JP2020133677A - Flange structure for resin pipe - Google Patents

Abstract

To provide a flange structure for a resin pipe in which liquid leakage is unlikely to occur.SOLUTION: A flange structure for a resin pipe is configured such that two resin pipe flange joints 10, 20 facing each other are fastened with a plurality of bolts B and a plurality of nuts N screwed to the bolts. In the two opposite pipe flange joints 10, 20, in at least one of annular parts 10b, 20b on the side opposite to flange surfaces 10a, 20a, an annular washer 11 having a plurality of bolt insertion holes is concentrically provided on the pipe flange joints 10, 20, or preferably, two annular washers 11A, 11B are provided in an overlapped manner. In the latter case, the two washers are each divided into two by two surfaces that pass through a concentric axis O and intersect with each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to a flange structure for a resin pipe capable of suppressing the occurrence of liquid leakage.

Since resin piping such as polypropylene is lightweight and has excellent chemical resistance, it is often used for sending process liquids, waste liquids, and the like in various plants. In the connection between the pipe flange joints of this resin pipe, generally, after sandwiching the gasket in the gap between the flange surfaces facing each other (hereinafter, this is also referred to as the surface), a plurality of bolts of both pipe flange joints are used. Bolts are inserted into each of the insertion holes and tightened with nuts.

At that time, as described in Patent Document 1, the space between the surfaces of these pipe flange joints is measured with a caliper while considering the thickness of the gasket so that the sandwiched gasket is not tightened on one side. , These multiple bolts and nuts are tightened and fixed in a well-balanced and even manner. As a result, the gasket can be brought into close contact with the gasket from both sides with a uniform surface pressure, so that it is possible to prevent the fluid inside from leaking from between the surfaces.

Japanese Unexamined Patent Publication No. 2001-254870

In this way, when joining the pipe flange joints of resin pipes, it is necessary to tighten the gasket evenly in the circumferential direction, but this work varies greatly depending on the operator, and it is overtightened to deform the flange. It sometimes leaked. In particular, in the case of a chemical solution in which the temperature of the internal fluid repeatedly rises and falls between a normal temperature and a high temperature of about 60 ° C. The internal fluid sometimes leaked at the flange of the pipe. If this amount of liquid leakage is large, it is necessary to stop the operation of the plant and perform work such as repair, which may adversely affect productivity.

Further, in a resin piping system, a loose flange may be used for one of the pipe flange joints in a place where it is difficult to make adjustments so that the flange surfaces face each other at an appropriate distance. In this case, since the outer edges of the flange surfaces of the two pipe flange joints facing each other are separated from each other, the outer edge of the flange surface is compared with a general flange structure in which a load is applied to almost the entire surface of the flange surface. A load is easily applied to the portion, and depending on the tightening force of the bolt, the flange surface may be greatly bent and the gasket may not be compressed evenly. As a result, the gasket may be deteriorated at an early stage, misalignment of the piping may easily occur, and liquid leakage may occur at the flange joint due to these factors. The present invention has been made in view of the above-mentioned problems of the resin piping system, and an object of the present invention is to provide a flange structure for resin piping in which liquid leakage is unlikely to occur.

In order to achieve the above object, the flange structure for resin piping according to the present invention is a resin in which two resin pipe flange joints facing each other are fastened with a plurality of bolts and a plurality of nuts screwed to them. In at least one of the two opposing pipe flange joints having a flange structure for manufacturing piping, an annular seat having a plurality of bolt insertion holes is provided in the pipe flange joint on an annular portion opposite to the flange surface. It is characterized in that it is provided concentrically.

According to the present invention, even a easily deformable resin pipe flange joint can be reliably tightened without bending the flange surface. This makes it possible to suppress the occurrence of liquid leakage even in a piping system in which contraction and expansion due to heat are repeated, for example. In addition, it is possible to suppress the occurrence of liquid leakage due to individual differences in the tightening method of the operator.

It is a partial cross-sectional front view of one Embodiment of the flange structure for resin piping of this invention. It is a partial cross-sectional front view of another embodiment of the flange structure for resin piping of this invention. It is a top view of a specific example of two pairs of annular washers used in the flange structure for resin piping of the present invention. It is an exploded perspective view which shows the case where two pairs of annular washers of FIG. 3 are attached to a pipe flange joint.

Hereinafter, embodiments of a flange structure for resin piping according to the present invention will be described with reference to the drawings. The flange structure of the embodiment of the present invention comprises two opposing resin pipe flange joints connecting the resin pipes to each other, and these are provided in a plurality of bolt insertion holes provided at equal intervals in the circumferential direction. It is fastened by a plurality of bolts inserted and a plurality of nuts screwed into them. Then, in at least one of these two opposing pipe flange joints, an annular washer having a plurality of through holes for inserting bolts in an annular portion on the side opposite to the flange surface (also referred to as a flange seal surface or a gasket surface). Is provided concentrically on the pipe flange joint.

