06/08/2026
Emergency Venting at Half the Speed of Sound?
💨 We recently reviewed the vent system design for a set of ethanol mixing and storage tanks, checking compliance with NFPA 30 and the referenced API 2000 standard.
What stood out?
📌 Neither standard explicitly limits vent line velocity—or prescribes the line size—only the tank connection size.
When we ran the numbers, the required flowrate (based on emergency venting conditions) resulted in a calculated line velocity of ~150 m/s.
For context—that’s nearly half the speed of sound. 🚀
Had this been left unaddressed, the system would’ve created significant back pressure, potentially pushing the tanks beyond their design pressure during an emergency. Not to mention the noise and vibration caused during venting.
Luckily, we caught this early and adjusted the design to:
🔹 Reduce line velocity
🔹 Prevent excessive back pressure
🔹 Maintain safe, compliant operation under emergency venting conditions
This system was also located in an ATEX-zoned area, and included inline ATEX-rated equipment, adding further complexity to the design.
💡 Emergency venting is rarely needed—but when it is, the system needs to perform safely and effectively. It’s easy to overlook flow dynamics when the focus is only on connection sizes. We’re glad we could help ensure this system won’t add risk in a worst-case scenario.
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