JPH10227677A - High-temperature type coriolis flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate stress generated in a high-temperature fluid that flows through an inner tube by forming a support for joining inner and outer tubes as a coaxial double tube using a thin-plate elastic material with an improved heat conductivity that can be easily and elastically deformed. SOLUTION: An outer tube 3 is supported at both edges by a support 4 with an inner tube 2 where a high-temperature fluid to be measured flows. The support 4 is made of a thin-plate elastic plate, for example, a stainless steel plate. The support body 4 seals the inner tube 2 and the outer tube 3 by welding or spot welding with U-shaped opening edges 4a and 4b. When a high-temperature fluid flows to the inner tube 2, the inner tube 2 is thermally inflated immediately. However, the support 4 causes the thermal inflation of the inner tube 2 in axial direction and eliminates the stress in axial direction of the inner tube 2 and the outer tube 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature Coriolis flowmeter, and more particularly, to a high-temperature type Coriolis flowmeter, and more particularly, to a double-tube system comprising an inner tube and outer tubes whose both ends are supported by supports on the outside of the inner tube. In Coriolis flowmeters,
The present invention relates to a high-temperature Coriolis flowmeter having a stress removing structure for removing a stress acting on a double pipe when a high-temperature fluid is caused to flow through the inner tube to measure a mass flow rate.

[0002]

2. Description of the Related Art A single tube type Coriolis flow meter is a small direct type mass flow meter having a straight-line flow tube having the simplest shape.
Further, when foreign matter adheres to the flow tube, there is an advantage that maintenance work for removing the foreign matter can be easily performed. Although the Coriolis force is extremely small compared to the excitation force, in a straight flow tube with high bending rigidity, the phase displacement acting on the flow tube due to the Coriolis force is on the order of μm even at the maximum flow rate,
Detecting this with high accuracy requires advanced technology.

The applicant of the present invention has previously proposed a double-tube Coriolis flowmeter in order to eliminate the above-mentioned drawbacks of a single-tube Coriolis flowmeter and to enable high-accuracy mass flow measurement. The double tube type Coriolis flowmeter is configured such that a single flow tube is used as an inner tube and an outer tube whose both ends are fixed to the outside of the inner tube via a support block is formed as a double tube. This is a straight pipe type Coriolis flowmeter that drives outer tubes in opposite phases.

FIG. 6 is a partial sectional view in the flow direction for explaining a conventional double tube type Coriolis flowmeter.
Is a double tube, 21 is an inner tube, 22 is an outer tube, and 23 is a support block.

The Coriolis flowmeter shown in FIG. 6 has a single inner tube 21 through which a fluid to be measured flows in the direction of arrow Q, and outer ends coaxially supported and joined at both ends to a joint 23a of a support block 23. The main body is a double tube 20 composed of a tube 22. FIG. 6 shows only one end of the double tube 20. Also, 2
A driving unit (not shown) for driving the inner tube 21 and the outer tube 22 in the + F and -F directions at opposite coupled vibration frequencies with the support block 23 as a node portion, A sensor (not shown) for detecting a phase difference signal proportional to the Coriolis force acting on the tube 21 is provided.

In the double tube type Coriolis flowmeter shown in FIG. 6, the inner tube 21 and the outer tube 22 are driven in opposite phases at the coupled vibration frequency, so that a large driving amplitude can be obtained with a small driving force. The detection sensitivity is increased, and the shortcomings of the single tube can be compensated.

