Flare Seal Drum
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Flare Seal Drum Calculator

API 537 §H.9 / API 521 Liquid Seal Drum Sizing

Size a flare liquid-seal drum to API 537 §H.9 + API 521. The diameter is set by the governing of three independent criteria — vapor/seal-liquid disengagement (API 521 droplet-settling, Eq 37), seal-liquid volume to hold the seal under the design header vacuum (API 537 Eq H.18), and anti-pulsing (§H.9.8: gas area ≥ 3× inlet-pipe area). Seal submergence sets the break pressure (Eq H.21).

Flow & Fluids

lb/hr
lb/ft³
cP
lb/ft³
µm

Seal & Inlet

in
in
in WC
psi

Geometry

ft
in

📚 Theory

Flashback prevention, anti-pulsation velocity, seal break P, water inventory.

Read Guide →

Method — diameter = max of three criteria

1. Disengagement / re-entrainment (API 521 Eq 37):

uc = 1.15·√[ g·Dp·(ρl−ρv) / (ρv·C) ]  →  Ddis = √(4·Qv / (π·uc))

2. Seal-liquid volume for vacuum (API 537 Eq H.18):

Dvol = d·√(H/h + 1)

3. Anti-pulsing (API 537 §H.9.8):

Dpulse = √3·d  (gas area ≥ 3× inlet-pipe area)

Break pressure (API 537 Eq H.21):

Pbreak = ρl · h / 144

Related

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Blowdown to flare.