What is the main function of venting systems in storage tanks according to API 650?

• A. To enhance the tank's appearance.
• B. To prevent vacuum or pressure buildup.
• C. To allow for faster filling and emptying.
• D. To circulate air within the tank.

Answer: (B)

The main function of venting systems in storage tanks, according to API 650, is to prevent vacuum or pressure buildup. This is crucial for maintaining the integrity and safety of the storage tank. When a tank is filled or emptied, changes in the volume of liquid can lead to fluctuations in the internal pressure. Without proper venting, these fluctuations could create a vacuum that might collapse the tank or excessive pressure that could lead to structural failure or even catastrophic incidents such as explosions.

Venting systems are designed to allow air in and out of the tank while preventing the escape of vapors, thus balancing the pressure. This keeps the tank operating within safe limits and helps ensure compliance with safety regulations. Ensuring that a storage tank is properly vented protects the tank and its contents, fostering a safe storage environment for hazardous materials like oil.