JPH0526075B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for screwing in a separable anti-corrosion pipe end joint using an anti-corrosion pipe end core in a joint portion of a resin-lined steel pipe for water supply, for example, and a jig used in the method. (Conventional technology) Resin-lined steel pipes for water supply (hereinafter simply referred to as "steel pipes")
In order to prevent the iron part from being exposed at the pipe end, a corrosion-proof pipe end core is used in the joint part of the pipe. By the way, the pipe end anti-corrosion joint has
There are two types: a separate type, in which the fitting and tube end core are separated, and a built-in type, in which the tube end core is integrated into the fitting. Hereinafter, a conventional example of a separate type anti-corrosion pipe end joint to which the present invention is directed will be described. Figure 6 shows a socket type separable anti-corrosion core joint. In the figure, 1 is a joint body, and by this and pipe end cores 3, 3 fitted to the pipe ends of steel pipes 2, 2 connected by this joint body 1,
Constructs a pipe end anti-corrosion joint. Inside the joint body 1, female iron threads 4, 4 are formed from both ends, and a female resin thread 5 is formed in the center. The tube end core 3 also includes a collar portion 7 having a male thread 6 that is screwed into the female iron thread 4 and female resin thread 5 of the joint body 1, and a body portion 8 that is inserted into the steel pipe 2. The external thread 6 and the tapered external thread 9 formed on the steel pipe 2 are screwed into the joint body 1 with the collar 7 in contact with the pipe end of the steel pipe 2. Figure 6 shows one side screwed in.
The other side shows a state in the middle of being screwed in, and in the screwed state, only the resin female thread 5 of the joint body 1 and the tube end core 3 are exposed inside the joint, and the iron female thread 4 of the joint body 1 is exposed inside. The tapered external thread 9 of the steel pipe 2 and the end face of the steel pipe 2 are completely covered. Therefore, the iron parts are prevented from coming into contact with water, making it possible to prevent corrosion and prevent the generation of red water. (Problems to be Solved by the Invention) By the way, in the conventional configuration as described above, since the joint body 1 and the tube end core 3 are separated, variations in the thread diameter dimension and tightening problems occur during screw connection. Due to variations in torque, the fitting between the joint body 1 and the steel pipe 2 may be too deep or too shallow. If the former is too deep, as shown in Fig. 7 A and B, collisions between the tube end cores 3 and 3 and collision deformation of the incomplete resin threaded portion 5' will occur, especially the external thread 6 of the core 3. It can also cause destruction of. The tube end core 3 is originally supposed to be fixed by fitting the male thread 6 with the resin female thread 5 of the joint 1. Therefore, if the tube end core 3 is subjected to the compressive force of ice during freezing and thawing, for example, the tube end There is a problem that the core 3 falls off and moves, which adversely affects water flow. In addition, if the tube end core 3 deforms or moves, it also means that a gap is created and the iron part is exposed, which means that it no longer functions as a corrosion-proof joint to prevent red water. There's a problem. On the other hand, if the latter is too shallow, a part of the female iron thread 4 of the joint body 1 may be exposed even though the tube end core 3 is fitted to the tube end of the steel tube 2, as shown in FIG. Because it comes into contact with water, it can lead to red water phenomenon. In other words, even though the pipe end core 3 and the joint body 1 constitute a corrosion-proof joint, the pipe end core 3 was too shallow to reach the resin female thread 5, so it came into contact with water and caused the red water phenomenon. There was also a problem in that it could not function as an anti-corrosion joint. By the way, as mentioned above, the reason why the fitting of the steel pipe 2 to the joint body 1 is too deep or too shallow occurs is that there are variations in the diameter dimension etc. and variations in the tightening torque as described above. Therefore,
The problem of occurrence of these variations will be explained below. First, variations in thread diameter dimensions, etc. will be explained. Here, the dimensions of the iron female thread 4 of the joint main body 1 are m as shown in FIG. 6, and the resin female thread 5 of the joint main body 1 is m.
