Bypass type coriolis effect flowmeter

• US 5,861,561 A
• Filed: 02/25/1997
• Issued: 01/19/1999
• Est. Priority Date: 01/17/1996
• Status: Expired due to Term

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Inventors: Loving, Roger Scott, Van Cleve, Craig Brainerd
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): PATEL, HARSHAD R
• Application Number:
  US08/805,474
• Time in Patent Office: 693 Days
• Field of Search: 73/861.355, 73/861.356, 73/861.357, 73/54.06, 73/54.24, 73/202, 73/861.61, 73/861.63, 73/861.64
• US Class Current: 73/861.52
• CPC Class Codes: G01F 1/8404 details of flowmeter manufacturing methods
• CPC Class Codes: G01F 1/8495 with multiple measuring conduits
• CPC Class Codes: G01F 15/024 involving digital counting
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow

Abstract

A bypass flowmeter for measuring the material flow in a conduit. An optimum pressure drop is developed across the flowmeter by coupling the material outlet of the flowmeter to the throat of a venturi positioned within the conduit. This increased pressure drop improves the material flow rate through the flowmeter. This enhances flowmeter accuracy and sensitivity and the flowmeter'"'"'s ability to measure mass flow rates for low density materials such as gas. The ratio of the material flow within the flowmeter to that of the conduit is derived with improved precision over prior arrangements which assume a constant ratio of material flow between the flowmeter and the conduit. The material flow information for the conduit is obtained for materials having a varying viscosity by the use of a differential pressure sensor which measures the pressure drop across the flowmeter and transmits this information to instrumentation which uses it to derive material flow information for the conduit with improved precision. An alternative embodiment not having a venturi operates in the same manner to derive the material flow ratio between the flowmeter and the conduit and, in turn, the total material flow in the conduit.

Claims

1. Flow measurement apparatus for measuring material flow in a conduit, said apparatus comprising:

a flowmeter;

a material inlet for diverting some of said material flow in said conduit to said flowmeter, wherein said material inlet is positioned within an interior of said conduit and coupled to said flowmeter;

a material outlet for returning material flowing in said flowmeter to said conduit, wherein said material outlet is positioned within said interior of said conduit and coupled to said flowmeter;

means for determining the mass flow rate and flow velocity and density of said material flow in said flowmeter;

means responsive to said determination of said mass flow rate and said flow velocity and density of said material flow in said flowmeter for determining the flow velocity and mass flow rate of said material in a portion of said conduit between said material inlet and said material outlet; and

means responsive to said determination of said mass flow rate in said flowmeter and in said conduit portion for determining a total mass flow rate of said material in said conduit.

2. The apparatus of claim 1 wherein said means for determining said flow velocity and mass flow rate of said material in a portion of said conduit between said material inlet and said material outlet comprises a means for determining the ratio of the flow velocity between said material in said flowmeter and said material in said portion of said conduit.

3. The apparatus of claim 1 further comprising:

means for determining the viscosity of said material in said flowmeter;

means responsive to said determination of said viscosity and to said determination of said flow velocity and said mass flow rate and said density of said material in said flowmeter for determining said flow velocity and said mass flow rate of said material in said portion of said conduit; and

said means responsive to said determination of said flow velocity and mass flow rate of said material in said conduit portion determines said total material mass flow rate in said conduit.

4. The apparatus of claim 3 wherein said means for determining said flow velocity and mass flow rate of said material in said portion of said conduit between said material inlet and said material outlet comprises a means for determining the ratio of the flow velocity between said material in said flowmeter and said material in said portion of said conduit.

5. The apparatus of claim 1 wherein said flowmeter comprises a Coriolis mass flowmeter.

6. The apparatus of claim 5 wherein said Coriolis mass flowmeter further comprises:

pressure sensing means coupled to said material inlet and to said material outlet for producing a measurement of a material pressure drop between said material inlet and said material outlet; and

means responsive to said measurement of said material pressure drop for determining the viscosity of said flowing material.

7. The apparatus of claim 6 wherein said means for determining said total mass flow rate of said material in said conduit comprises:

said means for determining said flow velocity and said mass flow rate of said material in said flowmeter as well as said material density and said material viscosity; and

said means responsive to said determination of said flow velocity, mass flow rate, density and viscosity of said material in said flowmeter determines said mass flow rate of said material in said portion of said conduit between said material inlet and said material outlet.

