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อัปเดต 2026-09-07
Relief valve / PRV
overpressure protection
A pressure-relief / pressure-reducing device that opens to protect against overpressure. Sizing follows API RP 520/521 and the relevant relief standard.
เมื่อไรจึงใช้
- Overpressure protection; PRV/PSV rating; back-pressure checks in a relief header.
ค่าที่ต้องกรอก
| ค่า | คำอธิบาย |
|---|---|
| Set pressure & orifice | The set point and orifice/area basis for the relief. |
| Back pressure | Built-up + superimposed; checked against MABP. |
คำนวณอย่างไร
On a network solve, the device presence promotes a global blocking honesty note (A1) so a datasheet is gated until the relief scenario is valid. The dedicated relief engine sizes the orifice per API RP 520 — a critical-flow vapor form and a liquid form — and checks built-up back-pressure against MABP.
สมการ
API 520 vapor (critical flow) area
W = relief mass flow, C = coefficient from the specific-heat ratio k, K_d = discharge coefficient, P₁ = relieving pressure (abs), K_b / K_c = back-pressure & combination corrections, T,Z,M = temperature, compressibility, molar mass.
API 520 liquid area
Q = flow (gpm), G = specific gravity, P_s = set pressure, P_b = back pressure, K_w/K_v = back-pressure & viscosity corrections (US units; A in in²).
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