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Blowdown Time Calculator

Modified Walworth / API 521

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Pressure Blowdown Calculator
Determines gas release rates and volumes during emergency depressurization events. Critical for flare system sizing and safety system design per API RP 521 depressuring guidelines.

Pipe Segment & Pressures

psig
psig
miles
inches

Vent Stack & Valve

inches

Gas Properties & Conditions

Air=1
°F
ft
psia

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About This Calculator

Calculates pipeline depressurization (blowdown) time using modified Walworth equation with compressibility correction.

Key Considerations:

  • API 521: 15 min minimum for fire case
  • Choked Flow: Critical pressure ratio 0.528
  • Temperature: Joule-Thomson cooling effect
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