JPH0355717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pipe joint device, and more particularly to a pipe joint device applied to a gas piping system mainly made of steel pipes.

[Prior Art] A conventional pipe fitting device includes a metal fitting body having a packing storage section inside, an annular fitting housed in the fitting storage section, and an annular fitting equipped on the outer surface of the fitting in the axial direction. and a retainer of
A metal cylindrical tube having an inclined surface whose diameter gradually decreases in the axial direction on the inner circumferential surface which presses the packing via the retainer by screwing into the circumferential surface on the opening side of the joint body. A plurality of balls are provided around the piping, interposed between a push ring, the inclined surface of the push ring, and the pipe inserted from the opening of the joint body, and bit into the pipe by pressure from the inclined surface of the push ring. A structure is known that includes a tube withdrawal prevention body embedded and held by an annular retaining band.

[Problems to be Solved by the Invention] In the case of this conventional pipe joint device, if it is heated by an external fire, there is a risk that the annular gasket stored in the gasket storage section of the joint body will be burned out.
If this annular packing is burned down to some extent, there is a risk that a large amount of gas inside the pipe will leak to the outside.

The present invention has been made in view of the above circumstances, and its purpose is to significantly suppress gas leakage in the event of a fire without changing the arrangement of each component of the conventional pipe joint device. There is a particular thing.

[Means for Solving the Problems] In order to achieve the above object, the pipe joint device of the present invention has the structure of the conventional pipe joint device, in which the retaining band of the pipe pull-out prevention body thermally expands in the event of a fire. The retaining band of the tube pull-out prevention body is made of rubber mixed with a predetermined amount of thermally expanding graphite so that the space between the slope of the push ring and the piping is filled and the amount of gas leaking inside the piping is less than 1 per minute. It is.

[Example] Hereinafter, an example of the pipe joint device of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 11 denotes a joint body made of a metal material and having a gasket storage section inside, 13 an annular gasket made of a rubber material such as NBR stored in the gasket storage section of the joint body 11, and 14 a gasket 11 made of a rubber material. This is an annular retainer installed on the outer surface in the axial direction, and is formed by covering the entire surface of a core ring 14a made of a metal material with an electrically insulating resin layer 14b. Further, 12 is screwed onto the circumferential surface of the opening side of the joint body 11 so as to connect the retainer 14.
It is a cylindrical press ring made of a metal material that presses the packing 13 through the press ring, and an inclined surface 12a whose diameter gradually decreases in the axial direction outward is formed on the inner circumferential surface. Also, 1
Reference numeral 5 denotes a tube pull-out prevention body interposed between the inclined surface 12a of the push ring 12 and the pipe 16 inserted from the opening of the joint body 11, and the pipe 16 is pulled out by the pressure of the inclined surface 12a of the push ring 12. A plurality of balls 15a are embedded and held at equal intervals by an annular holding band 15b provided around the piping 16.
For example, it is made of electrically insulating and mechanically strong material such as ceramic or resin.
In such a configuration, the current flowing between the pipes 16 and 16 made of metal pipes such as steel pipes is set to 1 mA or less by the insulating retainer 14, the balls 15a, and the holding band 15b.
In addition, in the case of this embodiment device, the joint body 11
The inner surface of one or both of the push rings 12 may be coated entirely or partially with a coating layer 11a, 12b of an electrically insulating material to further improve electrical insulation performance. On the other hand, in order to prevent the packing 13 from being burned out and leaking fluids such as gas in the event of a fire, in other words, to obtain fire resistance, the holding band 15b is made of thermally expanding graphite (hereinafter referred to as thermally expandable graphite). It is composed of chloroprene rubber mixed with a predetermined amount of .).

By the way, the reason why the current flowing between the pipes 16 and 16 is suppressed to 1 mA or less by the above-mentioned electrically insulating inclusion is as follows.

