🛡️ PSV Sizing (API 520 / 526)

Size pressure safety relief valve orifice areas according to API RP 520 / API 526 for gas, steam, and liquid relief with backpressure derating.

⚡ Fortran 90 Engine Double Precision (IEEE 754) ✓ ISO / ASME Validated

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👁️ Consultations 40

⚡ Calculs faits 32

💾 Téléchargements 220 📦 Code Fortran 4.4 KB

📅 Mise en service Jun 2026

⏱️ Latence < 1 ms

🛡️ API 526 Spring-Loaded Relief Valve Dynamic Lift & Discharge Plume

Real-time visual simulation of spring compression & sonic nozzle expansion

📝 Configuration & Presets

🔥 Methane Separator (25 bar) ♨️ Steam Header (40 bar) 💧 Liquid Thermal Relief (16 bar) 🚒 Fire Emergency Case (16%)

⚙️ Service & Pressure Settings

Relief Fluid Service Type:

Set Pressure P_set [bar gauge]:

Backpressure P_b [bar gauge]: Superimposed + Built-up backpressure

Allowable Overpressure [%]: Standard: 10% (Operating), 16% / 21% (Fire case)

🌡️ Relief Conditions & Required Flow

Required Relief Rate W [kg/h]:

Relieving Temperature T [°C]:

Molecular Weight MW [g/mol]:

Specific Heat Ratio k (Cp/Cv):

Compressibility Factor Z:

Liquid Density ρ_L [kg/m³] (if liquid):

API 520 Sizing Formulations:
• Gas Choked: A = [W / (C · K_d · P₁ · K_b)] · √[(T · Z) / M]
• Steam: A = W / (51.5 · K_d · P₁ · K_b)
• Liquid: A = W / [11.78 · K_d · K_w · √(ρ · ΔP)]
• Relieving Pressure: P₁ = P_set · (1 + Overpressure) + P_atm

📊 Sizing Results & Orifice Selection

📊 Output Summary
💾 Fortran Source

Recommended API 526 Standard Orifice

Orifice Letter "L"

Standard Area = 1,841.0 mm² (2.854 in²)

+50.6% Overcapacity

Required Orifice Area (A_req) 1222.1 mm² 1.8943 sq.in

Rated Orifice Capacity (W_rated) 12,804 kg/h Required = 8,500 kg/h

Relieving Pressure (P₁) 7.97 bar(a) Backpressure = 1.01 bar(a)

Discharge Coefficient (K_d) 0.975 Backpressure Factor K_b = 1.000

📈 Required Orifice Area vs Set Pressure

📊 Standard API 526 Orifice Capacities

=================================================================
 THERMOFLUIDCALC — API 520 / 526 RELIEF VALVE SIZING REPORT
=================================================================
Case Title                 : Chemical Reactor External Fire Emergency Relief Case
Service Mode               : Gas/Vapor
Set Pressure (P_set)       : 6.00 bar(g)
Overpressure Allowance     : 16.0 %
Relieving Pressure (P1)    : 7.973 bar(a) (797.32 kPa a)
Backpressure (Pb)          : 1.013 bar(a) (101.33 kPa a)
Required Mass Flow (W)     : 8,500.0 kg/h
-----------------------------------------------------------------
Calculated Required Area   : 1222.14 mm2 (1.8943 sq.in)
Selected API 526 Orifice   : Letter [L]
API 526 Standard Area      : 1841.00 mm2 (2.8536 sq.in)
Rated Orifice Flow Rate    : 12,804.2 kg/h
Overcapacity Margin        : +50.64 %
=================================================================

📘 Calculation Methodology & Engineering Standards

API 520 Part I Formulations

For compressible vapors and gases under critical (choked) flow conditions where $P_b / P_1 \le [2/(k+1)]^{k/(k-1)}$:

                    A = [W / (C · Kd · P₁ · Kb)] · √[(T · Z) / M]
                

Discharge coefficient $K_d = 0.975$ with certified derating factor applied per ASME Sec VIII.

API 526 Standard Orifice Letters

Standardized letter designations from D ($0.110\,\text{in}^2$) through T ($26.0\,\text{in}^2$) specify minimum effective nozzle flow areas for flanged safety relief valves.

Key Engineering Assumptions

Certified effective coefficient of discharge $K_d = 0.975$ (gas/steam) or $0.65$ (liquid).
Ideal gas behavior corrected with compressibility factor $Z$.
Backpressure derating factor $K_b$ evaluated for conventional or balanced bellows valves.

ThermoFluidCalc Engineering Report