JPH07120332A - Method for determining the fastening state of pipe joints containing Teflon resin - Google Patents

Abstract

(57) [Summary] [Structure] The internal thread portion 1 has a shoulder surface 1c inside.
Pipe 2 with pipe joint 1 provided with Teflon resin 1d in the middle of a
When the Teflon resin 1d is deformed when screwed into
The resulting inflection point B of the tightening torque and the pipe end surface
Tightening torque generated by contact with the holder surface 1c
Of the inflection points A of the pipe joints between these inflection points 1
The Teflon resin 1d can be deformed normally depending on the number of turns
Tightening torque when making a pass / fail judgment
And the number of turns is sampled and stored every predetermined time
It A certain number less than the final number of turns at the end of tightening
Perform the difference calculation of the stored data within the number of turns
Calculate the change rate of tightening torque. This rate of change is
Number of turns N below the threshold_BAnd the number of turns N at the inflection point A _A
The fastening state is determined by the difference between and. [Effect] Judgment of fastening condition of pipe joint with Teflon resin
Can be judged automatically with high accuracy, and labor for judgment work can be saved.
It

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a shoulder surface inside which a sealing action is made by contact with a pipe end surface, and a Teflon resin is provided on the internal thread portion thereof, for connecting oil well pipes, for example. The present invention relates to a method for determining whether or not a screwed type pipe joint used is fastened.

[0002]

2. Description of the Related Art Pipe joints for oil well pipes used in the field of oil mining are required to have high sealing performance against high pressure in the pipes, and to have sufficient strength to withstand a large number of connections. Therefore, conventionally, a screw-in type pipe joint as shown in FIG. 5, which is configured to perform a sealing action by a metal touch and further provided with Teflon resin in the middle portion of the female screw portion, has been adopted.

That is, a pipe joint 1 containing Teflon resin
Has a female threaded portion 1a having a predetermined length from both ends on its inner circumference, and a taper-shaped sealing surface 1b having a diameter that is reduced further toward the inner side of the female thread 1a.
A shoulder surface 1c which is continuous with b and is substantially orthogonal to the axis of the pipe joint 1 is formed, and a Teflon resin 1d is provided in the middle of the female screw 1a.

On the other hand, at the pipe end portion of the pipe 2 connected by the pipe joint 1 described above, a seal end face 2a substantially orthogonal to the axial core line of the pipe 2 and a seal connected to the outer peripheral side of the seal end face 2a are provided. A tapered sealing surface 2b corresponding to the surface 1b,
A male screw portion 2c which is continuous with the sealing surface 2b and which is screwed into the female screw portion 1a is formed.

As described above, the pipe joint 1 and the pipe 2 are joined to each other by fitting the end portion of the pipe 2 inside the pipe joint 1 and then moving the pipe joint 1 around the axis as shown in FIG. Rotate the tube 2
This is done by screwing the female threaded portion 1a of the pipe joint 1 into the male threaded portion 2c.

By the way, among the screw-in type pipe joints as described above, those in which the internal thread portion is not provided with Teflon resin are described in JP-A-63-229272 and JP-A-4-83988. The tightened state can be determined by a method or the like.

[0007]

However, in the case of the screw-in type pipe joint in which the internal thread portion is provided with Teflon resin as shown in FIG. 5, the method of judging the tightened state is not established yet. .

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for determining the tightened state of a screw-in type pipe joint in which a female thread portion is provided with Teflon resin.

