JP2009150676A - Apparatus and method for measuring internal pressure in pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve measurement which is easily used for a pipe without processing of the pipe such as drilling, or welding and joining, and can measure the internal pressure in a pipe. <P>SOLUTION: A pipe internal pressure calculation means 14 determines the internal pressure in a pipe P by a formula p=(ε<SB>θ</SB>-ε<SB>z</SB>)Eä(k<SP>2</SP>-1)/(1+ν)} with ν representing Poisson's ratio based on a circumferential direction distortion ε<SB>θ</SB>of the pipe surface detected by a circumferential direction distortion detection device 15, an axis direction distortion ε<SB>z</SB>of the pipe surface detected by an axis direction distortion detection device 16, a Young's modulus E of a pipe material determined by a Young's modulus calculation means 13 and a ratio between the inside diameter and the outside diameter of the pipe k input from an input device 17. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pipe internal pressure measuring apparatus and method for measuring the pressure of liquid or gas inside a pipe.

  The pipe internal pressure measuring device that measures the pressure of liquid or gas inside the pipes of various plants is provided with a branch pipe for guiding the pressure from the pipe, and a Bourdon pressure gauge or semiconductor pressure gauge attached to the branch pipe. Yes.

As a pressure measurement device, a pipe for guiding a fluid having a pressure different from the pressure of the fluid connected to the primary pressure introduction port is connected to the secondary pressure introduction port, and a Bourdon is connected to the pressure chamber communicating with the secondary pressure introduction port. There is one in which a tube is arranged (see, for example, Patent Document 1).
JP 11-281510 A

  However, when a Bourdon tube pressure gauge or a semiconductor pressure gauge is used to measure the pressure of the liquid or gas inside the pipe, work for arranging the pressure gauge is required. For example, it is necessary to perform processing such as drilling a pipe and screwing a pressure guiding pipe into a hole or welding. Moreover, when it becomes necessary to attach a pressure gauge after installation of piping facilities in a plant, it is necessary to stop and install the piping facilities, which is costly. In addition, there is a risk of leakage and the like because the number of joints increases after the pressure gauge is installed.

  An object of the present invention is to obtain a pipe internal pressure measuring device and method which can be easily applied to pipes and can measure the pressure inside the pipes without requiring processing such as drilling or welding in the pipes.

A pipe internal pressure measuring device according to a first aspect of the present invention includes a circumferential strain detection device that detects circumferential strain on a pipe surface, an axial strain detection device that detects axial strain on a pipe surface, and a pipe temperature. , A Young's modulus calculating means for calculating the Young's modulus of the piping material based on the piping temperature detected by the temperature detector, an input device for inputting the inner diameter / outer diameter ratio of the piping, and the circumference The circumferential strain of the pipe surface detected by the directional strain detector, the axial strain of the pipe surface detected by the axial strain detector, the Young's modulus of the piping material obtained by the Young's modulus calculator, and the input device A pipe internal pressure calculating means for obtaining an internal pressure of the pipe based on an inner diameter / outer diameter ratio of the pipe. The pipe internal pressure calculating means calculates a circumferential distortion of the pipe surface as ε _θ and an axial distortion of the pipe surface. ε _z , pipe material Yan It is characterized in that the internal pressure of the pipe is obtained from the following formula, where E is the gating ratio and k is the inner diameter / outer diameter ratio of the pipe.
p = (ε _θ −ε _z ) E {(k ² −1) / (1 + ν)}
Where ν is Poisson's ratio.

  According to a second aspect of the present invention, there is provided the pipe internal pressure measuring device according to the first aspect of the invention, wherein the circumferential strain detection device and the axial strain detection device are provided with an optical fiber on the surface of the pipe to respond to the strain of the pipe. The strain sensor is a strain sensor that detects the strain in the circumferential direction or the axial direction of the pipe by measuring the elongation of the optical fiber.

The pipe internal pressure measuring method according to the invention of claim 3 detects the circumferential strain ε _{θ of} the pipe surface and the axial strain ε _z of the pipe surface, while detecting the pipe temperature to obtain the detected pipe temperature. Based on the calculated Young's modulus E of the piping material, the input pipe inner and outer diameter ratio k, the detected circumferential strain ε _θ of the piping surface and the axial strain ε _{z of} the piping surface, Based on the Young's modulus E, the internal pressure p of the pipe is obtained from the following equation.
p = (ε _θ −ε _z ) E {(k ² −1) / (1 + ν)}
Where ν is Poisson's ratio.

