A return bend for use in a heater treater, production separator, or furnace is designed to join adjacent tubes. The return bend includes a pipe constructed in a continuous piece. The pipe includes: a first end forming a first opening of the pipe facing a first direction; a second end opposite the first end, the second end forming a second opening facing the first direction; and at least one curving section that bends with a continuously smooth curvature of the pipe wall from the first end to the second end.

A joint having connection surface has a main body including a first connection surface and a second connection surface, each of which is structured to connect to a connection target such as a port of hydraulic equipment, a piping, and a joint, the connection target having a path in which a hydraulic oil flows, a first opening end opened on the first connection surface and connecting to the path, first coupling holes each structured as a threaded hole, which are opened on the first connection surface and arranged on a circle concentric with the first opening end, a second opening end opened on the second connection surface and connecting to the path, and second coupling holes each structured as a through hole or a threaded hole, which are opened on the second connection surface and arranged along a circle concentric with the second opening end.

A bonded brazing ring secured to an end of a tube having a solvent or a solvent with a binder applied to the surface of the tube, and a method of adhering a brazing ring to a tube using a solvent or a solvent with a binder is provided. The brazing ring is secured to the tube prior to a brazing operation.