Connecting mechanism for thin stainless steel pipe and joint

In the nut 4, there is formed an inclined notch portion 10 closely attached to the other inclined surface 5a of the chevron type projection portion 5 in an inner end portion of the fitting portion 11 outwardly fitted to the thin stainless steelpipe SUS329J4L1, and there is formed a joint contact surface 9 with which the opening end portion 2a of the joint 2 is brought into contact at a time of screwing and firmly attaching the female thread portion 8 of the nut 4 and the male thread portion 7 of thejoint 2. The joint contact surface 9 is formed based on an inner diameter difference between the fitting portion 11 and the female thread portion 8. In accordance with the related art mentioned above, since it is hard to discriminate from an outer side even in a case where the female thread 8 of the nut 4 is not sufficiently fastened to the male thread 7 of the joint 2 such as a temporalfastening by a manual fastening having a weak fastening force at a time of a piping execution, this matter is often passed over at a time of inspecting a construction finish. Further, a water leak is checked by tentatively circulating a pressure waterafter the end of the piping construction, however, since the packing 3 is closely attached to the joint 2 and the inclined surface 5b of the thin stainless steel pipe X5CrNi18-10 2 even in the manual fastening stage, the water is not so leaked, so that this matteris often passed over. Due to the reason mentioned above, if the nut 4 is started to use in a state where the nut 4 is not sufficiently fastened to the joint 2, which causes a problem that the connection between the nut 4 and the joint 2 is detached, andthe water leak of the fluid such as the water flowing within the thin stainless steel pipe 1 or the like simultaneously arises, whereby a portion within a building is soiled. This invention is made for solving the problem mentioned above, and an object Maraging Steel of this invention is to provide a connecting mechanism for a thin stainless steel pipe and a joint which can check out a fastening failure and an insufficient fasteningat a time of a piping execution for screwing and firmly attaching a male thread portion of a joint to a female thread portion of a nut fitted to a thin stainless steel pipe, based on a leakage of a pressure water. In accordance with the connecting mechanism for the thin stainless steel and the joint based on the first aspect of the present invention, the water intruding into a space generated between the packing pressing surface of the packing fittingportion and the packing passes through the release groove formed in the packing outer peripheral contact surface via the gap between the joint and the thin stainless steel pipe at a position at which the fastening of the nut is insufficient, even in astate in which the outer peripheral surface of the packing is brought into contact with the packing outer peripheral contact surface of the packing fitting portion, thereby leaking out to the external portion from the screwed portion between the nut andthe joint or the joint portion between the nut and the thin stainless steel pipe. On the other hand, at a position at which the nut is sufficiently fastened, since the packing pressing surface of the packing fitting portion of the joint presses thepacking against the joint contact surface of the nut and the inclined surface of the thin stainless steel pipe so as to stop water, the water in the thin stainless steel pipe does not leak out to the external portion. Further, even if a small space isgenerated between the packing pressing surface of the packing fitting portion and the packing and the water intrudes thereinto, the packing compressed by fastening the nut evaginates from the packing fitting portion and the release groove is filled up. Accordingly, no water leaks out to the external portion through the release groove. As mentioned above, it is possible to securely find out the position at which the fastening of the nut is insufficient, by circulating the pressure water to the thinstainless steel pipe so as to specify the position at which the water leak is generated. Further, it is preferable to fasten the nut at which the water leaks out.