JPH0452517A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To make it possible to obtain an output signal of a pickup in a stable manner and thereby to enable accurate measurement of a flow rate by providing a pipeline holding mechanism so that it allows displacement of a straight pipe part constituting a pipeline in the axial direction, while it regulates the displacement thereof in the radial direction. CONSTITUTION:An outflow pipe 8 constituting a pipeline 3 is provided with bellows 11. When a high-temperature fluid passes through the pipeline 3, accordingly, displacement of sensor tubes 6 and 7 in the axial direction (direction of an arrow A) due to thermal expansion is absorbed by the bellows 11. A holding mechanism 4 is constructed of a diaphragm 12 and a tubular support 13. The diaphragm 12 is fixed to the outer circumference of the outflow pipe 8 and also to the entire periphery of the end part of the support 13, and the support 13 is fixed to the side wall 2c of a casing 2. Accordingly, displacement of the outflow pipe 8 in the radial direction is prevented, while displacement thereof in the axial direction is allowed. Since the casing 2 has sufficient rigidity, besides, external vibration is not transmitted to the pipeline 3. Therefore the vibrational operation of the tubes 6 and 7 is stabilized and accurate measurement of a flow rate can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mass flow meter, and more particularly to a mass flow meter configured to allow a flow rate to be measured to pass through a linear sensor tube.

Conventional technology The flow rate of the fluid to be measured depends on the type of fluid and its physical properties (density, viscosity, etc.)
, it is desirable that it be expressed as a mass that is not affected by process conditions (temperature, pressure).

Therefore, various types of mass flow meters are being developed to measure the mass flow rate of the fluid to be measured. There are flowmeters that directly measure the amount of water.

An example of this type of conventional mass flowmeter is JP-A-63
There is a flowmeter disclosed in Publication No.-30721.

The mass flowmeter described in this publication vibrates a linearly extending sensor tube in the radial direction to reduce pressure loss when the measured fluid passes through it, and detects the displacement of the sensor tube due to Coriolis proportional to the flow rate. It is configured like this.

Furthermore, the sensor tube is provided with an accordion-shaped bellows near the flange where the inlet and outlet are located to allow thermal expansion of the sensor tube in the axial direction when measuring the flow rate of high-temperature fluid. A sufficiently heavy clamping ring is fixed between them in order to prevent external vibrations from being transmitted to the vibrating part of the sensor tube.

Problems to be Solved by the Invention In the mass flowmeter described above, the sensor tube is forcibly vibrated by the electromagnetic force of the excitation coil of the vibrator (consisting of a magnet and an excitation coil), and the highest mechanical Q (
The sensor tube is vibrated in a resonant state at a frequency that provides the reciprocal of the damping factor. In this way, the Q of the sensor tube needs to be high in order to prevent disturbances and stabilize the output signal, or it is difficult to increase the Q with a straight tube type sensor tube, so conventionally the bellows etc. mentioned above have been used. This absorbs the axial displacement caused by vibration of the sensor tube. However, conventional mass flowmeters have a problem in that the bellows section absorbs the axial displacement of the sensor tube and is constantly bent, making it easy for the vibrating section of the sensor tube to shift in radial directions as well as in the axial direction. . In particular, in the case of the above publication, the heavy load of the tightening ring acts on the bellows, so the bellows part may deform over time, which may cause variations in the vibration characteristics of the sensor tube or unstable pickup output, making it difficult to measure the flow rate accurately. Problems may arise, such as the inability to carry out

Therefore, an object of the present invention is to provide a mass flowmeter that solves the above problems.

Means for Solving the Problems The present invention provides a conduit having a straight pipe portion extending linearly between an inlet into which a fluid to be measured flows in and an outflow port through which a fluid to be measured flows out; a vibrator that vibrates the section in the radial direction, a pickup that detects the radial displacement of the straight tube section due to the vibration of the straight tube section, and a pipe line configured to absorb the axial displacement of the straight tube section. and a holding mechanism that holds the conduit so as to restrict displacement of the straight pipe part in the radial direction but allow displacement of the straight pipe part in the axial direction.

