JPH0499918A - Mass flowmeter - Google Patents

Abstract

PURPOSE:To measure the correct flow rate by providing a projecting part which projects to a direction different from an exciting direction of a exciter in the outer periphery of a straight pipe of a conduit to extend in a direction parallel to the straight pipe. CONSTITUTION:An upper rib (projecting part) 9 and a lower rib 10 of metal are provided in the outer periphery of a sensor tube 2. The ribs 9, 10 project upward, downward from an upper part, a lower part of the tube 2, respectively, and extend in a longitudinal direction of the tube 2. Accordingly, the ribs 9, 10 project in a direction orthogonal to a exciting direction with 180 deg. distance on the circumference of the tube 2. Since the ribs 9, 10 of the tube 2 vibrated by a exciter 3 are held by supporting members 11-14, even if the external vibration is transmitted to the tube 2, the tube 2 is sufficiently strong against the vibrating components in the other directions than a horizontal direction, so that the vibration in the other directions than the horizontal direction can be restricted. Pickups 4, 5 are accordingly capable of detecting the displacement only in the horizontal direction of the tube 2 and prevented from detecting the displacement resulting from the external vibration. The displacement of the tube 2 can be correctly detected in this manner.

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 fluid to be measured to pass through a 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 to express it in terms of mass that is not affected by process conditions (temperature, pressure).

For this reason, various mass flowmeters are being developed that 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 the
There is a flowmeter disclosed in Japanese Patent No.-174814.

The mass flowmeter disclosed in this publication uses a vibrator to vibrate the central part of the linearly extending sensor tube in the radial direction in order to reduce pressure loss when the measured fluid passes through it. The sensor tube is configured to detect displacement of the sensor tube using a pickup.

Furthermore, the excitation method in the straight sensor tube is as follows:
A substantially central portion of the sensor tube is excited in the radial direction, causing the sensor tube to vibrate in a first-order vibration mode. In this way, when fluid flows inside the vibrating sensor tube,
Coriolis occurs in opposite directions in the upstream pipe line and the downstream pipe line, using the vibrating portion as a branch point, and a secondary vibration mode is generated in the straight sensor tube. Therefore, in the above mass flowmeter, there is a time difference between the output of the pickup that detects the displacement between the upstream pipe line and the downstream pipe line due to the frequency of the secondary vibration mode, and the flow rate is measured based on this time difference. Ta.

Problem to be Solved by the Invention In the mass flowmeter having the straight sensor tube described above,
Since the straight pipe is configured to vibrate in the radial direction, the structure is such that the straight pipe is easily vibrated not only in the direction of vibration by the vibrator but also in other radial directions. Therefore, when external vibrations propagate to the mass flowmeter, the straight sensor tube vibrates in any radial direction (360° direction), making it susceptible to external vibrations and causing various vibration sources in the surrounding area. Accurate flow rate measurements were sometimes not possible when equipment was installed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a mass flowmeter that solves the above problems by having a structure in which a straight pipe line is difficult to vibrate in a direction different from the direction of vibration by the vibrator.

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 vibration exciter that vibrates the straight pipe section in the radial direction; and a pickup that detects the radial displacement of the straight pipe section due to the vibration of the straight pipe section; A protrusion that protrudes in a direction different from the vibration direction of the vibrator extends in the extending direction of the straight pipe.

The protrusion provided on the outer periphery of the straight pipe part of the working pipe line makes it difficult for the pipe line to vibrate in directions other than the vibration direction even when external vibrations are applied, and the vibration of the pipe line during flow rate measurement is stabilized, making it possible to measure the flow rate. can be performed well.

Embodiment FIGS. 1 to 3 show an embodiment of a mass flowmeter according to the present invention.

In each figure, a mass flowmeter 1 includes a straight sensor tube (pipe line) 2 made of stainless steel or the like, and a vibrator 3 that vibrates approximately the longitudinal center of the sensor tube 2 in the horizontal direction (X direction). and a pair of pickups 4 and 5 that detect the displacement of the sensor tube 2. An inlet flange 6 (having an inlet 6a) is fixed to the upstream end of the sensor tube 2, and an outlet flange 7 (having an outlet lower a) 7 is fixed to the downstream end. The mass flow meter 1 has an inflow side flange 6 connected to an upstream side piping (not shown), an outflow side flange 7 connected to a downstream side piping (not shown),
The fluid from the upstream piping flows through the flow path 8 (
(shown as a broken line) and flows out to the downstream piping.

The sensor tube 2 has an upper rib (protrusion) 9 and a lower rib (protrusion) 10 made of metal on the outer periphery. As shown in Figure 3,
The lower rib 9 protrudes upward from the upper part of the sensor tube 2,
Moreover, it extends in the longitudinal direction of the sensor tube 2. Further, the lower rib 10 projects downward from the lower part of the sensor tube 2 and extends in the longitudinal direction of the sensor tube 2. Therefore, the upper rib 9 and the lower rib 1O are 1 on the circumference of the sensor tube 2.
They protrude in a direction perpendicular to the vibration direction (X direction) at intervals of 80 degrees.

