JPH0341319A - Coriolis mass flowmeter - Google Patents

Abstract

PURPOSE:To obtain a flowmeter facilitating maintenance and washing and having excellent earthquake resistance by vibrating the central parts of a measuring tube and a dummy body and the vicinity thereof with a resonance frequency of the measuring tube and the dummy body. CONSTITUTION:A flowmeter is constructed of a measuring tube 1, a dummy body 11 having the same resonance frequency as the measuring tube, and a vibration-proof frame 13 to which the respective opposite ends of the dummy body 11 and the measuring tube 1 are fixed. A fluid to be measured is made to flow through the measuring tube 1 and the central parts of the measuring tube 1 and the dummy body 11 and the vicinity thereof are vibrated with the resonance frequency of the measuring tube 1 and the dummy body 11 by a vibrator 3. Then the measuring tube 1 and the dummy body 11 vibrate in the same direction. When an angular velocity in the direction of vibration denoted by 'omega' and a flow velocity of the fluid flowing inside the measuring tube 1 by 'V', a Coriolis force of Fc = -2m'omega' X 'V' acts. A change in a shape is caused in the measuring tube 1 by the Coriolis force according to the direction of the flow velocity 'V' and the shape of the measuring tube 1 changes. The displacement of the measuring tube 1 on the occasion is detected by displacement detecting sensors 4 and 5 provided near the opposite end parts of the measuring tube 1 and the dummy body 11, and thereby a flow rate is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a Coriolis mass flowmeter that is easy to maintain and clean and has good seismic resistance.

<Prior Art> FIG. 4 is a diagram illustrating the configuration of a conventional example that has been commonly used.

In the figure, 1 is a U-shaped measurement tube attached to piping A at both ends.

2 is a flange for attaching the measuring tube 1 to the conduit A.

Reference numeral 3 denotes a vibrator provided at the tip of the U-shaped measuring tube 1.

4.5 are displacement detection sensors provided on both sides of the measuring tube 1, respectively.

In the above configuration, the measurement fluid is flowed through the measurement tube 1, and the vibrator 3 is driven. The angular velocity of the vibrator 3 in the vibration direction “ω
1. Assuming that the flow velocity of the fluid to be measured is 'VJ (hereinafter, the symbol enclosed in quotation marks represents a vector quantity), Fc = -2mrωJ Mass flow rate can be measured.

However, in general, the amplitude of vibrations proportional to Coriolis is extremely smaller than the amplitude of vibrations caused by excitation, and it is only possible to directly detect the amplitude of vibrations proportional to Coriolis.

Now, when viewed from the Z direction in Fig. 4, the vibration direction is divided into α and β due to the vibration of the vibrator 3, and the flow velocity is “V”.
As shown in FIGS. 5(A) and 5(B), the direction of Coriolis differs depending on the direction of the coriolis, resulting in an opposite phase, and the measuring tube 1 vibrates while being twisted.

The displacement is detected by the displacement detection sensors 4 and 5, for example, a magnetic sensor, and the phase difference between the displacements of the displacement detection sensors 4 and 5 is (
The mass flow rate can be determined because it is proportional to (amplitude of vibration proportional to Coriolis)/(amplitude of vibration due to excitation).

Since the phase difference can be measured as the difference Δt between the times when the waveform crosses zero, Coriolis can be measured as a result.

FIG. 5 is a diagram illustrating the configuration of another conventional example that has been commonly used.

In this conventional example, the measuring tube 1 is of a two-tube type in order to further reduce noise and increase the signal.

<Problems to be Solved by the Invention> However, although the device shown in FIG. 5 improves seismic resistance against external vibrations, the measurement flow path is separated into two, and cleaning of the measurement tube is difficult. It has drawbacks such as difficulty in handling and the tendency for deposits to accumulate at the branching part.

The present invention solves this problem.

An object of the present invention is to provide a Coriolis mass flowmeter that is easy to maintain and clean and has good earthquake resistance.

