อัปเดต 2026-09-07

NPSH Available & Cavitation Margin

ANSI/HI 9.6.1 margin ratio

Standalone NPSHa / cavitation-margin screen. Delegates the head-balance physics verbatim to pumpSizing.ts (single source of truth) and adds the HI 9.6.1 margin-ratio classification plus a flow- or temperature-vs-NPSHa sensitivity sweep.

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Same closed-form NPSHa balance as pump-sizing; the margin is then classified by BOTH the absolute difference (m) and the ratio NPSHa/NPSHr per ANSI/HI 9.6.1 guidance (a difference-only test misses that NPSHr is defined at the 3%-head-drop point, i.e. incipient cavitation starts above it).

สมการ

NPSHa head balance (Crane TP-410)

N P S H a = \frac{P _{a t m} + P _{g} - P _{v}}{ρ g} \pm h_{s t a t i c} - h_{f}

Identical equation and code path as pump-sizing's npshaBreakdown() — imported, not re-derived.

HI 9.6.1 margin ratio & difference

M R = \frac{N P S H a}{N P S H r}, Δ M = N P S H a - N P S H r

Regime bands: 'ok' requires MR ≥ 1.3 AND ΔM ≥ 1.0 m; 'cavitating' when ΔM ≤ 0 or NPSHa < 0; otherwise 'marginal'. A simplified, fixed-band reading of HI 9.6.1's suction-energy-dependent guidance (1.1–1.3+ typical process, higher for high-energy service).

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