Hot bolting is a method of replacing the bolts on a live line. Normally done one bolt at a time. Hot bolting should be used only when there is no other reasonable choice.
The criteria typically followed is something like: • The operating pressure must be less than 75% of the MAWP as allowed under ANSI B16.5 at the operating temp of the piping or process system to be hot bolted. • The flange must have a minimum of 8 bolts • The process temperature must be between 4°and 71° C. • All flanges and associated system equipment must be adequately supported, i.e. no excessive vibration or pulsation.
Monitoring for hydrocarbons is also a must during the operation. Generally the procedure for hot bolting is the same sequence as for a tightening operation. • The gasket area must not show signs of leakage. Piping, flanges, and bolts must not be severely corroded, i.e., to the point of affecting their integrity. • Existing flange bolts/nuts must be tight and of the correct size and grade.