Differential pressure diagnostic for process fluid pulsations

• US 7,770,459 B2
• Filed: 07/18/2008
• Issued: 08/10/2010
• Est. Priority Date: 07/20/2007
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Lemke, Joel Robert, Klosinski, Andrew Juri
• Primary Examiner(s): Allen; Andre J
• Application Number:
  US12/218,803
• Publication Number:
  US 20100011869A1
• Time in Patent Office: 753 Days
• Field of Search: None
• US Class Current: 73/716
• CPC Class Codes: G01F 1/363 with electrical or electro-mechanical indication G01F1/37 and G01F1/38 take precedence
• CPC Class Codes: G01F 1/42 Orifices or nozzles
• CPC Class Codes: G01F 1/72 Devices for measuring pulsing fluid flows
• CPC Class Codes: G01F 15/024 involving digital counting
• CPC Class Codes: G01F 25/10 of flowmeters

Abstract

A process pulsation diagnostic system comprises a primary element, a sensor and a processor. The primary element generates a differential pressure along a fluid flow. The sensor samples the differential pressure. The processor generates a pulsation diagnostic based on a standard deviation of the differential pressure, such that the pulsation diagnostic is indicative of a degree of process pulsation in the fluid flow.

Claims

1. A process pulsation diagnostic system comprising:

a primary element positioned to generate a differential pressure along a fluid flow;

a sensor positioned to sense the differential pressure across the primary element; and

a processor connected to the sensor, wherein the processor generates a pulsation diagnostic based on a standard deviation of the differential pressure, such that the pulsation diagnostic is indicative of process pulsations in the fluid flow.

2. The system of claim 1, wherein the processor further generates a pulsation indicator based on a change in the pulsation diagnostic.

3. The system of claim 1, wherein the pulsation diagnostic is indicative of an amplitude of the process pulsations via correlation with a square root error of the differential pressure.

4. The system of claim 3, wherein the processor further generates the square root error of the differential pressure based on the correlation with the pulsation diagnostic.

5. The system of claim 1, wherein the pulsation diagnostic is indicative of an amplitude of the process pulsations via correlation with a normalized root mean square of the differential pressure.

6. The system of claim 5, wherein the processor further generates the normalized root mean square of the differential pressure based on the correlation with the pulsation diagnostic.

7. The system of claim 1, further comprising an interface for transmitting the pulsation diagnostic over a loop wire having a maximum current of about 20 mA or less.

8. The system of claim 1, wherein the primary element comprises an orifice plate for generating the differential pressure.

9. The system of claim 1, wherein the primary element comprises a Pitot tube or an averaging Pitot tube for generating the differential pressure.

10. The system of claim 1, wherein the sensor samples the differential pressure at a sampling rate that is less than four times a frequency of the process pulsations.

11. The system of claim 10, wherein the sampling rate is less than twice the frequency of the process pulsations.

12. The system of claim 1, wherein a frequency of the process pulsations exceeds a sampling rate of the sensor.

13. A method for monitoring process pulsations, the method comprising:

sampling a differential pressure along a fluid flow at a sampling rate; and

generating a pulsation diagnostic as a function of the differential pressure, such that a change in the pulsation diagnostic is indicative of a change in an amplitude or frequency of the process pulsations;

wherein the function of the differential pressure comprises a standard deviation of the differential pressure; and

wherein the sampling rate is less than twice a frequency of the process pulsations.

14. The method of claim 13, wherein the sampling rate is at least 20 Hz.

15. The method of claim 14, further comprising generating a pulsation indicator as a function of an increase in the pulsation diagnostic.

16. The method of claim 13, wherein the pulsation diagnostic is correlated with a square root error of the differential pressure.

17. The method of claim 16, further comprising generating the square root error of the differential pressure based on the correlation with the pulsation diagnostic.

18. The method of claim 13, wherein the pulsation diagnostic is correlated with a root mean square of the differential pressure.

19. The method of claim 18, further comprising generating the root mean square of the differential pressure based on the correlation with the pulsation diagnostic.

20. The method of claim 13, further comprising transmitting the differential pressure and the pulsation diagnostic over a loop wire having a maximum current of about 20 mA or less.

21. A pressure monitoring device comprising:

a sensor positioned to sense a differential pressure;

a signal processor connected to the sensor, wherein the signal processor generates a process pressure value from the differential pressure;

a statistical processor connected to the sensor, wherein the signal processor generates a pulsation diagnostic based on a standard deviation of the differential pressure, such that the pulsation diagnostic is correlated with changes in an amplitude or frequency of the process pulsations; and

an interface for transmitting the process pressure value and the pulsation diagnostic to a process system controller.

22. The device of claim 21, wherein the sensor has a sampling rate that is less than twice a frequency of the process pulsations.

23. The device of claim 21, wherein the device operates on no more than 50 mW of power.

24. The device of claim 21, further comprising a differential pressure generator positioned in a fluid flow in order to generate the differential pressure.

25. The device of claim 24, wherein the differential pressure generator comprises an orifice plate.

26. The device of claim 24, wherein the differential pressure generator comprises a Pitot tube or an averaging Pitot tube.

27. The device of claim 21, wherein the frequency of the process pulsations exceeds a sampling rate of the sensor.