Fatigue Screening Calculator

Free fatigue analysis screening per ASME Section VIII Division 2, paragraph 5.5.2 — determine whether a detailed fatigue evaluation is required, using Method A (cycle counting against Table 5.9, materials ≤ 552 MPa UTS), Method B (a simplified stress-amplitude estimate), or Method C (comparable-equipment documentation checklist). Jump to how it works ↓

Method ACycle counting (UTS ≤ 552 MPa)

Method BStress amplitude estimate

Method CComparable equipment

Material & Construction

Tensile Strength (MPa)

Construction Type

Component Location (Table 5.9)

Design Pressure (MPa)

Process Conditions

Material & Design Parameters

Design Stress Intensity, S (MPa)

Yield Strength, Sy (MPa)

Design Pressure, P (MPa)

Thermal Expansion Coefficient, α (1/°C)

Elastic Modulus, E (GPa)

Table 5.10 — Construction Type (Kfb)

Construction

Attachment/nozzle in knuckle region of formed head (Hc = 1.35, else 1.0)

Process Conditions

⚠ Method B here is a simplified illustrative estimate, not the exact ASME VIII-2 Annex 3-F procedure. Kfb and Hc come from Tables 5.10/5.11, but the allowable-cycles curve is a generic high-cycle approximation, not the real material- and temperature-specific design fatigue curve. Do not use this in place of a full Method B evaluation on an actual project.

Comparable Equipment Documentation

Equipment Description

Service Years

Cycles Experienced

Service History & Inspection Record

Select a method, enter your data, and click Calculate.

How This Fatigue Screening Calculator Works

ASME Section VIII Division 2, paragraph 5.5.2 lets you determine whether a detailed fatigue evaluation is required for a pressure vessel component subject to cyclic loading, without running a full elastic or elastic-plastic fatigue analysis. If any one of three screening options is satisfied, a fatigue analysis is not required for that component.

The Three Screening Methods

Method A — 5.5.2.3

Cycle-counting against Table 5.9's allowable limits. Only applies to materials with specified minimum tensile strength ≤ 552 MPa (80,000 psi). Classifies every process condition as full-range pressure, operating pressure, or thermal, applies Table 5.8's temperature factors, and compares the total against the applicable limit.

Method B — 5.5.2.4

Applies to all materials regardless of tensile strength. Computes stress amplitudes for pressure and thermal cycles using Table 5.10/5.11 factors, then checks cumulative Miner's-rule damage against the material's design fatigue curve (Annex 3-F in the full Code procedure).

Method C — 5.5.2.2

A qualitative exemption based on documented successful experience with comparable equipment under similar loading. The Code defines no numeric score — this is an engineering-judgment decision informed by the documentation checklist below.

Table 5.8 — Temperature Difference Factors

Metal Temperature Differential	Factor F
28°C (50°F) or less	0
29–56°C (51–100°F)	1
57–83°C (101–150°F)	2
84–139°C (151–250°F)	4
140–194°C (251–350°F)	8
195–250°C (351–450°F)	12
Greater than 250°C (450°F)	20

Table 5.9 — Allowable Screening Cycles (Method A)

Construction	Component	Limit
Integral	Knuckle-region attachments/nozzles	350
Integral	All other components	1,000
Nonintegral	Knuckle-region attachments/nozzles	60
Nonintegral	All other components	400

📖 Want a fully worked example walking through classification, Table 5.8 thermal factors, and the Table 5.9 pass/fail check step by step? Read the companion guide: Fatigue Screening Criteria Under ASME VIII Div.2 Explained: A Worked Example →