According to API 650, each manhole reinforcing plate shall have a telltale hole of what diameter for leakage detection?

• A. 1/2"
• B. 1/4"
• C. 3/8"
• D. 5/16"

Answer: (B)

In the context of API 650, the requirement for a telltale hole in each manhole reinforcing plate serves a critical function in leakage detection. The correct diameter of the telltale hole is established at 1/4 inch. This specific dimension ensures that if there is any leakage of liquid from the tank, it can be effectively communicated through this hole, allowing for prompt maintenance and remediation actions to be taken.

The 1/4 inch diameter strikes a balance, allowing sufficient fluid to escape and become noticeable without compromising the structural integrity of the reinforcing plate. If the hole were too large, it could lead to excessive wear or weakening of the plate. Meanwhile, if it were too small, it might not allow for effective detection of leaks in a timely manner. This design consideration is an essential aspect of maintaining the safety and operational efficiency of oil storage tanks, ensuring environmental protection and compliance with industry standards.