Means for Solving the Problems> To achieve this object, the present invention provides a Coriolis mass flowmeter that measures mass flow rate using Coriolis force, which includes: a measurement tube through which a measurement fluid flows; a dummy body that is provided in parallel and has a resonance frequency similar to that of the measurement tube; a vibration isolation frame to which both ends of the dummy body and the measurement tube are fixed; It is characterized by comprising a vibrator that vibrates at a resonance frequency of the measurement tube and the dummy body, and first and second displacement detection sensors provided near both ends of the measurement tube and the dummy body, respectively. This is a Coriolis mass flowmeter.

<Operation> In the above configuration, the measurement fluid is flowed into the measurement tube, and the vibrator is driven. The measuring tube and the dummy body are vibrated in the same direction by the vibrator.

If the angular velocity ``ω'' in the vibration direction and the flow rate ``■J'' of the measuring fluid flowing inside the measuring tube, F c = -2m Irωl The tube is deformed by Coriolis, and the measuring tube is deformed. 1st.
The second displacement detection sensor measures displacement due to Coriolis.

On the other hand, with respect to the vibration of the main pipe that acts as noise on the measured values, the measuring pipe and the tube are fixed near both ends with vibration isolating frames, so it is difficult to receive external vibrations.

Hereinafter, a detailed explanation will be given based on examples.

<Example> FIG. 1 is an explanatory diagram of the main part of an embodiment of the present invention.

In the figure, the same symbol m as in FIG. 4 represents the same function.

Hereinafter, only the differences from FIG. 4 will be explained.

Reference numeral 11 denotes a dummy body which is provided in parallel with the measuring tube 1 and has a resonant frequency similar to that of the measuring tube 1. In this case, pipes are used.

12 is an auxiliary dummy pipe. The auxiliary dummy tube 12 is for ensuring the symmetry of the structure.

13 is a vibration isolation frame to which both ends of the dummy body 11 and the measuring tube 1 are fixed.

The vibrator 3 vibrates near the center of the measuring tube 1 and the dummy body 11 at the resonant frequency of the measuring tube 1 and the dummy body 11.

1st. The second displacement detection sensors 4 and 5 are respectively provided near both ends of the measuring tube 1 and the terminal body 11-.

In the above configuration, the measurement fluid is flowed through the measurement tube 1, and the vibrator 3 is driven. The measuring tube 1 and the dummy body 11 are vibrated in the same direction by the vibrator 3.

If the angular velocity in the vibration direction is ``ω'', and the flow rate of the measuring fluid flowing inside the measuring tube 1 is ``V'', then Fc = -2m Fω' 1 is deformed by Coriolis, and the measuring tube 1 is deformed. 1st. The second displacement detection sensor 4.5 measures the displacement caused by Coriolis.

On the other hand, since the measuring tube 1 and the dummy body 11 are fixed near both ends by the vibration isolating frame 13, it is difficult to receive external vibrations from the vibration of the main piping, which acts as noise on the measured values.

That is, (1) Figure 2 shows the operation when the flow rate of the measured fluid is zero.

FIG. 2(A) does not show the vibration a of the measuring tube 1 and the vibration of the dummy tube 11 at the position of the displacement detection sensor 4 or the displacement detection sensor 5.

Both are in the opposite direction of vibration.

FIG. 2(B) shows the output C of the displacement detection sensor 4 or the displacement detection sensor 5.

The displacement detection sensor 4 or the displacement detection sensor 5 is connected to the measurement tube 1
The difference between the vibration of the dummy tube 11 and the vibration of the dummy tube 11 is detected.

When the flow rate of the measurement fluid is zero, the output of the displacement detection sensor 4 or the displacement detection sensor 5 is exactly the same.

(2>:a The operation when a constant fluid is flowing through the measuring tube 1 is shown in FIG. 3.

FIG. 3(A) shows the measurement tube 1 at the position of the displacement detection sensor 4.
The vibration d of the dummy tube 11 and the vibration e of the dummy tube 11 are shown.

The vibration e of the dummy tube 11 is the same as that shown in FIG.
Vibration d2 caused by Coriolis is added, and the waveform of the vibration changes.

