance be added after the pressure formula calculation?

The ASME formula calculates the structural pressure-retaining boundary thickness (t_req) required to hold internal pressure. The corrosion allowance (CA) is sacrificial metal intended to be eaten away over the 20-30 year vessel life. Therefore, nominal fabricated plate thickness t_nom = t_req + CA.