Let L be the total length of the screw including the length (from the end face to the center for socket type). Regarding the above dimension m,
In JIS B2301 (threaded malleable cast iron pipe fittings), dimensions are determined for each nominal diameter of the fitting.
Since this JIS specifies only the minimum value and does not specify the maximum value, there is considerable variation in this dimension m in actual joints (described later). Also,
The dimension L is affected by the fact that the fixing position of the injection molding insert jig changes slightly due to variations in the standoff (thread diameter tolerance) of the iron female screw 4, especially when processing the resin female screw 5. This causes variation. Furthermore, this dimension L varies depending on the type of product, such as socket type and elbow type. Table 1 below shows the maximum value (m nax ) for the dimension m and the maximum value (m _nax ) for the dimension L for each type of various joints with the same nominal diameter of 20A. This is a pick-up of the minimum value (L _nio ). In other words, the selection was made based on the tendency for problems (fitting too deep or too shallow) to occur more easily, but even though the fittings have the same nominal diameter, depending on the product, the size m
It can be seen that there are variations in and L.

【table】

[Table] Next, the variation in the tightening torque, which is one of the causes of the variation in the fitting depth between the joint body 1 and the steel pipe 2, will be explained. Even if the above-mentioned thread dimensions m and L are reliably machined correctly, a stable connection cannot be obtained unless the tightening work (ie, constant tightening torque, etc.) is performed correctly. Although improvements have recently been made to tightening tools, torque wrenches, etc., there is no reliable adjustment method, and the current situation is that they rely on the intuition and experience of the operator. In addition, incorrect management methods have become commonplace in some places, and are still insufficient. Furthermore, since the resistance during tightening varies greatly depending on the type and condition of the thread sealant, this is a factor that hinders the standardization of tightening operations. As a result, if the torque is insufficient, for example, immediately after tightening, the sealant is temporarily filled between the threads and no leakage will occur, but the sealant may harden and its volume shrinks, or external forces may be applied to the pipe after joining. Leakage occurs when In addition, in the case of excessive torque, the taper screw has a cut-out part of the thread machining, so it rides on this, and the tangent line of the taper screw becomes discontinuous, resulting in a gap between the male and female threads, and leakage occurs from this gap. will happen. Furthermore, in the case of excessive torque, even if incomplete threads such as raised parts are not engaged, excessive torque will partially expand the joint end, causing plastic deformation and cracking, leading to leakage. Sometimes. This often occurs due to a synergistic effect between the joint and the variation in thread diameter of the steel pipe. The present invention has been made in view of the above-mentioned conventional problems, and in order to fully demonstrate the performance of a separate type pipe end anti-corrosion joint, it is possible to prevent the collision of the pipe end core within the joint. , provides a method for completely covering the iron female threads of a joint body, and a jig for use in the method. (Means for Solving the Problems) In order to solve the above problems, the screwing method of the separable type pipe end anti-corrosion joint of the first invention includes a method for screwing in a corrosion-proof pipe end core to the pipe end threaded portion of the lining steel pipe. A screwing method for a separable pipe end anti-corrosion joint that is fitted using a pipe. When the total length of the female thread including the thread is L, and the threaded portion dimension of the tube end core is c, the threaded length l of the fitting into the female threaded portion of the tube end satisfies both l≧m-c and l≦L-c. By setting the relationship in advance according to the pipe diameter so that the relationship satisfies the formula, and measuring the dimension D between the marking line and the screwed joint end face at a position a certain distance H from the pipe end face, H- D=
