pressure-vessel-nozzle

name	pressure-vessel-nozzle
description	Pressure vessel nozzle design — area replacement method (ASME VIII UG-37), nozzle reinforcement, opening limits, local loads (WRC-107/WRC-297), hillside nozzles, trunnion loads.
metadata	{"priority":7,"promptSignals":{"phrases":["pressure vessel nozzle","nozzle reinforcement","area replacement","UG-37","WRC-107","nozzle local load","nozzle pad"],"minScore":3}}

Pressure Vessel Nozzle Design — Complete Skill

Nozzle Reinforcement — ASME VIII UG-37

Area Replacement Method

When a hole is cut in a shell, the removed area must be compensated (replaced) within the "zone of reinforcement"

Required area (A_required): A_req = d × t_r × F + 2 t_n × t_r × F × (1 - f_r1)

d = finished diameter of opening (corroded bore) t_r = required shell thickness (from ASME UG-27, pressure only) F = correction factor (1.0 for radial nozzles; 0.5 for nozzles at angles to axis) t_n = nozzle wall thickness; f_r1 = S_n/S_s (ratio of nozzle to shell allowable stress)

Available reinforcement area (A_available): A₁ = (t_s - t_r) × d [excess shell thickness] A₂ = (t_n - t_rn) × 2h [excess nozzle wall; h = ±2.5t_n inward + outward projection] A₄₃ = reinforcing pad area A₃ = (W_pad × t_pad) (add pad if A₁ + A₂ < A_req)

Acceptance: A₁ + A₂ + A₃ ≥ A_req

Zone of reinforcement: Width = max(d, r_n + t_s + t_n) Height = max(2.5 t_s, 2.5 t_n + t_pad)

Large Opening Exceptions (> half shell OD)

UG-36(b)(1): may require WRC bulletin analysis or FEA UG-37 not valid for openings > 1/2 shell OD (separate methods apply)

Nozzle Wall Thickness (UG-45)

Minimum nozzle neck thickness (for pressure): t_n,min = max(t_rn, t_n,structural)

t_rn = P r_n / (S_n E - 0.6P) (same as shell formula but for nozzle) t_n,structural = minimum structural per UG-45(b): 0.875 × standard wall for pipe nozzle

Standard Nozzle Loadings (ASME and Vendor)

Internal pressure only → UG-37 area replacement External loads → WRC-107 or WRC-297 (stress in shell at nozzle junction)

WRC-107 (Wichman-Hopper-Mershon): Charts for local stresses due to radial force, circumferential moment, longitudinal moment, torsion Stress at 4 locations: top/bottom/left/right of nozzle junction Input: D_m/T_shell (shell parameter), d/D_m (nozzle-to-shell ratio) Output: dimensionless stress coefficients → multiply by F_p, M_c, M_L, M_T

WRC-297: More accurate for d/D_m up to 0.5; extended range

Combined stress check: σ_combined = P×D_m/(2T) + σ_local (from WRC) vs. allowable (ASME Section VIII App. L) For fatigue: peak stress range from WRC analysis → number of cycles (Div. 2)

Nozzle Flexibility

API 610 (pump standards) and API 650 (storage tanks) specify maximum nozzle loads API 610 allowable loads (per Table 5): F_r = allowable radial force; F_a = allowable axial; M_a, M_b = allowable moments Typically scale with nozzle size; e.g., 6" nozzle: F_r ≈ 2700 N, M_a ≈ 3050 N·m

When loads exceed API 610: provide secondary support or redesign piping for lower reaction

Hillside (Offset) Nozzles

Nozzle axis does not pass through vessel centerline F-factor modification for angle to meridian: F = sin(θ_angle) approximately Hillside increases structural loads at one side of nozzle → asymmetric reinforcement WRC-107 conservative for hillside → use FEA for accuracy

Nozzle-to-Shell Welding (ASME IX / D1.1)

Full penetration weld (Set-in or Set-on, per UW-16): Set-in nozzle (inserted through shell): inside corner weld + outside fillet/partial pen Set-on nozzle (abutting shell OD): full or partial penetration weld

Minimum weld size: per UW-16(d); full pen preferred for elevated temperature / cyclic AWS D1.1 / ASME Section IX weld procedure qualification required

Trunnion and Lifting Lug Loads

Trunnion: cylindrical protrusion welded to vessel for support/transport Local loads from trunnion: FEA preferred; WRC-107 conservative approximation Minimize: use wide trunnion base; reinforce shell locally; check shell at attachment

Lifting lug: ASME PCC-1 / vendor guidance; check lug and attachment weld Lug design: shear + bearing + out-of-plane bending from dynamic factor (DAF = 2.0 typical)

ASME Code References

UG-27: Shell thickness under internal pressure UG-28: Shell under external pressure UG-36: Openings and their reinforcement (general) UG-37: Reinforcement required; area replacement UG-45: Nozzle wall thickness Appendix 1: Supplementary rules Appendix L: Fatigue of vessels

Output

Provide: A_req [mm²], A₁ + A₂ + A₃ [mm²] (adequacy check), pad dimensions (if required), nozzle wall thickness t_n [mm] vs. t_n,min, WRC-107 stress results [MPa] at critical location, comparison to ASME allowable, nozzle external loads vs. API 610 limits.