What device is used to connect piping up to IN and allows piping to be removed for repairs?

The correct answer is unions. Unions are specialized fittings designed specifically to connect two segments of piping while allowing for easy disconnection. This feature is particularly useful in maintenance scenarios, as they enable quick removal of pipes for repairs without having to cut the piping or disturb any welding or threaded connections.

Unions typically consist of three pieces: two end fittings and a center nut, which when tightened, creates a secure seal. When repairs are necessary, loosening the center nut allows the two ends of the pipe to be separated rapidly.

Flanges also allow for connections and disconnections of pipes, but they generally require additional gaskets and bolts, making them less convenient for quick repairs. Fittings serve various purposes in piping, such as changing directions or connecting different sizes of pipes, but do not typically allow for easy removal. Couplings are used to connect two lengths of pipe together but don’t inherently provide a way to easily disconnect the pipes for maintenance. Unions are specifically the most appropriate choice when the ability to easily remove and reattach pipes is required.