The expansion and contraction part absorbs the displacement of the linearly extending sensor tube in the axial direction, and the holding mechanism holds the end of the sensor tube so that it does not shift in any radial direction other than the axial direction. can be stably obtained.

Embodiment FIGS. 1 to 4 show a first embodiment of a mass flowmeter according to the present invention.

In each figure, the mass flow meter 1 is a sealed box-shaped casing 2.
A pipe line 3 through which a fluid to be measured passes, and a holding mechanism 4 that holds the pipe line 3 so as to be displaceable in the axial direction are provided. The pipe line 3 is formed by an inlet pipe 5 having an inlet 5a, a pair of sensor tubes 6.7, and an outlet pipe 8 having an outlet 8a.

The inflow pipe 5 has a flange 5b connected to an upstream pipe (not shown) at the inflow side end, the other end of the inflow pipe 5 passes through the side wall 2a of the casing 2, and the case 9 is connected to the inflow side manifold. , an upstream connection port 9a to which the inflow pipe 5 is connected and fixed, and downstream connection ports 9b and 9c to which the upstream end of the sensor tube 6.degree. 7 is connected and fixed. The upstream connection port 9a and the downstream connection ports 9b and 9c communicate with each other via branch channels 9d and 9e.

Reference numeral 10 denotes an outflow side manifold, which has a pair of connection ports 10a, 10 to which the downstream end of the sensor tube 6.7 is connected and fixed.
b and the connection port where the upstream end of the outflow pipe 8 is connected] 0'
It has c. Moreover, a pair of connection ports 10a are provided in the outflow side manifold 10.

A flow path 10d communicates the connection port 10b with the connection port 10c.

10e is drilled.

The pair of sensor tubes 6.7 are straight pipes extending linearly in the fluid flow direction (direction A), and are provided in parallel between the inflow side manifold 9 and the outflow side manifold 10. The sensor tube 6.7, which is a straight pipe, has a small pressure loss when the measured fluid passes through it, and is processed into a complicated shape.The outflow pipe 8 is connected and fixed to the upstream end or to the connection port 10c of the outflow side manifold 10. The downstream end portion penetrates the side wall 2C of the casing 2 and protrudes toward the downstream side (direction A). Note that an outflow port 8a is opened at the downstream end of the outflow pipe 8, and a flange 8b connected to a downstream pipe (not shown) is provided on the outer periphery of the outflow port 8a.

1 is a bellows (expandable part) formed in a bellows shape, and is provided in the outflow pipe 8. Therefore, the high temperature fluid
The displacement in the axial direction (direction A) due to thermal expansion of the sensor tube 6° 7 is absorbed by the bellows 11 in the shape of an accordion.

Further, the holding mechanism 4 includes a diaphragm 12 fixed to the outer periphery of the outflow pipe 8 and a cylindrical support 13 that supports the diaphragm 12. The diaphragm 12 is made of, for example, a rigid metal, and is provided to restrict the displacement of the outflow pipe 8 in the radial direction, but to allow the outflow pipe 8 to be displaced in the axial direction. Further, the diaphragm 12 is fixed to the entire circumference of the end of a cylindrical support 13, and the support 13 is fixed to the side wall 2c of the casing 2.

Since the casing 2 has sufficient rigidity, it holds the inflow pipe 5 and the outflow pipe 8 so that external vibrations are not transmitted to the pipe line 3. Furthermore, the diaphragm 12 is connected to the casing 2
Since the outflow pipe 8 is firmly held by the struts 13 fixed to the holder, the outflow pipe 8 is allowed to be displaced in the axial direction, and the outflow pipe 8 is prevented from being displaced in the radial direction.

A vibrator is installed between the pair of sensor tubes 6.7 installed between the inflow side manifold 9 and the outflow side manifold 10 to vibrate the center portions of the pair of sensor tubes 6.7 in the radial direction (X direction). 14, and a pickup 15.16 that is provided above and downstream of the vibrator 14 and detects displacement due to vibration of the sensor tube 6.7. The vibrator 14 has substantially the same configuration as an electromagnetic solenoid, and includes a coil portion 14a provided on the sensor tube 6 side and a magnet portion 14b provided on the sensor tube 7 side, and the coil portion 14a is energized. and sensor tube 6.7
are driven in the X direction toward or away from each other.