The ribs 9, 1 protrude from the sensor tube 2 as described above.
0 is partially welded to the outer periphery of the sensor tube 2, and in this embodiment, the vibration exciter 3. The pickups 4 and 5 are welded to the outer periphery of the sensor tube 2 at three opposing points A-C. Further, first to fourth support members 11 to 14 are attached to the sensor tube 2. The support members 11-14 are a pair of Zapoto halves 11a-14a.

11b to 14b are combined.

That is, as shown in FIG.
a is an arcuate portion 11a that comes into contact with the outer periphery of the sensor tube 2;
+ and a contact portion 11a2 that contacts the side surface of the upper rib 9;
The contact part 11a3 comes into contact with the side surface of the lower rib 10, and the other half support 11b is connected to the opposite support 11a.
Although it is symmetrical, it is said that they have the same shape. The other support members/members 12 to 14 also have the same configuration as the support/member 11 described above.

1st. The second support member 11.12 has an upper rib 9. The lower rib 10 is disposed on the downstream side above point A where the sensor tube 2 is welded, and is connected to the outer periphery of the sensor tube 2 and the upper rib 9.
．． It is welded to the side surface of the lower rib 1o. Also, 3rd. The fourth support member 13° 14 has an upper rib 9. A lower rib 1o is provided upstream and downstream of the zero point welded to the sensor tube 2, and the upper rib 9. It is welded to the side surface of the lower rib 1o. Therefore, the upper rib 9. Lower rib 1° is A above
- Welded to the sensor tube 2 at point C and the first to
The sensor tube 2 is supported by the fourth support members 11 to 14.
is fixed to.

Note that the vibrator 3 and the pickups 4 and 5 are supported on the side of the sensor tube 2 by a support member (not shown).

When measuring the flow rate, the sensor tube 2 is vibrated by the vibrator 3 while fluid is flowing in the flow path 8 .

As described above, the outer periphery of the sensor tube 2 is provided with an upper rib 9.degree. and a lower rib 10 that protrude upward and downward perpendicular to the X direction, and the upper rib 9. Since the lower rib 10 is held by the first to fourth support members 11 to 14, the sensor tube 2 is configured to be difficult to displace in the vertical direction and easily displace in the horizontal direction.

Therefore, as shown by the solid line in FIG.
The sensor tube 2 vibrated at is vibrated in the primary vibration mode so that the intermediate portion (near point B) is largely displaced in the horizontal direction. In this way, when fluid flows through the flow path 8 of the vibrating sensor tube 2, Coriolika Fc is generated whose size is proportional to the flow rate. This Coriolika Fc acts in opposite directions on the upstream and downstream sides with the vibrating portion (point B) of the straight sensor tube 2 as a branch point. Therefore, the sensor tube 2 is displaced in opposite horizontal directions on the upstream and downstream sides, and vibrates in the secondary vibration mode (shown by the one-dot chain line and the two-dot chain line in FIG. 4).

A pair of pickups 4 and 5 detect horizontal displacements of the sensor tube 2 at points A and 0, respectively, and output signals thereof. The phase difference between the signals from both pickups 4.5 is proportional to the flow rate.

As mentioned above, the sensor tube 2 vibrated by the vibrator 3 is moved to the upper rib 9. It has a lower rib 10, and upper and lower ribs 9.
, 10 are held by the support members 11 to 14, so even if external vibration propagates to the sensor tube 2, it has sufficient strength against vibration components in directions other than the horizontal direction. vibration is suppressed. Therefore, the pickups 4 and 5 can detect only the horizontal displacement of the sensor tube 2, and are prevented from detecting displacement caused by external vibration, allowing more accurate detection of the displacement of the sensor tube caused by Coriolis according to the flow rate. can.

In addition, since the □ sensor tube 2 is reinforced by the upper and lower ribs 9 and 10, it is prevented from bending due to the stress of the pipe itself, and the straight pipe precision at the time of manufacture can be maintained for a long period of time. Therefore, a decrease in measurement accuracy due to deflection of the sensor tube 2 is prevented.

FIG. 5 shows a modification of the present invention. In FIG. 5, a mass flowmeter 21 has a pair of sensor tubes 24 and 25 between an inlet flange 22 and an outlet flange 23.

The pair of sensor tubes 24 and 25 are made of straight stainless steel pipes and are provided in parallel.

As shown by the broken line in FIG. 5, the inlet flange 22 has an inlet 22a bored in its upstream end, and an inlet 22a in its downstream end.
It has a pair of connection ports 22b and 22c branched off from 2a. The outflow side flange 23 has a pair of connection ports 2 on the upstream end surface.
3b and 23c are bored, and the downstream end face has an outlet 23a where the connection ports 23b and 23c merge.

