JP4128855B2 - Polyethylene resin short pipe with flange - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flanged polyethylene resin short pipe used when a polyethylene resin pipe is flange-joined.
[0002]
[Prior art]
Polyethylene resin pipes are often used in water pipes or gas pipes, particularly in residential land pipes. This is because even when crustal deformation such as an earthquake occurs, it is difficult to break due to the stretchability and toughness of the polyethylene resin pipe, and it has been proved that secondary disasters can be prevented.
On the other hand, synthetic resin pipes such as cast iron pipes, steel pipes, and hard vinyl chloride pipes are used as water pipes or gas pipes buried under public roads having a relatively large diameter.
Therefore, when polyethylene resin pipes are used as residential water pipes or gas pipes, it is necessary to join different types of pipes such as cast iron pipes and hard polyvinyl chloride pipes.
[0003]
In such a case, conventionally, a polyethylene resin short pipe with a flange is joined to the end of the polyethylene resin pipe, and the flange is joined to a flange provided on a different pipe side using this flange. Yes. An example is shown in FIG. In the example shown in FIG. 4, a polyethylene resin short pipe c with a flange c1 is attached to the end of a polyethylene resin pipe a by an electric fusion joint (socket) b, while a flange d1 and a flange provided on the cast iron pipe d side. An example is shown in which a plate packing e is sandwiched between c1 and a metal flange c2 on the back side of the flange d1 and the flange c1 are fastened by tightening bolts and nuts.
[0004]
[Problems to be solved by the invention]
In joining by the conventional flange fastening, due to vibration, thermal expansion, and thermal contraction of the pipe line, tightening with bolts and nuts may be loosened, and water or gas may leak even with very slight looseness. In particular, when the pressure of the fluid is high and the pipe line is bent, the fastening between the flanges is easy to loosen, and coupled with the high pressure of the fluid, there is a drawback that the fluid is likely to leak.
[0005]
In view of this, the present inventor has considered that a seal ring mounting groove is provided on a flange end face that is commonly used as a sealing means in flange joining, and an O-ring is mounted in this groove.
However, when internal water pressure was applied for a long time, cracks occurred at the inner peripheral corner of the bottom of the seal ring mounting groove, and the flange was loosened, resulting in a defect leading to leakage.
When the flange is loosened due to vibration or thermal expansion, the O-ring mounted in the groove is pushed outward by the internal water pressure. Then, the O-ring was cut in the circumferential direction at the outer peripheral corner of the flange end face of the seal ring mounting groove, and a defect was found that the sealing function was lost and leakage occurred.
[0006]
[Means for Solving the Problems]
The present invention provides a flanged polyethylene resin short pipe that eliminates a fluid leak-prone defect in flange fastening between a polyethylene resin pipe and a dissimilar pipe and that does not leak even if the flange fastening is loosened somewhat. Objective.
[0007]
The flanged polyethylene resin short pipe according to claim 1 is a flanged polyethylene resin short pipe integrally provided with a flange at an end, and a seal ring mounting groove is provided on the flange end surface, and the flange is attached to the seal ring. Thickness of groove bottom t1 ≧ resin short pipe outer diameter D / 11, dimensional difference between flange outer periphery and seal ring mounting groove outer periphery t2 ≧ flange outer diameter D1 / 11, and flange end surface outer peripheral corner of seal ring mounting groove Chamfering is performed on the inner peripheral corner of the bottom of the seal ring mounting groove.
A flanged polyethylene resin short tube according to claim 2 is the flanged polyethylene resin short tube according to claim 1, characterized in that the chamfer is an arc surface having a radius of 0.1 to 2 mm.
[0008]
In the present invention, the thickness t1 of the bottom surface of the seal ring mounting groove of the flange ≧ resin short pipe outer diameter D / 11, and the dimensional difference t2 between the outer periphery of the flange and the outer periphery of the seal ring mounting groove ≧ flange outer diameter D1 / 11. .
This is called the SDR (Standard Dimension Ratio), the relationship between the outer diameter D of the polyethylene pipe and the wall thickness t. The wall thickness of the polyethylene pipe for water distribution is a safety factor against the 50-year creep strength at the maximum operating pressure. It is designed by Naday's formula to be 2, and SDR = D / t = 11 is proposed by the water distribution polyethylene pipe association, and based on this, the basic dimensions of the water distribution polyethylene pipe are standardized. .
In applying the Naday equation, the maximum operating pressure is calculated by assuming that the maximum operating water pressure is 0.75 hydrostatic pressure + water hammer pressure 0.25 = 1.0 MPa, and the 50-year creep strength is 100 MPa.
[0009]
In the present invention, the flange dimension when the seal ring mounting groove is provided is determined based on this SDR = D / t = 11, so that it can withstand 50-year creep of the flange with a safety factor of 2. is there.
[0010]
Further, in the present invention, chamfering is performed on the outer peripheral corner portion of the flange end surface of the seal ring mounting groove and the inner peripheral corner portion of the bottom portion of the seal ring mounting groove.
