CA2567284C - Restriction flowmeter - Google Patents
Restriction flowmeter Download PDFInfo
- Publication number
- CA2567284C CA2567284C CA2567284A CA2567284A CA2567284C CA 2567284 C CA2567284 C CA 2567284C CA 2567284 A CA2567284 A CA 2567284A CA 2567284 A CA2567284 A CA 2567284A CA 2567284 C CA2567284 C CA 2567284C
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- Prior art keywords
- measuring tube
- primary
- tube
- pressure
- restrictor
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
- G01F1/50—Correcting or compensating means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
- G01F1/36—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure the pressure or differential pressure being created by the use of flow constriction
- G01F1/40—Details of construction of the flow constriction devices
- G01F1/44—Venturi tubes
Abstract
A measuring tube (31) includes two members, a primary measuring tube (31A) and a secondary measuring tube (31B). The primary measuring tube (31A) includes a primary pressure outlet (4) and is flange-connects to a bent tube (21) after being angularly adjusted about an axis with respect to the secondary measuring tube (31B).
With the angular adjustment of the primary measuring tube (31A), the height of a substantially average primary pressure (PH) of measurement fluid (7) near the primary pressure outlet (4) substantially coincides with the height of the primary pressure outlet (4).
With the angular adjustment of the primary measuring tube (31A), the height of a substantially average primary pressure (PH) of measurement fluid (7) near the primary pressure outlet (4) substantially coincides with the height of the primary pressure outlet (4).
Description
Specification Restriction Flowmeter Technical Field The present invention relates to a restriction flowmeter which is used in various types of plants such as a natural gas plant, petrochemical plant, chemical industry plant, and the like.
Background Art A restriction flowmeter is conventionally used as one type of restriction flowmeter which measures the flow rates of various types of fluids such as liquid, gas, steam, and the like flowing through a pipeline in the form of a steady flow. In this restriction flowmeter, a differential pressure generated by a restriction mechanism is guided to a measuring portion and converted into an electrical signal. The flow rate is calculated from the signal. More specifically, assume that the pipeline has a restriction mechanism which decreases the sectional area of the pipeline midway along it. When the fluid flows through the restriction mechanism, a pressure difference is generated between before and after the restriction mechanism. The pressure difference has correlation with the flow rate. By measuring the pressure difference, the flow rate of the measurement fluid flowing in the pipeline can be obtained. As the restriction mechanism, an orifice, flow nozzle, Venturi tube, or the like is used (for example, see Japanese Patent Laid-Open Nos. 7-139979, 06-213694, 9-159498, 10-160529, and 8-319730).
Fig. 5 is a sectional view of a conventional restriction flowmeter. This restriction flowmeter 1 comprises a measuring tube 2 formed of a straight tube.
The measuring tube 2 integrally has a restrictor 3 in it.
The tube wall of the measuring tube 2 has a primary pressure outlet 4 and secondary pressure outlet 5 on the upstream side (primary side) and downstream side (secondary side), respectively. The restrictor 3 is cylindrical. Part of an almost elliptic curve, the diameter of which is minimal at the center and increases toward the two ends, forms the inner sectional shape of the restrictor 3. Such a restrictor 3 is also called an elliptic restrictor. The primary pressure outlet 4 is located upstream of the restrictor 3. The secondary pressure outlet 5 is located at the minimal restrictor diameter portion (or a portion displaced downstream of the minimal restrictor diameter potion) of the restrictor 3.
The primary pressure outlet 4 and secondary pressure outlet 5 are usually open to the upper portion of the tube wall of the measuring tube 1. Then, if measurement fluid 7 is gas, the drain does not usually stay in primary and secondary pressure guide tubes 8 and 9. The primary pressure outlet 4 and secondary pressure outlet 5 connect to a diaphragm type differential pressure gauge 10 through the primary and secondary pressure guide tubes 8 and 9.
The differential pressure gauge 10 comprises a container 12 which seals a sealed liquid 11 such as silicone oil, a center diaphragm 14 which partitions the interior of the container 12 into two chambers, i.e., a primary chamber 13a and secondary chamber 13b, a high- and low-pressure-receiving diaphragms 15 and 16 which are respectively provided to the two side surfaces of the container 12, and the like. An outer chamber 17a is formed on the outer surface of the high-pressure-receiving diaphragm 15. The primary pressure guide tube 8 guides a primary pressure PH of the measurement fluid 7 flowing in the measuring tube 2 to the outer chamber 17a. Similarly, an outer chamber 17b is formed on the outer surface of the low-pressure-receiving diaphragm 16. The secondary pressure guide tube 9 guides a secondary pressure PL of the measurement fluid 7 in the measuring tube 2 to the outer chamber 17b.
In the restriction flowmeter 1 having the above structure, when the measurement fluid 7 flows in the measuring tube 2, its pressure changes between before and after the elliptic restrictor 3. The primary pressure guide tube 8 guides the primary pressure PH
Background Art A restriction flowmeter is conventionally used as one type of restriction flowmeter which measures the flow rates of various types of fluids such as liquid, gas, steam, and the like flowing through a pipeline in the form of a steady flow. In this restriction flowmeter, a differential pressure generated by a restriction mechanism is guided to a measuring portion and converted into an electrical signal. The flow rate is calculated from the signal. More specifically, assume that the pipeline has a restriction mechanism which decreases the sectional area of the pipeline midway along it. When the fluid flows through the restriction mechanism, a pressure difference is generated between before and after the restriction mechanism. The pressure difference has correlation with the flow rate. By measuring the pressure difference, the flow rate of the measurement fluid flowing in the pipeline can be obtained. As the restriction mechanism, an orifice, flow nozzle, Venturi tube, or the like is used (for example, see Japanese Patent Laid-Open Nos. 7-139979, 06-213694, 9-159498, 10-160529, and 8-319730).
Fig. 5 is a sectional view of a conventional restriction flowmeter. This restriction flowmeter 1 comprises a measuring tube 2 formed of a straight tube.
The measuring tube 2 integrally has a restrictor 3 in it.
The tube wall of the measuring tube 2 has a primary pressure outlet 4 and secondary pressure outlet 5 on the upstream side (primary side) and downstream side (secondary side), respectively. The restrictor 3 is cylindrical. Part of an almost elliptic curve, the diameter of which is minimal at the center and increases toward the two ends, forms the inner sectional shape of the restrictor 3. Such a restrictor 3 is also called an elliptic restrictor. The primary pressure outlet 4 is located upstream of the restrictor 3. The secondary pressure outlet 5 is located at the minimal restrictor diameter portion (or a portion displaced downstream of the minimal restrictor diameter potion) of the restrictor 3.