[0007]

However, when the mass flow rate of the high temperature fluid is measured with a double tube type Coriolis flowmeter, the outer tube 22 maintained at room temperature and the inner tube 21 maintained at high temperature fluid temperature are obtained. Temperature difference between
The heavy pipe receives stress in the direction of arrow P due to expansion and contraction due to the temperature difference. In addition, since heat transfer from the inner tube 21 to the outer tube 22 is performed through the support block 23 having a large heat capacity, it takes a long time to reach thermal equilibrium. Therefore, the temperature of the fluid to be measured, that is, the temperature difference between the inner tube 21 and the outer tube 22 is limited as an abrupt temperature difference, and the temperature of the fluid to be measured is limited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a heat conductive member which is not a highly rigid body but is easily elastically deformed is used as a support block for joining an inner tube and an outer tube as a coaxial double tube. The stress is reduced as a good thin plate elastic material, and the heat conduction time from the inner tube to the outer tube is shortened by making it thin and having a small heat capacity, so that a stable instrumental difference characteristic can be obtained in a short time. It is another object of the present invention to provide a high-temperature Coriolis flowmeter in which an outer tube can be extended and contracted in a longitudinal direction to remove the stress.

[0009]

According to a first aspect of the present invention, there is provided a double tube comprising: an inner tube through which a fluid to be measured flows; and an outer tube coaxially supporting both ends of the inner tube via a support outside the inner tube. Having a high-temperature fluid flowing through the inner tube, driving the inner tube and the outer tube in antiphase at a coupled vibration frequency, and controlling a mass flow rate of the high-temperature fluid in proportion to the Coriolis force acting on the inner tube. In the required high-temperature Coriolis flowmeter,
The support or the outer tube of the heavy pipe has a rigidity in a direction perpendicular to the axis of the double pipe, and has a stress removing structure acting in the axial direction in the axial direction.

According to a second aspect of the present invention, in the high-temperature Coriolis flowmeter according to the first aspect, the support is formed in a U-shape in which an axial cross-sectional shape of the double pipe is opened in the axial direction, and is perpendicular to the axis. It is formed of a thin plate elastic material having good thermal conductivity and a circular cross section in the direction.

According to a third aspect of the present invention, in the high-temperature Coriolis flowmeter according to the first aspect, the support has an L-shaped cross section in the axial direction and an annular cross section in the direction perpendicular to the axis. It is made of a thin plate elastic material having good thermal conductivity.

According to a fourth aspect of the present invention, in the high-temperature Coriolis flowmeter according to the third aspect, the support and the outer tube are integrally formed of a thin elastic material having good heat conductivity at the same time. An annular enlarged portion having a diameter larger than the outer diameter of the outer tube is provided at a boundary with the outer tube.

According to a fifth aspect of the present invention, in the high temperature Coriolis flowmeter according to the first aspect, a balance weight is provided at a longitudinal center of the outer tube so as to have a natural frequency equal to the natural frequency of the inner tube. The outer tube is divided at each of at least two places sandwiching the balance weight, and an enlarged portion is formed by welding the outer tube so as to form an enlarged opening at the divided portion.

According to a sixth aspect of the present invention, in the high-temperature Coriolis flowmeter according to the fifth aspect, the enlarged portion and the outer tube are integrally molded at the same time.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partial sectional view of a high-temperature Coriolis flowmeter for describing an embodiment of the first and second aspects of the present invention. Reference numeral 3 denotes an outer tube, and reference numeral 4 denotes a support. In FIG. 1, a drive unit and a sensor, which are essential components of the Coriolis flowmeter, are omitted for simplification.

In the high-temperature Coriolis flowmeter shown in FIG. 1, one inner tube 2 through which a high-temperature fluid to be measured flows in the direction of arrow Q is used as an axis, and outer tubes 3 are provided at both ends outside the inner tube 2 (FIG. 1). (Only one end is shown) is supported by the support 4. The support 4 is made of a thin elastic plate, for example, a stainless steel plate. The support 4 supports the inner tube 2 and the outer tube 3 coaxially. Has a U-shape.

The support 4 is fixed to the inner tube 2 and the outer tube 3 by welding or spot welding at U-shaped open ends 4a and 4b. Although the U-shaped opening of the support 4 is provided on the outside, it may face inward. Further, the support 4 is not limited to an integral annular body, but may be, for example, a U-shaped plate in which the inner tube 2 and the outer tube 3 are divided into four supporting the upper, lower, left, and right sides. However, in order to accelerate heat conduction from the inner tube 2 to the outer tube 3, an annular shape is preferable.