  According to the present invention, the circumferential strain on the pipe surface and the axial strain on the pipe surface are measured, and the pressure inside the pipe is obtained based on these strains. Therefore, it is only necessary to install a strain detection device on the outer surface of the pipe. Low cost. In addition, since drilling and welding are not required in the piping, the reliability of the piping equipment is also improved.

  Furthermore, since the internal pressure of the pipe is obtained by using the difference between the distortion in the circumferential direction of the pipe surface and the axial distortion of the pipe surface, the distortion due to the thermal expansion of the pipe material can be removed, and the measurement accuracy of the internal pressure of the pipe can be improved. improves.

  Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram showing an example of a pipe internal pressure measuring apparatus according to an embodiment of the present invention. The temperature T of the pipe is detected by the temperature detector 11 and input to the Young's modulus calculating means 13 of the arithmetic unit 12. The temperature detector 11 detects the temperature of the piping. For example, it is directly measured by a thermocouple, a resistance temperature detector, an optical fiber, or the like. Moreover, since the temperature of the internal fluid can be set to the pipe temperature in a portion where the temperature of the pipe is kept, it is also possible to use measurement data from a temperature detector that detects the temperature of the fluid. In addition, because the Young's modulus of the piping material is temperature-dependent, if the pipe temperature is high or the pipe thickness is large, the pipe is kept warm in order to eliminate the Young's modulus distribution in the pipe radial direction. It is desirable.

  The piping temperature T detected by the temperature detector 11 is input to the Young's modulus calculating means 13, and the Young's modulus calculating means 13 calculates the Young's modulus E of the piping material. Since the Young's modulus E of the piping material has temperature dependence, it is obtained from a temperature-Young's modulus curve prepared in advance.

The Young's modulus calculation means 13 may output a constant value with a constant Young's modulus when the pipe temperature is near room temperature. The Young's modulus E calculated by the Young's modulus calculating means 13 is input to the pipe internal pressure calculating means 14.

On the other hand, the circumferential strain ε _{θ of} the pipe surface detected by the circumferential strain detector 15 and the axial strain ε _z of the pipe surface detected by the axial strain detector 16 are input to the pipe internal pressure calculation means 14. The As the circumferential strain detector 15 and the axial strain detector 16, a strain gauge or a strain sensor using an optical fiber is used. Further, the pipe inner pressure calculating means 14 is inputted with the inner diameter / outer diameter ratio k of the pipe from the input device 17. The inner diameter / outer diameter ratio k of the pipe is obtained from the design data of the pipe or an actually measured value.

The pipe internal pressure calculation means 14 is a pipe material Young's modulus E calculated by the Young's modulus calculation means 13, a pipe surface circumferential strain ε _θ detected by the circumferential strain detection device 15, and an axial strain detection device 16. The internal pressure p of the pipe is calculated based on the detected axial strain ε _{z of} the pipe surface and the inner diameter / outer diameter ratio k of the pipe input from the input device 17. The internal pressure p of the pipe calculated by the pipe internal pressure calculating means 14 is stored in the storage device 18 and output to the output device 19. The output device 19 is, for example, a display device or a printing device.

Next, calculation of the pipe internal pressure p in the pipe internal pressure calculation means 14 will be described. When the inner diameter / outer diameter ratio of the pipe is k, the inner pressure of the pipe is p, the Young's modulus of the pipe material is E, the Poisson's ratio is ν, the temperature of the pipe is T, and the thermal expansion coefficient of the pipe material is α, the circumference of the pipe surface The direction strain ε _θ is expressed by the equation (1), and the axial strain ε _z on the pipe surface is expressed by the equation (2).

ε _θ = {(2-ν) / (k ² −1)} · {p / E} + Tα (1)
ε _z = {(1-2ν) / (k ² −1)} · {p / E} + Tα (2)
In order to eliminate the influence of the distortion Tα due to the thermal expansion of the piping material, the difference between the formulas (1) and (2) is obtained, and the internal pressure p of the pipe is obtained, thereby obtaining the formula (3).

_{p = (ε θ -ε z)} E {(k 2 -1) / (1 + ν)} ... (3)
Thus, in the embodiment of the present invention, by measuring the circumferential strain ε _θ on the pipe surface and the axial strain ε _z on the pipe surface, the liquid or gas inside the pipe is measured based on the equation (3). The pressure p is measured.

