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Relief Valve Sizing: Q
API 526/520 standard pressure relief valve orifice designations — effective orifice areas, rated discharge coefficients (Kd), back-pressure correction factors (Kb), and inlet/outlet connection sizes for orifices D through T
| orifice | Kb balanced bellows 50pct (dimensionless) | Kb conventional (dimensionless) | Kd (dimensionless) | Ksh sat (dimensionless) | area in2 (in2) | area mm2 (mm2) | inlet size in (in) | outlet size in (in) | standard |
|---|---|---|---|---|---|---|---|---|---|
| Q | 0.8 | 1 | 0.975 | 1 | 11.05 | 7,129 | 8 | 10 | API 526 Table 1; API 520 Part I 9th Ed |
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