What is the maximum out-of-plumbness for the tank shell relative to its bottom?

• A. 1/100 of the total tank height
• B. 1/200 of the total tank height
• C. 1/300 of the total tank height
• D. 1/400 of the total tank height

Answer: (B)

The correct answer identifies that the maximum out-of-plumbness for the tank shell relative to its bottom is set at 1/200 of the total tank height. This standard is established to ensure structural integrity and stability of the tank. Out-of-plumbness refers to the degree to which the tank shell leans away from the vertical alignment. Allowing for a specific tolerance helps in minimizing the risk of structural failure, particularly under operational loads such as liquid pressure, wind forces, and seismic activity.

Maintaining this tolerance is crucial because tanks that are not adequately plumb can experience uneven stress distribution, which can lead to localized failures or compromise the tank’s sealing performance. The specified limit of 1/200 balances practical construction tolerances with necessary safety considerations for the function and longevity of the tank. Thus, adherence to this standard helps ensure both safety and operational efficiency in oil storage tanks.