Reference Tables
API 2000 Tank Venting Reference
Normal and emergency venting requirements for atmospheric and low-pressure storage tanks per API Standard 2000, 7th ed.
API2000 Venting
API 2000 — Tank Venting Requirements Quick Reference · Rev 1 — 2026-04-16 | Per API Std 2000, 8th Ed. (2024) / ISO 28300 · Table 1 — Normal Venting: Thermal Breathing (SCFH Air Equivalent)
| 100 | 600 | 400 | 600 | 400 | 0.5 | API 2000 Table 2 |
|---|---|---|---|---|---|---|
| 500 | 1200 | 800 | 1200 | 800 | 0.5 | |
| 1000 | 2400 | 1600 | 2400 | 1600 | 0.5 | |
| 2000 | 4200 | 2800 | 4200 | 2800 | 0.5 | |
| 3000 | 5400 | 3600 | 5400 | 3600 | 0.5 | |
| 5000 | 7800 | 5200 | 7800 | 5200 | 0.5 | |
| 10000 | 12000 | 8000 | 12000 | 8000 | 0.5 | |
| 20000 | 18000 | 12000 | 18000 | 12000 | 0.5 | |
| 30000 | 24000 | 16000 | 24000 | 16000 | 0.5 | |
| 50000 | 30000 | 20000 | 30000 | 20000 | 0.5 | |
| 100000 | 48000 | 32000 | 48000 | 32000 | 0.5 | For hexane-like stock |
| 180000 | 60000 | 40000 | 60000 | 40000 | 0.5 | Largest standard table entry |
| Table 2 — Emergency Venting: Fire Exposure (SCFH Air Equivalent) | ||||||
| 20 | 21100 | API 2000 Table 3 — fire case | ||||
| 50 | 42200 | Based on Q = 21,000 × A^0.566 for A ≤ 200 ft² | ||||
| 100 | 62600 | |||||
| 200 | 92700 | |||||
| 300 | 119000 | Q = 963,400 × A^0.338 for 200 < A ≤ 1000 ft² | ||||
| 400 | 141000 | |||||
| 600 | 176000 | |||||
| 800 | 206000 | |||||
| 1000 | 232000 | |||||
| 1400 | 278000 | Q = 963,400 × A^0.338 for 1000 < A ≤ 2800 ft² | ||||
| 1800 | 318000 | |||||
| 2800 | 414000 | Max table entry; beyond this, engineering judgment | ||||
| KEY NOTES | ||||||
| • Venting rates are in SCFH of air at 14.7 psia, 60°F. Convert to actual gas using MW ratio: Q_gas = Q_air × √(29/MW_gas) | ||||||
| • For insulated tanks (API 2000 Sec 4.3.2): multiply thermal venting by insulation factor (typ. 0.5 for 1" mineral wool, R ≥ 4) | ||||||
| • Emergency venting: credit for 2 psig set pressure = 0.5× multiplier; for 1 psig = 0.7× multiplier (API 2000 Table 5) | ||||||
| • Wetted area for fire case: use API 2000 Annex A methodology; horizontal tanks use full wetted perimeter up to max liquid level | ||||||
| • For floating-roof tanks: emergency venting only (no thermal breathing required per API 2000 Sec 4.3.1) | ||||||
| • Combined vent capacity = normal venting + emergency venting per API 2000 Sec 4.4.1 | ||||||
| REFERENCES | ||||||
| API Std 2000, 8th Ed. (2024) — Venting Atmospheric and Low-Pressure Storage Tanks | ||||||
| ISO 28300 — Petroleum and Natural Gas Industries — Venting of Atmospheric and Low-Pressure Storage Tanks | ||||||
| NFPA 30 — Flammable and Combustible Liquids Code (emergency venting coordination) | ||||||
| API RP 520 Part I — Sizing, Selection, and Installation of Pressure-Relieving Devices (supplementary) |
Source: API_2000_Tank_Venting_Reference_v1.xlsx
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