What does the term "hot bolt" refer to when dealing with flanges?

The term "hot bolt" in the context of flanges refers specifically to the practice of removing one bolt at a time, lubricating it, and reinstalling it. This method is crucial in maintaining the integrity of flange connections, especially in high-stress applications where thermal expansion or contraction might occur. By replacing one bolt at a time, the overall tension on the flange can be kept relatively stable, preventing leaks and ensuring that the joint remains secure.

This approach helps avoid the potential for the flange to warp or become misaligned due to uneven pressure being applied if multiple bolts were removed at once. Therefore, lubricating the bolt also aids in reducing friction during installation and ensures an even distribution of load across the flange.

The other options do not adequately describe the term or practice associated with it. For example, removing all bolts simultaneously could lead to a loss of pressure and potential leakage, while heating bolts before installation or using special bolts refers to different practices that serve specific purposes in different contexts.