JPS61136091A - Pipe joint device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pipe joint device, and more specifically to a pipe joint with electrical insulation and fire resistance that is applied to gas piping systems mainly made of steel pipes. It is related to the device.

[Conventional technology]

In general, in gas piping systems that mainly use this type of steel pipe, in order to prevent electrical corrosion caused by stray currents and macro cells in buried piping, in other words, for cathodic protection, it is necessary to apply a corrosive current to a part of the gas piping system. It is effective to use a pipe joint device with an electrically insulating structure that can electrically interrupt the flow.

Conventional cathodic protection methods for gas piping systems and the like include the following methods. Namely.

a) A galvanic anode method in which a metal with a high ionization tendency is connected to the piping to provide corrosion protection.

b) An external power supply method that obtains anti-corrosion effect by connecting the negative pole side of the DC current obtained by rectifying the commercial power supply to the piping, and the positive pole side to the electrode for the external power supply.

C) Drainage method that eliminates stray current from train tracks etc. by electrical connection to the outside and obtains anti-corrosion effect.

etc.

[Problem that the invention seeks to solve]

However, each of these conventional methods requires the addition of various equipment configurations to the piping and pipe fittings to obtain anticorrosive effects, which makes them not only structurally complex and expensive, but also expensive. However, there are disadvantages in that construction during piping and maintenance and inspection of the anti-corrosion structure are not easy, and on the other hand, there are other problems such as requiring a separate fireproof structure for the overhead piping.

[Means for solving problems]

In view of these conventional problems, this invention has a configuration that is as simple and easy to install as possible, prevents electrical corrosion after connection, and even in the event of a fire, minimizes gas leakage. It is an object of the present invention to provide a pipe joint device that is applicable to gas piping systems and has electrical insulation and fire resistance.

That is, the present invention provides a pipe joint formed by joining a joint body and a press ring for interconnecting gas piping made of steel pipes, etc., in which there is an electrical connection between the joint body and press ring to be joined, and the piping. The pipes are connected to each other by interposing an insulating member and a fireproof member, and the corrosion current flowing between the pipes after connection is reduced to 1 mA.
The following is a pipe joint device characterized in that the amount of gas leakage in the event of a fire is suppressed to less than IJL per minute.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pipe joint device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a longitudinal sectional view of a pipe joint device according to this embodiment.

In this example device, reference numeral 11 is a joint body made of a metal material, and 12 is a push ring also made of a metal material, which is screwed onto the joint body 11, and an inclined surface 12a is formed on the inner peripheral surface of the joint part. has been done. 13 is the joint body 11
A gasket made of a rubber material such as NBR is housed in the inner circumferential surface of the joint, and 14 is a retainer interposed between the push ring 12 and the push ring 13, and a core ring 14a made of a metal material.
is formed by covering the entire surface with an electrically insulating resin layer 14b. Further, 15 is an inner peripheral inclined surface 1 of the joint portion of the press ring 12.
2a, a plurality of balls 15a are held at equiangularly spaced positions by an annular holding band 15b having fireproof and electrical insulation properties, and each ball +5a is The connected pipe, in this case, the pipe 16 made of a metal pipe such as a steel pipe, is made of an electrically insulating material 1, such as ceramic or resin, which has a mechanical strength that can bite into the inclined surface 12a to prevent the pipe from being pulled out. It is formed. Also, in such a configuration,
The current flowing between the pipes 18 and 18 is set to 1 mA or less due to the insulating retainer 14, balls 15a, and holding band 15b. In the case of this embodiment device, coating layers 11a and 12 made of an electrically insulating material are applied to the inner surface of either or both of the joint body 11 and the press ring 12 over the entire surface or a part thereof.
b may be coated to further improve the electrical insulation performance. Furthermore, in the case of overhead piping, the packing 13. One or both of the holding bands 15b may be made of, for example, chloroprene rubber containing a predetermined amount of thermally expandable graphite.

By the way, the reason why the current flowing between the pipes 18 and 18 is suppressed to 1 mA or less by the above-mentioned electrically insulating inclusions is as follows.

