What is the maximum internal pressure allowed for welded steel storage tanks according to API 650?

• A. 1.5 psi
• B. 2.5 psi
• C. 3.0 psi
• D. 5.0 psi

Answer: (B)

The correct answer is 2.5 psi, which aligns with the guidelines set forth in API 650 for welded steel storage tanks. API 650 recognizes that while these tanks are primarily designed for atmospheric pressure, they may experience some internal pressure due to thermal expansion, filling, and other variables. To ensure the structural integrity of the tank and safety during operation, a maximum internal pressure limit of 2.5 psi is established.

This limit takes into account various factors like the type of materials used, tank design, and safety considerations. Exceeding this pressure can lead to structural failure, leaks, or catastrophic incidents. The API 650 standard thus serves to balance operational needs with safety requirements, establishing a framework within which tanks must operate efficiently.

Understanding this maximum internal pressure is crucial for engineers and operators in ensuring that the design, construction, and maintenance of welded tanks comply with industry standards, minimizing risks associated with storage tank operations.