This is determined as l. In addition, the jig of the second invention forms a base with a joist having a scribing portion spaced apart by a dimension H in order to insert a scribing line at a position of a certain dimension H from the pipe end surface, and also forms a base with a scribing portion having a distance of a dimension H from the pipe end surface. In order to measure that the difference (H-l=D) from the threaded length l to the pipe end thread is within a certain tolerance range, an index recess is placed at a certain distance d from the edge of the handle. It was formed. (Function) In the present invention, by setting the threaded length of the joint and the steel pipe to be in the range of dimensions (m-c) to (L-c), the pipe The male threaded part of the end core will always be in a position where it will fit into the female resin threaded part, and collisions will occur between the tube end cores and the male threaded part of the tube end core will collide with the incomplete resin female threaded part. Therefore, the iron female threaded portion of the joint body is completely covered. (Example) Examples of the method of the present invention will be described in detail below based on the drawings. In the drawings of the embodiments of the present invention, the same reference numerals as in the above-mentioned conventional example indicate the same functional parts (or parts, etc.). FIG. 1 shows a state in which steel pipes 2, 2 are screwed into a joint body 1 with tube end cores 3, 3 fitted. In the same figure, the dimension of the female iron thread 4 of the joint body 1 is m, and the dimension of the total thread length (1/2 of the total length of the joint body in the case of a socket type) from the center of the female iron screw 4 and the female resin thread 5 is L. , the dimension of the threaded portion 6 of the tube end core 3 is c, and the dimension of the tapered male thread 9 formed at the end of the steel pipe 2 screwed into the joint body 1 is l, first, the collision between the tube end cores 3 occurs. In order to prevent this from occurring, the formula L≧l+c... must hold true, and in order to completely cover the female iron thread 4 of the joint body 1, the formula m≦l+c... has to hold true. be. From the above formula, m-c≦l≦L-c... The formula holds true, and the screw length l should be within the range of (m-c) to (L-c). In the method of the present invention, the screwing length l is confirmed by a marking line 10 marked at a distance H from the end of the steel pipe 2. That is, if the above-mentioned dimension H is marked as a constant dimension, the difference D from the above-mentioned screw-in length l can be measured as the dimension between the marking line 10 and the end face of the joint body 1, and l=H-D... ... It can be obtained as a formula. A jig 11 shown in FIG. 2 is used to mark the marking line 10 at a position of the dimension H from the end surface of the steel pipe 2 and to measure the dimension D. In the jig 11 shown in FIG. 2, 12 is a handle part, and a jig 14 having a scribing part 13 at the tip.
and a corresponding base portion 15 with a constant dimension H, and dimensions d ₁ to 15 within a certain tolerance range (details will be described later) from the handle end surface A and tip surface B, respectively.
Index recesses 16 _-6 to 16 _-6 are formed in the _d6 portion. Here, each of the index recesses 16 _-1 to 16 _-6 indicates a certain tolerance range, and for example, whether the above-mentioned dimension D is within the tolerance range of d ₁ to _{d 6} corresponding to six types of nominal diameters. It measures whether or not it is true. That is, as shown in FIG. 3, a colored marking 17 is first applied to the vicinity of the dimension H from the pipe end of the steel pipe 2 using an oil-based pen or the like, and the base part 1 of the jig 11 is
5 on the tube end surface, and mark the colored marking 1 above.
A scribing line 10 is marked on part 7 using the scribing part 13. Then, when connecting the joint 1 to the steel pipe 2, as shown in FIG. _-4 above marking line 10
Dimension D is a fixed allowable dimension depending on whether it is included or not.
It is determined whether _the screw-in length l is within a predetermined tolerance range or not. Next, the index recesses 16 _-1 to 1 in the tool 11
An example of setting the dimensions d ₁ to _{d 6} up to the formation position of _6-6 will be explained. Here, the tube end core 3 is as follows:
An example using the configuration shown in FIG. 5, which was previously proposed by the inventors of the present application, will be described. That is,
This tube end core 3 has an introduction part 7' having a smaller diameter than the thread 6 part formed on the front surface of a collar part 7 having a male thread 6, and the thread part dimension excluding this part is _c1 , and the including dimension is Let c be ₂ . And nominal diameter 20A
In _{case of}
c ₂ and the formula is c ₁ . This is because if the fit is deep and the tube end cores collide with each other or run over an incompletely threaded part, the introduction part 7' will be involved, but if the fit is shallow and the iron threaded part of the joint body is exposed, This is because this introductory part 7' must be excluded from consideration. When these c ₁ and c ₂ are applied to the equation, m−c ₁ ≦l≦L−c ₂ ……′. Therefore, based on the data in Table 1 above, when using the tube end core 3 shown in Fig. 5, in order to prevent collisions and completely cover the female iron thread, m For L, take the largest value m _nax = 15.8 mm (different diameter elbow 20/15) in Table 1, and for L, take the smallest value L _nio = 18.0 mm.
