Joint including connection surface, pipe including pipe joint, and piping structure including same

A piping structure, comprising:

• a joint having a connection surface, including 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, 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, and a communication path communicating the first opening end with the second opening end, wherein arrangement of the first coupling holes and that of the second coupling holes of the main body are made identical to each other, a first plane including the first connection surface of the main body is perpendicular to a second plane including the second connection surface, the first connection surface is a square with the first opening end as a center of the first connection surface, the second connection surface is a rectangle including a square identical to the foregoing square with the second opening end as the center of the square, the rectangle having one side longer than a side of the square by a depth of the first coupling holes;
• and
• a pipe with a pipe joint including the pipe structuring piping,
• the pipe including at a first end portion of the pipe, a first side pipe joint including a first side pipe insertion hole into which the first end portion of the pipe is inserted with a gap between the first side pipe insertion hole and the first end portion of the pipe, a first side connection hole serially provided to the first side pipe insertion hole and having a diameter corresponding to an inner diameter of the pipe, a first side connection surface on which the first side connection hole is opened, a surface on which the first side pipe insertion hole is opened, a sealing groove on the first side connection surface, which is arranged on a periphery of the first side connection hole, and coupling through holes arranged on the outer periphery of the sealing groove, along a circle concentric with the first side connection hole, wherein the first side pipe joint is fixed by welding an inner surface of the first end portion of the pipe and the inner surface of the first side connection hole, and welding the outer circumference of the pipe and the surface on which the first side pipe insertion hole is opened;
• and including at a second end portion of the pipe, a second side pipe joint including a second side pipe insertion hole into which said second end portion of the pipe is inserted with a gap between the second side pipe insertion hole and said second end portion of the pipe, a second side connection hole serially provided to the second side pipe insertion hole and having a diameter corresponding to the inner diameter of the pipe, a second side connection surface on which the second side connection hole is opened, a surface on which the second side pipe insertion hole is opened, and threaded coupling holes arranged on the second side connection surface along a circle concentric with the second side connection hole, which are in positions corresponding to those of the coupling through holes, wherein the second side pipe joint is fixed by welding an inner surface of said second end portion of the pipe and the inner surface of the second side connection hole, and welding the outer circumference of the pipe and the surface on which the second side pipe insertion hole is opened, and
• the connection surface of the joint having the connection surface and the pipe joint of the pipe with a pipe joint are being fixed by means of threaded-coupling.