METHOD OF CORRECTING FLOW METER VARIABLE

Abstract

A method for correcting a flow variable (509) based on an inner pressure inside a Coriolis flow meter (202) comprises the steps of receiving a first outside pressure (503) measured with a first pressure sensor (204) located in a first process conduit (208a) positioned on a first end (212a) of the Coriolis flow meter (202), determining a second outside pressure (505) in a second process conduit (208b) positioned on a second end (212b) opposing the first end (212a) of the Coriolis flow meter (202), determining an estimated inner flow meter pressure (507) based on the first outside pressure (503) and the second outside pressure (505), receiving the flow variable (509), and generating a corrected flow variable (512) based on the estimated inner flow meter pressure (507), a pressure compensation factor (510), and the flow variable (509).

Claims

1. A method for correcting a flow variable (509) based on an inner pressure inside a Coriolis flow meter (202), the method comprising: receiving a first outside pressure (503) measured with a first pressure sensor (204) located in a first process conduit (208a) positioned on a first end (212a) of the Coriolis flow meter (202); determining a second outside pressure (505) in a second process conduit (208b) positioned on a second end (212b) opposing the first end (212a) of the Coriolis flow meter (202); determining an estimated inner flow meter pressure (507) based on the first outside pressure (503) and the second outside pressure (505); receiving the flow variable (509); and generating a corrected flow variable (512) based on the estimated inner flow meter pressure (507), a pressure compensation factor (510), and the flow variable (509).

2. A method as claimed in claim 1, wherein determining the second outside pressure (505) is based on a pressure loss coefficient, a fluid velocity, a fluid viscosity, and a density.

3. The method as claimed in claim 1, wherein determining the second outside pressure (505) further comprises receiving a second outside pressure measurement from a second pressure sensor (206) located in the second process conduit (208b).

4. A method as claimed in claim 1, wherein determining the estimated inner flow meter pressure (507) based on the first outside pressure (503) and the second outside pressure (505) further comprises averaging the first outside pressure (503) and the second outside pressure (505).

5. A method as claimed in claim 1, wherein determining the estimated inner pressure is further based on a cross-sectional area of a process conduit, a diameter of the process conduit, a cross-sectional area of a flow tube of the Coriolis flow meter (202), a measured density ρ, and a measured flow rate M.

6. A method as claimed in claim 1, wherein the pressure compensation factor (510) is correlated to a pressure inside the flow tubes.

7. A method as claimed in claim 1, wherein the flow variable (509) is at least one of: a mass flow, a volume flow, or a density.

8. A method as claimed in claim 1, wherein determining the estimated inner flow meter pressure (507) is further based on a flow meter direction.

9. An electronics for correcting a flow variable (509) based on an inner pressure inside a Coriolis flow meter (202), the electronics comprising an interface for receiving a first outside pressure (503) from a first pressure sensor (204), and a processing system in communication with the interface, with the processing system configured to: receive a first outside pressure (503) measured with a first pressure sensor (204) located in a first process conduit (208a) positioned on a first end (212a) of the Coriolis flow meter (202); determine a second outside pressure (505) in a second process conduit (208b) positioned on a second end (212b) opposing the first end (212a) of the Coriolis flow meter (202); determine an estimated inner flow meter pressure (507) based on the first outside pressure (503) and the second outside pressure (505); receive the flow variable (509); and generate a corrected flow variable (512) based on the estimated inner flow meter pressure (507), a pressure compensation factor (510), and the flow variable (509).

10. An electronics as claimed in claim 9, wherein the processing system is further configured to determine the second outside pressure (505) based on a pressure loss coefficient, a fluid velocity, a fluid viscosity, and a density.

11. An electronics as claimed in claim 9, wherein the processing system is further configured to determine the second outside pressure (505) by receiving a second outside pressure measurement from a second pressure sensor (206) located in the second process conduit (208b).

12. An electronics as claimed in claim 9, wherein the processing system is further configured to determine the estimated inner flow meter pressure (507) based on the first outside pressure (503) and the second outside pressure (505) by averaging the first outside pressure (503) and the second outside pressure (505).

13. An electronics as claimed in claim 9, wherein the processing system is further configured to determine the estimated inner pressure based on a cross-sectional area of a process conduit, a diameter of the process conduit, a cross-sectional area of a flow tube of the Coriolis flow meter (202), a measured density ρ, and a measured flow rate M.

14. An electronics as claimed in claim 9, wherein the pressure compensation factor (510) is correlated to a pressure inside the flow tubes.