[0009]

In order to achieve the above-mentioned object, the method for determining the fastening state of a pipe joint containing Teflon resin according to the present invention has a shoulder surface which forms a sealing action by contact with the pipe end surface inside thereof. In addition, when the pipe joint provided with Teflon resin in the middle portion of the female screw is screwed into the pipe with a predetermined tightening torque and fastened, the inflection point B of the tightening torque caused by the deformation of the Teflon resin and the end face of the pipe are A method of determining the inflection point A of the tightening torque generated by the contact with the shoulder surface, and determining whether the Teflon resin is deformed normally or not according to the number of turns of the pipe joint between these inflection points. There
The tightening torque and the number of turns are sampled at predetermined time intervals and sequentially stored in association with each other, and stored in each of the stored data within the range of the number of turns smaller than the final number of turns at the end of the tightening by a predetermined number. Then, the difference calculation is performed to obtain the change rate of the tightening torque,
The number of turns N _{B at} which this rate of change is less than a predetermined reference value,
The fastening state is determined based on the difference between the tightening torque generated by the contact between the end surface of the pipe and the shoulder surface and the number of turns N _A at the inflection point A.

[0010]

In the present invention, the pipe joint is screwed into the pipe.
Tightening applied to pipe fittings from start to finish
Sampling the torque and the number of turns every predetermined time
Memorize and read the stored data after tightening
First, from the number of turns at the end, a predetermined number (in some cases
Within the range of less turns.
The difference between the stored data and the tightening torque.
Calculate the rate of change of Luke, and if this rate of change is less than a predetermined reference value,
Number of lower turns N_BAnd the end of the pipe and the shoulder of the pipe fitting
At the inflection point A of the tightening torque caused by contact with the surface
Number of turns N _AThe fastening state is determined by the difference between and.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an example of an apparatus for carrying out the method of the present invention, FIG. 2 is a diagram showing the number of turns and torque conditions during tightening of a pipe joint, and FIG. 3 is an end face of the pipe and a shoulder face of the pipe joint. 1 of the difference result after tightening the pipe joint for obtaining the inflection point A of the tightening torque caused by the contact with
FIG. 4 is a diagram showing an example, and FIG. 4 is a diagram showing an example of the result of the difference calculation after tightening the pipe joint for obtaining the inflection point B of the tightening torque caused by the deformation of the Teflon.

In FIG. 1, reference numeral 1 is a Teflon resin-containing pipe joint, and 2 is a pipe connected by the pipe joint 1, each of which has the structure described above. The pipe joint 1 and the pipe 2 are provided with a fixed chuck 11 and a rotary chuck 12 which are concentrically arranged side by side.
3 and is automatically fastened by the operation of the fastening machine 13.

That is, in the fastener 13, the pipe joint 1 is used as the rotary chuck 12, and the vicinity of the end of the pipe 2 is fixed as the fixed chuck 1.
1 is firmly gripped, and both are coaxially positioned, and then the drive motor 14 is driven to rotate the chuck 12
The pipe 2 while rotating the pipe joint 1 around the axis.
The male threaded portion 1a formed on the inner circumference of the pipe joint 1 is screwed into the male threaded portion 2c formed on the outer circumference of the end of the pipe 2, whereby the pipe joint 1 is fastened to the pipe 2.

At this time, the tightening torque applied to the pipe joint 1 and the cumulative number of revolutions (turns) of the pipe joint 1 from the start of fastening are determined by the torque detector 15a mounted on the fixed chuck 11 and the rotary chuck 12. The torque detected by each of the mounted turn detectors 15b and detected by the torque detector 15a is output to the fastening control unit 16 which controls the fastening operation of the fastening machine 13, and the detected torque and the turn detector 15b are also provided. The number of turns detected by is output to the fastening state determiner 17 which determines the quality of the fastening state according to the method of the present invention.

The fastening control unit 16 includes a torque detector 15
Using the torque detected by a as a feedback signal,
A drive command is output to the drive control unit 18, and the drive current to the drive motor 14 of the rotary chuck 12 is adjusted by the operation of the drive control unit 18 in accordance with this drive command.
Is given a sufficient tightening torque to resist the resistance at the time of screwing, and the fastening to the pipe 2 proceeds.

Then, the fastening control unit 16 stops the output of the drive command to the drive control unit 18 immediately before the detected torque given from the torque detector 15a reaches a preset upper limit torque, and drives according to this stop. By the operation of the control unit 18, the power supply to the drive motor 14 is cut off, and the screwing of the pipe joint 1 into the pipe 2 is completed. By the above operation, the pipe joint 1 and the pipe 2 are fastened with the final tightening torque close to the upper limit torque.

