อัปเดต 2026-09-07

PSV Datasheet (combined)

API 520-I + 520-II + API 526

One-page vendor RFQ datasheet combining API 520-I orifice sizing (gas/vapor or steam, reused from the Relief Valve calculator) with the API 520-II installation checks — inlet-line 3% rule and built-up backpressure — plus reaction-force geometry, so an engineer fills in once and gets a complete, print-ready spec.

Open the calculator

คำนวณอย่างไร

No new physics — it is a composition layer. It calls reliefValve.ts's sizeGasRelief()/sizeSteamRelief() for the orifice area and psvLinePressureDrop.ts's inletLineCheck()/builtUpBackpressureCheck()/reactionForce() for the installation checks, then renders a single pass/warn/fail datasheet via assessPsv().

สมการ

Orifice sizing (gas/vapor critical flow), API 520-I §5.6

A = \frac{W}{C K _{d} P _{1} K _{b} K _{c}} \frac{T Z}{M}

Same equation as the standalone Relief Valve calculator (steam mode uses the Napier form instead); this page picks the mode via a tab.

Inlet-line 3 % rule, API 520-II §4.2/§4.3

\frac{Δ P _{in l e t}}{P _{se t}} \leq 0.03

Non-recoverable inlet-line pressure loss must not exceed 3 % of set pressure, or the valve is at risk of chatter/rapid cycling.

Built-up backpressure limit, API 520-II §7

\frac{Δ P _{o u tl e t}}{P _{se t}} \leq L_{b p}

L_bp = 0.16 for a conventional spring-loaded valve (with a stricter 0.10 rule-of-thumb also flagged), 0.50 for balanced-bellows or pilot-operated.

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