FIG. 2 is a perspective view of an example of a pipe that is a measurement target of the pipe internal pressure measuring apparatus according to the embodiment of the present invention. FIG. 2 shows a case where the thickness of the pipe 20 is uniform in the longitudinal direction, the inner diameter of the pipe 20 is a, the outer diameter of the pipe 20 is b, and the inner diameter / outer diameter ratio k of the pipe 20 is k = The case of b / a is shown. The circumferential strain ε _θ on the surface of the pipe 20 is detected by the circumferential strain detector 15, and the axial strain ε _z on the pipe surface is detected by the axial strain detector 16. Further, the present invention can be applied not only when the thickness of the pipe 20 is uniform in the longitudinal direction but also when the thickness of the pipe 20 changes loosely on the taper. Further, the inner diameter / outer diameter ratio k is applied when there is no change in the inner diameter of the pipe, such as pipe thinning, oxide scale, and the like, and no change in the outer diameter due to external corrosion of the pipe so that it can be treated as a constant constant.

FIG. 3 is a configuration diagram illustrating an example of an optical fiber strain detection sensor using optical fibers as the circumferential strain detection device 15 and the axial strain detection device 16. The circumferential strain detector 15 transmits the optical fiber 21A, the bent portion 22A to the optical fiber 21A located on the surface of the pipe 20, and the light generated by the circumferential extension of the bent portion 22A by transmitting light to the optical fiber 21A. a received optical transmitting section 23A, bending the scattered light received from the optical transmission section 23A, the circumferential direction strain detecting a strain epsilon _theta circumferential direction of the pipe by measuring one of such Brillouin scattered light, the Bragg reflected light It is comprised from the detection part 24A.

Similarly, the axial strain detection device 16 is generated by the optical fiber 21B, the bent portion 22B to the optical fiber 21B located on the surface of the pipe 20, and the axial extension of the bent portion 22B by transmitting light to the optical fiber 21B. The axial transmission distortion ε _z is detected by measuring any one of the optical transmitter 23B that receives the transmitted light and the bending scattered light, Brillouin scattered light, Bragg reflected light, etc. received from the optical transmitter 23B. It is comprised from the axial direction distortion detection part 24B.

  FIG. 4 is an explanatory diagram of the principle of strain detection by the optical fiber strain detection sensor. FIG. 4A shows an initial state of the bent portion 22 (optical fiber strain detection sensor portion) of the optical fiber 21 attached to the pipe 20. FIG. 4B shows a state of the optical fiber 21 of the bent portion 22 in a state where the pipe 20 is stretched.

  As shown in FIG. 4A, the optical fiber 21 is provided with a bent portion 22 for detecting elongation, and the optical fiber 21 is connected to the pipe 20 by fixing portions 25a and 25b with the bent portion 22 interposed therebetween. Fix it. Now, as shown by the dotted arrow in FIG. 4, when light of a predetermined intensity is incident on the optical fiber 21 from the A direction, the light travels in the B direction through the optical fiber 21. In this case, since leakage light is generated outside at the bent portion 22, the light intensity at the B location after passing through the bent portion 22 is smaller than the light intensity at the A location.

  On the other hand, as shown in FIG. 4B, when the elongation Δd indicated by the solid line arrow occurs in the pipe 20, the bent portion 22 extends. Since the leakage light at the bent portion 22 is reduced by the extension of the bent portion 22, the light intensity at the B point after passing through the bent portion 22 is healthy when the extension Δd does not occur (in the case of FIG. 4A). ).

  FIG. 5 is a graph showing the relationship between the strain at the bent portion 22 of the optical fiber 21 and the transmitted light intensity. The bent portion 22 of the optical fiber 21 is disposed on the outer surface of the pipe 20 so that light is incident on the optical fiber 21 and the internal pressure of the pipe 20 is changed to cause distortion on the pipe surface, whereby the transmitted light intensity of the bent portion 22 is increased. By measuring, the distortion which generate | occur | produces according to the internal pressure of the piping 20 was measured.

  As shown in FIG. 5, in the initial state in which the bent portion 22 of the optical fiber 21 is arranged in the pipe 20, the transmitted light intensity of the bent portion 22 is about 34.9 dB, and the distortion is about 16 μST by changing the internal pressure of the pipe 20. The transmitted light intensity of the bent portion 22 is about 34.95 dB, and the transmitted light intensity of the bent portion 22 is about 35.00 dB when the strain is about 30 μST. Similarly, the relationship curve S is obtained by changing the internal pressure of the pipe 20 and plotting the relationship between the strain and the transmitted light intensity.