15. An electronics as claimed in claim 9, wherein the flow variable (509) is at least one of: a mass flow, a volume flow, or a density.

16. An electronics as claimed in claim 9, wherein determining the estimated inner flow meter pressure (507) is further based on a flow meter direction.

17. A flow meter correction system configured to correct a flow variable (509) based on an inner pressure inside a Coriolis flow meter (202), the system comprising: a first pressure receiving module configured to receive a first outside pressure (503) from a first pressure sensor (204) located in a first process conduit (208a) positioned on a first end (212a) of the Coriolis flow meter (202); a second pressure receiving module for determining a second outside pressure (505) in a second process conduit (208b) positioned on a second end (212b) opposing the first end (212a) of the Coriolis flow meter (202); an inner flow meter pressure estimation module configured to determine an estimated inner flow meter pressure (507) based on the first outside pressure (503) and the second outside pressure (505); a flow variable receiving module configured to receive a flow variable (509); and a flow variable correction module configured to generate a corrected flow variable (512) based on the estimated inner flow meter pressure (507), a pressure compensation factor (510), and the flow variable (509).

18. A flow meter correction system as claimed in claim 17, wherein the second pressure receiving module is further configured to determine the second outside pressure (505) based on a pressure loss coefficient, a fluid velocity, a fluid viscosity, and a density.

19. A flow meter correction system as claimed in claim 17, wherein the second pressure receiving module is further configured to receive a second outside pressure measurement from a second pressure sensor (206) located in the second process conduit (208b).

20. A flow meter correction system as claimed in claim 17, wherein the inner flow meter pressure estimation module is further configured to average the first outside pressure (503) and the second outside pressure (505).

21. A flow meter correction system as claimed in claim 17, wherein the inner flow meter pressure estimation module is further configured to determine the estimated inner pressure based on a cross-sectional area of a process conduit, a diameter of the process conduit, a cross-sectional area of a flow tube of the Coriolis flow meter (202), a measured density ρ, and a measured flow rate M.

22. A flow meter correction system as claimed in claim 17, wherein the pressure compensation factor (510) is correlated to a pressure inside the flow tubes.

23. A flow meter correction system as claimed in claim 17, wherein the flow variable (509) is at least one of: a mass flow, a volume flow, or a density.

24. A flow meter correction system as claimed in claim 17, wherein the inner flow meter pressure estimation module is further configured to determine the estimated inner flow meter pressure (507) based on a flow meter direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The same reference number represents the same element on all drawings. It should be understood that the drawings are not necessarily to scale.

[0039] FIG. 1 depicts a flow meter 100, in accordance with an embodiment;

[0040] FIG. 2 depicts a flow meter system 200, in accordance with an embodiment;

[0041] FIG. 3 depicts a method 300, in accordance with an embodiment;

[0042] FIG. 4 depicts electronics 400, in accordance with an embodiment; and

[0043] FIG. 5 depicts system 500, in accordance with an embodiment.

DETAILED DESCRIPTION

[0044] FIGS. 2-5 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the Application. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the Application. Those skilled in the art will appreciate that the features described below may be combined in various ways to form multiple variations of the Application. As a result, the Application is not limited to the specific examples described below, but only by the claims and their equivalents.

[0045] FIG. 2 depicts flow meter system 200, in accordance with an embodiment. Flow meter system 200 may be used to correct a flow variable based on an inner pressure inside a Coriolis flow meter. Flow meter system 200 may include a Coriolis flow meter 202, a first pressure sensor 204, a first process conduit 208a, a second process conduit 208b, and an electronics 210.

[0046] In embodiments, Coriolis flow meter 202 may be similar to Coriolis flow meter sensor 100. In further embodiments, however, the Coriolis flow meter 202 sensor may include a different configuration. For example, Coriolis flow meter 202 may comprise one or more flow tubes that are straight or curved, as will be understood by those of skill.

[0047] In FIG. 2, the process fluid enters and exits Coriolis flow meter 202 via first process conduit 208a and second process conduit 208b. In the embodiment depicted, first process conduit 208a is associated with a fluid inlet at a first end 212a, and second process conduit 208b is associated with a fluid outlet at a second end 212b of Coriolis flow meter 202. This is not intended to be limiting, however. In embodiments, second process conduit 208b and second end 212b may be associated with an inlet. In further embodiments, flow meter system 200 may be bidirectional, meaning that each of first end 212a and second end 212b may alternatingly serve as an inlet or an outlet.