When a corrosive fluid such as sulfuric acid with a liquid temperature of about 70 ° C flows in this resin pipe, it is recommended to use heat-resistant PVC for the pipe flange joint in the part where PVC is used for the pipe material based on the construction standards. preferable. In this case, the piping may be provided with FRP lining in order to further improve reliability. Alternatively, polypropylene may be used as the material of the pipe and the pipe flange joint in order to reduce the equipment cost.

The type of the pipe flange joint targeted by the flange structure of the embodiment of the present invention is not particularly limited, and is used for, for example, a plug-in welding type flange, a socket welding type flange, a butt welding type flange, a screw type flange, a loose flange and the like. Can be done. Among these, in one of the two opposing pipe flange joints, a brim-shaped pipe joint called a stub end is provided at the end, and by hooking the flange-shaped part, the pipe moves in the axial direction and the circumferential direction of the pipe. When a flexible loose flange is adopted, the effect of the present invention can be exhibited more remarkably.

That is, in the loose flange, the flange-shaped portion of the stub end protrudes from the flange surface in the direction facing the pipe flange joint on the mating side, so that the peripheral portion provided with the bolt insertion hole is on the mating side. Cannot be brought into contact with the flange surface of the pipe flange joint. Therefore, the bolt / nut fastening portion between these two pipe flange joints is separated, and the flange surface is more easily deformed than the pipe flange joint having a structure in which both flange surfaces are brought into contact with each other over the entire surface, and the bolt / nut When tightened beyond the allowable torque, a large amount of bending occurs on the flange surface.

In a pipe flange joint, since this flange surface is a flange seal surface to which the gasket abuts, if bending occurs in this portion as described above, it becomes difficult to evenly compress the gasket over the entire surface. As a result, the gasket deteriorates at an early stage, misalignment of the piping, etc. occurs, and liquid leakage due to these causes is likely to occur. The problem of bending of the flange surface is not limited to the loose flange, but the same problem may occur if the peripheral edges of the flange are separated at the time of fastening, such as a flat seat (raised face). ..

Therefore, in the flange structure of the embodiment of the present invention, as shown in FIG. 1, in two pipe flange joints 10 and 20 facing each other, at least one of the annular portions 10b and 20b on the opposite sides of the flange surfaces 10a and 20a. An annular washer 11 having through holes for inserting a plurality of bolts B is provided on the pipe flange joints 10 and 20 on a concentric shaft. As a result, when the pipe flange joints 10 and 20 are fastened with the plurality of bolts B and the plurality of nuts N screwed thereto, it is possible to prevent the flange surfaces 10a and 20a from bending, and thus the flange joint portion. The problem of liquid leakage from the flange is less likely to occur.

In the flange structure of the embodiment of the present invention, the annular washer is divided into two pairs on the surface passing through the central axis so that the annular washer can be easily incorporated into the pipe flange joint of the existing piping system. It may be composed of pieces. In this case, it is preferable to provide two pairs of divided pieces in an overlapping manner. For example, as in another embodiment of the present invention shown in FIG. 2, two pairs of annular washers 11A and 11B are provided on one pipe flange joint in an overlapping manner, and the other pipe flange joint is also provided with an annular washer 11A. , 11B may be provided in an overlapping manner, or two pairs of annular washers 11A and 11B may be provided in an overlapping manner only on one of the pipe flange joints.

Further, when two washers 11A and 11B are superposed and provided on the pipe flange joint, it is preferable that the divided surfaces do not match when viewed from the axial direction of the pipe flange joint. That is, it is preferable that the washers 11A and 11B are set so as to be divided into two by two intersecting surfaces passing through the concentric shaft O of the pipe flange joint. In this case, the angle at which the above two surfaces intersect is not particularly limited, and is appropriately determined in consideration of the number of bolt insertion holes provided in each pipe flange joint, the nominal diameter of the pipe flange joint, and the like. Generally, it is preferable to intersect at right angles as shown in FIG.

As described above, when an annular washer composed of divided pieces is used, the reason why the annular washer composed of two pairs of divided pieces is used so as not to coincide with the divided surfaces is that the divided surfaces are flanged. This is because if they match in the circumferential direction of the surfaces, it becomes difficult to uniformly tighten the flange joints of both pipes in the circumferential direction, and liquid leakage due to one-sided tightening is likely to occur.

