Process fluid flow device with variable orifice

• US 20060112773A1
• Filed: 12/01/2004
• Published: 06/01/2006
• Est. Priority Date: 12/01/2004
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Hedtke, Robert C.
• Granted Patent: US 7,255,012 B2
• Time in Patent Office: Days
• US Class Current: 73/861.610
• CPC Class Codes: F16K 3/03 with a closure member in the form of an iris-diaphragm
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence

Abstract

A process device providing total fluid flow control is provided. The device includes a closure mechanism disposed in a flow conduit. The closure mechanism, which is preferably an iris-type diaphragm, provides a variable internal diameter. The device includes a differential pressure sensor for sensing the differential pressure on opposite sides of the diaphragm. A controller receives an indication of differential pressure and generates a control signal to an actuator that actuates the closure mechanism. The closure mechanism, differential pressure sensor and controller create a closed-loop flow controller in a single process device.

Claims

1. A process fluid flow control device comprising:

a closure mechanism disposed in a flow conduit, the closure mechanism providing a selective degree of fluid flow obstruction through the flow conduit;

an actuator coupled to the closure mechanism to control the selective degree of fluid flow obstruction based upon a control signal;

a differential pressure sensor disposed to sense differential process fluid pressure across the fluid flow obstruction;

measurement circuitry coupled to the differential pressure sensor, the measurement circuitry configured to obtain an indication of differential pressure from the differential pressure sensor;

a controller coupled to the measurement circuitry and the actuator, the controller executing a control algorithm to generate the control signal based on the indication of differential pressure; and

a loop communication module coupled to a plurality of loop terminals and the controller, the loop communication module being adapted to communicate in accordance with a process industry standard protocol.

2. The device of claim 1, wherein the closure mechanism is an iris-type diaphragm.

3. The device of claim 2, wherein the iris-type diaphragm is comprised of a plurality of fingers that are extendable into the flow conduit.

4. The device of claim 3, wherein the plurality of fingers are constructed from polytetrafluoroethylene.

5. The device of claim 3, wherein the plurality of fingers are constructed from polytetrafluoroethylene-coated metal.

6. The device of claim 2, wherein each finger includes a curved surface to create a curved inner diameter.

7. The device of claim 2, wherein the iris-type diaphragm is self-sealing.

8. The device of claim 1, wherein the actuator includes an electric motor.

9. The device of claim 8, wherein the electric motor generates a back electromotive force (emf) that provides a secondary indication of differential pressure.

10. The device of claim 1, wherein the actuator includes a pneumatic motor.

11. The device of claim 10, wherein differential pressure across the pneumatic motor provides an indication of process fluid differential pressure across the closure mechanism.

12. The device of claim 1, wherein the actuator includes a manual actuator.

13. The device of claim 1, wherein the controller is a microprocessor.

14. The device of claim 13, and further comprising memory containing a relationship between beta ratio and internal diameters of the closure mechanism.

15. The device of claim 14, wherein the relationship is a mathematical relationship.

16. The device of claim 14, wherein the relationship is approximated in a look-up table stored in the memory.

17. The device of claim 1, and further comprising a power module couple to the plurality of terminals and being adapted to power the device with energy received through the plurality of terminals.

18. The device of claim 17, wherein the device is wholly powered over the same conductors upon which it communicates.

19. The device of claim 1, and further comprising a high-pressure shut-off valve coupled to the flow conduit.

20. A process fluid flow control device comprising:

means for selectively obstructing fluid flow;

means for sensing differential pressure of the process fluid across the means for selectively obstructing fluid flow; and

means for controlling the means for obstructing fluid flow based upon a control algorithm and the sensed differential pressure.

21. A method of controlling process fluid flow using a single process device, the method comprising:

measuring a differential pressure of process fluid flowing through an iris-diaphragm;

generating a control output based upon a selected fluid flow setpoint and the measured differential pressure; and

adjusting the iris-diaphragm based upon the control output.

22. The method of claim 21, wherein the setpoint is conveyed to the device over a process communication loop.

23. The method of claim 22, and further comprising providing electrical power to the device from the process communication loop.

24. The method of claim 21, wherein adjusting the iris-diaphragm includes choosing among pre-selected closure levels.

25. The method of claim 21, wherein adjusting the iris-diaphragm includes selecting a continuous closure level.

26. A method of measuring process fluid flow, the method comprising:

directing the process fluid flow through a variable orifice;

measuring differential pressure of the process fluid across the variable orifice; and

adjusting the variable orifice if the measured fluid flow meets a selected threshold.

27. The method of claim 26, wherein adjusting the variable orifice is done automatically.

28. A method of verifying operation of a process fluid flow device having a variable orifice and a differential pressure sensor disposed to sense differential pressure across the variable orifice, the method comprising:

measuring a first differential pressure across the variable orifice when the variable orifice is set to a first closure level;

setting the variable orifice to a second closure level different than the first closure level;

measuring a second differential pressure across the variable orifice set to the second closure level; and

comparing the first differential pressure with the second differential pressure to generate a verification output.

29. The method of claim 28, and further comprising providing the process fluid flow device with an indication that the fluid flow is constant, such that the first and second measured differential pressures can be used to check for span.

30. A method of performing a calibration check on a process fluid flow device, the method comprising:

ceasing flow of process fluid through the device; and

zeroing the process fluid flow device while the flow is ceased.

31. The method of claim 30, wherein ceasing flow of process fluid includes closing a shut-off valve.

32. The method of claim 31, wherein the shut-off valve is a component of the process fluid flow device.