🛡️ API 521 Seals (Molecular Seal vs Velocity Seal, Nitrogen/Fuel Gas Purge SCFM)

Flare Molecular & Velocity Seal Purge Calculator

Size molecular buoyancy seals and aerodynamic velocity seals (John Zink / Zeeco) installed below flare tips under API 521: calculate continuous purge gas flow (SCFM of nitrogen or natural gas) required to prevent oxygen back-diffusion down the flare stack (<0.5% O2 at stack base), eliminate flashback explosions, and purge gas savings.

1. Project & Operating Inputs

Flare Stack Diameter (Inches e.g. 48.0" Heavy Refinery Flare Stack)

Purge Velocity (FPS e.g. 0.05 FPS with High-Efficiency Molecular Seal)

Annual Purge Gas Expense without Molecular Seal ($ / Yr e.g. $145,000)

Turnkey 304L Stainless Molecular Seal Retrofit & Installation ($)

2. Financial Breakdown & Yield

API 521 FLARE SEALS

Annual Flare Purge Gas Savings Profit

Refinery Process Safety Margin

0.0%

Gross Revenue / Bill

Total Project CapEx

Operating / Direct Cost