JPH0345145Y2 - - Google Patents

Description

[Detailed description of the invention] Technical field This invention uses multiple elements with almost the same characteristics to prevent electrical elements such as the drive and detection of Coriolis flowmeters from becoming unmeasurable due to disconnection, etc. The purpose is to install and switch between them.

Prior Art There is a Coriolis flowmeter as a means for measuring mass flow rate. Coriolis force occurs in a direction perpendicular to the angular velocity vector and the flow velocity vector when a fluid flowing in a flow tube is rotated or vibrated, and its magnitude is equal to the mass flow rate of the fluid when the angular velocity is constant. is proportional to. The flowmeter disclosed in Japanese Patent Application Laid-Open No. 59-92314 uses end plates to partition the fluid inside a manifold with inflow and outflow ports in order to reduce excitation energy and pressure loss. The curved pipe is fixed by opening the fluid in the manifold, a support is provided at a position slightly apart from this fixed point, and the planar U-shaped curved pipe is substantially fixed by penetrating and fixing the support. The structure is such that equal amounts of fluid flow in parallel to each other.
In other words, the parallel curved tubes form a tuning fork with the fixed parts as nodes, so they vibrate at their natural frequency, and
Since the flow is parallel, the excitation energy and pressure loss are reduced. The excitation means is to attach a ring coil to the tip of the U-shaped curved tube on one side and a magnet inserted into the ring-shaped coil on the other side, and apply an alternating current equal to the natural frequency of the U-shaped curved tube to the ring coil. The detection means is to install a coil and a magnet facing each other on the shoulders of each U-shaped curved pipe, express the phase difference with respect to a reference plane at a stationary position as a time difference, and calculate the mass flow rate proportional to this. ing. In addition, the U-shaped curved pipe is driven by the natural frequency of the fluid, but depending on the pipe material, the Young's modulus changes due to changes in temperature, etc., causing a change in the natural frequency, which causes errors as described above. becomes. For this reason, a thermometer such as a resistance wire is usually attached to the surface of the U-shaped tube to sense the temperature, and the change in natural frequency is corrected based on this.

Problems As mentioned above, the conventional Coriolis flowmeter reduces driving energy and pressure loss, and detects the Coriolis force by converting it into a moment about the axis of the U-shaped curved pipe. However, as the shape of the flowmeter becomes larger, in the event of an accident such as disconnection of electrical components in the drive means, detection means, etc., it will be necessary to replace the accidental element or replace it. There was a problem in that it was difficult to inspect whether there were any changes in characteristics due to this, resulting in long suspensions of measurement operation.

Means for Solving the Problems The present invention solves the above-mentioned problems by arranging a plurality of drive means, detection means, temperature sensing means, etc. in parallel, and usually each of them is operated by one means. There are, but
When a problem such as a disconnection occurs, the system switches to another of the corresponding multiple means, and furthermore, this switching is done by superimposing a separable signal on the electrical frequency that is applied and output during flowmeter operation. This is automatically performed by detecting the disappearance of this signal. The technology described above is
Although the present invention relates to the flowmeter disclosed in Japanese Patent No. 92314, the present invention is not limited to U-shaped curved pipes, but is also applicable to straight pipe type Coriolis type flowmeters.

Embodiment FIG. 1 is a perspective view for explaining an embodiment of a Coriolis flowmeter according to the present invention. In the figure, 1 is a flow tube, and 2 and 3 are fluid tubes to be measured (not shown). flange for connecting to the pipe, 4 and 5 are partition plates provided in the pipe 1, 6 and 7 are curved pipes, 8
is support plate (vibration fixing plate), 10A ₁ , 10A ₂ ; 10
B ₁ and 10B ₂ are detection means, 11A and 11B are drive means, 12A and 12B are temperature sensing means, and each detection means 10A ₁ , 10A ₂ , 10B ₁ and 10B ₂ is a magnet 10 ₁
and a coil ₁₀₂ , each driving means 11A,
11B is made up of a magnet 11 ₁ and a coil 11 ₂ , and as is well known, the fluid to be measured introduced from the flange 2 into the flow tube 1 passes through the dividing plate 4 in the flow tube 1,
5, an equal flow rate is divided into curved pipes 6 and 7,
The fluid flows out through the flange 3 into a measured fluid conduit (not shown). The arrangement, angles, etc. of the dividing plates 4, 5 are selected so as to achieve the above-mentioned equally divided flow rate. The Coriolis flowmeter measures the mass flow rate of the fluid to be measured by detecting the Coriolis force acting on the curved pipe when the fluid flows through the curved pipe as described above. The torsional torque acting on the curved pipe is detected. In other words, in the curved tubes 6 and 7, each curved tube is axially symmetrical with respect to the second axes Q ₁ and Q ₂ that are perpendicular to the first axes P ₁ and P ₂ connecting the fixed points on the support plate 8, respectively. 6 and 7, and the turning angle at which the curved tube turns around the second axis due to the Coriolis force couple acting on the curved tube is based on the neutral plane when the curved tube is at rest. The detection means detects and measures the phase difference when the curved tube passes through the reference plane. The temperature is detected by pasting a platinum wire or the like between the fixing point of the curved tube and the support in the section where Coriolis does not reach, and detecting the temperature from the resistance change of this platinum wire. This is to correct the change in natural frequency that occurs.
In addition, pressure detection means may be added when correcting changes in the natural frequency due to the influence of expansion of the curved pipe due to pressure changes. Therefore, in the Coriolis type flowmeter as described above, when the shape of the meter becomes large, as mentioned above, the driving means, the detection means,
When an electrical component in a temperature-sensing device, etc. causes an accident such as a disconnection, it is difficult to replace the faulty component and to inspect whether there is a change in characteristics due to the replacement, resulting in a prolonged suspension of measurement operation. .