FIG. 6 is a flowchart showing the contents of the pipe internal pressure measuring method according to the embodiment of the present invention. First, the pipe temperature T, the pipe surface circumferential strain ε _θ or the axial strain ε _z are detected (S1). Then, the Young's modulus E of the piping material is obtained based on the temperature T of the piping (S2), and the internal pressure of the piping is calculated based on the above-described equation (3) (S3). The calculated internal pressure of the pipe is stored in the storage device 18 and output to the output device 19 (S4).

According to the embodiment of the present invention, the circumferential strain ε _θ and the axial strain ε _z are measured, and the internal pressure of the pipe is obtained by the equation (3), so that the influence of the strain due to the thermal expansion of the piping material can be reduced. The internal pressure p of the removed pipe can be obtained. Further, in particular, when an optical fiber is used as the strain detection device among the strain detection devices 15 and 16, it is easy to implement without the need to supply power, and there is little noise and distortion value drift due to the influence of electromagnetic waves, and high accuracy. Measurement is possible for a long time.

The block diagram which shows an example of the piping internal pressure measuring apparatus concerning embodiment of this invention. The perspective view of an example of piping which is a measuring object of the piping internal pressure measuring device concerning an embodiment of the invention. The block diagram which shows an example of the optical fiber distortion detection sensor which used the optical fiber as the circumferential direction strain detection apparatus and axial direction strain detection apparatus in embodiment of this invention. The principle explanatory view of distortion detection in the optical fiber distortion detection sensor in an embodiment of the invention. The graph which shows the relationship between the distortion in the bending part of the optical fiber shown in FIG. 4, and transmitted light intensity. The flowchart which shows the content of the piping internal pressure measuring method concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Temperature detector, 12 ... Arithmetic unit, 13 ... Young's modulus calculation means, 14 ... Pipe internal pressure calculation means, 15 ... Circumferential strain detection device, 16 ... Axial strain detection device, 17 ... Input device, 18 ... Memory | storage device , 19 ... output device, 20 ... piping, 21 ... optical fiber, 22 ... bent part, 23 ... optical transmission / reception part, 24A ... circumferential strain detection part, 24B ... axial strain detection part, 25 ... fixing part

Claims (3)

A circumferential strain detector for detecting circumferential strain on the pipe surface, an axial strain detector for detecting axial strain on the pipe surface, a temperature detector for detecting the temperature of the pipe, and the temperature detector Young's modulus calculating means for calculating the Young's modulus of the piping material based on the detected piping temperature, an input device for inputting the inner diameter / outer diameter ratio of the piping, and the circumferential strain on the piping surface detected by the circumferential strain detecting device Based on the axial strain of the pipe surface detected by the axial strain detector, the Young's modulus of the pipe material obtained by the Young's modulus calculating means, and the inner diameter / outer diameter ratio of the pipe input from the input device A pipe internal pressure calculating means for obtaining an internal pressure, wherein the pipe internal pressure calculating means is ε _θ for the circumferential strain on the pipe surface, ε _z for the axial strain on the pipe surface, E for the Young's modulus of the pipe material, When the inner diameter / outer diameter ratio is k, A pipe internal pressure measuring device that calculates the internal pressure p of a pipe from the following formula.
p = (ε _θ −ε _z ) E {(k ² −1) / (1 + ν)}
Where ν is Poisson's ratio.   The circumferential strain detection device and the axial strain detection device attach an optical fiber to the surface of a pipe, measure the elongation of the optical fiber in accordance with the strain of the pipe, and determine the circumferential or axial strain of the pipe. The piping internal pressure measuring device according to claim 1, wherein the piping internal pressure measuring device is a strain sensor to detect. The pipe surface circumferential strain ε _θ and the pipe surface axial strain ε _z are detected. On the other hand, the pipe temperature is detected and the Young's modulus E of the piping material is calculated based on the detected pipe temperature. Based on the following equation, the internal pressure of the pipe is calculated based on the calculated pipe Young's modulus E based on the calculated pipe inner diameter / outer diameter ratio k, the detected pipe surface circumferential strain ε _θ and the pipe surface axial strain ε _z . A method for measuring the internal pressure of a pipe, wherein p is obtained.
p = (ε _θ −ε _z ) E {(k ² −1) / (1 + ν)}
Where ν is Poisson's ratio.

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