This chamfer may be an arc surface or a flat corner surface, but is preferably an arc surface having a radius of 0.1 to 2 mm. This is because cracks can be prevented from occurring at the inner peripheral corner of the bottom of the seal ring mounting groove, and cutting of the seal ring can be prevented.
If the chamfering amount is smaller than 0.1 mm, the effect of the chamfering surface is not exhibited, cracks are generated, and the seal ring is cut. If the chamfering amount is larger than 2 mm, the seal ring is increased when the fluid pressure in the pipe is increased. Is pushed into the chamfered portion, and if the fluid pressure changes strongly, the sealing performance deteriorates and leakage occurs, which is not preferable.
[0011]
In the flanged polyethylene resin short pipe of this invention, the seal ring mounting groove is provided on the flange end face. The thickness t1 of the flange bottom surface of the seal ring mounting groove is equal to or greater than the outer diameter of the resin short pipe D / 11. The difference in dimension between the outer periphery of the seal ring mounting groove t2 ≧ flange outer diameter D1 / 11 maintains the strength of the flange, and the outer peripheral corner of the flange end face of the seal ring mounting groove and the inner periphery of the bottom of the seal ring mounting groove. By chamfering the corner portion, it is possible to prevent the occurrence of cracks and the cutting of the seal ring, and to allow the polyethylene resin tube and the dissimilar tube to be joined without leakage.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described based on examples with reference to the drawings.
FIG. 1 is a front view partially showing a sectional view of an embodiment of a flanged polyethylene resin short pipe according to the present invention. FIG. 2 is an enlarged cross sectional view showing a part of a flanged polyethylene resin short pipe. 3 is an enlarged cross-sectional view of the seal ring mounting groove of the flange.
In the figure, 1 is a polyethylene resin short tube with a flange. The short pipe 1 includes a polyethylene resin short pipe 11 and a flange 12 integrally provided at one end thereof, and a seal ring mounting groove 13 is provided on an end surface of the flange 12. 14 is mounted. Reference numeral 15 denotes a fastening flange, which is a metal flange for fastening the flange 12 to a flange of a different kind of pipe, and is fitted to the resin short pipe 11 so as to be freely movable.
[0013]
The dimensions of the flange 12 and the shape of the seal ring mounting groove 13 provided in the flange 12 will be described in detail with reference to FIGS.
The thickness t1 of the bottom surface of the seal ring mounting groove 13 of the flange 12 is equal to or greater than the outer diameter D11 of the short resin pipe, and the dimensional difference t2 between the outer periphery of the flange 12 and the outer periphery of the seal ring mounting groove 13 is equal to or greater than the outer diameter D1 of flange 12. ing.
Further, the seal ring mounting groove 13 of the flange 12 is a groove having an annular cross-sectional rectangular shape, but the flange 12 end surface outer peripheral corner portion 13a of the seal ring mounting groove 13 and the bottom inner peripheral corner portion 13b of the seal ring mounting groove 13 are formed. Is provided with a chamfered surface formed of an arc surface.
[0014]
A seal ring 14 is mounted in the seal ring mounting groove 13.
The seal ring 14 may be made of the same material as an O-ring used in ordinary water pipes and gas pipes. For example, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), butadiene rubber (BR), chloroprene. Rubber (CR), ethylene propylene rubber (EPM, EPDM), etc., and the hardness is 50 to 90 in terms of spring hardness defined by JIS K6301.
The cross-sectional shape of the seal ring 14 is a circle, an ellipse, a rectangle with a circular outer peripheral surface, a ring having a protrusion in the annular circumferential direction of the outer peripheral surface, and the height thereof is the depth of the mounting groove 13. It is about 1.5 to 2 times. If it is smaller than 1.5 times, the compression rate of the seal ring 14 is small and the sealing performance is poor. On the other hand, if it is more than twice, the compression ratio becomes too large, permanent deformation occurs in the seal ring, and the sealing performance is inferior.
[0015]
The flanged polyethylene resin short pipe 1 is joined to the end of the polyethylene resin pipe 2 by an electrofusion joint (socket) 3, and a cast iron pipe is formed by the flange 12 formed at the end of the polyethylene resin pipe 2. Or a different kind of pipe 4 such as a hard vinyl chloride resin pipe.
The different types of pipes 4 are provided with flanges 41, the end surfaces of the flanges 12 are butted against the flanges 41, and the fastening flanges 15 and the flanges 41 are fastened with bolts and nuts at a plurality of locations in the circumferential direction of the flanges. The In order to connect the flange 41 and the flange 12 concentrically, it is preferable to provide an uneven fitting surface on the flange surface to be abutted.
[0016]
[Examples and Comparative Examples]
The present invention will be described in more detail with reference to examples and comparative examples.