The present invention was made to solve the above-mentioned problems, and specifically, as shown in the figure,
There are two sets of electric components such as detection means, drive means, temperature sensing means, etc. that are likely to cause accidents, and when one breaks down, it automatically switches to the other to continue measurement operation, and during that time This is to repair or replace failed parts in preparation for the next failure.

FIG. 2 shows an automatic switching circuit for switching between the driving means 11A and 11B.
Switching between 0A, 10A ₁ and 10A ₂ and 10B, 10B ₁ and 10B ₂ and switching between temperature sensing means 12A and 12B can be performed in the same manner. However, in the case of detection means and temperature-sensitive means,
Furthermore, switching of the calculation section and the output section is added. Second
In the figure, 21, 22, 23 are changeover switches, 24 is a drive power supply, 25 is an abnormality detection power supply, and 26
27 is a signal separation circuit, 27 is an abnormality determination circuit, and 28 is a switching means, in which the driving means 11A continues to vibrate at the natural frequency from the driving power source 24 via the switching switch 21. As the abnormality detection power supply 25, a minute direct current or a high frequency current of several tens of times the drive frequency or more is superimposed on the drive power supply via the changeover switch 22. In this way, the driving means 11A is driven by a voltage on which the driving and abnormality detection power supply voltages are superimposed, and this superimposed signal is supplied to the signal separation circuit 26 via the changeover switch 23, Here, the abnormal signal is separated, and for example, (i) if the abnormality detection power source is DC, the AC is cut off, (ii) if the abnormality detection power source is AC, the DC is cut off, and the level of the abnormal signal is below a predetermined value. The abnormality determination circuit 27 determines whether or not the value has decreased, and when the value has decreased to a predetermined value or less, the switching means 28 is activated to switch the changeover switch 2.
1, 22, and 23 to the drive means 11B side.
From then on, the drive means 11B switches between the changeover switches 21 and 2.
It is driven by a drive power supply 24 and an abnormality detection power supply 25 via a drive means 11B, and its abnormality is monitored by an abnormality determination circuit 27 via a switch 23 which is switched to the driving means 11B side. Similar monitoring is performed between the detection means 10A and 10B and between the temperature sensing means 12A and 10B.
This is also done between 12B.

Effects As is clear from the above explanation, according to the present invention, even if the operating drive means, detection means, temperature sensing means, etc. break down, other drive means, detection means, etc. that are on standby are automatically automatically activated. or temperature-sensing means, continuous operation is possible without interruption regardless of the failure of these parts.

[Brief explanation of drawings]

FIG. 1 is a perspective view for explaining an embodiment of a Coriolis flowmeter according to the present invention, and FIG. 2 is a diagram showing an example of an electric circuit used in the embodiment of the present invention. 1... Fluid pipeline to be measured, 2, 3... Flange,
4, 5...Split plate, 6,7...Curved pipe, 10A ₁ ,
10A ₂ , 10B ₁ , 10B ₂ ... detection means, 11A,
11B... Drive means, 12A, 12B... Temperature sensing means, 21-23... Changeover switch, 24... Drive power supply, 25... Abnormality detection power supply, 26... Signal separation circuit, 27... Abnormality determination circuit, 28...Switching means.

Claims (1)

[Scope of utility model registration request] A tube body supported at both ends and through which fluid flows, a driving means for driving the tube body around the support point at a predetermined frequency, and a detection means for detecting Coriolis force acting on the tube body by the driving means. In the Coriolis flowmeter, which detects the mass flow rate of fluid from the Coriolis force, the driving means, the detection means, and other electrical components are provided in plurality, each having substantially the same characteristics, and usually in plurality. Among the electrical components of
An abnormality detection power supply that allows only one to function and superimposes an abnormality detection signal that can be separated other than the signal that is present during regular measurement on the plurality of electrical components, and a signal separation that separates the abnormal signal from the superimposed signal. A Coriolis flowmeter comprising: a means for determining an abnormality in a separated abnormal signal; an abnormality determining circuit for determining an abnormality in a separated abnormal signal; and a switching circuit for switching to another electrical component based on an abnormality detection signal of the abnormality determining circuit. .