What is installed on a floating roof tank to help prevent out of roundness?

A wind girder is designed to provide structural integrity to a floating roof tank, particularly in maintaining its round shape during windy conditions. This component is crucial because, without it, the roof may experience distortions or 'out of roundness' due to external forces such as wind pressure or thermal expansion.

The wind girder is typically installed along the perimeter of the floating roof and acts as a stabilizing element, ensuring that the roof remains level and evenly supported. Its design helps to distribute loads and resist deformation, thus preserving the integrity of the tank's structure.

In contrast, the other options serve different functions. A ring wall is intended to contain the tank and separate it from surrounding areas, the floating roof is an operational component that floats on the product inside the tank, and the shell support beams are structural elements meant to support the tank walls. While they are essential in their own right, they do not specifically address the issue of maintaining the roundness of the roof under varying conditions.