Calculation Mode:

Header Pressure Drop Header Sizing Knockout Drum

Gas Properties & Flow

Mass Flow Rate

lb/hr

Gas Specific Gravity

(air=1)

Operating Temperature

°F

Operating Pressure

psig

Liquid Mass Fraction

Header Parameters

Header Diameter (ID)

Header Length

Pipe Roughness

Maximum Mach Number

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Comprehensive guide to flare system design, API RP 521 methodology, and knockout drum sizing principles.

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Formulas

Header Pressure Drop (Darcy-Weisbach)

ΔP = f × (L/D) × (ρ × V²) / (2 × g_c)

KO Drum Velocity (Souders-Brown)

V_max = K × √[(ρ_L - ρ_G) / ρ_G]

Standards & References

API RP 521
Pressure-Relieving and Depressuring Systems (7th Ed.)
GPSA
ASME B31.3
Process Piping

Design Guidelines

Mach ≤ 0.5: Recommended for flare headers per API RP 521 to prevent acoustic fatigue and excessive backpressure.
Mach ≤ 0.7: Maximum allowable for flare headers; avoid sustained operation above this limit.
KO Drum K-values: Range 0.10-0.35 depending on service. Lower K for foaming/dirty service.
Retention time: Typically 10-20 minutes for knockout drums to ensure proper liquid separation.
H/D Ratio: Typical 2-4 for vertical knockout drums; higher ratios improve vapor-liquid separation.

Flare Disposal System Design

Gas Properties & Flow

Header Parameters

Knockout Drum Parameters

📚 Learn the Theory

Pressure Drop Results

Header Sizing Results

KO Drum Sizing Results

Formulas

Standards & References

Design Guidelines

Flare Disposal System Design

Gas Properties & Flow

Header Parameters

Knockout Drum Parameters

📚 Learn the Theory

Pressure Drop Results

Header Sizing Results

KO Drum Sizing Results

Formulas

Standards & References

Design Guidelines

Related Calculators

Flare Backpressure

Flare Radiation

PSV Header Sizing

Relief Valve Sizing