The primary pressure outlet 4 and secondary pressure outlet 5 are usually open to the upper portion of the tube wall of the measuring tube 1. Then, if measurement fluid 7 is gas, the drain does not usually stay in primary and secondary pressure guide tubes 8 and 9. The primary pressure outlet 4 and secondary pressure outlet 5 connect to a diaphragm type differential pressure gauge 10 through the primary and secondary pressure guide tubes 8 and 9.
The differential pressure gauge 10 comprises a container 12 which seals a sealed liquid 11 such as silicone oil, a center diaphragm 14 which partitions the interior of the container 12 into two chambers, i.e., a primary chamber 13a and secondary chamber 13b, a high- and low-pressure-receiving diaphragms 15 and 16 which are respectively provided to the two side surfaces of the container 12, and the like. An outer chamber 17a is formed on the outer surface of the high-pressure-receiving diaphragm 15. The primary pressure guide tube 8 guides a primary pressure PH of the measurement fluid 7 flowing in the measuring tube 2 to the outer chamber 17a. Similarly, an outer chamber 17b is formed on the outer surface of the low-pressure-receiving diaphragm 16. The secondary pressure guide tube 9 guides a secondary pressure PL of the measurement fluid 7 in the measuring tube 2 to the outer chamber 17b.
In the restriction flowmeter 1 having the above structure, when the measurement fluid 7 flows in the measuring tube 2, its pressure changes between before and after the elliptic restrictor 3. The primary pressure guide tube 8 guides the primary pressure PH
near the center diaphragm 14 to the outer chamber 17a of the pressure-receiving diaphragm 15. The secondary pressure guide tube 9 guides the secondary pressure PL
in the elliptic restrictor 3 to the outer chamber 17b of the pressure-receiving diaphragm 16. Thus, the two pressure-receiving diaphragms 15 and 16 displace in accordance with a differential pressure AP (PH - PL) between the primary pressure PH and secondary pressure PL. The sealed liquid 11 guides this displacement to the center diaphragm 14. Accordingly, the center diaphragm 14 also displaces in accordance with the differential pressure AP. Conversion of the displacement amount into an electrical signal and arithmetic processing of the electrical signal enables measurement of the flow rate of the measurement fluid 7 flowing in the measuring tube 2.
Disclosure of Invention Problem to be Solved by the Invention In this restriction flowmeter 1, the connection structure of the measuring tube 2 with respect to a tube 20 is as follows. Assume that the measurement fluid 7 is gas. Generally, the measuring tube 2 connects to the tube 20 with the primary pressure outlet 4 and secondary pressure outlet 5 facing up, as shown in Fig. 5. This prevents the drain from staying in the pressure guide tubes 8 and 9. In this connection structure of the measuring tube 2 with respect to the tube 20, when using the measuring tube 2 by flange-connecting it to immediately after a bent tube 21 provided midway along the tube 20, the measurement fluid 7 flowing in the bent tube 21 is a drift flow (swirling flow) which is a composite flow of the main flow (a concentric flow about a center 0 of the bent tube 21 as the center) and the secondary flow (a radial flow toward the center 0). Due to the centrifugal force generated by the swirling flow, the pressure of the measurement fluid 7 changes in one section perpendicular to the axis of the bent tube 21 to form a pressure gradient. More specifically, a pressure (P1) is high outside the bend of the bent tube 21, and a pressure (PZ) is low inside the bend of the bent tube 21 (P1 > PZ).
The primary pressure PH of the measurement fluid 7 which has flown into the measuring tube 2 through the bent tube 21 also changes near the primary pressure outlet 4 in a section perpendicular to the axis to form a pressure gradient. More specifically, as shown in Fig. 5, when the bent tube 21 is an elbow tube which curves by almost 90 in the vertical plane, the primary pressure PH near the primary pressure outlet 4 becomes a pressure PH1 on the upper side of the inner wall of the measuring tube 2 and a pressure PH2 in the lower portion of the inner wall. The pressure PHl becomes higher than the pressure PHZ, and an almost average pressure PH is obtained at the center of the interior of the measuring tube 2. As a result, the pressure PH1 which is higher than the average primary pressure PH in the section perpendicular to the axis of the measuring tube 2 is guided from the primary pressure outlet 4 to the differential pressure gauge 10 through the primary pressure guide tube 8, to generate a measurement error. Thus, highly accurate measurement cannot be performed.
Inside the bend of the bent tube 21, the measurement fluid 7 forms a stable boundary layer as its pressure drops in the flowing direction until a center AB of the bent tube 21. Passing through the center AB, a vortex flow 19 is generated to cause a turbulent flow.
Outside the bend of the bent tube 21, the boundary layer of the measurement fluid 7 separates from the wall surface until the measurement fluid 7 reaches the center AB to form a vortex flow 19', causing a turbulent flow.
If a pipeline formed of a straight tube having a required length horizontally connects to the downstream of the bent tube 21, the turbulent flows 19 and 19' gradually stabilize to be restored to laminar flows.
The pressure of the measurement fluid 7 in the section perpendicular to the axis also gradually averages and the pressure gradient disappears. Therefore, if the primary pressure outlet 4 is formed at a position where the flow and pressure of the measurement fluid 7 stabilize, no measurement error is generated, and highly accurate measurement can be performed. A length L1 of the straight tube (when the measuring tube 2 directly connects to the bent tube 21, the length from the downstream open end of the bent tube 21 to the primary pressure outlet 4 of the measuring tube 2) which is necessary for the flow and pressure of the measurement fluid 7 to stabilize must be 10 times the diameter D
where D is the diameter of the measuring tube 2. Thus, the length of the measuring tube 2 itself increases to largely hinder downsizing and weight reduction.
One of countermeasures to prevent the influence of the pressure fluctuation caused by the bent tube 21 may be fabricating various types of measuring tubes in each of which a primary pressure outlet 4 and secondary pressure outlet 5 are shifted in the circumferential direction and selectively employing them in accordance with the location. More specifically, assume that a measuring tube is fabricated in which a primary pressure outlet 4 and secondary pressure outlet 5 are shifted by 90 in the circumferential direction, and that this measuring tube connects to the bent tube 21 such that the primary pressure outlet 4 faces sideways and the secondary pressure outlet 5 faces up.