FIG. 3(B) shows the measurement tube 1 at the position of the displacement detection sensor 5.
The vibration f of the dummy tube 11 and the vibration g of the dummy tube 11 are shown.

The vibration g of the dummy tube 11 is the same as the vibration shown in FIG. 2, or the waveform of the vibration changes as the vibration f2 due to Coriolica is added to the vibration of the measuring tube 1 along with the excitation indicated by the broken line f1.

Since Coriolis is opposite to that in the case of the displacement detection sensor 4, the vibration f2 due to Coriolis is also opposite to that in the case of the displacement detection sensor 4.

FIG. 3(C) shows the outputs of the displacement detection sensors 4 and 5.

Indicates i.

The outputs of the displacement detection sensors 4 and 5, i, are the vibrations caused by Coriolis d2. Since f2 is opposite, the phase is slightly shifted.

This phase shift corresponds to a phase change due to Coriolis.

Therefore, by detecting this phase shift, Coriolis, that is, mass flow rate can be measured.

As a result, it is made up of − pipes, and the liquid pool,
Since there are no branching parts, maintenance and cleaning are easy.

Furthermore, since the difference between the vibrations of the two tubes is used to detect vibrations, external vibrations are not easily detected.

In addition, in the above-mentioned embodiment, the dummy body 11 was described as having a pipe shape, but the dummy body 11 is not limited to this.
For example, the measuring tube 1 may be shaped like a rod or a plate.
It is sufficient if it has the same resonant frequency as .

In addition, the measuring tube 1 is not a straight tube, but a U-shaped tube or an S-shaped tube.
Of course, the tubular shape is also good.

<Effects of the Invention> As explained above, the present invention provides a Coriolis mass flowmeter that measures mass flow rate using the Coriolis force, which includes a measurement tube through which a measurement fluid flows, and a measurement tube installed parallel to the measurement tube. a vibration-proof frame to which both ends of the dummy body and the measuring tube are fixed, and a central portion of the measuring tube and the dummy body are integrally connected to the measuring tube and the housing. A Coriolis mass flowmeter comprising: a vibrator that vibrates at a resonance frequency; and first and second displacement detection sensors provided near both ends of the measurement tube and the dummy body, respectively. Configured.

As a result, it consists of − pipes, a liquid pool,
Since there are no branching parts, maintenance and cleaning are easy.

Furthermore, since the difference between the vibrations of two bones is used to detect vibrations, it is difficult to receive external vibrations.

Therefore, according to the present invention, it is possible to realize a Coriolis mass flowmeter that is easy to maintain and clean and has good earthquake resistance.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the main part configuration of an embodiment of the present invention, FIG.
Fig. 3 is an explanatory diagram of the operation of Fig. 1, Fig. 4 is an explanatory diagram of the configuration of a conventional example commonly used, Fig. 5 is an explanatory diagram of the operation of Fig. 4, and Fig. 6 is an explanatory diagram of the conventional example commonly used. FIG. 2 is an explanatory diagram of the configuration of another conventional example. DESCRIPTION OF SYMBOLS 1...Measurement tube, 2...Flange mounting, 3...Vibrator, 4.5...Displacement detection sensor, 1]...Dummy tube, 12...Auxiliary dummy tube, 13... ...An anti-vibration frame. 1 Figure 2 JP-A-3-41319 (5) Figure 3

Claims (1)

[Claims] A Coriolis mass flowmeter that measures mass flow rate using the Coriolis force includes: a measurement tube through which a measurement fluid flows; and a dummy installed parallel to the measurement tube and having the same resonance frequency as the measurement tube. a vibration isolation frame to which both ends of the dummy body and the measurement tube are fixed; and a vibration that excites a central portion of the measurement tube and the dummy body at a resonant frequency of the measurement tube and the dummy body. A Coriolis mass flowmeter, comprising: a first displacement detection sensor, and first and second displacement detection sensors provided near both ends of the measurement tube and the dummy body, respectively.