Inner tube 2 when no fluid is flowing
The outer tube 3 supported by the annular support 4 is kept at normal temperature, but when a high-temperature fluid flows through the inner tube 2, the inner tube 2 immediately expands thermally. But,
The support 4 displaces the thermal expansion of the inner tube 2 in the axial direction and the direction perpendicular to the axis, thereby removing the axial stress between the inner tube 2 and the outer tube 3. Also, since the support 4 is thin, the heat capacity is small. In addition, the time for thermal equilibrium between the inner tube 2 and the outer tube 3 can be shortened, and the time from when the fluid flows to when stable measurement can be performed can be shortened.

FIG. 2 is a partial sectional view of a high-temperature Coriolis flow meter for explaining an embodiment of the third aspect of the present invention.
In the figure, reference numeral 5 denotes an outer tube, and 6 denotes a support. Parts having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

The double pipe 1 of the high temperature Coriolis flowmeter shown in FIG. 2 has a support 6 for supporting the outer tube 5 at both ends on the inner tube 2, a circle having a surface perpendicular to the axis of the double pipe 1. The connection between the support 6 and the inner tube 2 is made by a circular projection which is opened in a direction perpendicular to the surface of the toroid so that the inner diameter side of the support 6 overlaps the outer peripheral surface of the inner tube 2. At 6a, it is fixed by welding or the like. The connection between the support 6 and the outer tube 5 is performed by the outer peripheral surface 6b of the support 6.
And an expanded cylindrical surface 5a obtained by enlarging the end cylindrical surface of the outer tube 5 in the direction perpendicular to the axis of the double pipe 1 by welding.

The surface of the support 6 of the double tube 1 is perpendicular to the axis of the inner tube 2, has high rigidity in the direction perpendicular to the axis, and keeps exactly coaxial. Also, since it is easy to elastically deform in the axial direction,
Stress caused by a temperature difference between the inner tube 2 and the outer tube 3 can be completely removed. Further, since the heat capacity is small, thermal equilibrium can be realized in a short time.

FIG. 3 is a partial sectional view of a high-temperature Coriolis flow meter for explaining an embodiment of the invention according to claim 4;
In the figure, reference numeral 7 denotes an outer tube, and the same drawing numbers as those in FIG.

The high-temperature Coriolis flowmeter shown in FIG. 3 is one in which the outer tube 7 is integrally molded simultaneously with the support tube by drawing or the like. That is, the outer tube 7 is composed of the straight pipe portion 7a and the support portion 7b.
The plane b is perpendicular to the axis of the straight pipe portion 7a, the support 7b is an end face of the straight pipe portion 7a, and each boundary is an enlarged portion 7c. The inner periphery of the support portion 7b is a circumferential portion 7d overlapping the outer periphery of the inner tube 2, and is joined by welding or the like.

In the double pipe 1, the outer tube 7 has a straight pipe portion 7
a and the support portion 7b are formed simultaneously and integrally via the enlarged portion 7c, so that the spring action in the longitudinal direction of the straight pipe portion 7a having the enlarged portion 7c does not require welding, and the support portion 7b It is possible to obtain an inexpensive double pipe 1 which promotes the spring action and has the same action as the first and second aspects.

FIG. 4 is a partial sectional view of a high-temperature Coriolis flowmeter for explaining an embodiment of the invention according to claim 5;
In the drawing, 8 is an outer tube, 8a and 8b are partial tubes of the outer tube 8, 9a is an enlarged opening of the partial tube 8a, 9b is an enlarged opening of the partial tube 8b, 10 is a support block, and 11 is a balance weight. .

In the high-temperature Coriolis flowmeter shown in FIG. 4, the outer tube 8 is constituted by a partial tube 8a at both ends and a partial tube 8b at the center, and the joint between the partial tube 8a and the partial tube 8b is The outer peripheral surfaces of the enlarged opening 9a of the partial tube 8a and the enlarged opening 9b of the partial tube 8b, which are enlarged substantially at right angles to the axis of the double pipe 1, are joined by welding or the like. The outer tube 8 in which the partial tube 8a is joined to both sides of the partial tube 8b is supported coaxially with the inner tube 2 via the support block 10 at both ends. A balance weight 11 for equalizing the natural frequencies of the inner tube 2 and the outer tube 8 driven in opposite phases with the support block 10 as a node is fixed to the central partial tube 8b.

