What are tube stubs commonly referred to when used to connect fittings to drums and headers?

Tube stubs are commonly referred to as nozzles when they are used to connect fittings to drums and headers. The term "nozzle" specifically describes a tube or pipe fitting that serves as a termination point for a pipe or allows for the connection of other components, such as valves or gauges, to the vessel. In the context of pressure vessels and pipes, nozzles are critical because they provide access points for either input or output of fluids or gas.

When discussing components like fittings, manifolds, and flanges, it is important to understand their specific applications. Fittings are general connectors in piping systems. Manifolds refer to a structure that allows for the connection of multiple pipes or systems, typically leading to a single outlet or inlet. Flanges are flat surfaces or rings used to join two parts, usually with bolts. Unlike these terms, "nozzle" is specifically pertinent to the connection of tubes to vessels and serves a more specialized function, making it the correct choice in this context.