JP2013148468A - Pressure measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure measuring device which can accurately measure pressure by the strain of a pipeline accompanied by a slight pressure change of fluid in the pipeline in spite of using a strain gauge.SOLUTION: In an inline type pressure measuring device 1 which measures a pressure of fluid flowing in a pipeline, a part 20 having smaller curvature than other parts is formed at least at one place in a circumferential direction of a measuring pipe 2 forming a part of the pipeline, and a strain gauge G1 is provided on a surface of the part 20 having the smaller curvature.

Description

  The present invention relates to a pressure measuring device, and more particularly to an improvement of a pressure measuring device that measures the pressure of a fluid flowing in a pipe line.

Conventionally, as a pressure measuring device for measuring the pressure of a fluid flowing in a pipe, a pressure receiving fluid is sealed behind a thin film pressure receiving portion in contact with the fluid, and a pressure gauge detects the pressure received by the pressure receiving fluid. Generally used for general purposes (see, for example, Patent Document 1).
However, since the pressure receiving fluid is used, in the unlikely event that the thin film pressure receiving portion in contact with the fluid flowing in the pipe is damaged, the pressure receiving fluid leaks into the pipe and contaminates the pipe containing the fluid. there were.

  In order to deal with such problems, the pipe itself is used as a pressure-sensitive part, a strain gauge is provided on the surface thereof, and the distortion of the pipe caused by a change in the pressure of the fluid flowing in the pipe is measured by the strain gauge. A pressure measuring device that measures the pressure of a fluid flowing in a pipeline has been proposed (see, for example, Patent Documents 2 to 3).

  By the way, this pressure measuring device measures strain of a pipeline accompanying a change in internal pressure with a strain gauge. However, when the pressure of the fluid flowing through the pipeline is low, the strain amount of the pipeline is small. However, it cannot be measured accurately with a strain gauge, and even if it is attempted to reduce the thickness of the portion of the pipe where the strain gauge is disposed in order to obtain a sufficient amount of strain, there is a limit to reducing the thickness of the pipe. There is a problem that it is difficult to perform accurate measurement.

JP-A-10-153505 Japanese Patent Laid-Open No. 10-132676 JP 2005-148002 A

  In view of the problems of the conventional pressure measuring device described above, the pressure measuring device using a strain gauge is accurate because of distortion of the pipeline accompanying a slight pressure change of the fluid in the pipeline. An object of the present invention is to provide a pressure measuring device capable of measuring a proper pressure.

  In order to achieve the above object, a pressure measuring device according to the present invention is an in-line type pressure measuring device that measures the pressure of a fluid flowing in a pipe, and is arranged in the circumferential direction of a measuring pipe that forms a part of the pipe. A portion having a smaller curvature than other portions is formed in at least one portion, and a strain gauge is disposed on the surface of the portion having the small curvature.

  In this case, the thickness of the measurement tube can be set to 100 to 500 μm.

  Moreover, a temperature compensation strain gauge can be provided in the measurement tube.

  Furthermore, an outer tube having a wall thickness greater than the wall thickness of the measuring tube is provided on the outer peripheral side of the measuring tube. be able to.

  According to the pressure measuring device of the present invention, a portion having a smaller curvature than the other portions is formed in at least one place in the circumferential direction of the measuring pipe constituting a part of the pipe, and the surface of the place having the small curvature is formed. A strain gauge is installed in the pipe to measure the strain at the location where the strain amount caused by the pressure change of the fluid in the pipeline becomes larger, so that the strain amount can be accurately measured and the fluid pressure can be measured. Can be measured.

  In addition, by setting the thickness of the measurement tube to 100 to 500 μm, it is possible to ensure sufficient strength as a conduit through which the fluid flows and to generate sufficient distortion due to a change in the pressure of the fluid.

  In addition, by installing a temperature-compensated strain gauge in the measurement tube, even if the temperature of the fluid flowing through the pipe fluctuates and the strain due to heat occurs in the measurement tube, only the strain due to heat is caused by the temperature-compensated strain gauge. , And by adjusting the amount of strain caused by heat from the amount of strain measured by the strain gauge, only the amount of strain caused by the pressure change can be accurately measured.

