JPH06235485A - Tube joint for stainless steel tube - Google Patents

Abstract

PURPOSE:To prevent generation of red water due to rust and leakage due to gap corrosion by installing a rubber packing on a water contact part of a tapered outer surface on the small diametrical part of a pressure welding part and an inner surface of an expanded part and by doubly sealing by way of pressure contacting the tapered outer surface on the large diametrical part rather than an installation part with the inner surface of the expanded part. CONSTITUTION:An end part of a tube fitting main body 10 having a male screw 11 for screwing a box nut 20 on an outer surface end part is formed on a convergent tapered outer surface 12, and between the end part and a tip part 14 a circular groove 13 and a circular cut-off part 15 of a smaller diameter than an extension of the tapered outer surface 12 are formed. Thereafter, a rubber packing 30 is installed from the circular groove 13 to the circular cut-off part 15, and the rubber packing 130 is made to reach the head end part 14. Additionally, a part to engage with the circular grove 13 is made circular arc. Thereafter, by interposing a stainless tube 40 between the outer surface of the rubber packing 30 and the inner surface of the box nut 20, pressure welding the inner surface of the stainless tube 20 on the rubber packing 30 by fastening of the box nut 20 and directly making it contact with the tapered outer surface 12, it is doubly sealed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flare connection type pipe joint, and more particularly to a pipe joint suitable for connecting stainless pipes.

[0002]

2. Description of the Related Art Conventionally, Japanese Utility Model Laid-Open No. 52-86718 discloses a flare type pipe joint shown in FIG. In this case, the tip portion 1a of the pipe 1 is fitted into the cap nut 2, and the tip portion 1a of the pipe is expanded in a taper shape along the inner bottom surface of the cap nut to make the cap nut 2 rotatable. A joint body 4 having a taper tip and an O-ring packing 5 mounted on the taper surface is screwed into and connected to the cap nut 2. The O-ring packing 5 mounted on the taper surface of the joint body 4 ensures the airtightness with the expanded surface of the pipe.

[0003]

In the above-mentioned prior art, the expanded surface of the pipe 1 is pressed against the packing 5 to maintain airtightness, but the taper surface of the joint body 4 has the packing 5 interposed therebetween. In particular, the taper surface 6 on the large diameter side of the packing 5 and the taper on the small diameter side
The connection may be completed in a state where one of the contact surfaces 7 is not pressed. In particular, since the expansion of the pipe 1 is performed at the construction site, the portion 8 at the beginning of the expansion of the pipe tends to have a gentle shape, and the expanded end portion 1a of the pipe is located near the tightening screw of the main body 4 and the cap nut 2. Therefore, the pipe 1 has a taper surface 6 on the large diameter side.
And the tightening of the cap nut 2 is completed, and the screw tightening of the cap nut is easily completed in the state where a gap is created between the expanded inner surface of the pipe and the taper surface 7 on the small diameter side of the packing 5. .

When the pipe 1 is a stainless steel pipe, after the pipes are connected, a small gap between the expanded inner surface of the pipe and the taper surface 7 on the smaller diameter side of the packing 5 of the joint body 4 is provided inside the pipe 1. Water penetrates and causes a skimmer corrosion peculiar to stainless steel at the contact portion between the pipe 1 and the joint body 4. Therefore, rust may be generated over a long period of time, which may cause red water and water leakage due to gap corrosion. The present invention solves the above-mentioned problems and provides a flare connection type pipe joint for a stainless steel pipe which does not cause skimmer corrosion peculiar to stainless steel at a connection portion and has excellent sealing performance for a long period of time.

[0005]

DISCLOSURE OF THE INVENTION The gist of the present invention is a pipe joint for a stainless steel pipe having a flared expansion portion at an end thereof, the joint main body having a tapered outer surface at the end, -In a flare type pipe joint consisting of a cap nut having a par-shaped inner peripheral surface, wherein the taper outer surface and the expanded portion inner surface are pressure-contacted to each other by screwing and tightening the joint body and the cap nut,
A rubber packing to be mounted and compressed is provided on at least a portion of the outer surface of the taper on the small diameter side of the pressure contact portion and an inner surface of the expanded portion which is in contact with water in the stainless pipe, and the rubber packing on the larger diameter side of the mounting portion of the rubber packing A pipe joint for a stainless steel pipe, wherein an outer surface of a taper is brought into pressure contact with an inner surface of a widened portion for double sealing. In the above, in the rubber packing, the shape of the packing mounting portion or the rubber packing can be set so that the crushing margin of the rubber packing to be compressed differs depending on the packing portion. Further, in the above, an annular groove and an annular notch that separates from the expanded inner surface of the stainless steel pipe are provided on the end side of the taper outer surface of the joint body that is screwed into the cap nut, up to the tip of the joint body. A rubber packing extending to the outer surface of the distal end portion of the joint body can be mounted and connected to the annular groove and the annular notch.

