JP3182719B2 - Throttle mechanism of throttle flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throttle mechanism of a throttle flow meter used in various plants such as petrochemical and chemical industries.

[0002]

2. Description of the Related Art A throttle flowmeter of this type used for measuring the flow rate of various fluids such as liquid, gas and vapor flowing in a steady flow in a pipe line uses a differential pressure tube generated by a throttle mechanism with two pressure guiding tubes. The flow is led to a differential pressure gauge, which converts it into an electric signal and calculates the flow rate from the signal. That is, if a throttle mechanism for reducing the cross-sectional area of the pipe is installed in the middle of the pipe, a pressure difference occurs before and after the throttle mechanism when a fluid flows therethrough. Since there is a certain relation between the pressure difference and the flow rate, the flow rate of the fluid flowing in the pipeline can be obtained by measuring the pressure difference.

There are various types of throttle mechanisms such as a concentric orifice, a flow nozzle, a venturi tube, a circular orifice, and an eccentric orifice. The most common one uses a concentric orifice or a venturi tube.

[0004] When the fluid to be measured is a slurry fluid, the differential pressure gauge is connected with a pressure receiving diaphragm facing the pressure outlet of the measuring tube so that solid particles or the like do not flow into the measuring section and cause malfunction. A diaphragm type differential pressure gauge is used in which a pipe is connected and its displacement is guided through a pressure transmission medium sealed in the connection pipe. (Example: Shoko 5)
No. 9-22508, Japanese Utility Model Publication No. 56-135126, etc.)

FIG. 7 is a cross-sectional view showing a conventional example of a throttle flow meter using a Venturi tube as a throttle mechanism. This throttle flow meter 1 has an inner diameter D having a venturi tube 3 in the center.
Measuring tube 2, diaphragm type differential pressure gauge 4, measuring tube 2
Connecting pipes 7, 8 for connecting the differential pressure gauge 4 to the first and second pressure outlets 5, 6 provided on the pipe wall. The first pressure outlet 5 on the high pressure side is provided on the upstream side of the venturi tube 3. On the other hand, the second pressure outlet 6, which is on the low pressure side, is formed so as to communicate with the inside of the Venturi tube 3, but may be on the downstream side. The connection pipes 7 and 8 are formed of capillary tubes, and a pressure transmission medium 10 such as silicone oil is sealed therein.
Pressure receiving diaphragms 11 and 12 are provided at the side ends, respectively. Such connection pipes 7 and 8 are respectively connected to flanged connection sections 13 and 14 integrally projecting from the outer circumference of the measurement pipe 2 corresponding to the first and second pressure outlets 5 and 6, respectively. The pressure receiving diaphragm 1 is connected via a sealing member.
1 and 12 face the respective pressure outlets 5 and 6.

In such a throttle flow meter 1, when the fluid 16 to be measured flows through the measuring pipe 2, the pressure of the fluid changes before and after the venturi pipe 3. By guiding the displacement of the pressure receiving diaphragms 11 and 12 due to this pressure to the differential pressure gauge 4 via the pressure transmission medium 10, the flow rate of the fluid 16 to be measured can be measured.

[0007]

In the above-mentioned conventional venturi-type throttle flowmeter 1, since it is necessary to provide the tapered portion 15 at least on the upstream side of the venturi tube 3, solid particles and the like are deposited on the upstream side portion. There is a problem that the material 17 accumulates and adversely affects the flow rate measurement. Therefore, it is necessary to remove the deposit 17 periodically or as needed.

Further, such a problem is caused by the venturi tube 3.
However, the same occurs in orifices, flow nozzles, and the like. That is, as shown in FIG. 8A, in the case of an orifice, the outer peripheral edge of a disk-shaped orifice plate 19 having a circular orifice 18 formed in the center is fixed to the tube wall of the measuring tube 2. Orifice plate 1
9 itself becomes a barrier to the fluid 16 to be measured, and deposits 17 are deposited on the upstream side of the orifice plate 19,
Stays. In the case of the flow nozzle, as shown in FIG. 8B, the upstream end of the flow nozzle 21 formed in a cylindrical body is bent radially outward and connected to the tube wall of the measurement tube 2. The deposit 17 is deposited before and after the flow nozzle 21 in the same manner as in the venturi tube 3 described above.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a throttle mechanism of a throttle flow meter which can reduce the accumulation of deposits such as slurry. To provide.

