A fuel piping includes an outer pipe that has a connecting head extending outward in a radial direction in at least one end portion thereof and an inner pipe that is built in a part of the outer pipe and is connected to both end portions of the connecting head in an axial direction.

A fluid connector assembly comprising a reversible connector body having female and male end portions. The male end portion having an outer diameter smaller than the outer diameter of the female end portion. The female end portion including an internal bore extending through the female end portion from an annular opening to an inner seat. The male end portion including an internal bore extending from an abutment face at a head end of the male end portion to an opening at the female end portion inner seat. A first tube having a concave flared end installed on the inner seat of the reversible connector body engages a spherical/convex flared end of a second tube installed on the abutting face of another reversible connector body when the male end portion of the another reversible connector body is installed in the female end portion of the reversible connector body.

A dual containment fitting may include a primary tubing, a secondary tubing, and a dual containment body. The secondary tubing may surround and be concentric with a first portion of the primary tubing forming a first leak containment space between the primary tubing and the secondary tubing. The dual containment body may include a flare fitting portion and a primary containment nut portion. The flare fitting portion may surround and be concentric with the primary tubing forming a second leak containment space between the primary tubing and the flare fitting portion. The primary containment nut portion may surround and be concentric with the flared end of the primary tubing forming a third leak containment space between the primary tubing and the primary containment nut portion. The primary containment nut portion may include at least one leak passage hole connecting the third leak containment space with the second leak containment space.

A leak-proof tube fitting assembly structure includes a liquid tube, a liquid tube fitting, and a nut for locking and connecting the liquid tube and the liquid tube fitting. The liquid tube fitting has a first connecting end, a first threaded connecting portion and a second connecting end that are axially arranged in sequence in a forward direction. The first threaded connecting portion has a first external thread. Thereby, the sealing performance of the connection of the liquid tube and the liquid tube fitting is improved to prevent leakage.

A leak-proof tube fitting assembly structure includes a liquid tube, a liquid tube fitting, and a nut for locking and connecting the liquid tube and the liquid tube fitting. The liquid tube fitting has a first connecting end, a first threaded connecting portion and a second connecting end that are axially arranged in sequence in a forward direction. The first threaded connecting portion has a first external thread. Thereby, the sealing performance of the connection of the liquid tube and the liquid tube fitting is improved to prevent leakage.

An inner ring of a pipe joint includes a first tapered surface formed at one axial end portion of an inner circumferential surface such that a diameter thereof gradually increases from another axial side toward one axial end thereof in a state before a bulge portion is press-fitted into an end portion of a tube. A diameter increase starting point of the first tapered surface is located in a range from a deformation starting point, which serves as a starting point from which an inner circumferential surface is deformed due to the bulge portion receiving external force from the tube when the bulge portion is press-fitted into the end portion of the tube, to a position, on the inner circumferential surface, corresponding to one axial end of an outer circumferential surface of a body portion.

A pipe joint is connected with a connecting pipe, and includes a pipe joint body and a nut member. When the connecting pipe formed with a bead expanded in the radial direction is connected with this pipe joint, a male thread of the pipe joint body is engaged with a female thread of the nut member to hold the bead between a tapered face and a tapered face. In addition, the joined portion between the bead and the tapered face forms a first sealed portion, and a joined portion between the bead and the tapered face forms a second sealed portion. Still further, a tapered face of the pipe joint body is joined with the tapered face of the nut member to form a third sealed portion.

A screw connection device for connecting two pipes with flared ends, comprises a screw, a nut and a spacer. The nut has a front end aperture from which an accommodating space extends to a rear end aperture in a rear end wall. A surface of the nut in the accommodating space has a threaded section which extends toward the rear end wall which has a flange face in the accommodating space. In a pre-installed state, the spacer and a first pipe end with a first flare are accommodated in the nut, such that the spacer is held undetachable between the first flare and the internal thread. A second pipe end with a second flare can be held in the accommodating space by the screw, threaded into the nut such that the second flare is pressed against a sealing surface of the spacer and the spacer is pressed with a further sealing surface against the first flare.

A pipe joint contains a body having a fluid passage in the interior thereof, a tightening cap screw-engaged with an end of the body for connecting a tube thereto, and an indicator ring interposed between a stopper of the body and an end of the tightening cap. The indicator ring is equipped with a flat section and an inclined section, which is inclined with respect to the flat section, and is formed with a smaller diameter than an outer circumferential surface of the tightening cap. When the tightening cap is screw-rotated to thereby connect the tube, as a result of the inclined section being pressed and deformed by movement of the tightening cap, the inclined section projects radially outward with respect to the outer circumferential surface of the tightening cap, whereby a tightened condition is visually confirmed by the outer edge of the indicator ring.

A tube connector comprising a male portion having a male portion thread on an outer surface, a first tube having a first tube surface disposed at a seat angle (θ) of approximately 37° to a tube connector centerline, the male portion having a clearance engagement with the first tube, a nut having a clearance engagement with a second tube, the nut engagable with the male portion thread, the second tube having a second tube surface disposed at a seat angle (θ′) in the range of (θ′)=(θ+x)°, were x=+0° up to 1°, and the first tube surface compressed by the nut and the male portion against the second tube surface for a sealing engagement between the first tube surface and the second tube surface.