That is, as an assumption for theoretical basic calculations, the difference in polarization potential between the macro anode and macro cathode that constitute the macro cell is ΔE, and the resistance value of the environment between them is R.
Then, the current (2) flowing through this macro cell can be expressed as (1) = ΔE/R (1). Now, if we focus on a single corrosion hole on the pipe surface due to electrical corrosion and approximate this corrosion hole to a hemispherical shape with radius r, then the resistance of the macrocell is entirely determined by the resistance value near the corrosion hole. , R=p/20,000V (2)
However, ρ is the resistivity of the soil. Although the corrosion hole is semispherical, it is convex and has a radius of curvature opposite to the actual corrosion pattern, and was used as a rough guide.

Therefore, from equations (1) and (2) above, the current I is 1=
2πrΔE/ρ ...(3),
Further, assuming that the area of the macro anode is 2,000, the corrosion current i is as follows: i=2ΔE/ρr (4).

Therefore, in equation (4) above, for example, ΔE = 0.5v (potential difference when one meal is eaten).

If ρ=2000Ω-cm and the corrosion current i is used as a variable, the life expectancy of the pipe 16 is plotted from the size of r (corrosion hole) as shown in FIG. 2.

In other words, as is clear from this figure 2, the corrosion current is 1
If it is less than mA, the service life of the piping will be rapidly extended beyond that point, and considering the current number of years of pipe replacement due to electrolytic corrosion and economic efficiency, the corrosion current i should be at least 1 mA. It is preferable to extend the life of the piping by suppressing it to below.

Furthermore, when the pipe joint device in the above embodiment is applied to overhead piping, the seal 13. Holding band 15b
A predetermined amount of thermally expandable graphite blended into one or both of them expands thermally and fills the inside of the joint, suppressing the leakage of fluid gas inside the piping to a very small amount, usually less than 1 cubic meter per minute. At the same time, the plurality of balls 15a held by the pipe pull-out preventing body 15 inside the joint cooperate with each other to prevent the pipes 18, 18 from being pulled out in the joined state.

〔Effect of the invention〕

As described in detail above, according to the present invention, an electrically insulating member and a fireproof member are interposed between the joint body, press ring, and piping to be joined, thereby providing electrical insulation,
By providing fire resistance, it is possible to effectively suppress electrical corrosion in underground pipes, sufficiently extending the service life of the pipes, and in the case of overhead pipes, even in the event of a fire, gas leakage can be prevented. In addition, the overall structure of the pipe joint itself is simple, it is easy to construct, and it can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a schematic configuration of an embodiment of a pipe joint device according to the present invention, and FIG. 2 is a graph showing the relationship between corrosion current and life expectancy to explain the above action. 11...Joint body, lla...Coating layer on the inner surface of the joint body, 12...Press ring, 12a...
- Inclined surface on the inner surface of the press ring, 12b... Coating layer on the inner surface of the press ring, 13... Packing, 14... Retainer, 14a... Core ring of the retainer, 14b.
...Surface electrically insulating resin layer of retainer, 15...
Pipe removal prevention blocker, 15a... electrically insulating ball of ball band, 15b... holding band of ball band, 16... piping.

Claims (5)

[Claims] (1) In a pipe joint formed by joining a joint body and a push ring to connect gas pipes made of steel pipes or the like, there is a gap between the joint body and push ring to be joined, and the piping.
The pipes are connected to each other by interposing an electrically insulating member and a fire-resistant member, and after connection, the corrosion current flowing between the pipes is 1 mA or less, and the amount of gas leakage in the event of a fire is 1 liter per minute. A pipe joint device characterized by suppressing the following: (2) An electrically insulating member is coated on the entire surface or part of the inner surface of the joint body, press ring, or both, and this coated layer suppresses the corrosion current value after connection to 1 mA or less. A pipe joint device according to claim 1. (3) The fire-resistant member is a packing member containing thermally expandable graphite interposed in the joint body or the joint between the press ring and the piping, and the thermal expansion of this packing member in the event of a fire reduces the amount of gas leakage. The pipe joint device according to claim 1 or 2, characterized in that the flow rate is suppressed to 1 liter per minute or less. (4) An inclined surface is formed on the inner surface of the joint of the joint body or the push ring, and a ball member made of an electrically insulating material is interposed on this inclined surface, and the ball member biting into the inclined surface allows the piping to be connected between each other. A pipe joint device according to any one of claims 1 to 3, characterized in that the pipe joint device has a pull-out prevention effect. (5) The pipe joint device according to claims 3 and 4, characterized in that the ball member is held within a packing member containing thermally expandable graphite.