The pickup 15.16 is composed of coil parts 15a, 16a and magnet parts 15b, 16b, similar to the vibrator 14, and outputs a signal corresponding to the relative displacement of the sensor tube 6.7 due to the vibration of the sensor tube 6.7. get.

When measuring the flow rate, the pair of sensor tubes 6.7 are connected to the vibrator 14.
It is excited with fluid flowing inside. still,
The fluid flowing into the pipe line 3 from the inlet port 5a is divided into two by the branch channels 9d and 9e of the inflow side manifold 9, and then flows into the sensor tube 6.
．． 7 at the same flow rate, and further merge at flow paths 10d and 1'Oe of the outflow side manifold 10, and flow out from the outflow pipe 8 to the downstream piping. In this way, when fluid flows through the vibrating sensor tube 6.7, Coriolis is generated in accordance with the flow rate. Therefore, there is a delay in operation between the inlet and outlet sides of the straight sensor tube 6.7, resulting in a phase difference between the output signals of the pickups 15 and 16. Since this phase difference is proportional to the flow rate, the flow rate can be determined based on the phase difference between the output signals from the pickups 15 and 16.

The principle of flow rate measurement in which the pickup 15.16 detects the displacement caused by Coriolis generated in response to the flow rate passing through the vibrating sensor tube 15.16 is the same as that of the previously filed mass flowmeter, so it will not be described here. A detailed explanation of the flow rate measurement operation will be omitted.

Furthermore, the bellows 11 easily deforms elastically as it absorbs displacement due to thermal expansion of the sensor tube 6.7, but since the outflow pipe 8 is held by the holding mechanism 4 having the diaphragm 12, there is no movement in the bellows 11 in any direction other than the axial direction. It has a structure that is difficult to deform because no force is applied to it.

A second embodiment of the present invention is shown in FIGS. 5 and 6.

In both figures, a mass flow meter 21 includes a pair of sensor tubes (pipe lines) 23 and 24 arranged in parallel within a cylindrical casing 22. The openings at both ends of the casing 22 are provided with an inflow side manifold 25. The outflow side manifold 26 is fitted and fixed. The inflow side manifold 25 has sensor tubes 23 and 24.
A pair of channels 25a into which the inflow side ends are inserted and fixed.

25b is bored. Further, the outflow side manifold 26 has a pair of channels 26a and 26b into which the outflow side ends of the sensor tubes 23 and 24 are inserted and fixed. The pair of sensor tubes 23 and 24 are straight pipes extending in the A direction, and both ends of the sensor tubes 23 and 24 are connected to the inflow side manifold 25. Support plates 27 and 28 are connected and fixed to the outflow side manifold 26, and horizontally extend near the ends thereof to fix the sensor tubes 23 and 24 to each other. Between the support plates 27 and 28, there is a vibrator 29 that vibrates the intermediate position of the sensor tube 23, 24 in the X direction, and a sensor tube 23, 24 that vibrates above and downstream of the vibrator 29. Pick-ups 30 and 31 are provided to detect the displacement of. In addition, vibrator 2
9 and pickups 30 and 31 have substantially the same construction as the vibrator 14 and the pickups 15 and 16 of the first embodiment, so a description thereof will be omitted.

An accordion-shaped bellows 32, 33 is provided near the outflow end of the sensor tube 23, 24.

Therefore, the axial displacement due to thermal expansion of the sensor tube 23.24 when hot fluid passes through the sensor tube 23.24 is absorbed by the expansion and contraction movement of the bellows 32.33.

Reference numeral 34 denotes a holding mechanism, which, as shown in FIG. 6, consists of a pair of columns 35 and 36 that protrude from the end surface of the outflow side manifold 26, and a cross-shaped support plate 37 supported by the columns 35 and 36. The support plate 37 has support parts 37a and 37b fixed to the support columns 35 and 36, and holding parts 37c and 37d that protrude in the X direction orthogonal to the support parts 37a and 37b. Sensor tubes 23 and 24 penetrate and are fixed to the ends of the holding parts 37c and 37d.