The height of the primary pressure outlet 4 almost coincides with the height of the average pressure PH of the measurement fluid 7 flowing near this primary pressure outlet 4. This allows extraction of the average primary pressure PH from the primary pressure outlet 4 to enable highly accurate measurement. Also, this can shorten a distance L1 from the primary open end of the measuring tube 2 to the primary pressure outlet 4 to 10D or less.
In this case, however, as the measuring tubes 2, one in which the primary pressure outlet 4 and secondary pressure outlet 5 are not shifted in the circumferential direction and one in which they are shifted and, depending on the location to set the measuring tube 2, one in which the primary pressure outlet 4 opens to the left and one in which it opens to the right must be prepared. This increases the number of types of the measuring tubes 2. To fabricate, store, and manage these measuring tubes 2 is cumbersome, which is not preferable.
The present invention has been made to solve the conventional problem described above, and has as its object to provide a restriction flowmeter in which even if the bent tube generates a drift flow in the measurement fluid to change the pressure, adjustment of the primary pressure outlet to an optimal height enables extraction of an average primary pressure without increasing the length of the measuring tube itself, thus enabling highly accurate measurement.
Means of Solution to the Problem In order to achieve the above object, there is provided a restrictor flowmeter comprising a measuring tube through which a measurement fluid is to flow, wherein the measuring tube comprises a primary measuring tube and a secondary measuring tube that are divisionally formed, the primary measuring tube having a primary pressure outlet and the secondary measuring tube having a secondary pressure outlet and a restrictor, and the primary measuring tube connects to the secondary measuring tube to be angularly adjustable about an axis.
Effects of the Invention According to the present invention, by attaching the primary measuring tube to the secondary measuring tube after being angularly adjusted about the axis in accordance with the installing conditions of the measuring tube, the primary pressure outlet can have a height that almost coincides with the height of the average primary pressure of the measurement fluid. For example, assume that the bent tube curves within a vertical plane, and that its upstream open end is located on the lower side and its downstream open end is located on the upper side. If the primary measured tube connects to the bent tube such that the primary pressure outlet faces sideways (horizontal direction), this allows extraction of the average pressure near the primary pressure outlet as the primary pressure. Thus, even if a drift flow is generated, the measurement error is small, and the measurement accuracy can improve.
in the elliptic restrictor 3 to the outer chamber 17b of the pressure-receiving diaphragm 16. Thus, the two pressure-receiving diaphragms 15 and 16 displace in accordance with a differential pressure AP (PH - PL) between the primary pressure PH and secondary pressure PL. The sealed liquid 11 guides this displacement to the center diaphragm 14. Accordingly, the center diaphragm 14 also displaces in accordance with the differential pressure AP. Conversion of the displacement amount into an electrical signal and arithmetic processing of the electrical signal enables measurement of the flow rate of the measurement fluid 7 flowing in the measuring tube 2.
Disclosure of Invention Problem to be Solved by the Invention In this restriction flowmeter 1, the connection structure of the measuring tube 2 with respect to a tube 20 is as follows. Assume that the measurement fluid 7 is gas. Generally, the measuring tube 2 connects to the tube 20 with the primary pressure outlet 4 and secondary pressure outlet 5 facing up, as shown in Fig. 5. This prevents the drain from staying in the pressure guide tubes 8 and 9. In this connection structure of the measuring tube 2 with respect to the tube 20, when using the measuring tube 2 by flange-connecting it to immediately after a bent tube 21 provided midway along the tube 20, the measurement fluid 7 flowing in the bent tube 21 is a drift flow (swirling flow) which is a composite flow of the main flow (a concentric flow about a center 0 of the bent tube 21 as the center) and the secondary flow (a radial flow toward the center 0). Due to the centrifugal force generated by the swirling flow, the pressure of the measurement fluid 7 changes in one section perpendicular to the axis of the bent tube 21 to form a pressure gradient. More specifically, a pressure (P1) is high outside the bend of the bent tube 21, and a pressure (PZ) is low inside the bend of the bent tube 21 (P1 > PZ).
The primary pressure PH of the measurement fluid 7 which has flown into the measuring tube 2 through the bent tube 21 also changes near the primary pressure outlet 4 in a section perpendicular to the axis to form a pressure gradient. More specifically, as shown in Fig. 5, when the bent tube 21 is an elbow tube which curves by almost 90 in the vertical plane, the primary pressure PH near the primary pressure outlet 4 becomes a pressure PH1 on the upper side of the inner wall of the measuring tube 2 and a pressure PH2 in the lower portion of the inner wall. The pressure PHl becomes higher than the pressure PHZ, and an almost average pressure PH is obtained at the center of the interior of the measuring tube 2. As a result, the pressure PH1 which is higher than the average primary pressure PH in the section perpendicular to the axis of the measuring tube 2 is guided from the primary pressure outlet 4 to the differential pressure gauge 10 through the primary pressure guide tube 8, to generate a measurement error. Thus, highly accurate measurement cannot be performed.
Inside the bend of the bent tube 21, the measurement fluid 7 forms a stable boundary layer as its pressure drops in the flowing direction until a center AB of the bent tube 21. Passing through the center AB, a vortex flow 19 is generated to cause a turbulent flow.
Outside the bend of the bent tube 21, the boundary layer of the measurement fluid 7 separates from the wall surface until the measurement fluid 7 reaches the center AB to form a vortex flow 19', causing a turbulent flow.
If a pipeline formed of a straight tube having a required length horizontally connects to the downstream of the bent tube 21, the turbulent flows 19 and 19' gradually stabilize to be restored to laminar flows.
The pressure of the measurement fluid 7 in the section perpendicular to the axis also gradually averages and the pressure gradient disappears. Therefore, if the primary pressure outlet 4 is formed at a position where the flow and pressure of the measurement fluid 7 stabilize, no measurement error is generated, and highly accurate measurement can be performed. A length L1 of the straight tube (when the measuring tube 2 directly connects to the bent tube 21, the length from the downstream open end of the bent tube 21 to the primary pressure outlet 4 of the measuring tube 2) which is necessary for the flow and pressure of the measurement fluid 7 to stabilize must be 10 times the diameter D
where D is the diameter of the measuring tube 2. Thus, the length of the measuring tube 2 itself increases to largely hinder downsizing and weight reduction.
