When a nozzle is added to a pressure vessel shell or head, the opening removes material from the pressure boundary. In most cases, the ASME Code requires that this lost area be replaced. One common way to do this is by adding a reinforcing pad, often called a “repad,” around the outside of the nozzle. The repad helps distribute the stresses around the opening and restores the required cross-sectional area.

Repads are required to include a small weep hole or tell-tale hole. This hole serves two important purposes. First, it allows the space between the repad and vessel wall to be tested for leaks after welding. Second, it prevents pressure from being trapped behind the pad if a leak develops in service. After testing, the hole is usually left open or filled with grease. It should never be seal welded shut. Proper reinforcing pad design and installation are important details in ensuring nozzle openings remain safe and code compliant.