Piping Criticality Evaluation Calculator (API 580/581 Screening Rubric) — Sample Report

1 · Design inputs

A toxic-service line at large bore, routed through an occupied area, running at high temperature with mild cyclic service and low corrosion. No code-check utilization has been entered yet.

2 · Method

consequence = fluid + size + location (each 0–3, max 9)

likelihood = temp + cyclic + corrosion (each 0–3, max 9)

score = consequence + likelihood (max 18)

Class assignment, with the utilization flag (any code-check ratio > 0.9) lowering the score needed to escalate a tier:

score ≥ 12, or (utilization flag AND score ≥ 9) → CLASS 1 — HIGH

score ≥ 8, or (utilization flag AND score ≥ 6) → CLASS 2 — MEDIUM

score ≥ 4 → CLASS 3 — LOW

otherwise → CLASS 4 — MINOR

The flag only ever escalates a class — a line that scores low on consequence and likelihood is not pushed to CLASS 1 by a high utilization alone unless the combined score also clears the lowered threshold for that tier.

3 · Calculation

1. Consequence: fluid=toxic (3) + size=large (2) + location=occupied (2) = 7.
2. Likelihood: temp=high (2) + cyclic=mild (1) + corrosion=low (1) = 4.
3. Combined score: 7 + 4 = 11.
4. No maxUtilization entered, so the utilization flag stays no — the escalation rule is not in play.
5. Class threshold: score ≥ 12 fails (11 < 12); score ≥ 8 passes → CLASS 2 — MEDIUM (full code check + periodic inspection).

4 · Results COMPUTED

5 · Verification statement

The result values above are locked as fixture criticality.json, case “toxic large occupied, high temp mild cyclic low corrosion -> 7+4=11 CLASS 2”, tolerance undefined, in the calc-core continuous verification gate (see https://pipingtoolset.com/trust/validation.html). Allowable-stress and factor data are user-supplied inputs; citations: API 580 — Risk-Based Inspection. · API 581 — Risk-Based Inspection Methodology.