By the way, the drive command issued by the fastening control unit 16 is also output to the fastening state determiner 17, and the fastening state determiner 17 determines the quality of the fastening state according to the drive command as described below. To do.

That is, the fastening state determination unit 17 includes a sampling storage unit 17a, a difference calculation unit 17b, a first reference value setting unit 17c, an inflection point extraction unit 17d, a determination unit 17e, and a second reference value setting unit 17f. The drive signal output from the fastening control unit 16 is output to the sampling storage unit 17a and the difference calculation unit 17b, and the detection signals of the torque detector 15a and the turn detector 15b are output to the sampling storage unit 17a. There is.

The sampling storage unit 17a receives the drive signal from the fastening control unit 16 while in other words, in other words,
While the fastening operation is being performed by the fastening machine 13, the fastening torque and the number of turns respectively detected by the torque detector 15a and the turn detector 15b are sampled at predetermined time intervals and stored in association with each other. Make an action.

The sampling interval at this time can be freely changed by, for example, manually setting the sampling interval setting device 19 provided outside, and the sampling interval in the sampling storage unit 17a is the screw length. It is set as appropriate according to the fastening conditions, such as the length and the required accuracy of judgment.

As a result of the above operation, for example, when n times of sampling is performed before the completion of the fastening, the sampling storage unit 17a is marked with a circle on the graph of FIG. 2 showing the changing state of the tightening torque. The set of tightening torque and the detected value of the number of turns obtained at each sampling time point shown by n is stored.

The difference calculation unit 17b starts its operation when the drive command from the fastening control unit 16 is stopped, that is, when the fastening operation by the fastening machine 13 is finished, and first, the n sets of storages stored in the sampling storage unit 17a are stored. The data is collectively read, and a set of storage data that satisfies the condition that the difference from the number Nn of turns in the n-th set of storage data obtained immediately before the fastening is smaller than a predetermined value α is extracted. As shown in FIG. 2, for example, when the above condition is satisfied in the stored data up to the mth set, that is, when Nn−Nm <α, (n−m + 1) th set from the mth set to the nth set. The stored data is extracted, and the subsequent processing is performed only for these.

It should be noted that the predetermined value α is the inflection point B of the tightening torque caused by the deformation of the Teflon resin 1d on the graph showing the manner of change of the tightening torque expected when proper tightening is performed, 2 seal end face 2a
It is needless to say that the inflection point A of the tightening torque generated by the contact between the pipe joint 1 and the shoulder surface 1c of the pipe joint 1 is set in advance so as to be sufficiently included in the extraction range.

After extracting the processed data as described above, the difference calculator 17b calculates the difference value Xi [X] for each processed data.
i = (T _i −T _{i −1} ) / (N _i −N _{i −1} )], the change rates of the tightening torque are obtained, and these change rates are calculated by the first reference value setting unit 17c and the inflection. It is output to the point extraction unit 17d.

[0025] In the first reference value setting unit 17c, supplied from the difference calculation unit 17b (n-m) the maximum value X _max in number of difference data Xi, i.e. the rate of change of the tightening torque within a processing range mentioned above Of the inflection point A is obtained, and then a reference value X serving as an extraction reference of the inflection point A is set by multiplying this by a predetermined coefficient set in advance, and the result is given to the inflection point extraction unit 17d. The coefficient is a constant that is empirically determined based on many fastening results, and differs depending on the type, inner diameter, and fastening conditions of the pipe joint 1.

In the inflection point extraction unit 17d, the difference data within the above-described processing range output from the difference calculation unit 17b and the reference value X set by the first reference value setting unit 17c.
Is performed in the reverse order of the storage in the sampling storage unit 17a, that is, from the Xn corresponding to the final data in order, and the difference value that first falls below the reference value X is extracted, and the difference value is corresponded to this difference value. The stored data to be stored is read from the difference calculation unit 17b, and this stored data is given to the determination unit 17e as corresponding to the inflection point A.