[0006]

Since the present invention has the above-mentioned structure, when the joint body and the cap nut are screwed together, the expanded inner surface of the stainless steel tube first comes into contact with the rubber packing to compress the rubber packing between the joint body and the rubber packing. Next, the expanded inner surface of the stainless steel pipe abuts and closely contacts the outer surface of the taper on the larger diameter side than the packing of the joint body, and the tightening connection of the cap nut is completed.

Therefore, the expanded inner surface of the stainless steel pipe is securely sealed by the rubber packing extending to the tip of the outer peripheral surface of the joint body on the inner peripheral side of the expanded portion, and the water in the pipe is directly connected to the joint body and the stainless steel pipe. Do not intrude into the part on the larger diameter side than the abutting rubber packing. For this reason, the skimmer corrosion peculiar to stainless steel due to the abutting of metal members does not occur, so there is no risk of leakage due to the generation of red water or corrosion of the stainless steel pipe. Also, double sealing is performed by the contact between the expanded inner surface of the pipe and the outer surface of the taper of the joint body, and the excessive compression and tightening of the rubber packing is prevented.
And long life can be secured.

Since the rubber packing is locked by providing the joint body with an annular groove, the rubber packing is prevented from coming off from the joint body. Moreover, by making the crushing allowance of the rubber packing different depending on the place where the packing is compressed, it is possible to secure the initial sealability against the uneven surface of the inner surface, such as the bead of the stainless steel pipe, at the part where the crushing allowance is large. , The durability of the packing is improved and the long-term sealing property is secured at the portion where the crushing margin is small.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are partial cross-sectional views before and after connection,
FIG. 3 is an enlarged sectional view of a main part. In the figure, 10 is a joint body made of stainless steel, and has an external thread 11 for screwing with a cap nut at the outer surface end. A taper taper on the end side
An annular groove 13 on the outer side of the taper 12 and the outer side of the taper 12 and an annular notch 15 continuing from the annular groove 13 to a tip 14 of the joint body on a smaller diameter side than an extension line 16 on the outer surface of the taper.
Is provided.

Reference numeral 30 denotes an annular cutout 1 from the annular groove 13.
As shown in the enlarged cross-sectional view of FIG. 3, the rubber packing attached to No. 5 has a cross-section that engages with the annular groove 13 of the joint body and has a cross section extending from the arc portion 31 to the tip portion 14 of the joint body. It consists of 32. When it is attached to the joint body 10, it protrudes outward from the extension line 16 of the taper outer surface 12 of the joint body. About this protruding amount is compressed by the expanded inner surface 41 of the stainless steel tube 40. The band-shaped portion 32 of the packing compressed by the annular notch portion 15 has a crushing margin of about 2
It is set to 5 to 45%, and the crushing allowance of the arcuate portion 31 of the packing compressed by the annular portion 13 is set to about 8 to 25%.

The cap nut 20 is made of a stainless steel material and has an inner diameter 21 which is slightly larger than the outer diameter of the stainless pipe 40 to be connected and a taper inner surface 22 which is substantially the same as the taper outer surface 12 of the joint body. Cap nut 20 at the end of pipe 40
After the insertion, the end portion of the stainless pipe 40 is flared with a jig at substantially the same angle as the taper inner surface 22 of the cap nut to form a flared inner surface 41. Next, when the cap nut 20 is screwed into the joint body 10, first, the expansion inner surface 41 is axially pressed by the cap nut, so that the small diameter side of the expansion inner surface abuts the rubber packing 30 as shown in FIG. 20 cap nuts
When the rubber packing 30 is tightened, the rubber packing 30 is compressed between the annular groove 13 of the joint body 10 and the notch portion 14, and the large-diameter-side expanded inner surface 41 of the pipe 40 is separated from the taper outer surface 12 of the joint body.
And the contact portion is crimped.