8. The apparatus of claim 1 wherein said flowmeter is a volumetric flowmeter.

9. The apparatus of claim 1 further comprising:

means for increasing said flow velocity of said material in said conduit at a conduit location proximate said material outlet between said material inlet and said material outlet;

said material outlet being coupled to said conduit at said location having an increased flow velocity of said material in said conduit for generating an optimum pressure drop between said material inlet and said material outlet to increase said flow velocity of said material within said flowmeter.

10. The apparatus of claim 9 wherein said flowmeter comprises a Coriolis mass flowmeter.

11. The apparatus of claim 10 wherein said Coriolis mass flowmeter further comprises:

pressure sensing means coupled to said material inlet and to said material outlet for producing a measurement of a material pressure drop between said material inlet and said material outlet; and

means responsive to said measurement of said material pressure drop for determining the viscosity of said flowing material.

12. The apparatus of claim 11 wherein said means for determining said total mass flow rate of said material in said conduit comprises:

said means for determining said flow velocity and said mass flow rate and said density as well as said viscosity of said material in said flowmeter;

means responsive to said determination of flow velocity, mass flow rate, density and viscosity of said material in said flowmeter for determining said flow velocity and mass flow rate of said material in said conduit portion of increased flow velocity; and

said means responsive to said determination of said flow velocity and mass flow rate of said material in said conduit portion determines said total mass flow rate of said material in said conduit.

13. The apparatus of claim 9 wherein said flowmeter is a Coriolis mass flowmeter;

and

wherein said means for determining said material flow velocity and said mass flow rate of said material in said portion of said conduit between said material inlet and said material outlet comprises a means for determining the ratio of the flow velocity between said material in said flowmeter and said material in said portion of said conduit.

14. The apparatus of claim 13 wherein said Coriolis mass flowmeter further comprises:

pressure sensing means coupled to said material inlet and said material outlet for measuring the material pressure drop between said material inlet and said material outlet; and

means responsive to said measurement of said material pressure drop for determining the viscosity of said flowing material.

15. The apparatus of claim 14 wherein said means for increasing said flow velocity of said material comprises a venturi positioned internal to said conduit;

and

wherein said material outlet is coupled to a throat area of said venturi.

16. The apparatus of claim 13 wherein said venturi is affixed to the inner surface of said conduit.

17. The apparatus of claim 15 wherein said venturi and said throat area are spaced apart from the inner surfaces of said conduit.

18. The apparatus of claim 13 wherein said Coriolis mass flowmeter is positioned external to said conduit.

19. The apparatus of claim 1 wherein said material outlet is positioned upstream of said material inlet in said conduit.

20. The apparatus of claim 1 wherein said material outlet is positioned downstream of said material inlet in said conduit.

21. The apparatus of claim 20 wherein said Coriolis mass flowmeter is positioned within said conduit.

22. The apparatus of claim 21 wherein said Coriolis mass flowmeter comprises:

an elongated body positioned internal to said conduit with said body and said conduit having parallel longitudinal axes;

an upstream end of said body having said material inlet for receiving material to be extended through said Coriolis mass flowmeter;

a downstream end portion of said body having said material outlet for discharging material from said body back to said interior of said conduit;

a pair of parallel flow channels within said body having longitudinal axes parallel to said longitudinal axis of said body;

means coupling the downstream end portion of said flow channels with said downstream end portion of said body;

means coupling the upstream end portion of said flow channels with said upstream end portion of said body;

wherein material that enters said inlet of said body is extended through said flow channels and said outlet of said body and is returned back to said material flowing in said conduit;

means for vibrating said channels transversely and longitudinally with respect to each other; and

means including sensor means coupled to said flow channels and responsive to said vibrating while material flows through said flow channels for determining said total material mass flow rate in said conduit.

23. The apparatus of claim 22 wherein said downstream end portion of said body comprises a venturi and wherein said outlet of said body is positioned proximate the throat of said venturi.

24. The apparatus of claim 23 wherein said Coriolis mass flowmeter further comprises:

pressure sensing means coupled to said material inlet and said material outlet for measuring the material pressure drop between said inlet and said outlet;

means responsive to said measurement of said material pressure drop for determining the viscosity of said flowing material; and

means responsive to said determining of said viscosity to determine the flow velocity and mass flow rate of said material in said venturi and, in turn, the total mass flow rate of said material in said conduit.