[0010]

In order to achieve the above object, the present invention provides a throttle mechanism of a throttle flowmeter which is provided in a measurement pipe of a throttle flowmeter and generates a differential pressure. It is arranged by being supported by the support member, forms an annular throttle gap with the pipe wall, and is provided with a low-pressure side pressure outlet opening to the outer peripheral surface. Further, the present invention is characterized in that the support member is provided with a passage communicating with the pressure outlet on the low pressure side.

In the present invention, the throttle mechanism is disposed at the center of the inside of the measuring tube, and forms an annular throttle gap for generating a differential pressure between the measuring tube and the wall of the measuring tube. . Further, the inner diameter of the measuring tube can be made constant. The support member has a function of holding the throttle mechanism by providing the passage, and a function of connecting the pressure outlet to the differential pressure gauge.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a sectional view of a throttle flow meter provided with a throttle mechanism according to the present invention, and FIG.
FIG. 3 is a sectional view taken along line II-III of FIG.
In the drawings, the same components as those shown in the section of the prior art are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

In these figures, an inner diameter D of the measuring tube 2 is constant over its entire length, and an aperture member 23 which constitutes an aperture mechanism supported by two horizontal support members 22A and 22B is provided at the center of the inside thereof. Are aligned with the axis of the measuring tube 2. The aperture member 23 is formed in a streamlined cylindrical body of stainless steel or the like, so that the front end 23a on the upstream side with respect to the fluid 16 to be measured has a columnar shape, and the front end surface has a hemispherical shape. A rear end portion 23b downstream of the front end portion 16 is formed in a truncated conical shape whose diameter decreases rearward. The reason for adopting such a streamline shape is to reduce the fluid resistance and prevent the generation of turbulence and eddies. The streamline shape is not limited to such a shape, and as shown in FIG.
b may be formed in a truncated cone shape, the front end surface may be hemispherical, and the central portion 23c may be a column-shaped maximum diameter portion.

An annular throttle gap 25 is formed between the central portion 23c, which forms the maximum outer diameter of the throttle member 23, and the inner wall of the measuring tube 2. As in the case of the orifice, the venturi tube, and the flow nozzle, a pressure difference can be generated before and after the throttle member 23. In the central portion 23c forming the throttle gap 25, a second pressure outlet 6 on the low pressure side is formed so as to penetrate therethrough so as to open on the upper and lower surfaces of the throttle member 23. The pressure outlet 6 is communicated with a distal end side of a conduction hole 26 formed in the center of the throttle member 23 in the axial direction. The conduction hole 26 is formed of a non-through hole formed in the center of the rear end surface of the diaphragm member 23, and the opening is hermetically sealed by a stopper 27.

Two concave portions 28A and 28B are formed on both sides of the intermediate portion of the outer peripheral surface of the rear end portion 23b of the diaphragm member 23 so as to correspond to the support members 22A and 22B. By fitting the inner ends of the support members 22A and 22B, the aperture member 23 is supported.
A communication hole 29 communicating with the conduction hole 26 is formed in the center of the bottom surface of the concave portion 28B on the right side in FIG.

One support member 22A is made of a bolt,
Mounting member 3 fixed to the outer peripheral surface of measurement tube 2 by welding
0 and faces inside the measuring tube 2 and is fixed by welding. The other support member 22B is formed in a cylindrical body having both ends open, so that the center hole 31 is formed in the communication hole 2.
9 and through the communication hole 26, the pressure outlet 6 is connected to the mounting member 32 fixed to the outer peripheral surface of the measuring tube 2 by welding via an O-ring 33, and the nut 34 is loosened by vibration or the like. Has been prevented. The inner end of the support member 22B is fitted into the recess 28B via a gasket 34 to ensure a liquid seal. The outer end of the support member 22B is connected to a differential pressure gauge 4 (see FIG. 5) via a capillary tube (not shown). The pressure outlet 5 on the high pressure side is formed in the measuring tube 2 at a position upstream of the throttle member 23, and is also connected to the differential pressure gauge 4 via a capillary tube. The cross-sectional shape of the inner ends of the support members 22A and 22B protruding into the measurement tube 2 is, as in the case of the throttle member 23, a shape having a small resistance to the fluid 23 to be measured, for example, a circular shape. It is preferable that the shape be an oval or rhombus that is long in the axial direction.
Further, in order to prevent the rotation of the aperture member 23, the concave portion 28 is provided.
A, 28B are filled with an adhesive to support members 22A, 22B.
It is preferable to fix the inner end of B. In this case, the supporting members 22A, 22B are welded from the downstream side of the measuring tube 2 by welding.
Or the tip portions of the support members 22A, 22B and the recesses 28A, 28B are formed into a polygonal or elliptical shape that can be fitted to each other.
The 2A and 22B may be fastened and fixed to the tube wall of the measuring tube 2 with a nut or the like, or the rotation of the throttle member 23 may be prevented by using three support members.