The double tube 1 in which the inner tube 2 and the outer tube 8 are coaxially joined by a highly rigid support block 10
Is that the stress caused by the temperature difference between the inner tube 2 and the outer tube 8 cannot be removed by the support block 10, but the enlarged portion where the enlarged opening 9a of the partial tube 8a and the enlarged opening 9b of the partial tube 8b are joined expands and contracts in the axial direction. , The stress can be removed.

FIG. 5 is a partial sectional view of a high-temperature Coriolis flowmeter for explaining an embodiment of the invention according to claim 6, wherein 12 is an outer tube, 12a and 12b are enlarged portions, and FIG. Parts having the same functions as in FIG. 4 are given the same reference numerals as in FIG.

The high-temperature Coriolis flowmeter shown in FIG. 5 is provided with enlarged portions 12a and 12b at two positions sandwiching a balance weight 11 fixed at the center of the outer tube 12 in the longitudinal direction. , 12b are formed by integrally drawing the outer tube 12 by drawing.
Both ends of 2 are supported coaxially with the inner tube via a support block 10.

In the case of FIG. 5, as in the case of the outer tube 8 shown in FIG.
Due to the axial expansion and contraction action of 2b, the stress caused by the temperature difference between the inner tube 2 and the outer tube 12 is absorbed. In addition, since the enlarged portions 12a and 12b are integrally formed by drawing, a welding process is not required, and the inexpensive double pipe 1 is formed.
Can be obtained.

[0031]

【The invention's effect】

Advantageous Effects Corresponding to Claim 1: In the double-tube high-temperature Coriolis flowmeter, the support member for supporting the outer tube and the inner tube that constitute the double tube coaxially has a stress removing structure that elastically deforms in the axial direction. Therefore, stress caused by the temperature difference between the inner tube and the outer tube due to the high temperature fluid flowing through the inner tube is effectively removed, and the inner tube and the outer tube vibrate in opposite phases to each other, but have rigidity in the vibration direction. Stable vibration can be obtained, and the applicable temperature range can be expanded.

According to a second aspect of the present invention, in the high-temperature Coriolis flowmeter according to the first aspect, the support for supporting both ends of the outer tube on the inner tube is formed in an annular body made of a thin plate elastic material and has an axial sectional shape. Since the U-shape is used, the same effects as those of the first aspect can be obtained, and the rigidity in the axial direction is small and the heat capacity is also small, so that stress can be more effectively removed.

According to the third aspect of the present invention, in the high-temperature Coriolis flowmeter according to the first aspect, the support has a simple shape of an annular shape made of a thin plate elastic body and an L-shaped cross-section in the axial direction. The same effect as the second aspect is obtained.

According to a fourth aspect of the present invention, in the high-temperature Coriolis flowmeter according to the first aspect, the outer tube and the support portion of the double tube are integrally formed of the same thin elastic material to support the outer tube. Since the boundary portion with the body portion is an annular enlarged portion, the same effect as in claim 2 can be obtained, and a welding step between the outer tube and the support portion is not required, so that a less expensive double pipe can be provided. can do.

According to a fifth aspect of the present invention, in the high temperature Coriolis flowmeter according to the first aspect, a balance weight for equalizing the natural frequencies of the outer tube and the inner tube at the center of the outer tube of the double tube. And fix
Since the outer tube portion is enlarged and opened at the symmetrical position sandwiching the balance weight and the enlarged portion joined at the outer periphery is provided, the outer tube can freely expand and contract in the axial direction.
Since the stress caused by the temperature difference between the inner tube and the outer tube can be easily absorbed, the applicable temperature range can be expanded. Moreover, the conventional outer tube without the enlarged portion has a high bending rigidity, so that the weight of the balance weight for equalizing the natural frequency of the inner tube becomes large, but the provision of the enlarged portion reduces the bending rigidity. Thus, the weight of the balance weight can be reduced.