  In addition, an outer tube having a wall thickness larger than the wall thickness of the measuring tube having an inner peripheral surface to which the outer peripheral surfaces of both ends in the axial direction of the measuring tube are joined is provided on the outer peripheral side of the measuring tube. As a result, the measurement tube can be protected from external impact.

It is front sectional drawing which shows one Example of the pressure measuring device of this invention. The measurement tube of the same pressure measuring device is shown. (A) is a cross-sectional plan view of the measurement tube material. (B) is a measurement tube material fitted into a mold and pressed and clamped by a pressing mold. Sectional plan view in a state where a portion having a smaller curvature than other portions is formed, (c) is a side view of the same section, and (d) is an arrangement of strain gauges when strain measurement is performed by changing the internal pressure. The side view which shows an installation location, (e) is a perspective view of the state which has arrange | positioned the strain gauge and the temperature compensation strain gauge. It is a graph which shows the relationship between internal pressure and distortion. The usage example of the pressure measuring device of this invention is shown, (a) is a front view, (b) is a side view.

  Hereinafter, embodiments of a pressure measuring device of the present invention will be described with reference to the drawings.

1 to 3 show an embodiment of the pressure measuring device of the present invention.
This pressure measuring device 1 is an in-line type pressure measuring device that measures the pressure of a fluid flowing in a pipe T, and is at least one place in the circumferential direction of a measuring pipe 2 that constitutes a part of the pipe T. A portion 20 having a smaller curvature than the other portions is formed on the surface, and a strain gauge G1 is disposed on the surface of the portion 20 having the smaller curvature.

In the present embodiment, as shown in FIG. 1, the outer peripheral side of the measuring tube 2 is provided with an inner peripheral surface to which the outer peripheral surfaces of both axial ends 21 and 21 of the measuring tube 2 are joined. An outer tube 3 having a thickness t2 larger than the thickness t1 of the measuring tube 2 is provided, and both ends are joined by welding.
Thereby, the measuring pipe 2 can be protected from an impact from the outside, a load transmitted from the pipe T, and the like.

  Here, the portion 20 having a smaller curvature than the other portions formed in at least one place in the circumferential direction of the measuring tube 2 includes a curved surface having a small curvature and a flat surface, and this is not excluded. Absent.

The strain gauge G1 is a semiconductor strain gauge manufactured by using a thin film manufacturing tool such as a bulk type, vacuum deposition, plasma CVD, etc., and is disposed by being bonded and fixed (bulk method) to a portion 20 having a small curvature. ing.
Moreover, the strain gauge G1 can also be formed in the location 20 with a small curvature using film-forming techniques, such as direct sputtering.

Next, a method for manufacturing the measurement tube 2 in this embodiment will be described.
The material of the measuring tube 2 is preferably a precipitation-hardening type material that has corrosion resistance that does not corrode easily even when used in pharmaceutical bio, sanitary, and food-related applications. Uses a SUS630H1150 material and, for example, by manufacturing the cylindrical tube material 2A in a cylindrical shape (a state where the portion 20 having a small curvature is not formed) by cutting, the reduction of the material and the reversibility are obtained. Yes.
At this time, the dimensions of the measurement pipe material 2A differ depending on the pipe to be measured. In this embodiment, as shown in FIG. 2A, the inner diameter is 14 mm, the thickness is 100 to 500 μm, and the length. Only the axial ends 21 and 21 welded to the inner peripheral surface of the outer tube 3 are 80 mm, and the outer diameter is 15 mm.
As described above, by setting the thickness of the measurement tube material 2A (measurement tube 2 in which the portion 20 having a small curvature is formed) to 100 to 500 μm, sufficient strength is ensured as the conduit T through which the fluid flows, and the fluid Necessary strain can be generated by a change in pressure.