In the throttle flow meter provided with the throttle member 23 having such a structure, the measurement tube 2 having the constant inner diameter D over the entire length can be manufactured. Since the annular throttle gap 25 is formed between the tube 2 and the tube wall, solid particles and the like hardly accumulate inside the measurement tube 2, which is suitable for measuring a slurry fluid. If the amount of the deposit is small, the operation of removing the deposit is unnecessary, and the maintenance of the measuring tube 2 is easy. FIG.
In the case of the venturi tube 3 shown in FIG. 2, since it is necessary to provide the taper portion 15 at least on the upstream side, the total length (L) of the measurement tube 2 becomes long. The overall length can be reduced.

FIGS. 5A and 5B are a cross-sectional view and a rear view showing another embodiment of the present invention. In this embodiment, the aperture member 23 is provided such that the rear end thereof is located near the downstream opening end of the measurement tube 2.
The pressure outlet 6 on the low pressure side is provided in the tube wall of the measurement tube 2 corresponding to the throttle gap 25 of the throttle member 23. Aperture member 2
The third support members 22A and 22B have outer ends welded to the inner wall of the measurement tube 2 and a cylindrical body 41 similarly welded to the inner end. The aperture member 23 is fitted to the cylindrical body 41 and fixed by bolts 42.

FIG. 6 is a sectional view showing still another embodiment of the present invention. In this embodiment, the measuring tube 2
A fitting recess 45 is provided in a flange 2 a provided at a downstream opening of the support member 22, and a support member 22
At the inner ends of A and 22B, there is provided a cylindrical body 41 to which the rear end of the drawing member 23 is fitted and fixed by welding, screws or the like, and at the outer end, an annular member 46 having a U-shaped cross section is welded, screws or the like. The annular member 46 is fitted in the fitting concave portion 45, temporarily fixed with screws, pins, or the like, and fixed with paper screws, welding, or the like. The inner diameter of the annular member 46 is substantially equal to the inner diameter of the measuring tube 2.

In such a structure, the pressure outlet 6 on the low pressure side is provided on the tube wall side of the measuring tube 2 in correspondence with the throttle gap 25, so that the hole diameter is larger than when the throttle member 23 is provided. Can be provided, and clogging due to deposits can be reduced. Further, in the embodiment shown in FIG. 5, the assemblability of the throttle member 23 is excellent,
Installation and removal work is easy.

[0021]

As described above, the restricting mechanism of the restricting flow meter according to the present invention is disposed at the center of the inside of the measuring tube by being supported by the support member, and forms a restricting gap between the measuring tube and the wall of the measuring tube. Therefore, the measuring tube can be constituted by a tube having a constant inner diameter over the entire length, and solid particles and the like hardly accumulate inside the measuring tube, which is suitable for measuring a slurry fluid.

Further, since the support member is provided with a passage communicating with the pressure outlet on the low pressure side, it is not necessary to connect a pipe made of a separate member to the pressure outlet, and the number of parts can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a throttle flow meter provided with a throttle mechanism according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a cross-sectional view showing another embodiment of the aperture member.

FIGS. 5A and 5B are a cross-sectional view and a rear view showing another embodiment of the present invention.

FIG. 6 is a cross-sectional view showing still another embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a conventional example of a Venturi-type throttle flowmeter.

FIG. 8A is a cross-sectional view of a main part of an orifice-type throttle flowmeter, and FIG. 8B is a cross-sectional view of a main part of a flow nozzle-type throttle flowmeter.

[Explanation of symbols]

2 ... Measuring tube, 3 ... Venturi tube, 4 ... Differential pressure gauge, 5 ... First pressure outlet, 6 ... Second pressure outlet, 7,8 ... Connection piping, 11,12 ... Pressure receiving diaphragm, 22A, 22B
... a support member, 23 ... a throttle member, 25 ... a throttle gap.

Claims (2)

(57) [Claims] 1. A throttle mechanism for a throttle flowmeter, which is provided in a measurement pipe of a throttle flowmeter and generates a differential pressure, wherein the throttle mechanism is supported by a support member at the center of the inside of the measurement pipe, and is disposed between the measurement pipe and a pipe wall. To form an annular throttle gap
A throttle mechanism for a throttle flow meter, wherein a pressure outlet on the low pressure side is provided on the outer peripheral surface . 2. The throttle mechanism of a throttle flow meter according to claim 1, wherein a passage communicating with the low-pressure side pressure outlet is provided in the support member .