mm (different diameter socket 32/20) is required. Therefore, from the formula '15.8-3.63≦l≦18.0-4.30 12.17≦l≦13.7, and if the threaded length l is in the range of 12.17mm to 13.7mm, any type of joint with a nominal diameter of 20A will work. It will be possible to achieve the intended purpose. Here, if the above dimension H is 50 mm, the positional dimension d ₂ of the index recess 16 _-2 for the nominal diameter 20 A in the above jig is d ₂ if the screw length l is within the allowable range of 12 to 14 mm. It can be set as =50-(12~14) _d2 =36~38mm. By similar means, nominal diameters 15A, 25A, 32A, 40A, 50
Similarly for A, l and d ₁ to _{d 6} can be obtained. The results are shown in Table 2 below.

[Table] (Effects of the Invention) As explained above, the present invention has the dimensions of the iron female thread of the joint body in m, the total length of the thread including the resin female thread at the back thereof, and the dimension of the threaded part of the tube end core in c. If the threaded length of the joint and the steel pipe is l, then l≧m−
Since both the formulas c and l≦L-c are satisfied, the tube end cores do not collide with each other or ride on incompletely threaded parts, and the iron female threads are not exposed, allowing for proper operation. It is possible to obtain a fitted state. Furthermore, the threaded length can be easily obtained by simply measuring the dimension between the joint end face and a scribing line marked at a certain dimensional position from the end face of the steel pipe. In addition, using a special jig,
It is possible to mark a fixed dimension position from the pipe end surface, measure the threaded state, and measure its tolerance range, and the measurement and inspection can be performed extremely easily, quickly, and reliably, making it a very effective invention. be.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the method of the present invention, Fig. 2 is a front view of a jig used in the method, Figs. 3 and 4 are a perspective view and a sectional view of the jig in use, FIG. 5 is a sectional view showing a specific example of a tube end core, and FIGS. 6 to 8 are sectional views for explaining conventional examples. 1 is the joint body, 2 is the lining steel pipe, 3 is the pipe end core, 4 is the iron female thread, 5 is the resin female thread, 6 is the threaded part of the pipe end core, 9 is the tapered male thread of the steel pipe, 10 is the marking line , 11 is a jig, 12 is a handle, 13 is a marking part, 14 is a jig, 15 is a base, 16 _-1 ~ 1
6 _-6 is the index recess.

Claims (1)

[Claims] 1. A screwing method for a separate type anticorrosive pipe end joint that is fitted to a threaded end of a lined steel pipe using a pipe end core for anticorrosion, wherein the joint is fitted within a certain dimension m from the end face. If the total length of the female thread including both female threads is L, and the dimension of the threaded portion of the tube end core is c,
The threaded length l of the fitting to the female threaded part of the pipe end is
The relationship is set in advance according to the pipe diameter so that the relationship satisfies both the formulas l≧m-c and l≦L-c. A method for screwing a pipe end anticorrosive joint, characterized in that H-D=l is determined by measuring the dimension D with respect to the end surface. 2. Form a base with a fitting having a scribed portion with an interval of dimension H to insert a scribing line at a position of a certain dimension H from the pipe end surface, and also determine the above dimension H and the threaded length of the fitting to the threaded part of the pipe end. A tube end characterized in that an index concave portion is formed at a position of the constant dimension d from the edge of the handle portion in order to measure whether the difference between H and l (H-l=D) has fallen within an allowable range of a constant dimension. A jig used for screwing in anti-corrosion joints.