JPS645656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pipe joint for supplying high-frequency current to a pipe installed in a concealed area such as the ground so that the pipe can be detected from the outside.

When using conventional electrically insulating pipe fittings that cut off direct current corrosive current to prevent corrosion of metal pipes buried underground,
The high-frequency power supplied to underground metal pipes to detect the location of underground metal pipes from the ground is also cut off, making it impossible to detect metal pipes buried underground over long distances on the surface. become.

An object of the present invention is to provide a pipe joint for concealed pipe detection that can block corrosive current and pass high-frequency current for detection.

FIG. 1 is a sectional view of an embodiment of the present invention. Metal pipes 1 and 2 are buried in the ground 27, and these metal pipes 1 and 2 are fitted with a pipe joint 3 according to the present invention.
connected by. Direct current corrosion current flowing through the metal pipes 1 and 2 is blocked by the pipe joint 3. Further, a high frequency current supplied to the metal pipe 1 from the high frequency power supply 4 flows to the pipe joint 3. By this the ground 27
Above, the electromagnetic waves emitted from the metal tubes 1, 2 can be detected by the receiver 5. Therefore, it becomes possible to detect the buried locations of the metal pipes 1 and 2 from the ground.

FIG. 2 is a sectional view of the pipe joint 3. A socket 6 is formed at the end of the metal tube 1. This socket 6 has a conical surface 7 that narrows inward, a large-diameter cylindrical surface 8 connected to the conical surface 7, and a step surface 9. Step surface 9
is connected to a small diameter cylindrical surface 10 that transports fluid.
An outward flange 11 is formed at the end of the socket 6 . A plurality of insertion holes 12 are formed in this flange 11 at intervals in the circumferential direction. The insertion port 13 of the other metal tube 2 is inserted into the socket 6. An annular groove 14 is formed at the tip of the insertion port 13 . A metal annular lock ring 15 is fitted into this groove 14. The outer peripheral surface of this lock ring 15 faces the conical surface 7. Conical surface 7 and socket 13
A hard protection ring 16 is also interposed inward in the tube axis direction (towards the right in FIG. 2) between the tube and the outer peripheral surface of the tube. A soft annular sealing member 17 is interposed close to the protection ring 16 on the outside of the tube axis (to the left in FIG. 2) of the protection ring 16 . Seal member 1
7 is made of natural rubber or synthetic rubber, and is electrically insulating. Convex portion 1 of press ring 18 surrounding insertion port 13
9 comes into contact with the outer end surface of the seal member 17 in the tube axis direction. An insertion hole 20 is formed in the press ring 18 in correspondence with the insertion hole 12 . The insertion holes 12 and 20 include
Bolt 21 is inserted. By tightening the nut 22 screwed into the bolt 21, the push ring 18
The convex portion 19 pushes the sealing member 17 into the tube shaft of the socket 6.

The entire outer peripheral surfaces of the metal tube 1, socket 6, metal tube 2, insertion port 13, lock ring 15, and press ring 18 are coated with an electrically insulating coating with high peel strength, for example, a tar epoxy layer is applied to a thickness of 100μ. has been done.

FIG. 3 is a perspective view of the protection ring 16. This protective ring 16 prevents the sealing member 17 from coming into direct contact with the locking ring 15 and causing damage such as cracks, and also prevents the fluid introduced into the metal tubes 1 and 2 from coming into contact with the sealing member 17 and shortening its life. prevent that. The protective ring 16 is made of a mixture of an organic polymer material with excellent solvent resistance against the fluids transported in the metal tubes 1 and 2, such as neoprene rubber, NBR, butadiene rubber, and carbon or metal powder. . The protective ring thus preferably has a hardness of 65 to 75 Hs. A large number of sharp tapered protrusions are formed on the outer circumferential surface 16a and the inner circumferential surface 16b of the protective ring 16. Therefore, when the sealing member 17 is pushed inward in the tube axis direction by the push ring 18 and the protective ring 16 is pushed inward in the tube axis direction, the protrusion formed on the outer circumferential surface 16a of the protective ring 16 is pushed into the conical surface 7. The coating layer 23 is broken, thereby establishing electrical continuity between the protective ring 16 and the socket 6, and therefore with the metal tube 1. Further, the protrusion formed on the inner circumferential surface 16b of the protective ring 16 breaks the coating layer 24 of the socket 13, whereby the protective ring 16 becomes electrically conductive with the socket 13 and therefore the metal tube 2. become.