Then, the end of the measuring tube material 2A is formed with a sandwiching portion H1 whose one end is larger than the inner diameter of the measuring tube material 2A and a step with the sandwiching portion H1 and having a slightly smaller diameter than the inner diameter of the measuring tube material 2A. 2A, a measuring tube material 2A manufactured by cutting out into a mold K comprising a mounting portion D1 into which can be inserted, and a pressure receiving portion U extending from the mounting portion D1 and having a diameter smaller than the inner diameter of the measuring tube material 2A. Is inserted into the mold K, and the measurement tube material 2A attached to the mold K is attached to the mold K. The mounting portion D2 has a diameter slightly smaller than the inner diameter of the measurement tube material 2A from the other end. It is clamped and fixed by a fixture C having a clamping part H2 that is clamped and fixed with the clamping part H1.
The outer diameter of the pressure receiving portion U of the mold K is not particularly limited as long as it is smaller than the inner diameter of the measurement tube material 2A, but in this embodiment, the inner diameter of the measurement tube material 2A is 14 mm. 12 mm.

Next, a portion 20 having a smaller curvature than other portions is formed in at least one place in the circumferential direction of the measurement tube material 2A attached to the mold K.
In this embodiment, as shown in FIG. 2 (b), the measuring tube material 2A is sandwiched between the central portion of the measuring tube material 2A attached to the mold K by a pair of pressing dies P. By deforming, the portions 20 having a small curvature are formed at two locations so as to form a pair.
Although the surface of the measurement tube material 2A differs depending on the material of the measurement tube material 2A, the surface of the measurement tube material 2A is held flat as a result of being pressed, and the surface of the measurement tube material 2A has a slight curvature due to the nature of the material (spring back). In either case, the value measured by the strain gauge is displayed larger than the curvature of other portions.

The place where the small curvature portion 20 is formed is not particularly limited. In this embodiment, the central portion of the measurement tube material 2A, more specifically, the measurement tube material 2A having a length of 80 mm is used. In this case, the distance in the axial direction is about 20 mm from both ends so that the axial length is about 40 mm in the central portion.
The circumferential length of the portion 20 having a small curvature is inevitably determined by the outer diameter of the pressure receiving portion U of the mold K, the inner diameter of the measuring tube material 2A, and the thickness of the measuring tube material 2A. As in this embodiment, when the outer diameter of the pressure receiving portion U is 12 mm, the inner diameter of the measurement tube material 2A is 14 mm, and the thickness is 100 to 500 μm, the thickness is about 7.2 mm.
The pressing mold P only needs to have a pressing surface that can form the axial and circumferential lengths of the portion 20 having the small curvature described above, and in this embodiment, the end of the contact surface. R-chamfered axial length is 40 mm, a width for forming a circumferential length (a width of 7.2 mm or more) is 20 mm, and a thickness is 10 mm.

As shown in FIGS. 2 (b) to 2 (c), the measurement tube 2 manufactured in this way has a portion 20 having a smaller curvature than the other portions at two locations facing each other, as shown in FIGS. The strain gauge G1 is disposed at the formed portion 20 having a small curvature, and the temperature compensation strain gauge G2 is disposed at a location different from the location where the strain gauge G1 is disposed.
By disposing the temperature compensated strain gauge G2, even if the temperature of the fluid flowing through the pipeline fluctuates and the strain due to heat occurs in the measurement tube 2, only the strain due to heat is measured by the temperature compensated strain gauge. By adjusting the strain amount caused by heat from the strain amount measured by the gauge G1, only the strain amount caused by the pressure change can be accurately measured.
Further, the measurement pipe 2 constituting a part of the pipe T is formed by arranging the strain gauge G1 at a substantially center in the longitudinal direction of the measurement pipe 2 (range A shown in FIG. 2 (e)). In this range, the largest strain occurs, and the strain gauge can measure the strain as a large value with little influence of error.

In the present embodiment, the temperature-compensated strain gauge G2 is disposed in the vicinity of the two axial end portions 21 and 21 joined to the inner peripheral surface of the outer tube 3 as shown in FIG. It arrange | positions in the range B) shown to (e).
By disposing the temperature-compensated strain gauge G2 at a location that is away from the center and close to the inner peripheral surface of the outer tube 3, the temperature-compensated strain gauge G2 is less susceptible to strain caused by changes in internal pressure.

  Further, a semiconductor strain gauge in which a temperature correction circuit is integrated can be used as the strain gauge G1 without providing the temperature compensation strain gauge G2.