According to the sixth aspect of the present invention, in the high-temperature Coriolis flowmeter according to the fifth aspect, the enlarged portion provided on the outer tube is formed simultaneously with the straight pipe portion by drawing to form a single piece. The same effect can be obtained, and the welding step of the enlarged portion of the outer tube is not required, so that the outer tube can be made cheaper.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a high-temperature Coriolis flow meter for describing an embodiment of the first and second aspects of the invention.

FIG. 2 is a partial cross-sectional view of a high-temperature Coriolis flow meter for describing an embodiment of the invention of claim 3;

FIG. 3 is a partial cross-sectional view of a high-temperature Coriolis flow meter for describing an embodiment of the invention of claim 4;

FIG. 4 is a partial sectional view of a high-temperature Coriolis flow meter for describing an embodiment of the invention of claim 5;

FIG. 5 is a partial sectional view of a high-temperature Coriolis flow meter for describing an embodiment of the invention according to claim 6;

FIG. 6 is a partial sectional view in the flow direction for explaining a conventional double tube type Coriolis flowmeter.

[Explanation of symbols]

1: Double tube, 2: Inner tube, 3, 5, 7, 8, 1
2 ... outer tube, 4, 6 ... support, 8a, 8b ... partial tube of outer tube 8, 9a ... partial tube 8
a, 9b: enlarged opening of the partial tube 8b, 10: support block, 11: balance weight, 1
2a, 12b ... enlarged part.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kimihiro Ichinose 3-10-8 Kamiochiai, Shinjuku-ku, Tokyo Inside the oval company (72) Inventor Osamu Futagawa 3-10-8, Kamiochiai, Shinjuku-ku, Tokyo Oval Corporation (72) Inventor Seiji Kobayashi 3-10-8 Kamiochiai, Shinjuku-ku, Tokyo Oval Corporation (72) Inventor Kazuhide Kobayashi 3-10-8, Kamiochiai, Shinjuku-ku, Tokyo In Oval Corporation

Claims (6)

[Claims] An inner tube through which a fluid to be measured flows;
A double pipe comprising an outer tube supporting both ends coaxially via a support outside the inner tube, flowing a high-temperature fluid through the inner tube, and coupling the inner tube and the outer tube to a vibration frequency; In a high-temperature Coriolis flowmeter for determining the mass flow rate of the high-temperature fluid in proportion to the Coriolis force acting on the inner tube, the support or the outer tube of the double tube is connected to the double tube. A high-temperature Coriolis flowmeter characterized by having a rigidity in a direction perpendicular to the axis of the tube and a stress relief structure acting in the axial direction in the axial direction. 2. The support body is formed of a thin elastic material having good thermal conductivity, wherein the double pipe has a U-shape in cross section in the axial direction and an annular cross section in a direction perpendicular to the axis. The high-temperature Coriolis flowmeter according to claim 1, wherein 3. The support body is formed of a thin elastic material having good heat conductivity, wherein the double pipe has an L-shaped cross-sectional shape in an axial direction and an annular cross-sectional shape in a direction perpendicular to the axis. The high temperature Coriolis flowmeter according to claim 1. 4. The support and the outer tube are integrally formed of a thin elastic material having good thermal conductivity at the same time, and a boundary between the support and the outer tube has a diameter larger than an outer diameter of the outer tube. The high temperature Coriolis flowmeter according to claim 3, further comprising an annular enlarged portion. 5. In the longitudinal center of the outer tube,
A balance weight for providing a natural frequency equal to the natural frequency of the inner tube is provided, and the outer tube is divided at each of at least two positions sandwiching the balance weight, and the divided portion becomes an enlarged opening. 2. The high-temperature Coriolis flowmeter according to claim 1, wherein an enlarged portion welded at the outer periphery is provided. 6. The high-temperature Coriolis flowmeter according to claim 5, wherein the enlarged portion and the outer tube are integrally formed at the same time.