One of countermeasures to prevent the influence of the pressure fluctuation caused by the bent tube 21 may be fabricating various types of measuring tubes in each of which a primary pressure outlet 4 and secondary pressure outlet 5 are shifted in the circumferential direction and selectively employing them in accordance with the location. More specifically, assume that a measuring tube is fabricated in which a primary pressure outlet 4 and secondary pressure outlet 5 are shifted by 90 in the circumferential direction, and that this measuring tube connects to the bent tube 21 such that the primary pressure outlet 4 faces sideways and the secondary pressure outlet 5 faces up.
The height of the primary pressure outlet 4 almost coincides with the height of the average pressure PH of the measurement fluid 7 flowing near this primary pressure outlet 4. This allows extraction of the average primary pressure PH from the primary pressure outlet 4 to enable highly accurate measurement. Also, this can shorten a distance L1 from the primary open end of the measuring tube 2 to the primary pressure outlet 4 to 10D or less.
In this case, however, as the measuring tubes 2, one in which the primary pressure outlet 4 and secondary pressure outlet 5 are not shifted in the circumferential direction and one in which they are shifted and, depending on the location to set the measuring tube 2, one in which the primary pressure outlet 4 opens to the left and one in which it opens to the right must be prepared. This increases the number of types of the measuring tubes 2. To fabricate, store, and manage these measuring tubes 2 is cumbersome, which is not preferable.
The present invention has been made to solve the conventional problem described above, and has as its object to provide a restriction flowmeter in which even if the bent tube generates a drift flow in the measurement fluid to change the pressure, adjustment of the primary pressure outlet to an optimal height enables extraction of an average primary pressure without increasing the length of the measuring tube itself, thus enabling highly accurate measurement.
Means of Solution to the Problem In order to achieve the above object, there is provided a restrictor flowmeter comprising a measuring tube through which a measurement fluid is to flow, wherein the measuring tube comprises a primary measuring tube and a secondary measuring tube that are divisionally formed, the primary measuring tube having a primary pressure outlet and the secondary measuring tube having a secondary pressure outlet and a restrictor, and the primary measuring tube connects to the secondary measuring tube to be angularly adjustable about an axis.
Effects of the Invention According to the present invention, by attaching the primary measuring tube to the secondary measuring tube after being angularly adjusted about the axis in accordance with the installing conditions of the measuring tube, the primary pressure outlet can have a height that almost coincides with the height of the average primary pressure of the measurement fluid. For example, assume that the bent tube curves within a vertical plane, and that its upstream open end is located on the lower side and its downstream open end is located on the upper side. If the primary measured tube connects to the bent tube such that the primary pressure outlet faces sideways (horizontal direction), this allows extraction of the average pressure near the primary pressure outlet as the primary pressure. Thus, even if a drift flow is generated, the measurement error is small, and the measurement accuracy can improve.
When rotating the primary measuring tube about the axis through a predetermined angle, this can direct the primary pressure outlet in any of the upward, downward, leftward, and rightward directions. This enables use of the primary measuring tube as a common component.
Brief Description of Drawings Fig. 1 is a perspective view showing the outer appearance of a restriction flowmeter according to the first embodiment of the present invention;
Fig. 2 is a sectional view of the restriction flowmeter shown in Fig. 1;
Fig. 3 is a sectional view showing a restriction flowmeter according to the second embodiment of the present invention;
Fig. 4 is a sectional view showing a restriction flowmeter according to the third embodiment of the present invention; and Fig. 5 is a sectional view showing a conventional restriction flowmeter.
Best Mode for Carrying Out the Invention A restriction flowmeter according to the present invention will be described in detail on the basis of the embodiments shown in the drawings.
Members that are identical to the constituent members shown in the prior art are denoted by the same reference numerals, and a description thereof will be - 10 - ' omitted when appropriate.
Referring to Figs. 1 and 2, a restriction flowmeter entirely denoted by reference numeral 30 comprises a measuring tube 31 which flange-connects to midway along a tube 20, and a differential pressure gauge 10 which detects a differential pressure AP (=
PH - PL) between a primary pressure PH and secondary pressure PL generated in the measuring tube 31.
The tube 20 comprises a vertical tube 20A
through which a measurement fluid 7 flows upward from below, a bent tube 21 which connects to the downstream opening of the vertical tube 20A, and a horizontal tube 20B which is located downstream of the bent tube 21.
The measuring tube 31 flange-connects to a portion between the bent tube 21 and horizontal tube 20B.
The bent tube 21 is formed of an elbow which has a circular section and curves by almost 90 within a vertical plane. The upstream open end of the bent tube 21 directs downward to flange-connect to the upper open end of the vertical tube 20A, and its downstream open end directs in the horizontal direction.
The measuring tube 31 is divided at its center in the longitudinal direction by a section perpendicular to the axis, so it comprises two members, i.e., a primary measuring tube 31A located on the upstream side and a secondary measuring tube 31B located on the downstream side. The primary measuring tube 31A is formed of a straight tube having a diameter D which is the same as that of the bent tube 21. The primary measuring tube 31A has a primary pressure outlet 4, through which the primary pressure PH in the primary measuring tube 31A is to be extracted outside, at the center in the longitudinal direction of its wall surface.
Flanges 32 integrally project respectively at two ends of the outer surface of the primary measuring tube 31A.
Each flange 32 has a plurality of bolt insertion holes 33 to equidistantly space apart from each other in the circumferential direction of the flanges 32. The bolt insertion holes 33 comprise eight bolt insertion holes 33 at angular intervals of, e.g., 450.
The secondary measuring tube 31B is formed of a straight tube having the same outer and inner diameters as those of the primary measuring tube 31A, and integrally has an elliptic restrictor 3 serving as a restrictor at the center of its interior. The elliptic restrictor 3 forms a cylinder having a circular section, in the same manner as the conventional elliptic restrictor 3 shown in Fig. 5. Part of an almost elliptic curve, the diameter of which is minimal at the center of the interior and increases toward the two ends, forms the inner sectional shape of the restrictor 3.
The secondary measuring tube 31B has a secondary pressure outlet 5 from which the secondary pressure PL
in the restrictor 3 is to be extracted. The inner end of the secondary pressure outlet 5 opens to the minimal restrictor diameter portion of the inner surface of the elliptic restrictor 3. The outer end of the secondary pressure outlet 5 opens to the outer surface of the secondary measuring tube 31B. Furthermore, flanges 35 integrally project respectively at the two ends of the outer surface of the secondary measuring tube 31B. Each flange 35 has bolt insertion holes 36 corresponding in number to those of each flange 32 equidistantly in the circumferential direction.
