Which type of joint is characterized as permanent or removable based on design?

The type of joint that is characterized as permanent or removable based on design is the flanged joint. Flanged joints use a flange on the pipe end that is bolted to a corresponding flange on another pipe or fitting, allowing for easy disassembly for maintenance or alterations. This feature makes flanged joints versatile for applications where accessibility is required, while still providing a strong and secure connection.

Push-fit joints are not the correct answer, as they create a quick installation method but are not designed for repeated disassembly; they typically provide a permanent seal once connected. Welded joints are also permanent since the welding process fuses the materials together, making them difficult to separate without cutting. Socket joints can be disassembled but are generally not characterized by the level of permanence that a flanged joint exhibits due to the adhesive or solvent methods used to secure them. Therefore, flanged joints indeed fulfill the criteria of being either permanent or removable based on their design.