In other words, as an assumption for theoretical basic calculations, if the difference in polarization potential between the macro anode and macro cathode that make up the macro cell is ΔE, and the resistance value of the environment between them is R, then the flow to this macro cell is The current I can be expressed as I=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 will all depend on the resistance value near the corrosion hole. Therefore, R=ρ/20,000V...(2) However, ρ is the resistivity of the soil. Although the corrosion hole is a hemisphere, it is convex and has a radius of curvature that is opposite to the actual corrosion pattern, and was used as a rough guide.

Therefore, from equations (1) and (2) above, the current I is I=2πrΔE/ρ...(3), and if the area of the macro anode is 20,000 ^r2 , the corrosion current i is i=2ΔE/ ρr...(4).

Therefore, in equation (4) above, for example, assuming ΔE = 0.5v (potential difference when corroded) and ρ = 2000Ω-cm, and using the corrosion current i as a variable, calculate the life expectancy of the pipe 16 from the size of r (corrosion hole). If you plot the number of years, it will look like Figure 2.

In other words, as is clear from Fig. 2, if the corrosion current is 1 mA or less, the service life of the piping will be rapidly extended beyond that point, and the number of years it will take to replace the piping due to current electrolytic corrosion will increase. If we consider the cost and economy, at least the corrosion current i is 1
It is preferable to suppress the current to less than mA in order to extend the life of the piping.

In addition, when the pipe joint device in the above embodiment is applied to overhead piping, in the event of a fire, the holding band 15b
A predetermined amount of thermally expandable graphite blended into is thermally expanded,
Filled between the inclined surface 12a of the push ring 12 and the pipe 16, it is possible to suppress the leakage of fluid gas inside the pipe to a very small amount, usually less than 1 per minute, and to hold the pipe in the pipe retainer inside the joint. The plurality of balls 15a cooperate with each other to connect each pipe 1 in the connected state.
6 and 16 from being pulled out.

〔Effect of the invention〕

As described above, according to the present invention, the retaining band of the pipe withdrawal prevention body expands thermally in the event of a fire, filling the space between the inclined surface of the pushing ring and the pipe, and the amount of gas leaking inside the pipe is reduced to 1/min.
As shown below, the retaining band of the rubber tube pull-out prevention body is configured to contain a predetermined amount of thermally expanding graphite, which makes it possible to significantly suppress gas leakage in the event of a fire. The arrangement of each component of the joint device is not changed, and the familiar assembly procedure for this conventional pipe joint device can be adhered to.

In addition, by incorporating thermally expanding graphite into the retaining band of the tube pull-out preventer, it is not necessary to incorporate thermally expanding graphite (impurities) into the packing in the packing storage area of the fitting body in order to obtain fire resistance. It's done too. Therefore, it is possible to avoid affecting the long-term and short-term sealing performance (elastic performance) of the packing, which has the advantage of maintaining the same long-term and short-term reliable sealing under normal conditions. .

[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. DESCRIPTION OF SYMBOLS 11...Joint body, 11a...Coating layer on the inner surface of the joint body, 12...Press ring, 12a...
Inclined surface of 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 (1)

[Scope of Claims] 1. A metal joint body having a packing storage section inside, an annular packing housed in the packing storage section, an annular retainer installed on an axially outer surface of the packing, and the above-mentioned. A metal cylindrical push ring having an inclined surface whose diameter gradually decreases axially outward on the inner circumferential surface which presses the packing via the retainer by screwing into the circumferential surface on the opening side of the joint body. and a plurality of balls are provided around the pipe, which are interposed between the inclined surface of the push ring and the pipe inserted from the opening of the joint body, and bite into the pipe by pressure from the inclined surface of the push ring. and a pipe pull-out prevention body embedded and held by a ring-shaped retaining band, and the retaining band of the pipe pull-out prevention body expands due to heat in the event of a fire, filling the space between the slope of the pushing ring and the pipe, and causing gas leakage in the pipe. A pipe joint device characterized in that the holding band of the pipe withdrawal prevention body is made of rubber mixed with a predetermined amount of thermally expanding graphite so that the rate of withdrawal is less than 1 per minute.