The primary measuring tube 31A and secondary measuring tube 31B integrally connect to each other by flange connection, i.e., by bringing the opposing flanges 32 and 35 in tight contact with each other through a packing 37 and inserting and fastening bolts (not shown) in the respective bolt insertion holes 33 and 36. In this case, the primary measuring tube 31A
connects to the secondary measuring tube 31B as it rotates through by 90 about the axis so that the primary pressure outlet 4 faces right sideways (horizontal direction). The bent tube 21 and primary measuring tube 31A flange-connect to each other similarly through a packing 38. The secondary measuring tube 31B flange-connects to the horizontal tube 20B
similarly through a packing 39 with the secondary pressure outlet 5 facing up.
The differential pressure gauge 10 comprises a container 12, a center diaphragm 14, primary and secondary pressure-receiving diaphragms 15 and 16, an arithmetic operation unit (not shown), and the like.
The container 12 seals a sealed liquid 11. The center diaphragm 14 partitions the interior of the container 12 into a primary pressure chamber 13a and secondary pressure chamber 13b. The primary and secondary pressure-receiving diaphragms 15 and 16 are arranged on the left and right side surfaces, respectively, of the container 12. The arithmetic processing unit converts the displacement of the center diaphragm 14 into an electrical signal and arithmetically processes it to calculate the flow rate of the measurement fluid 7 flowing in the measuring tube 31. A primary pressure guide tube 8 which guides the primary pressure PH in the measuring tube 31 to the differential pressure gauge 10 has one end that connects to the primary pressure outlet 4, and the other end that connects to an outer chamber 17a formed outside the primary pressure diaphragm 15.
Similarly, a secondary pressure guide tube 9 which guides the secondary pressure PL in the measuring tube 31 to the differential pressure gauge 10 has one end that connects to the secondary pressure outlet 5, and the other end that connects to an outer chamber 17b formed outside the secondary pressure diaphragm 16.
In the restriction flowmeter 30 having the above structure, when the measurement fluid 7, e.g., natural gas containing methane as the main component, flowing in the tube 20 flows to the measuring tube 31, the pressure changes before and after the elliptic restrictor 3. The differential pressure gauge 10 detects the differential pressure nP (PH - PL) to measure the flow rate of the measurement fluid 7 flowing in the measuring tube 31. More specifically, the primary pressure guide tube 8 guides the primary pressure PH of the measurement fluid 7 in the measuring tube 31 to the pressure-receiving diaphragm 15. The secondary pressure guide tube 9 guides the secondary pressure PL of the measurement fluid 7 in the measuring tube 31 to the pressure-receiving diaphragm 16. Hence, the pressure-receiving diaphragms 15 and 16 displace in accordance with the differential pressure AP. These displacements are transmitted to the center diaphragm 14 through the sealed liquid 11. The center diaphragm 14 displaces in accordance with the differential pressure nP. This displacement is converted into an electrical signal and arithmetically processed to measure a flow rate W of the measurement fluid 7 flowing in the measuring tube 31. The flow rate W can be obtained by the following equation (1):
W = CK = nP1/2 . . . ( 1) where C is an outflow coefficient, K is a constant (including the tube diameter, the density of the fluid, and the like), and nP is the differential pressure.
Brief Description of Drawings Fig. 1 is a perspective view showing the outer appearance of a restriction flowmeter according to the first embodiment of the present invention;
Fig. 2 is a sectional view of the restriction flowmeter shown in Fig. 1;
Fig. 3 is a sectional view showing a restriction flowmeter according to the second embodiment of the present invention;
Fig. 4 is a sectional view showing a restriction flowmeter according to the third embodiment of the present invention; and Fig. 5 is a sectional view showing a conventional restriction flowmeter.
Best Mode for Carrying Out the Invention A restriction flowmeter according to the present invention will be described in detail on the basis of the embodiments shown in the drawings.
Members that are identical to the constituent members shown in the prior art are denoted by the same reference numerals, and a description thereof will be - 10 - ' omitted when appropriate.
Referring to Figs. 1 and 2, a restriction flowmeter entirely denoted by reference numeral 30 comprises a measuring tube 31 which flange-connects to midway along a tube 20, and a differential pressure gauge 10 which detects a differential pressure AP (=
PH - PL) between a primary pressure PH and secondary pressure PL generated in the measuring tube 31.
The tube 20 comprises a vertical tube 20A
through which a measurement fluid 7 flows upward from below, a bent tube 21 which connects to the downstream opening of the vertical tube 20A, and a horizontal tube 20B which is located downstream of the bent tube 21.
The measuring tube 31 flange-connects to a portion between the bent tube 21 and horizontal tube 20B.
The bent tube 21 is formed of an elbow which has a circular section and curves by almost 90 within a vertical plane. The upstream open end of the bent tube 21 directs downward to flange-connect to the upper open end of the vertical tube 20A, and its downstream open end directs in the horizontal direction.
The measuring tube 31 is divided at its center in the longitudinal direction by a section perpendicular to the axis, so it comprises two members, i.e., a primary measuring tube 31A located on the upstream side and a secondary measuring tube 31B located on the downstream side. The primary measuring tube 31A is formed of a straight tube having a diameter D which is the same as that of the bent tube 21. The primary measuring tube 31A has a primary pressure outlet 4, through which the primary pressure PH in the primary measuring tube 31A is to be extracted outside, at the center in the longitudinal direction of its wall surface.
Flanges 32 integrally project respectively at two ends of the outer surface of the primary measuring tube 31A.
Each flange 32 has a plurality of bolt insertion holes 33 to equidistantly space apart from each other in the circumferential direction of the flanges 32. The bolt insertion holes 33 comprise eight bolt insertion holes 33 at angular intervals of, e.g., 450.
The secondary measuring tube 31B is formed of a straight tube having the same outer and inner diameters as those of the primary measuring tube 31A, and integrally has an elliptic restrictor 3 serving as a restrictor at the center of its interior. The elliptic restrictor 3 forms a cylinder having a circular section, in the same manner as the conventional elliptic restrictor 3 shown in Fig. 5. Part of an almost elliptic curve, the diameter of which is minimal at the center of the interior and increases toward the two ends, forms the inner sectional shape of the restrictor 3.
The secondary measuring tube 31B has a secondary pressure outlet 5 from which the secondary pressure PL
in the restrictor 3 is to be extracted. The inner end of the secondary pressure outlet 5 opens to the minimal restrictor diameter portion of the inner surface of the elliptic restrictor 3. The outer end of the secondary pressure outlet 5 opens to the outer surface of the secondary measuring tube 31B. Furthermore, flanges 35 integrally project respectively at the two ends of the outer surface of the secondary measuring tube 31B. Each flange 35 has bolt insertion holes 36 corresponding in number to those of each flange 32 equidistantly in the circumferential direction.