25. A method of measuring material flow in a conduit;

said method comprising the steps of;

diverting some of the material flow in a conduit to a flowmeter having a material inlet positioned within an interior of said conduit and coupled to said flowmeter;

returning material flowing in said flowmeter to said conduit via a material outlet positioned within said interior of said conduit and coupled to said flowmeter;

determining flow velocity and mass flow rate and density of said material in said flowmeter;

determining flow velocity and mass flow rate of said material in a portion of said conduit between said material inlet and said material outlet in response to said determination of flow velocity and mass flow rate and density of said material in said flowmeter; and

determining a total mass flow rate of said material in said conduit in response to said determination of said flow velocity and mass flow rate of said material in said flowmeter and of said material in said conduit portion.

26. The method of claim 25 wherein said flowmeter comprises a Coriolis mass flowmeter.

27. The method of claim 25 including the steps of:

coupling pressure sensing means to said material inlet and to said material outlet for producing a measurement of a material pressure drop between said material inlet and said material outlet; and

determining the viscosity of said flowing material in said flowmeter in response to said measurement of said material pressure drop.

28. The method of claim 27 including the steps of:

determining said flow velocity and said mass flow rate as well as said density and said viscosity of said material in said flowmeter;

determining the flow velocity and mass flow rate of said material in said conduit portion in response to said determination of said flow velocity, mass flow rate, density and viscosity of said material in said flowmeter, and

said step of determining said total mass flow rate of said material in said conduit.

29. The method of claim 25 further comprising the steps of:

increasing said flow velocity and mass flow rate of said material at a conduit portion proximate said material outlet; and

coupling said material outlet to said conduit at said location having an increased flow velocity and mass flow rate for generating an optimum pressure drop between said material inlet and said material outlet of said flowmeter to increase said material flow within said flowmeter.

30. The method of claim 29 wherein said flowmeter is a Coriolis mass flowmeter;

and

wherein said step of determining flow velocity and mass flow rate of said material in said portion of said conduit between said material inlet and said material outlet comprises a step of determining the ratio of the flow velocity between said material in said flowmeter and said material in said portion of said conduit.

31. The method of claim 30 including the steps of:

measuring a material pressure drop between said material inlet and said material outlet; and

determining the viscosity of said flowing material in response to said measurement of said material pressure drop.

32. The method of claim 31 including the steps of:

determining said flow velocity and said mass flow rate as well as said density and said viscosity of said material in said flowmeter;

determining said flow velocity and mass flow rate of said material in said conduit portion of increased flow velocity in response to said determination of said flow velocity, mass flow rate, density and viscosity of said material in said flowmeter, and

said step of determining said total mass flow rate of said material in said conduit in response to said determination of said flow velocity and mass flow rate of said material in said flowmeter and of said material in said conduit portion.

33. The method of claim 29 including the step wherein said increased flow velocity is obtained by positioning said material outlet proximate a throat of a venturi.

34. The method of claim 33 wherein said method further comprises the steps of:

operating pressure sensor means coupled to said flowmeter for measuring the material pressure drop between said material inlet and said material outlet of said flowmeter; and

determining the viscosity of said material flow in said flowmeter in response to said measurement of said material pressure drop.

35. The method of claim 25 including the steps of:

positioning an elongated body positioned of a Coriolis mass flowmeter internal to said conduit with said body and said conduit having parallel longitudinal axes;

extending material received by an upstream end portion of said body having said material inlet through said Coriolis mass flowmeter;

discharging material from said body back to said interior of said conduit via a downstream end portion of said body having said material outlet;

a pair of parallel flow channels within said body having longitudinal axes parallel to said longitudinal axes of said body;

connecting the downstream ends of said flow channels with said downstream end portion of said body;

connecting the upstream end portions of said flow channels with said upstream end portion of said body;

wherein material that enters said material inlet of said body is extended through said flow channels and said material outlet of said body and is returned back to said material flowing in said conduit;

vibrating said flow channels transversely with respect to each other; and

operating sensor means responsive to said vibrating while material flows through said channels for determining information pertaining to said material flow in said conduit.

36. The method of claim 35 including the steps of:

positioning said material outlet of said body proximate a throat of a venturi formed by said body.

37. The method of claim 36 including the steps of:

operating pressure sensor means coupled to said body for measuring the material pressure drop between said material inlet and said outlet of said flowmeter body;

determining the viscosity of said material flow in said flowmeter in response to said measurement of said material pressure drop; and

determining said total mass flow rate of said material in said conduit in response to said viscosity determination.