In this way, the protective ring 16 is placed between the metal tubes 1 and 2.
From the viewpoint of corrosion protection, it is desirable that a corrosion current of, for example, only 1 mA at most flow through the plate. In addition, the high frequency current for detecting the metal pipes 1 and 2 from the ground is, for example, 10 mA or more (preferably 10 mA or more).
300mA) is desired. The volume resistivity of the protective ring 16, which is capable of passing such a small direct current and a relatively large high frequency current, is according to the voltage-current method of the Japan Rubber Association standard SRIS-2301.
Desirably 20-3000Ω gold cm. When the volume resistivity becomes smaller than 20Ωcm, the protective ring 16
The strength of the seal member 17 becomes too small, and the protection of the seal member 17 becomes incomplete. In addition, if it is 3000 Ωcm or more, the resistance value when high frequency current is passed between the metal tubes 1 and 2 becomes too high, and the metal tubes 1 and 2 on the ground
becomes difficult to detect. Protective ring 16 like this
When installed between socket 6 and socket 13,
According to experiments conducted by the inventor of the present invention, the resistance value between the metal pipes 1 and 2 surrounding a single pipe joint was 1Ω to 150Ω.

According to the inventor's experiments, the outer diameter of the metal pipes 1 and 2 is 150 mmφ, and pipe joints are provided at one location every 2.5 m, and the resistance value between the metal pipes 1 and 2 per single pipe joint is When is 1Ω, the metal tube could be detected on the ground 27 over a distance of 500 m along the tube axis. Furthermore, when the resistance value was 150Ω, the detection distance was 14m, which was confirmed to be a value that can be used in practice.

Note that even if the volume resistivity of the protective ring 16 is relatively large within the above-mentioned range, the compression of the press ring 18 during installation of the joint increases the number of chains of metal powder and carbon particles, which causes The joint resistance between the metal pipes 1 and 2 per pipe joint is reduced.

As another embodiment of the present invention, the conical surface 7 of the socket 6
Instead, a right cylindrical inner peripheral surface parallel to the outer peripheral surface of the socket 13 may be formed. Lock ring 15 may be omitted. Although the protective ring 16 was annular in the embodiment described above, it may be divided in the circumferential direction as another embodiment of the present invention.

As described above, according to the present invention, the resistance of the protective ring made of a conductive organic polymer material prevents the corrosion current flowing through the socket and the socket, and also prevents electromagnetic waves having a strength that can be detected from the outside. Since the value is chosen to lead to a high frequency current of the magnitude that is received,
Corrosion of metal pipes is prevented, and metal pipes can be detected on the ground. In particular, in the present invention, the volume resistivity of the protective ring is selected to be 20 Ωcm or more and 3000 Ωcm or less, which allows sufficient strength to be obtained and also allows detection by passing a high frequency current.

Moreover, in the present invention, a large number of sharp protrusions are formed on the outer circumferential surface and the inner circumferential surface of the protective ring, and these protrusions break the electrically insulating coating layer of the receptacle and insertion port, and electrically connect with each metal tube. Since conduction is established between the two, high-frequency current can be reliably guided.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an entire embodiment of the present invention;
FIG. 2 is an enlarged sectional view of the pipe joint 3 according to the present invention, and FIG. 3 is a perspective view of the protective ring 16. 1, 2...metal pipe, 3...pipe joint, 6...socket, 13...insert, 15...lock ring, 16
...Protection ring, 17...Seal member, 18...
Push ring.

Claims (1)

[Claims] 1. Between the socket of a metal pipe on which an electrically insulating coating layer is formed and the outer peripheral surface of the socket of another metal pipe on which an electrically insulating coating layer is formed, which is inserted into the socket. A hard protective ring is interposed therebetween, and an annular sealing member made of a soft electrically insulating material is interposed adjacent to the protective ring on the outer side of the tube axis of the receptacle than the protective ring, and an annular sealing member surrounding the receptacle is interposed. In the device in which the sealing member is pushed into the tube shaft of the socket and fixed using a push ring, the protective ring is a mixture of an organic polymer material and conductive powder, and the volume resistivity of the protective ring is as follows: 20Ωcm or more, 3000
The protective ring has a large number of sharp protrusions formed on the outer and inner circumferential surfaces of the protective ring, and the protrusions break through the coating layer of the socket and insertion port to electrically connect to each metal pipe. A concealment tube characterized by conduction, thereby blocking direct current corrosive current flowing between the socket and the socket, and guiding a high-frequency current large enough to receive electromagnetic waves having a strength detectable from the outside. Detection pipe fitting.