[0048] In embodiments, first pressure sensor 204 may comprise any type of sensor, including, but not restricted to a resistive, capacitive, piezoelectric, optical, or MEMS pressure sensor or transducer.

[0049] In embodiments, flow meter system 200 may further comprise an electronics 210. Electronics 210 may be used to correct a flow variable based on an inner pressure within the Coriolis flow meter 202. In embodiments, electronics 210 may provide a corrected flow variable to an operator.

[0050] Electronics 210 is in communication with first pressure sensor 204 and either a meter electronics 20 or a meter assembly 10 associated with Coriolis flow meter 202. In further embodiments, electronics 210 may further be in communication with second pressure sensor 206. In embodiments, electronics 210 may provide a further interface to provide corrected flow variable information to an operator.

[0051] In embodiments, flow meter system 200 may comprise both electronics 210 and a meter electronics 20 associated with Coriolis flow meter 202. Alternatively, electronics 210 may comprise the only electronics for flow meter system 200, meaning that electronics 210 further provides the functions described with regards to meter electronics 20 above for Coriolis flow meter 202.

[0052] In further embodiments, flow meter system 200 may comprise a second pressure sensor 206. Second pressure sensor 206 may be the same type as, or a different type from first pressure sensor 204.

[0053] FIG. 3 depicts method 300, in accordance with an embodiment. Method 300 may be used to correct a flow variable based on an inner pressure inside a Coriolis flow meter. In embodiments, method 300 may be executed by electronics 210. In embodiments, the flow variable may comprise at least one of a mass flow, a volume flow, or a density measurement.

[0054] Method 300 begins with step 302. In step 302, a first outside pressure measured with a first pressure sensor located in a first process conduit positioned on a first end of the Coriolis flow meter is received. For example, a signal may be received from first pressure sensor 204 indicating a pressure of a process fluid in first process conduit 208a positioned at first end 212a.

[0055] Method 300 continues with step 304. In step 304, a second outside pressure in a second process conduit positioned on a second end opposing the first end of the Coriolis flow meter is determined.

[0056] In embodiments, determining the second outside pressure may be based on one or more pressure loss coefficients that are characteristic of the meter, in addition to a fluid velocity, a density, and a viscosity. The physics causing the pressure drop experienced by viscous flows across a section of conduit is described in several classic introduction to fluid mechanics textbooks. The one or more pressure loss coefficients characterize the pressure loss across at least a section of Coriolis flow meter, for example Coriolis flow meter 202. In embodiments, one or more of the pressure loss coefficients may comprise one or more predetermined values measured at the factory or determined based on a computational model. In embodiments, the one or more pressure loss coefficients may represent losses due to pipe friction and/or the physical features of the flow meter such as manifolds 150, 150′, flanges 103, 103′, the bends in the flow tubes 130, 130′, or any other physical feature known to those of skill. The fluid velocity may be determined based on a mass flow rate and density measured with Coriolis flow meter 202, and the cross-sectional area of the flow tube 130, 130′. With the pressure loss coefficient and fluid velocity, it is possible to determine a second outside pressure using the Darcy-Weisbach equation, or any other method known to those of skill.

[0057] In embodiments, fluid viscosity may be measured outside of flow meter system 200 and transmitted to electronics 210, or it may be entered by an operator based on a known process fluid. The density may be measured by Coriolis flow meter 202.

[0058] In further embodiments, determining the second outside pressure may comprise receiving a second outside pressure measurement located in the second process conduit. For example, in embodiments of flow meter system 200 that include second pressure sensor 206, it may be possible to determine the second outside pressure using second pressure sensor 206.

[0059] Method 300 continues with step 306. In step 306, an estimated inner flow meter pressure is determined based on the first outside pressure and the second outside pressure.

[0060] In embodiments, determining the estimated inner flow meter pressure comprises averaging the first outside pressure and the second outside pressure. For example, an estimated inner flow meter pressure P.sub.inner_1A may be determined via Equation 1A:

P.sub.inner_1A=½(P.sub.upstream+P.sub.downstream)=P.sub.upstream−½Δp.  (Equation 1A)

In Equation 1A, P.sub.upstream may comprise the first outside pressure, and P.sub.downstream may comprise the second outside pressure. Δp represents the pressure loss between the first outside pressure and the second outside pressure, which in embodiments may comprise the pressure loss over Coriolis flow meter 202, or over Coriolis flow meter 202 and parts of first process conduit 208a and second process conduit 208b.