The primary measuring tube 31A and secondary measuring tube 31B integrally connect to each other by flange connection, i.e., by bringing the opposing flanges 32 and 35 in tight contact with each other through a packing 37 and inserting and fastening bolts (not shown) in the respective bolt insertion holes 33 and 36. In this case, the primary measuring tube 31A
connects to the secondary measuring tube 31B as it rotates through by 90 about the axis so that the primary pressure outlet 4 faces right sideways (horizontal direction). The bent tube 21 and primary measuring tube 31A flange-connect to each other similarly through a packing 38. The secondary measuring tube 31B flange-connects to the horizontal tube 20B
similarly through a packing 39 with the secondary pressure outlet 5 facing up.
The differential pressure gauge 10 comprises a container 12, a center diaphragm 14, primary and secondary pressure-receiving diaphragms 15 and 16, an arithmetic operation unit (not shown), and the like.
The container 12 seals a sealed liquid 11. The center diaphragm 14 partitions the interior of the container 12 into a primary pressure chamber 13a and secondary pressure chamber 13b. The primary and secondary pressure-receiving diaphragms 15 and 16 are arranged on the left and right side surfaces, respectively, of the container 12. The arithmetic processing unit converts the displacement of the center diaphragm 14 into an electrical signal and arithmetically processes it to calculate the flow rate of the measurement fluid 7 flowing in the measuring tube 31. A primary pressure guide tube 8 which guides the primary pressure PH in the measuring tube 31 to the differential pressure gauge 10 has one end that connects to the primary pressure outlet 4, and the other end that connects to an outer chamber 17a formed outside the primary pressure diaphragm 15.
Similarly, a secondary pressure guide tube 9 which guides the secondary pressure PL in the measuring tube 31 to the differential pressure gauge 10 has one end that connects to the secondary pressure outlet 5, and the other end that connects to an outer chamber 17b formed outside the secondary pressure diaphragm 16.
In the restriction flowmeter 30 having the above structure, when the measurement fluid 7, e.g., natural gas containing methane as the main component, flowing in the tube 20 flows to the measuring tube 31, the pressure changes before and after the elliptic restrictor 3. The differential pressure gauge 10 detects the differential pressure nP (PH - PL) to measure the flow rate of the measurement fluid 7 flowing in the measuring tube 31. More specifically, the primary pressure guide tube 8 guides the primary pressure PH of the measurement fluid 7 in the measuring tube 31 to the pressure-receiving diaphragm 15. The secondary pressure guide tube 9 guides the secondary pressure PL of the measurement fluid 7 in the measuring tube 31 to the pressure-receiving diaphragm 16. Hence, the pressure-receiving diaphragms 15 and 16 displace in accordance with the differential pressure AP. These displacements are transmitted to the center diaphragm 14 through the sealed liquid 11. The center diaphragm 14 displaces in accordance with the differential pressure nP. This displacement is converted into an electrical signal and arithmetically processed to measure a flow rate W of the measurement fluid 7 flowing in the measuring tube 31. The flow rate W can be obtained by the following equation (1):
W = CK = nP1/2 . . . ( 1) where C is an outflow coefficient, K is a constant (including the tube diameter, the density of the fluid, and the like), and nP is the differential pressure.
A recorder records the flow rate W and outputs it to an external device.
As described with reference to Fig. 5, the measurement fluid 7 flowing in the bent tube 21 forms a swirling flow to cause pressure fluctuation. The pressure becomes P1 outside the bend and P2 inside the bend to form a pressure gradient (P1 > P2) between the two pressures. Thus, in the primary measuring tube 31A
as well, depending on the height, the primary pressure PH changes in the same section (E - F) which is perpendicular to the axis and includes the primary pressure outlet 4. A pressure PH1 of the measurement fluid 7 flowing along the upper portion of the inner wall surface becomes high, and a pressure PH2 of the measurement fluid 7 flowing along the lower portion of the inner wall surface becomes low, and the pressure near the height of the axis becomes an almost average pressure PH. Thus, when the primary measuring tube 31A
connects to the secondary measuring tube 31B with the primary pressure outlet 4 facing up, the pressure PH1 which is higher than the average pressure PH of the measurement fluid 7 is guided to the differential pressure gauge 10 as the primary pressure. This causes a measurement error by a difference n(= PH1 - PH) from the average pressure PH to degrade the measurement accuracy.
As in this embodiment, if the primary measuring tube 31A connects to the secondary measuring tube 31B with the primary pressure outlet 4 facing almost sideways to have a height equal to that of the axis of the measuring tube 31, it can guide the almost average pressure of the pressures PHl and PH2 to the differential pressure gauge 10 as the primary pressure (PH). Thus, the pressure fluctuation does not cause a measurement error, so that the measurement accuracy can improve.
Since the average primary pressure PH can be extracted, a distance L1 from the primary open end to the primary pressure outlet 4 of the primary measuring tube 31A need not increase to 10D or more to convert the measurement fluid 7 flowing in the primary measuring tube 31A into a stable laminar flow. This can decrease the length of the measuring tube 31. As the elliptic restrictor 3 contracts the measurement fluid 7 that has passed through the primary measuring tube 31A, the pressure fluctuation of the secondary pressure PL is very small. Accordingly, the direction of the secondary pressure outlet 5 is not specified, but is desirably upward so no drain stays in the pressure guide tube 9.
In the embodiment described above, the measuring tube 31 connects to the bent tube 21 which is laid to bend in a vertical plane. When connecting a measuring tube 31 to a bent tube 21 which is laid to bend in a horizontal plane, the inner and outer sides of the bend of the bent tube 21 in which pressure fluctuation occurs are on one horizontal plane, and the average pressure is generated at the upper and lower portions of the inner wall surfaces. Therefore, in this case, a primary measuring tube 31A may connect to a secondary measuring tube 31B such that a primary pressure outlet 4 faces up.
In the embodiment described above, the primary measuring tube 31A is angularly adjusted every 45 with respect to the secondary measuring tube 31B. However, angular adjustment is not limited to this, but can be performed by, e.g., every 15 or 30 by increasing the number of bolt insertion holes.
The bent tube 21 is not limited to an elbow having a bend angle of 90 but may be an elbow having an appropriate bend angle other than 90 , e.g., 45 .