  Since the change in resistance due to the strain of the strain gauge G1 is very small, in this embodiment, a well-known Wheatstone bridge circuit is used to convert the resistance change value into a voltage for measurement. At this time, the required output voltage is proportional to the resistance change, that is, an output voltage (minute voltage) proportional to the distortion is obtained, and the distortion is measured by expanding the minute voltage with an amplifier. I am doing so.

Next, the strain caused by a change in internal pressure when the strain gauge G1 is disposed at a portion 20 having a small curvature, and other portions (in this embodiment, the measuring tube 2 having an outer diameter of 14 mm and having a curvature) Table 1 shows the result of measuring the strain generated when the filter is disposed at a location of 1 / 0.014, and FIG. 3 shows a graph of the internal pressure and strain created based on Table 1.
Here, the measurement locations of the graphs shown in Table 1 and FIG. 3 are the locations S1 to S4 shown in FIG. 2D, but actually, the strain gauge G1 is placed at the locations S1 and S3 for reasons described later. Make sure to affix.

As apparent from Table 1 and FIG. 3, when the inner diameter and thickness of the measuring tube 2 are constant, the measured strain value is proportional to the internal pressure, and the internal pressure can be obtained from the strain.
In particular, when it is disposed at a location 20 (measurement locations S1 and S3) with a small curvature, the measured distortion is about 1.4 to 1 compared with the case where it is disposed at other locations (measurement locations S2 and S4). Since it is measured as a large value of .8 times, it is less affected by errors in the measured value, and more accurate internal pressure can be measured as compared to other locations.

And the thickness t1 of the measuring tube 2 provided with the inner peripheral surface to which the outer peripheral surfaces of both axial direction end parts 21 and 21 of the measuring tube 2 are joined to the outer peripheral side of the measuring tube 2 shown in FIG. The pressure measuring device 1 provided with the outer tube 3 having a larger wall thickness t2 is connected by using a clamp (not shown) via a flange 31 formed at the end of the outer tube 3. As shown in FIG. 4, a long bolt member 5 in which both end faces 30, 30 of the outer tube 3 are sandwiched by flange plates 4, 4 via seal members (not shown) and male screw portions 50, 50 are formed at both ends, A pipe for measuring a joint 41 which is fixed by screwing a nut 51 to the male threaded portion 50 and which is formed on the flange plate 4 and disposed at the end of the flow path 40 communicating with the measuring tube 2. It connects with the joints T1 and T1 disposed at the end of the path T.
The joint 41 can be easily attached when measuring the internal pressure of a pipeline used in pharmaceutical bio-related by using a joint having a leak-proof seal (for example, a joint having a seal made by Swagelok). The pressure of the fluid flowing in the pipe line can be measured.

  As mentioned above, although the pressure measuring device of this invention was demonstrated based on the Example, this invention is not limited to the structure described in the said Example, The structure is suitably changed in the range which does not deviate from the meaning. It is something that can be done.

  Since the pressure measuring device of the present invention has a characteristic that an accurate pressure can be measured by a distortion of a pipeline caused by a slight pressure change of a fluid in the pipeline, a strain gauge is used. It can use suitably for the use of a pressure measuring device.

DESCRIPTION OF SYMBOLS 1 Pressure measuring device 2 Measurement pipe | tube 20 Small curvature part 3 Outer pipe | tube 4 Flange board G1 Strain gauge G2 Temperature compensation strain gauge T Pipe line t1 Thickness t2 Thickness

Claims (4)

  In an in-line type pressure measuring device that measures the pressure of a fluid flowing in a pipe, at least one place in the circumferential direction of a measuring pipe that forms part of the pipe is formed with a portion having a smaller curvature than other places. And a strain gauge is provided on the surface of the portion having a small curvature.   2. The pressure measuring apparatus according to claim 1, wherein the measuring tube has a thickness of 100 to 500 [mu] m.   The pressure measuring device according to claim 1, wherein a temperature-compensated strain gauge is disposed on the measuring tube.   On the outer peripheral side of the measurement tube, an outer tube having a thickness larger than the thickness of the measurement tube provided with an inner peripheral surface to which the outer peripheral surfaces of both axial ends of the measurement tube are joined is provided. The pressure measuring device according to claim 1, 2, or 3.

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