The pipe flange joint targeted by the flange structure of the embodiment of the present invention preferably has a nominal diameter of 25 A or more and 80 A or less. If the nominal diameter is less than 25A or more than 80A, it becomes difficult to adjust the alignment of the piping, so that there is a risk of liquid leakage. Further, as the material of the annular washer used in the flange structure of the present invention, since corrosive chemicals are often handled in the piping system, it is preferable to use a punched stainless steel plate such as SUS304 or SUS316. The thickness of the annular washer is not particularly limited, but is preferably 2 mm or more and 5 mm or less. If this thickness is less than 2 mm, it may be easily deformed and the effect of the present invention may not be exhibited satisfactorily. On the contrary, if it exceeds 5 mm, the strength becomes higher than necessary, which is uneconomical.

In the flange structure of the embodiment of the present invention, the tightening torque when tightening both pipe flange joints with bolts and nuts is preferably 10 Nm or less. If this tightening torque exceeds 10 Nm, the flange may be deformed and liquid leakage may occur even if the annular washer is provided.

As described above, by using the resin piping flange mechanism of the present invention, it is possible to tighten the flange evenly in the circumferential direction without deforming the flange surface, and thus it is a flange joint portion that repeats expansion and contraction due to heat. However, it is possible to prevent liquid leakage. In particular, when a polypropylene loose flange is used for a piping system in which the liquid passing temperature repeatedly rises and falls, misalignment of the piping and early deterioration of the gasket are likely to occur, but even in that case, the washer can be attached in a short time. After that, the liquid leakage can be stopped. Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to such Examples and the like.

<Example>
As shown in FIG. 3, in the piping system of an existing wet chemical reaction plant in which the temperature of the chemical solution flowing in the pipe periodically changes between 30 and 65 ° C., one pipe flange joint is connected to each other. Two stainless steel annular washers divided into two on the surface passing through the central axis were provided in layers to evaluate the effect. In the two pipe flange joints facing each other, a loose flange having a nominal diameter of 50 A made of polypropylene was used on the upper side and a loose flange having a nominal diameter of 50 A made of polyethylene was used on the lower side.

When attaching the washer, first remove the bolts and nuts that have already been fastened, and then, as shown in FIG. 4, the above-mentioned annular portion 10b on the side opposite to the flange surface 10a of the upper pipe flange joint 10. Two pairs of annular washers (outer diameter 155 mm, inner diameter 100 mm, thickness 3 mm, bolt diameter 19 mm) 11A and 11B divided into two are orthogonal to each other when viewed from the central axis O direction of the pipe flange joint 10. Incorporated as. The annular washer was not incorporated in the lower pipe flange joint 20. After that, the bolts and nuts were tightened while adjusting with a caliper so that the alignment between the flange surfaces of the pipe flange joints 10 and 20 was uniform in the circumferential direction of the flange.

In this way, after removing the bolts and nuts with a wrench, which is a general tool, and replacing the gasket, and attaching two annular washers on top of each other, insert the bolts and adjust the alignment between the surfaces with a caliper. However, since the work was as simple as tightening with a wrench to a predetermined torque, the work time was about 20 minutes. After that, a chemical solution (sulfuric acid at 60 ° C.) was passed through the piping system, and the presence or absence of liquid leakage from the joint portion of the pipe flange joint was confirmed. As a result, no liquid leakage was observed. By superimposing and attaching two annular washers divided into two in this way, it was possible to stop liquid leakage only by adjusting the alignment.

<Comparison example>
A chemical solution is passed through the piping system of an existing wet chemical reaction plant in which there are 60 joints of pipe flange joints similar to those in the above embodiment except that the two-divided annular washer of the above embodiment is not used. As a result, the chemical liquid leaked from 20 of the 60 flange joints due to periodic thermal expansion and contraction.

B Bolt N Nut 10, 20 Pipe Flange Joint 10a, 20a Gasket Surface 10b, 20b Ring Part 11, 11A, 11B Washer

Claims (5)

A flange structure for resin piping in which two resin pipe flange joints facing each other are fastened with a plurality of bolts and a plurality of nuts screwed onto them, and at least one of the two facing pipe flange joints. The resin-made flange structure for piping, wherein an annular seat having a plurality of bolt insertion holes is provided concentrically in the pipe flange joint in an annular portion on the opposite side of the flange surface. Two of the annular washers are superposed on the pipe flange joint, and these two washers are each divided into two by two intersecting surfaces passing through the concentric axes. The resin piping flange structure according to claim 1. The resin piping flange structure according to claim 2, wherein the intersections are orthogonal to each other. The resin piping flange structure according to any one of claims 1 to 3, wherein the resin is polypropylene. The resin piping flange structure according to any one of claims 1 to 4, wherein one of the two opposing pipe flange joints is a loose flange.

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