[0061] In further embodiments, determining an estimated inner flow meter pressure based on the first outside pressure and the second outside pressure may further comprise accounting for a Bernoulli effect in the estimated inner flow meter pressure. Accounting for the Bernoulli effect in the estimated inner flow meter pressure may further comprise determining the estimated inner pressure based on a cross-sectional area of a process conduit, a diameter of the process conduit, a cross-sectional area of a flow tube of the Coriolis flow meter, a measured density ρ, and a measured mass flow rate M.

[0062] In embodiments, Equation 2 may be used to further correct the estimated inner flow meter pressure P.sub.inner_1, which may comprise the estimated inner flow meter pressure P.sub.inner_1A described in Equation TA or the estimated inner flow meter pressure P.sub.inner_1B described in Equation 1B below, to provide a further estimated inner flow meter pressure P.sub.inner_2:

P.sub.inner_2=P.sub.inner_1+½×ρ×v.sub.pipe.sup.2−½×ρ×v.sub.meter.sup.2.  (Equation 2)

In Equation 2, P.sub.inner_2 represents an estimated pressure in the flow tubes 130, 130′ after correction for the Bernoilli effect, ρ represents the density of the process fluid measured by Coriolis flow meter 202, v.sub.pipe represents the velocity of the process fluid in the first process conduit 208a where first pressure sensor 204 is located, and v.sub.meter represents the velocity of the process fluid in flow tubes 130, 130′. Equation 3 provides the velocity of the process fluid v.sub.pipe in the first process conduit 208a:

[00001]$\begin{array}{cc}{v}_{\mathrm{pipe}}=\frac{M}{\rho \times A_{\mathrm{pipe}}}=\frac{M}{\rho \times \frac{\pi d^2}{4}}.& \left(\mathrm{Equation}3\right)\end{array}$

In Equation 3, M is the mass flow rate measured by Coriolis flow meter 202, A.sub.pipe is the cross-sectional area of first process conduit 208a, and d is the diameter of first process conduit 208a. Equation 4 provides the velocity of the process fluid v.sub.meter in the flow tubes 130,130′:

[00002]$\begin{array}{cc}{v}_{\mathrm{meter}}=\frac{M}{\rho \times A_{\mathrm{meter}}}.& \left(\mathrm{Equation}4\right)\end{array}$

In Equation 4, A.sub.meter is the combined cross-sectional area of flow tubes 130, 130′ of Coriolis flow meter 202.

[0063] In embodiments, estimated inner flow meter pressure P.sub.inner_1 and further estimated inner flow meter pressure P.sub.inner_2 may allow for a more accurate correction of a flow meter variable for changes in meter stiffness.

[0064] In embodiments of flow meter system 200, Coriolis flow meter 202 may support both installations where a second pressure sensor 206 is located downstream in the second process conduit 208b and installations where the meter is used for bidirectional flow measurement such that pressure sensors 204 and/or 206 will be alternately located upstream or downstream as the flow direction alternates between forward and backward. Determining the estimated inner flow meter pressure may therefore be further based on a flow meter direction. In further embodiments of step 306, when the flow direction is reversed during bidirectional flow, P.sub.upstream may comprise a pressure inside second process conduit 208b, and P.sub.downstream may comprise a pressure inside first process conduit 208a. In such embodiments where only one pressure transmitter is available and it happens to be in the downstream position, Equation 1A may take the alternative form:

P.sub.inner_1B=½(P.sub.upstream+P.sub.downstream)=P.sub.downstream+½Δp.  (Equation 1B)

[0065] Method 300 continues with step 308. In step 308, the flow variable is received. In embodiments, the flow variable may comprise a density, a mass flow, or a volumetric flow of process fluid measured with Coriolis flow meter 202. In embodiments, the flow variable may be received from a meter electronics 20 associated with Coriolis flow meter 202, it may be read out of electronic storage from electronics 210, or it may be determined using raw pick-off sensor data received from a meter assembly 10 of Coriolis flow meter 202.

[0066] Method 300 continues with step 310. In step 310, a corrected flow variable is generated based on the estimated inner flow meter pressure, a pressure compensation factor, and the flow variable. The corrected flow variable represents the measured flow variable corrected for a change in pressure in the flow tubes.

[0067] The pressure compensation factor relates the pressure within the flow meter to a measurement correction for the change in flow tube stiffness. In embodiments, the pressure compensation factor may be determined during type-testing at the flow meter factory. The pressure compensation factor may be related to a particular model of flowmeter, a family of flow meter models comprising a similar size and design, or a single flow meter.