Fig. 3 shows a section showing the second embodiment of the present invention.
In this embodiment, the present invention is applied to a restriction flowmeter 42 which uses a Venturi tube 41 as the restrictor of a measuring tube 40.
The measuring tube 40 is dividedly formed of two portions to comprise a primary measuring tube 40A having a primary pressure outlet 43 and a secondary measuring tube 40B formed of a Venturi tube 41. The primary measuring tube 40A and secondary measuring tube 40B
flange-connect to each other. In the same manner as in the first embodiment described above, the primary measuring tube 40A flange-connects to the secondary measuring tube 40B, after being angularly adjusted about the axis in accordance with the setting situation (horizontal setting or vertical setting) of a bent tube 21, such that the height of an almost average pressure PH of a measurement fluid 7 flowing in the primary measuring tube 40A near the primary pressure outlet 43 coincides with the height of the primary pressure outlet 43. The primary pressure outlet 43 connects to a differential pressure gauge 10 through a primary pressure guide tube 8. The Venturi tube 41 has a secondary pressure outlet 44 at its minimal diameter portion. The secondary pressure outlet 44 connects to the differential pressure gauge 10 through a secondary pressure guide tube 9.
In the restriction flowmeter 42 which uses the Venturi tube 41 as the restrictor as well, when connecting the primary measuring tube 40A to the secondary measuring tube 40B after being angularly adjusted and extracting the average primary pressure PH, the same effect as that of the first embodiment can apparently be obtained.
Fig. 4 shows a section showing the third embodiment of the present invention.
In this embodiment, a measuring tube 50 comprises two members, i.e., a primary measuring tube 50A and secondary measuring tube 50B that are divisionally formed. The primary measuring tube 50A
flange-connects to the secondary measuring tube 50B
after being angularly adjusted about the axis. The primary measuring tube 50A has a primary pressure outlet 4 and flange-connects to a bent tube (not shown). The primary pressure outlet 4 connects to a differential pressure gauge 10 through a primary pressure guide tube 8. A restriction member 52 is disposed at the center of the interior of the secondary measuring tube 50B.
The front end face of the restriction member 52 of the secondary measuring tube 50B has the shape of a hemispherical bombshell. A support beam 54 supports the rear end of the restriction member 52. The axis of the restriction member 52 almost coincides with that of the secondary measuring tube 50B. An annular restriction space 55 forms between the outer surface of the restriction member 52 and the inner wall surface of the secondary measuring tube 50B. The restriction space 55 causes pressures PH and PL in a measurement fluid 7 flowing in the measuring tube 50.
First and second passages 56 and 57 form in the restriction member 52 to be perpendicular to each other. The first passage 56 extends in the radial direction of the restriction member 52 and has one end that opens to the maximal diameter portion of the outer surface of the restriction member 52 to form a secondary pressure outlet 56a. The inner end of the first passage 56 is located at the center of the interior of the restriction member 52 and connects to the second passage 57. The second passage 57 extends through the center of the interior of the restriction member 52 in the axial direction. The front end of the second passage 57 communicates with the first passage 56. The rear end of the second passage 57 extends through a passage 58 formed in the support beam 54 and connects to the differential pressure gauge 10 through a secondary pressure guide tube 9.
In the restrictor flowmeter comprising the restriction member 52 as well, if the primary measuring tube 50A connects to the secondary measuring tube 50B
after being angularly adjusted and the average primary pressure PH is extracted, the same effect as that of the first embodiment described above can apparently be obtained.
Industrial Applicability The restrictor flowmeter according to the present invention is effectively used in measurement of the flow rate of a measurement fluid such as natural gas.
As described with reference to Fig. 5, the measurement fluid 7 flowing in the bent tube 21 forms a swirling flow to cause pressure fluctuation. The pressure becomes P1 outside the bend and P2 inside the bend to form a pressure gradient (P1 > P2) between the two pressures. Thus, in the primary measuring tube 31A
as well, depending on the height, the primary pressure PH changes in the same section (E - F) which is perpendicular to the axis and includes the primary pressure outlet 4. A pressure PH1 of the measurement fluid 7 flowing along the upper portion of the inner wall surface becomes high, and a pressure PH2 of the measurement fluid 7 flowing along the lower portion of the inner wall surface becomes low, and the pressure near the height of the axis becomes an almost average pressure PH. Thus, when the primary measuring tube 31A
connects to the secondary measuring tube 31B with the primary pressure outlet 4 facing up, the pressure PH1 which is higher than the average pressure PH of the measurement fluid 7 is guided to the differential pressure gauge 10 as the primary pressure. This causes a measurement error by a difference n(= PH1 - PH) from the average pressure PH to degrade the measurement accuracy.
As in this embodiment, if the primary measuring tube 31A connects to the secondary measuring tube 31B with the primary pressure outlet 4 facing almost sideways to have a height equal to that of the axis of the measuring tube 31, it can guide the almost average pressure of the pressures PHl and PH2 to the differential pressure gauge 10 as the primary pressure (PH). Thus, the pressure fluctuation does not cause a measurement error, so that the measurement accuracy can improve.
Since the average primary pressure PH can be extracted, a distance L1 from the primary open end to the primary pressure outlet 4 of the primary measuring tube 31A need not increase to 10D or more to convert the measurement fluid 7 flowing in the primary measuring tube 31A into a stable laminar flow. This can decrease the length of the measuring tube 31. As the elliptic restrictor 3 contracts the measurement fluid 7 that has passed through the primary measuring tube 31A, the pressure fluctuation of the secondary pressure PL is very small. Accordingly, the direction of the secondary pressure outlet 5 is not specified, but is desirably upward so no drain stays in the pressure guide tube 9.
In the embodiment described above, the measuring tube 31 connects to the bent tube 21 which is laid to bend in a vertical plane. When connecting a measuring tube 31 to a bent tube 21 which is laid to bend in a horizontal plane, the inner and outer sides of the bend of the bent tube 21 in which pressure fluctuation occurs are on one horizontal plane, and the average pressure is generated at the upper and lower portions of the inner wall surfaces. Therefore, in this case, a primary measuring tube 31A may connect to a secondary measuring tube 31B such that a primary pressure outlet 4 faces up.
In the embodiment described above, the primary measuring tube 31A is angularly adjusted every 45 with respect to the secondary measuring tube 31B. However, angular adjustment is not limited to this, but can be performed by, e.g., every 15 or 30 by increasing the number of bolt insertion holes.
