Normal (thermal + liquid movement) and emergency (fire exposure) venting requirements for atmospheric/low-pressure storage tanks
◉ API STANDARD 2000, 5TH ED. STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only. Figures are sourced directly from API Standard 2000, Fifth Edition (April 1998) — Tables 1-4 and the Simplified Method equations. This tool implements the Simplified Method (Tables 3 & 4 + Equation 2A), which the standard itself offers as a lower-accuracy alternative to the Detailed Method (Equation 1, requiring fluid-specific latent heat, molecular weight, and relieving temperature) — not implemented here. All figures are based on hexane properties per the standard's own basis; sound engineering judgment is required when applying this to other fluids, per the standard's own foreword. A newer edition may exist since 1998 — confirm before relying on this for a real assessment. Units are English (barrels, ft, SCFH) matching the standard's primary tables.
Identification
Research entries stay private to you for practice/testing. Switch to Official once this is a real assessment your company should see.
Tank Geometry
Capacity in barrels (1 bbl = 5.615 ft³) feeds Table 2's thermal venting lookup. Wetted area for fire venting (below) uses the same geometry.
Normal Venting Requirements (Tables 1 & 2)
Liquid-movement venting: 5.6 SCFH/bbl emptying (inbreathing) regardless of flash point; 6 SCFH/bbl filling (outbreathing) if flash pt ≥100°F, or 12 SCFH/bbl if <100°F. Thermal venting is interpolated from Table 2 by tank capacity above.
Normal Venting Result
Inbreathing — liquid movement—
Inbreathing — thermal (Table 2)—
Total inbreathing (vacuum)—
Outbreathing — liquid movement—
Outbreathing — thermal (Table 2)—
Total outbreathing (pressure)—
Emergency Venting for Fire Exposure (Tables 3 & 4 — Simplified Method)
Wetted area: vertical tanks use shell circumference × height, capped at 30 ft (per the standard, fire credit doesn't extend beyond that). Horizontal/sphere tanks use 75%/55% of total surface area as the standard's primary rule — the alternative "surface to 30 ft height" rule isn't computed here since it needs tank elevation/geometry beyond what this form collects; override manually below if that alternative governs and gives a larger area.
Table 4's "concrete tank or fireproofing" category has no fixed F — the standard says to use the F factor for an equivalent insulation conductance value; pick the closest insulated option above.
Emergency Venting Result
Method used—
Base requirement (before F)—
Required emergency venting—
Save & Report
Total venting device capacity should cover normal venting plus emergency (fire) venting per the applicable case — see API 2000 §4.3.3 for how these combine for your specific tank construction (frangible roof-to-shell attachment changes what's required).