[0068] In embodiments, the corrected flow variable may be determined by multiplying the pressure compensation factor by the inner flow meter pressure. For example, Equation 5 may be used:

X.sub.corrected=X.sub.measured+(P.sub.inner−P.sub.baseline)*K,  (Equation 5)

where X.sub.corrected is the corrected flow variable, X.sub.measured is the measured flow variable, P.sub.inner is the estimated inner flow meter pressure, corresponding to P.sub.inner_1 or P.sub.inner_2 described above, P.sub.baseline is the pressure that was recorded as the inner pressure at the time when the meter was last calibrated against a reference standard, and K is the pressure compensation factor.

[0069] In embodiments, pressure compensation factor K may be correlated to the pressure inside the flow tubes during type testing. This may provide an improved correction of a flow variable for pressure over the prior art methods that use a pressure compensation factor K correlated to a position of the first pressure sensor 204.

[0070] FIG. 4 depicts an electronics 400 in accordance with an embodiment. Electronics 400 comprises a processing system 402, a storage system 404, and an interface 406. Electronics 400 may be used to correct a flow variable based on an inner pressure inside a Coriolis flow meter.

[0071] Processing system 402 may be configured to execute computer instructions, which, when executed on electronics 400, perform a portion or all of the methods described in relation to FIGS. 3 and 5. In embodiments, processing system 402 may include a single, or any multiple number of processors, as will be understood by those of skill in the art.

[0072] Storage system 404 may be an electronically readable medium or a computer readable medium configured to store computer program instructions. In examples, storage system 404 may include a non-transitory medium. Stored computer program instructions, when executed on the processing system 402, may perform a portion or all of the methods described in relation to FIGS. 3 and 5.

[0073] In examples, processing system 402 and storage system 404 may be incorporated into a custom chipset, such as a system on a chip.

[0074] In examples, portions of the methods described in relation to FIGS. 3 and 5 may be stored or executed outside of electronics 400. For example, a portion of the methods described in relation to FIGS. 3 to 5 may be stored or executed on a combination of a server and cloud storage facility via the Internet.

[0075] Interface 406 may be configured to communicate with devices external to electronics 400. Through interface 406, electronics 400 may communicate with first pressure sensor 204. Interface 406 may further communicate with a meter electronics 20 internal to Coriolis flow meter 202, or an external control room computer.

[0076] In embodiments, electronics 400 may comprise meter electronics 20. In further embodiments, however, electronics 400 may comprise a separate electronics in communication with a meter electronics 20.

[0077] FIG. 5 depicts a flow meter correction system 500 in accordance with an embodiment. Flow meter correction system 500 may be used to correct a flow variable based on an inner pressure inside a Coriolis flow meter 202 within flow meter system 200.

[0078] Flow meter correction system 500 comprises a first pressure receiving module 502. First pressure receiving module 502 is configured to receive a first outside pressure 503 from a first pressure sensor 204 located in a first process conduit 208a positioned on a first end 212a of the Coriolis flow meter 202. In embodiments, pressure receiving module 502 may execute step 302 of method 300, as described above.

[0079] Flow meter correction system 500 further comprises a second pressure receiving module 504. Second pressure receiving module 504 is configured to determine a second outside pressure 505 in a second process conduit 208b positioned on a second end 212b opposing the first end 212a of the Coriolis flow meter 202. In embodiments, second pressure receiving module 504 may execute step 304 of method 300, as described above.

[0080] Flow meter correction system 500 further comprises an inner flow meter pressure estimation module 506. Inner flow meter pressure estimation module 506 is configured to determine an estimated inner flow meter pressure 507 based on the first outside pressure 503 and the second outside pressure 505. In embodiments, inner flow meter pressure estimation module 506 may execute step 306 of method 300 or any variations thereof that are described above.

[0081] Flow meter correction system 500 further comprises a flow variable receiving module 508. Flow variable receiving module 508 is configured to receive a flow variable 509. In embodiments, flow variable receiving module 508 may execute step 308 of method 300, as described above.

[0082] Flow meter correction system 500 further comprises a flow variable correction module 511. Flow variable correction module 511 is configured to generate a corrected flow variable 512 based on the estimated inner flow meter pressure 507, a pressure compensation factor 510, and the flow variable 509. In embodiments, flow variable correction module 511 may execute step 310, as described above.

[0083] The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the present description. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the present description. Accordingly, the scope of the embodiments described above should be determined from the following claims.