(Example 1)
A flanged polyethylene resin short tube 1 made of high-density polyethylene having a nominal diameter of 75 mm was prepared by injection molding. The dimensions of the flanged polyethylene resin short pipe 1 are as follows: short pipe outer diameter D = 90.3 mm, short pipe wall thickness t = 8.8 mm, flange 12 seal ring mounting groove 13 bottom face thickness t 1 = 12 mm, flange 12 The dimension difference t2 between the outer periphery and the outer periphery of the seal ring mounting groove 13 is 18 mm, the flange 12 outer diameter D1 is 126 mm, the seal ring mounting groove 13 is 10 mm wide, and the depth is 5 mm. A chamfered surface formed of an arc surface having a radius of 0.5 mm is provided on the outer peripheral corner portion 13 a and the bottom inner peripheral corner portion 13 b of the seal ring mounting groove 13. The seal ring 14 mounted in the seal ring mounting groove 13 is a styrene butadiene rubber having a hardness of 55, and has a rectangular cross section with a width of 8 mm and an outer peripheral surface of a cylindrical surface with a radius of 4 mm and a height of 8 mm. I used something.
[0017]
And this polyethylene resin short pipe 1 with a flange is connected to the end part of the polyethylene pipe 2 by an electric fusion joint (socket) 3 as shown in FIG. 1, and the cast iron pipe 4, the flange 41 and the fastening flange 15 are connected to the bolt. A pipe line fastened with a nut was made and a water pressure resistance test was conducted.
As the water pressure resistance test, a water pressure resistance test to test the water leakage pressure when fully tightened with bolts, an underwater pressure resistance test to test the water leakage water pressure when the bolt tightening torque is 25%, and a water pressure of 2.5 MPa are applied. In this state, a bending water pressure resistance test was conducted to test whether the water stop performance can be maintained up to the number of bendings.
[0018]
As a result of the water pressure resistance test, in the water pressure resistance test and the undertight water pressure resistance test, the internal water pressure was applied up to 5 MPa, but no water leakage was observed. Further, in the bending water pressure test, bending was performed up to 30 degrees, but no water leakage was observed.
In this way, in the flanged polyethylene resin short pipe of the present invention, there is no water leakage even when the water pressure is high, the bolt fastening is weak, or the bending load is applied. In addition, it was found that it can be used without any problem in use as a gas pipe.
[0019]
(Comparative Example 1)
In the polyethylene resin short tube 1 with flange of Example 1, the flange 12 is not provided with the seal ring mounting groove 13, the outer diameter of the flange 12 is 126 mm, the seal packing has an outer diameter of 130 mm, an inner diameter of 78 mm, a thickness A pipe line was made in the same manner as in Example 1 except that a 3 mm flat plate was used, and a water pressure resistance test was performed.
As a result of the water pressure resistance test, water leakage was found at 3 MPa in the water pressure resistance test and 1 MPa in the undertightened water pressure test. In the bending water pressure resistance test, water leakage was observed when bent to 12 degrees.
[0020]
【The invention's effect】
In the flanged polyethylene resin short pipe of this invention, the seal ring mounting groove is provided on the flange end face. The thickness t1 of the flange bottom surface of the seal ring mounting groove is equal to or greater than the outer diameter of the resin short pipe D / 11. The difference in dimension between the outer periphery of the seal ring mounting groove t2 ≧ flange outer diameter D1 / 11 maintains the strength of the flange, and the outer peripheral corner of the flange end face of the seal ring mounting groove and the inner periphery of the bottom of the seal ring mounting groove. By chamfering the corner portion, it is possible to prevent the occurrence of cracks and the cutting of the seal ring, and to allow the polyethylene resin tube and the dissimilar tube to be joined without leakage.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a front view showing in partial cross section an embodiment of a flanged polyethylene resin short pipe of the present invention in use.
FIG. 2 is an enlarged sectional view showing a part of a flanged polyethylene resin short tube according to the present invention.
3 is an enlarged cross-sectional view of a seal ring mounting groove in FIG. 2. FIG.
FIG. 4 is a front view showing a partial cross section of an example of use of a conventional flanged polyethylene resin short pipe.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Polyethylene resin short pipe with flange 11 Polyethylene resin short pipe 12 Flange 13 Seal ring installation groove 13a Flange 12 end surface outer peripheral corner 13b of seal ring installation groove 13 Bottom inner peripheral corner 14 of seal ring installation groove 13 Seal ring 15 Fastening flange t1 Thickness of bottom surface of seal ring mounting groove 13 t2 Dimensional difference between outer periphery of flange 12 and outer periphery of seal ring mounting groove D Outer diameter of polyethylene resin short pipe D1 Outer diameter of flange 12

Claims (2)

A flanged polyethylene resin short pipe with a flange integrally provided at the end,
A seal ring mounting groove is provided on the flange end face,
The thickness t1 of the bottom surface of the seal ring mounting groove of the flange ≧ resin short pipe outer diameter D / 11, the dimensional difference t2 between the outer periphery of the flange and the outer periphery of the seal ring mounting groove ≧ the outer diameter of the flange D1 / 11.
A flanged polyethylene resin short pipe, wherein the flange end face outer peripheral corner of the seal ring mounting groove and the bottom inner peripheral corner of the seal ring mounting groove are chamfered.   2. The flanged polyethylene resin short tube according to claim 1, wherein the chamfer is an arc surface having a radius of 0.1 to 2 mm.

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