Which of the following describes a rupture disk in the context of API 650?

• A. A device that allows liquids to flow freely
• B. A pressure-relief device that ruptures
• C. A safety valve that regulates temperature
• D. A mechanism for enhancing tank aesthetics

Answer: (B)

A rupture disk in the context of API 650 is accurately described as a pressure-relief device that ruptures. This device is designed to provide a safety measure for welded tanks storing oil and other liquids by preventing excessive pressure buildup. When the pressure inside the tank exceeds a predetermined limit, the rupture disk will fail, allowing the contents to escape safely and thereby protecting the tank structure and its surroundings from potential catastrophic failure due to overpressure.

In oil storage tanks, managing internal pressure is crucial, as it ensures the safety and integrity of the tank and its contents. The rupture disk serves this purpose by acting as a passive system that operates without the need for external power or control systems. Once it ruptures, it can either be replaced or repaired, ensuring continued operational safety.

The other choices do not accurately represent the function of a rupture disk; it does not facilitate the free flow of liquids directly, nor does it regulate temperature like a safety valve. Additionally, its purpose is not aesthetic enhancement but rather a critical safety function.