The holding parts 37c and 37d of the support plate 37 hold the sensor tube 23.24 in a cantilevered state, so when the sensor tube 23.24 is displaced in the axial direction, the holding parts 37c and 37d
37d is bent in the axial direction and displacement in the axial direction is permitted. However, since the support plate 37 has rigidity in directions other than the axial direction, it supports the bellows 32 and 33 so that they do not bend in the radial direction.

Additionally, an inlet 38a is provided at the end of the manifold 25, 26.
A reducer 38, 39 having an outlet 39a is fixed thereto. The outer periphery of the end of the reducer 38, 39 has flanges 38b, 39b connected to upper and downstream piping (not shown).
is fixed.

The fluid to be measured from the upstream piping is branched from the inlet 38a into the channels 25a and 25b of the inflow manifold 25, and passes through the pair of sensor tubes 23.24. The sensor tubes 23, 24 vibrate in the X direction about the support plates 27, 28, and Coriolis is generated in proportion to the flow rate. Furthermore, the fluid flows through channels 26a and 2 of the outflow side manifold 26.
6b, join together, and flow out from the outlet 39a. Since the sensor tubes 23, 24 vibrate between the support plates 27 and 28, the frequency of the vibration excited by the vibrator 29 can be separated from the vibration frequencies of other modes. Therefore, a more stable output signal can be obtained with the pickup 30°31.

A third embodiment of the present invention is shown in FIGS. 7 and 8.

In both figures, a mass flow meter 41 has a cylindrical casing 42 and a pipe line 43 disposed in the outward direction. The pipe line 43 has an inflow pipe 44 having an inlet 44a at one end and a bellows 44b at the other end, a pair of sensor tubes 45 and 46 made of straight pipes arranged in parallel, and an outlet 47a at the end. and an outflow pipe 47 having a bellows 47b at the other end.

Reference numeral 48 denotes an inflow side manifold, which has a connection 048a to which the inflow pipe 44 is connected, and a pair of connection ports 48b and 48c to which the upstream ends of the sensor tubes 45 and 46 are connected. In addition, there is a connection port 4 in the inflow side manifold 48.
8a and the connection ports 48b and 48c are connected to each other through a flow path 48d,
48e is provided.

Reference numeral 49 denotes an outflow side manifold, which has the same configuration as the above-mentioned inflow side manifold 48, and has a connection port 49a to which the outflow pipe 47 is connected, and a pair of connection ports 49b to which the downstream ends of the sensor tubes 45 and 46 are connected. , 49c are bored. In addition, there is a connection port 49a in the outflow side manifold 49.
and 49b.

Flow paths 49d and 49e communicating with 49c are also provided.

Further, the inflow pipe 44 has a flange 44c on the inflow port 44a side, and the bellows 44b side passes through the side wall 42a of the casing 42 and is fixed to the inflow side manifold 48. The outflow pipe 47 also has a flange 47c on the outflow port 47a side, and the bellows 47b side passes through the side wall 42b of the casing 42 and is fixed to the outflow side manifold 49.

Between the pair of sensor tubes 45 and 46, there is a vibrator 50 that vibrates the intermediate position of the sensor tubes 45 and 46 in the X direction, and a sensor tube 4 that vibrates above and downstream of the vibrator 50.
Pick-ups 51 and 52 for detecting the displacement of 5.46 are provided. Furthermore, support plates 53, 54 are fixed above and downstream of the pickups 51, 52 to hold a pair of sensor tubes 45, 46 at a predetermined interval. Therefore, the pair of sensor tubes 45 and 46 are connected to the support plate 5.
3.54 as a fulcrum, and is held by the casing 2 and support plates 53 and 54, which have sufficient strength, so that it is not easily affected by external vibrations.

Reference numeral 55 denotes an inflow side holding mechanism, which is attached to the side wall 42a of the casing 42.
Supports 55a and 55b project further into the casing 42, and the sensor tube 45 is supported by the supports 55a and 55b.
46 and fixed to the inflow side manifold 48. 56 is an outflow side holding mechanism;
It consists of struts 56a and 56b that protrude into the casing 42 from the side wall 42b of the casing 42, and a fixed plate 56c that is supported by the struts 56a and 56b, is located between the sensor tubes 45 and 46, and is fixed to the outflow side manifold 49. .