The reference value Y is also input from the second reference value setting section 17f to the inflection point extracting section 17d, and the difference calculating section 17f.
In the same manner as above, the difference data in the processing range output from b and the reference value Y input from the second reference value setting unit 17f are compared, for example, the sampling storage unit 17a.
In the reverse order of the storage in step S1, that is, in order from Xn corresponding to the final data, the difference value below the reference value Y is extracted, the storage data corresponding to this difference value is read from the difference calculation unit 17b, and The stored data is given to the determination unit 17e as corresponding to the inflection point B. The reference value Y is a value determined by the size and length of the screw, the elastic coefficient of Teflon resin, etc. (FIG. 4).

The determination unit 17e, the difference between the number of turns N _B corresponding to the number of turns N _A and inflection point B corresponding to the inflection point A and the [N _A -N _B] is the thread size, If it is larger than a constant N _X determined by the length or the like, it is determined that good fastening is performed, and if it is smaller than the constant N _X , it is determined that fastening is defective, and this result is output to the display unit 20. Two
Display at 0. In the unlikely event that a large number of turns N _B corresponding to the inflection point B occur, the above-mentioned determination is performed for each of them.

As shown in FIG. 1, it is also possible to output the storage data of the sampling storage unit 17a to the display unit 20 and display all the storage data together with the determination result of the determination unit 17e.

[0030]

As described above, according to the method for determining the fastening state of the pipe joint containing the Teflon resin of the present invention, the fastening state of the threaded pipe joint provided with Teflon resin in the female thread portion can be automatically determined with high accuracy. It is possible to make a judgment, and the labor of the judgment work can be saved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a diagram showing a situation of the number of turns and torque during tightening of a pipe joint.

FIG. 3 is a diagram showing an example of a difference result after tightening of a pipe joint for obtaining an inflection point A of a tightening torque generated by contact between an end surface of the pipe and a shoulder surface of the pipe joint.

FIG. 4 is a diagram showing an example of a result of difference calculation after tightening a pipe joint for obtaining an inflection point B of tightening torque caused by deformation of Teflon.

FIG. 5 is a longitudinal sectional view showing a state before tightening of a pipe joint containing Teflon resin.

FIG. 6 is a longitudinal sectional view of an essential part showing a state after tightening of a pipe joint containing Teflon resin.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe joint 1a Female screw part 1c Shoulder surface 1d Teflon resin 2 Pipe 2a Seal end face 13 Fastener 15a Torque detector 15b Turn detector 17 Fastening state determiner 17a Sampling storage unit 17b Difference calculation unit 17c First reference value setting unit 17d Change Curve point extraction unit 17e Judgment unit 17f Second reference value setting unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroka Sumiya, 1850 Minato, Wakayama, Wakayama Prefecture Sumitomo Metal Industries, Ltd. Wakayama Works

Claims (1)

[Claims] 1. A pipe joint having a shoulder surface, which has a sealing action by contact with the pipe end surface, inside and a Teflon resin provided in the middle of the female thread, is screwed into the pipe with a predetermined tightening torque. And the inflection point B of the tightening torque caused by the deformation of the Teflon resin,
An inflection point A of the tightening torque generated by the contact between the end surface of the pipe and the shoulder surface is determined, and whether the Teflon resin is deformed normally or not is determined by the number of turns of the pipe joint between these inflection points. In the method, the tightening torque and the number of turns are sampled at predetermined intervals and sequentially stored in association with each other, and within a range of a number of turns smaller than the final number of turns at the end of the tightening by a predetermined number. The difference calculation is performed on each of the stored data in the table to obtain the rate of change of the tightening torque, and the number of turns N _{B at} which this rate of change is less than or equal to a predetermined reference value
When the end face and engaged determination of Teflon filled fitting, characterized by determining the engagement state by the difference between the number of turns N _A at the inflection point A of the tightening torque caused by contact with the shoulder surface of the pipe Method.