The bent tube 21 is not limited to an elbow having a bend angle of 90 but may be an elbow having an appropriate bend angle other than 90 , e.g., 45 .
Fig. 3 shows a section showing the second embodiment of the present invention.
In this embodiment, the present invention is applied to a restriction flowmeter 42 which uses a Venturi tube 41 as the restrictor of a measuring tube 40.
The measuring tube 40 is dividedly formed of two portions to comprise a primary measuring tube 40A having a primary pressure outlet 43 and a secondary measuring tube 40B formed of a Venturi tube 41. The primary measuring tube 40A and secondary measuring tube 40B
flange-connect to each other. In the same manner as in the first embodiment described above, the primary measuring tube 40A flange-connects to the secondary measuring tube 40B, after being angularly adjusted about the axis in accordance with the setting situation (horizontal setting or vertical setting) of a bent tube 21, such that the height of an almost average pressure PH of a measurement fluid 7 flowing in the primary measuring tube 40A near the primary pressure outlet 43 coincides with the height of the primary pressure outlet 43. The primary pressure outlet 43 connects to a differential pressure gauge 10 through a primary pressure guide tube 8. The Venturi tube 41 has a secondary pressure outlet 44 at its minimal diameter portion. The secondary pressure outlet 44 connects to the differential pressure gauge 10 through a secondary pressure guide tube 9.
In the restriction flowmeter 42 which uses the Venturi tube 41 as the restrictor as well, when connecting the primary measuring tube 40A to the secondary measuring tube 40B after being angularly adjusted and extracting the average primary pressure PH, the same effect as that of the first embodiment can apparently be obtained.
Fig. 4 shows a section showing the third embodiment of the present invention.
In this embodiment, a measuring tube 50 comprises two members, i.e., a primary measuring tube 50A and secondary measuring tube 50B that are divisionally formed. The primary measuring tube 50A
flange-connects to the secondary measuring tube 50B
after being angularly adjusted about the axis. The primary measuring tube 50A has a primary pressure outlet 4 and flange-connects to a bent tube (not shown). The primary pressure outlet 4 connects to a differential pressure gauge 10 through a primary pressure guide tube 8. A restriction member 52 is disposed at the center of the interior of the secondary measuring tube 50B.
The front end face of the restriction member 52 of the secondary measuring tube 50B has the shape of a hemispherical bombshell. A support beam 54 supports the rear end of the restriction member 52. The axis of the restriction member 52 almost coincides with that of the secondary measuring tube 50B. An annular restriction space 55 forms between the outer surface of the restriction member 52 and the inner wall surface of the secondary measuring tube 50B. The restriction space 55 causes pressures PH and PL in a measurement fluid 7 flowing in the measuring tube 50.
First and second passages 56 and 57 form in the restriction member 52 to be perpendicular to each other. The first passage 56 extends in the radial direction of the restriction member 52 and has one end that opens to the maximal diameter portion of the outer surface of the restriction member 52 to form a secondary pressure outlet 56a. The inner end of the first passage 56 is located at the center of the interior of the restriction member 52 and connects to the second passage 57. The second passage 57 extends through the center of the interior of the restriction member 52 in the axial direction. The front end of the second passage 57 communicates with the first passage 56. The rear end of the second passage 57 extends through a passage 58 formed in the support beam 54 and connects to the differential pressure gauge 10 through a secondary pressure guide tube 9.
In the restrictor flowmeter comprising the restriction member 52 as well, if the primary measuring tube 50A connects to the secondary measuring tube 50B
after being angularly adjusted and the average primary pressure PH is extracted, the same effect as that of the first embodiment described above can apparently be obtained.
Industrial Applicability The restrictor flowmeter according to the present invention is effectively used in measurement of the flow rate of a measurement fluid such as natural gas.
Claims (3)
1. A restrictor flowmeter characterized by comprising a measuring tube through which a measurement fluid is to flow, wherein said measuring tube is divided into a primary measuring tube and a secondary measuring tube, the primary measuring tube having a primary pressure outlet and the secondary measuring tube having a secondary pressure outlet and a restrictor, and the primary measuring tube connects to the secondary measuring tube to be angularly adjustable about an axis.
2. A restrictor flowmeter according to claim 1, characterized in that said primary measuring tube connects to downstream of a bent tube, and connects to said secondary measuring tube, after being angularly adjusted about the axis, such that a height of the primary pressure outlet substantially coincides with that of an average primary pressure of the measurement fluid which flows near said primary pressure outlet.
3. A restrictor flowmeter according to claim 1 or 2, characterized in that a restrictor arranged in said secondary measuring tube is any one of a Venturi tube, an elliptic restrictor, and a restrictor member having a bombshell shape.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2004/007931 WO2005121715A1 (en) | 2004-06-07 | 2004-06-07 | Restriction flowmeter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2567284A1 CA2567284A1 (en) | 2005-12-22 |
| CA2567284C true CA2567284C (en) | 2012-10-09 |
Family
ID=35503179
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2567284A Expired - Fee Related CA2567284C (en) | 2004-06-07 | 2004-06-07 | Restriction flowmeter |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2567284C (en) |
| WO (1) | WO2005121715A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105698877B (en) * | 2016-01-22 | 2018-11-30 | 重庆赫皇科技咨询有限公司 | A kind of fluids within pipes flow rate measuring system and method |
| JP2019196785A (en) * | 2018-05-08 | 2019-11-14 | 株式会社日立製作所 | Swirl flow adjustment device |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5631607A (en) * | 1979-08-23 | 1981-03-31 | Nippon Steel Corp | Venturi tube |
| JPH1096656A (en) * | 1996-09-24 | 1998-04-14 | Oval Corp | Vapor and liquid two-phase flow meter |
| JP3122984B2 (en) * | 1996-11-29 | 2001-01-09 | 株式会社山武 | Throttle flow meter |
| JP3182719B2 (en) * | 1997-03-14 | 2001-07-03 | 株式会社山武 | Throttle mechanism of throttle flow meter |
| JP2002372444A (en) * | 2001-06-14 | 2002-12-26 | Mitsubishi Heavy Ind Ltd | Flow rate measuring pressure detector and its manufacturing method |
-
2004
- 2004-06-07 CA CA2567284A patent/CA2567284C/en not_active Expired - Fee Related
- 2004-06-07 WO PCT/JP2004/007931 patent/WO2005121715A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| WO2005121715A1 (en) | 2005-12-22 |
| CA2567284A1 (en) | 2005-12-22 |
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