When high-temperature fluid passes through the pipe line 43 during flow rate measurement, the sensor tubes 45 and 46 are displaced in the axial direction (direction A) due to thermal expansion. In that case, the displacement of the sensor tubes 45, 46 is absorbed by the expansion and contraction movements of the bellows 44b of the inflow pipe 44 and the bellows 47b of the outflow pipe 47. bellows 4
4b, 47b are easily displaced in directions other than the axial direction, or the fixing plates 55c, 56c of the holding mechanism 55, 56 are bent, and the bellows 44b is bent together with the manifolds 48, 49.

47b is allowed to be displaced only in the axial direction.

That is, even if a radial force acts on the bellows 44b, 47b, the manifold 55.56 or the holding mechanism 55.5
6, radial displacement is prevented. Therefore, the pair of sensor tubes 45 and 46 perform stable vibration operation even when measuring the flow rate of high-temperature fluid, and an output signal corresponding to the flow rate can be stably obtained from the pickup.

In the above embodiment, the fixing plates 55c and 56c are positioned between the pair of sensor tubes 45 and 46, but of course the present invention is not limited to this. For example, in FIG. 7, a pair of fixing plates 55c' and 55c' are positioned above and below the sensor tube 45.46 and fixed to the outflow side manifold 48, as shown by the dashed line in FIG. 56c
' may be positioned above and below the sensor tubes 45 and 46 and fixed to the outflow side manifold 49.

Further, the fixing plate 55c and a pair of fixing plates 550'550
' is fixed to the inflow side manifold 48, and the fixing plate 56
c and the pair of fixing plates 56c560' may be fixed to the outflow side manifold 49.

In each of the above embodiments, the thermal expansion of the sensor tube is absorbed by the bellows, but it goes without saying that other configurations may be used to absorb the axial displacement of the sensor tube.

Effects of the Invention As described above, the mass flowmeter of the present invention is capable of absorbing axial displacement due to thermal expansion of the sensor tube by the expansion/contraction operation of the expansion/contraction part, even when measuring the flow rate of high-temperature fluid, for example. The holding mechanism can restrict the straight pipe section from being displaced only in the axial direction so that no force other than the axial direction is applied to the straight pipe section. Therefore, the vibration operation of the sensor tube is stabilized, and variations in the output signal for flow rate measurement can be prevented, making it possible to perform more accurate flow rate measurement.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a first embodiment of the mass flow meter according to the present invention, FIG. 2 is a longitudinal cross-sectional view of the mass flow meter shown in FIG. 1, and FIG.
The figure is a longitudinal sectional view taken along the line ■-■ in Fig. 2, Fig. 4 is a longitudinal sectional view taken along the line IV-IV in Fig. 2, and Figs. , a perspective view for explaining the holding mechanism, and FIGS. 7 and 8 are a cross-sectional view and a vertical cross-sectional view, respectively, of a third embodiment of the present invention. 1.21.41...Mass flow meter, 2...Casing, 3.43...Pipeline, 4.34,55.56...Holding mechanism, 6,7,23.24,45. 46...sensor tube, 9,25.48...inflow side manifold,
10.26.49... Outlet side manifold, 11゜3
2.33, 44b, 47b... bellows, 12...
Diaphragm, 27, 28, 53.54... Support plate, 13, 35.36... Support column, 37... Support plate,
44...Inflow pipe, 47...Outflow pipe. Figure 2

Claims (1)

[Scope of Claims] A conduit having a straight pipe portion extending linearly between an inlet into which a fluid to be measured flows in and an outflow port from which a fluid to be measured flows out, the straight pipe portion extending in a radial direction. a vibrator for vibrating; a pickup for detecting radial displacement of the straight pipe section due to the vibration of the straight pipe section; and a holding mechanism that holds the conduit in such a manner as to restrict displacement of the straight pipe part in the radial direction but allow displacement of the straight pipe part in the axial direction. Total.