Both ends of the sensor tubes 24 and 25 are fixedly connected to the connection ports 22b and 22c of the inflow side flange 22 and the connection ports 23b and 23c of the outflow side flange 23. Above and below the outer periphery of the sensor tube 24, 25, an upper rib 9° and a lower rib 10 (however, since FIG. 5 is a plan view, the lower rib 10 is not visible) protrude, similar to the embodiment shown in -F. extending in the direction.

Further, first to fourth support members 11 to 14 are attached to the outer periphery of the sensor tube 24 and 25, and upper and lower ribs 9,
10 is held by support members 11-14.

A vibrator 26 is provided between the sensor tubes 24 and 25, and vibrates the upper intermediate portions of both sensor tubes 24 and 25 in the longitudinal direction so as to bring them closer to each other or farther apart in the horizontal direction.

27 and 28 are pickups, sensor tubes 24 and 2
5 and detects the relative displacement of the sensor tubes 24 and 25.

One pickup 27 is disposed between the support members 11 and 12, and detects relative displacement of the upstream side of the sensor tubes 24 and 25. The other pickup 28 is disposed between the support members 13 and 14 and is connected to the sensor tube 24.
．． The relative displacement on the downstream side of 25 is detected.

During flow rate measurement, when fluid flows into the sensor tube 24.25 which is vibrated toward and away from the sensor tube 24 by the vibrator 26, Coriolis is generated in opposite directions on the inflow and outflow sides of the sensor tube 24.25. Therefore, when the pair of sensor tubes 24 and 25 are displaced in the proximal direction,
One sensor tube 24 is shown as a two-dot chain line in FIG. 4, and the other sensor tube 25 is shown as a one-dot chain line in FIG. Further, when the pair of sensor tubes 24 and 25 are displaced in the direction of separation, one sensor tube 24 becomes as shown by the one-dot chain line in FIG. 4, and the other sensor tube 25 becomes as shown by the two-dot chain line in FIG. It will be shown as follows.

Therefore, the pair of pickups 27.28 detect the displacement of the vibrating sensor tube 24.25 as described above, and the phase difference between the output signals from both pickups 27.28 is proportional to the flow rate.

Even in the sensor tube 24 and 25 that vibrate as described above, members 11 to 14 are connected to the upper and lower ribs 9 and 10 and the sabot 1.
Since displacement in directions other than the horizontal direction is prevented, the sensor tubes 24, 25 vibrate in the horizontal direction even if there is external vibration. Therefore, the pickups 27, 28 can stably detect the displacement of the sensor tubes 24, 25 according to the flow rate, and can accurately measure the flow rate.

In the above embodiment, the upper and lower ribs 9 and 10 are partially welded to the outer periphery of the sensor tube 2, but the present invention is not limited to this. You can also do it. In that case, support members 11-1
4 can be made unnecessary.

Further, the upper and lower ribs 9 and 10 may be provided on the upper or lower part of the sensor tube 2, but are not limited thereto, and may be made to protrude in a direction other than the vibration direction.

Further, in the above embodiments, the straight sensor tube has been described as an example, but the upper and lower ribs 9 and 10 may be provided on the straight portion of the sensor tube having a shape other than this.

Effects of the Invention As described above, the mass flowmeter according to the present invention is provided with a protrusion that protrudes in a direction different from the vibration direction of the vibrator on the outer periphery of the straight pipe part of the conduit, and this protrusion is connected to the straight pipe part. For example, even if external vibration is transmitted, the straight tube part can be prevented from vibrating in directions other than the excitation direction, and the displacement of the sensor tube according to the flow rate can be accurately detected. can. Therefore, noise caused by external vibrations is removed and more accurate flow rate measurement can be performed.

Furthermore, since the straight pipe section can be reinforced with the protrusion, it is possible to prevent the straight pipe section from bending, and the flow rate can be measured stably over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of a mass flowmeter according to the present invention;
Figure 2 is a front view of the mass flowmeter shown in Figure 1, Figure 3 is a sectional view of the sensor tube and upper and lower ribs, and Figure 4 is a plan view for explaining the displacement of the sensor tube during flow rate measurement. ,
FIG. 5 is a plan view of a modification of the present invention. l, 21... Mass flow meter, 2, 24. 25... Sensor tube, 3, 26... Vibrator, 4, 5, 27°2
8...Pickup, 9...Upper rib, 10...Lower rib, 11-14...Support member. 1st figure 1 screen [kabuto i so figure 2 figure 3 figure 4 figure X figure 5 22b11 12 24 131423bmouth・li/:
j'1.5 within

Claims (1)

[Claims] A pipe line having a straight pipe section extending linearly between an inlet where a fluid to be measured flows in and an outlet where the fluid to be measured flows out, and an exciter that vibrates the straight pipe part in a radial direction. , a pickup for detecting radial displacement of the straight pipe section due to vibration of the straight pipe section, in which a pickup is provided on the outer periphery of the straight pipe section of the conduit in a direction different from the excitation direction of the vibrator. A mass flowmeter characterized in that a protrusion protruding from the straight pipe extends in the extending direction of the straight pipe.