Clamping of the cap nut is completed by crimping the pipe 40 and the joint body 10 to each other on the metal surface. In this state, a seal with the rubber packing 30 and a metal seal by crimping the metal surfaces together. Heavy seal is fulfilled. Since the expanded inner surface 41 of the stainless steel pipe 40 compresses the rubber packing 30 to seal the space between the joint body and the inner surface 41 of the small diameter pipe, the water inside the pipe 40 is made into a metal surface. It does not penetrate into the crimped part of and does not cause skimmer corrosion peculiar to stainless steel. Also, the rubber packing 30 is used for pressure bonding between metal surfaces.
Since it is only on the large diameter side, a strong pressure bonding surface pressure can be obtained, and the sealability due to the metal seal can be maintained even in the event of a fire, for example.

FIG. 4 shows the shape of the end of the joint body and the rubber packing of another embodiment. The rubber packing 35 is the joint body 1
There is provided a portion 36 that covers the zero tip portion 14. Further, the cross section is substantially T-shaped, and the central portion is locked to the annular portion of the joint body. Also in this case, the same effect as that of the above-mentioned embodiment is obtained.

Next, the results of the corrosion test will be described below. 1. Sample joint: Conventional product of FIG. 5 and product of the present invention of FIG. 1 to FIG. 3, material of both main body nut is SUS304 pipe: SUS304, size 20su 2. Number of samples: 6 for each of the conventional product and the product of the present invention 3. Test method The pipe joint after connection with the pipe is 80 ° C test water, 200ppm
Immerse in Cl-water (pure water + NaCl) for 30 days, (15
Change to new test water on the day) In addition, measure the depth of pitting corrosion with a surface roughness meter.

[0015] 4. Test results Original product Conventional product NO pipe and joint rust NO Pipe inner surface rust and depth (μ) Joint side rust 1 No rust 7 2 places (15, 5) Tape surface 2 No rust 8 2 Location (5, 20) Tape surface and packing groove 3 No rust 9 1 location (20) Packing groove 4 No rust 10 4 locations (15, 20, 15, 15) Tape surface and packing groove 5 No rust 11 2 places (5, 6) Taper surface 6 No rust 12 2 places (5, 5) Packing groove 5. Discussion In the conventional product, the inner surface of the pipe and the end of the joint are corroded, and the degree of corrosion on the pipe side is particularly large. 1 depending on conditions
There is a risk of penetrating the pipe within a year. On the other hand, in the product of the present invention, neither the pipe nor the joint was observed at all.

[0016]

As described above, since the stainless steel pipe joint according to the present invention has no gap corrosion, there is no risk of generation of red water or leakage due to corrosion. In addition, the double inner seal is achieved by the contact between the expanded inner surface of the pipe and the outer surface of the taper of the joint body, and the excessive compression and tightening of the rubber packing is prevented. And longevity is ensured.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an embodiment before connection.

FIG. 2 is a partial cross-sectional view after connection showing an example.

FIG. 3 is an enlarged sectional view of an essential part showing an embodiment.

FIG. 4 is an enlarged sectional view of an essential part showing another embodiment.

FIG. 5 is a partial cross-sectional view showing a conventional technique before connection.

[Explanation of symbols]

 10 Joint body 12 Taper outer surface 13 Annular groove 14 Tip of joint body 15 Annular notch portion 20 Cap nut 22 Taper inner surface 30 Rubber packing 31 Arc portion 32 Strip portion 40 Stainless steel pipe 41 Expanded inner surface

Claims (2)

[Claims] 1. A pipe joint for a stainless pipe having a flared widened portion at an end thereof, the joint main body having a tapered outer surface of a taper at the end, and a cap nut having a tapered inner peripheral surface. In a flare-type pipe joint in which the outer surface of the taper and the inner surface of the expanded portion are pressure-contacted to each other by screwing and tightening the joint body and a cap nut, the outer surface of the taper portion on the small diameter side of the pressure-contacted portion is expanded. Provide a rubber packing that is attached to and compressed in at least a portion of the stainless steel pipe that contacts the inner surface of the open portion, and press-contacts the inner surface of the widened portion with the outer surface of the taper on the larger diameter side than the mounting portion of the rubber packing. A pipe joint for stainless steel pipes that features double sealing. 2. The pipe joint for a stainless steel pipe according to claim 1, wherein the rubber packing has different crushing allowances for compressing the rubber packing depending on parts of the packing.