Method and System for Detecting Deposit Buildup Within an Ultrasonic Flow Meter

• US 20090097354A1
• Filed: 10/16/2007
• Published: 04/16/2009
• Est. Priority Date: 10/16/2007
• Status: Active Grant

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Daniel Measurement and Control Incorporated (Emerson Electric Company)
• Inventors: Straub, Henry Charles JR.
• Granted Patent: US 8,170,812 B2
• Time in Patent Office: Days
• US Class Current: 367/13
• CPC Class Codes: G01F 1/668 Compensating or correcting for variations in velocity of sound
• CPC Class Codes: G01F 25/10 of flowmeters

Abstract

Methods and systems for detecting deposit buildup within an ultrasonic flow meter are disclosed. At least some of the illustrative embodiments are ultrasonic flow meters comprising a spool piece configured to couple within a flow of fluid, a first transducer pair mechanically mounted to the spool piece and configured to fluidly couple to the flow of fluids (wherein the first transducer pair comprises an upstream transducer and a downstream transducer in operational relationship to the upstream transducer and defines a first chord there between), and electronics electrically coupled to the first transducer pair. The electronics is configured to detect deposit buildup over an inner surface of the ultrasonic flow meter.

Claims

1. A system comprising:

an ultrasonic flow meter comprising;

a spool piece configured to couple within a flow of fluid; and

a first transducer pair mechanically mounted to the spool piece and configured to fluidly couple to the flow of fluid, the first transducer pair comprising an upstream transducer and a downstream transducer in operational relationship to the upstream transducer and defining a first chord there between; and

electronics electronically coupled to the first transducer pair, the electronics configured to;

determine diagnostic data based on acoustic signals transmitted between the first transducer pair, the diagnostic data comprising a speed of sound through the fluid; and

detect deposit buildup over an inner surface of the spool piece based on a trend of the speed of sound through the fluid.

2. The system of claim 1 wherein at least some of the electronics are contained within the meter.

3. The system of claim 1 wherein at least some of the electronics are remote to the meter.

4. The system of claim 1 wherein the electronics is further configured to determine the thickness of the deposit buildup.

5. The system of claim 4 wherein the electronics is further configured to generate a signal when the deposit thickness exceeds a threshold value.

6. The system of claim 1 wherein the electronics is further configured to determine the change in the volumetric flow rate through the meter caused by the deposit buildup.

7. The system of claim 1 wherein the diagnostic data further comprises transit times between the first transducer pair and wherein the electronics is further configured to calculate the speed of sound through the fluid.

8. The system of claim 1 wherein the electronics is further configured to store the diagnostic data.

9. A method comprising:

determining diagnostic data based on acoustic signals transmitted between a transducer pair of an ultrasonic flow meter, the diagnostic data comprising a speed of sound through a fluid flowing through the ultrasonic flow meter;

trending the speed of sound through the fluid with time; and

detecting deposit buildup over an inner surface of the ultrasonic flow meter using the trended speed of sound through the fluid.

10. The method of claim 9 further comprising determining the thickness of the deposit buildup.

11. The method of claim 10 further comprising generating a signal when the deposit thickness exceeds a threshold value.

12. The method of claim 10 wherein the deposit thickness is determined by substantially the following equation:

$t_{\mathrm{deposit}}=\frac{\mathrm{\Delta <br><br>}<br><br><br><br>T}{2}·<br><br>\frac{c_{\mathrm{fluid}}<br><br>c_{\mathrm{deposit}}}{c_{\mathrm{fluid}}-c_{\mathrm{deposit}}}$

wherein Δ

T is a timing error caused by the deposit buildup;

c_deposit is the speed of sound through the deposit; and

c_fluid is the speed of sound in a fluid flowing through the ultrasonic flow meter.

13. The method of claim 9 further comprising calculating the change in a volumetric flow rate of a fluid passing through the meter caused by the deposit buildup.

14. The method of claim 13 wherein the change in the volumetric flow rate is determined by substantially the following equation:

Δ

Q/Q=Δ

V/V+Δ

A_c/A_c

wherein Q, V and A_c are the volumetric flow rate, the average flow velocity associated with the first transducer pair and the cross-sectional flow area, respectively, in the absence of deposit buildup; and

Δ

Q, Δ

V and Δ

A_c are the error in the volumetric flow rate, the error in the average flow velocity associated with the first transducer pair and the error in the cross-sectional flow area, respectively, caused by the deposit buildup.

15. The method of claim 14 wherein Δ

A_c/A_c is determined by substantially the following equation;

Δ

A_c/A_c=−

4t_deposit/D

wherein D is the inner diameter of the ultrasonic flow meter in the absence of deposit buildup.

16. The method of claim 14 wherein Δ

V/V is determined by substantially the following equation;

$\frac{\mathrm{\Delta <br><br>}<br><br><br><br>V}{V}=\underset{i}{\overset{}{\sum <br><br>}}<br><br><br><br>2<br><br>W_i<br><br>t_{\mathrm{deposit}}<br><br>\left(\frac{1}{D<br><br>\left(1-f_i^2\right)}-\frac{2}{L_i}·<br><br>\frac{c-c_{\mathrm{deposit}}}{c_{\mathrm{deposit}}}\right)$

wherein i refers to a chord between the upstream and the downstream transducers;

t_deposit is the thickness of the deposit buildup;

D is the inner diameter of the ultrasonic flow meter in the absence of deposit buildup;

W_i is a chord-dependent weighting factor for chord i;

L_i is the length of chord i in the absence of deposit buildup;

f is the relative fractional distance between a plane containing the chord i and a plane through the center of the ultrasonic flow meter;

c is the speed of sound through the fluid; and

c_deposit is the speed of sound through the deposit.

17. A computer-readable media comprising a plurality of instructions that, when executed by a processor, cause the processor to:

detect deposit buildup within an ultrasonic flow meter using a trend of diagnostic data based on acoustic signals transmitted between a transducer pair, the diagnostic data comprising a speed of sound through a fluid flowing through the ultrasonic flow meter.

18. The computer-readable media of claim 17 wherein the instructions further cause the processor to determine the thickness of deposit buildup.

19. The computer-readable media of claim 18 wherein the instructions further cause the processor to generate a signal when the thickness of the deposit buildup exceeds a threshold value.

20. The computer-readable media of claim 17 wherein the instructions further cause the processor to calculate a volumetric flow rate through the ultrasonic flow meter as a function of the deposit buildup thickness.