SYSTEM AND METHOD FOR MONITORING AND CONTROL OF CAVITATION IN POSITIVE DISPLACEMENT PUMPS

• US 20130259707A1
• Filed: 03/28/2012
• Published: 10/03/2013
• Est. Priority Date: 03/28/2012
• Status: Active Grant

• Current Assignee: Circor Pumps North America LLC (Circor International Incorporated)
• Original Assignee: Imo Industries Incorporated (Enovis Corp.)
• Inventors: Yin, Dan
• Granted Patent: US 9,546,652 B2
• Time in Patent Office: Days
• US Class Current: 417/53
• CPC Class Codes: F04B 2205/01 Pressure before the pump inlet
• CPC Class Codes: F04B 2205/03 Pressure in the compression chamber
• CPC Class Codes: F04B 2205/05 Pressure after the pump outlet
• CPC Class Codes: F04B 2205/07 Pressure difference over the pump
• CPC Class Codes: F04B 49/00 Control , e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
• CPC Class Codes: F04B 49/022 by means of pressure
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: F04B 49/08 Regulating by delivery pressure
• CPC Class Codes: F04C 14/28 Safety arrangements; Monitoring
• CPC Class Codes: F04C 2270/18 Pressure
• CPC Class Codes: F04C 2270/86 Detection

Abstract

A system and method are disclosed for monitoring and controlling a positive displacement pump using readings obtained from a plurality of pressure sensors. The pressure sensors may be mounted at the suction, discharge and interstage regions of the pump. Signals from the pressure sensors are compared to obtain a ratio that is used to predict whether a cavitation condition exists within the pump. The ratio can be compared to user provided limits to change an operating characteristic of the pump to reduce predicted cavitation. The pump may be stopped, or pump speed changed, when the ratio is less than a predetermined value. In some embodiments, historical information regarding the ratio may be used to obtain standard deviation information which may then be used to predict whether gas bubbles are passing through the pump. Other embodiments are described and claimed.

Claims

1. A system for monitoring and controlling a positive displacement pump, comprising:

a plurality of pressure sensors mounted to a positive displacement pump; and

a controller for receiving input signals from the plurality of pressure sensors, and for processing said input signals to obtain a cavitation severity ratio, the cavitation severity ratio comprising a ratio of the difference between a measured interstage pressure of the pump and a measured suction pressure of the pump and the difference between a measured discharge pressure of the pump and a measured suction pressure of the pump;

the controller further configured to adjust an operating speed of the pump based on a comparison of the cavitation severity ratio to a predefined application based severity level.

2. The system of claim 1, wherein when the cavitation severity ratio is within a predetermined range of the application based severity level, a current operating speed of the pump is maintained.

3. The system of claim 1, wherein when the cavitation severity ratio is greater than the application based severity level, a speed of the pump is increased until the cavitation severity ratio is within a predetermined range of the application based severity level.

4. The system of claim 1, wherein when the cavitation severity ratio is less than the application based severity level, a speed of the pump is decreased until the cavitation severity ratio is within a predetermined range of the application based severity level.

5. The system of claim 1, wherein when the cavitation severity ratio is less than the application based severity level limit, the pump is stopped.

6. The system of claim 1, wherein the cavitation severity ratio Ra is obtained according to the formula:

7. The system of claim 1, wherein the simplified cavitation severity ratio Ra is obtained according to the formula:

8. The system of claim 1, the controller further configured to store a plurality of discrete values of cavitation severity ratio over time, and to obtain a standard deviation of the plurality of discrete values to determine if a change in the plurality of discrete values exceeds a predetermined limit.

9. The system of claim 8, wherein when the change in the plurality of discrete values exceeds the predetermined limit, the controller is configured to provide an indication to a user that gas bubbles are present in the pump cavity.

10. The system of claim 9, wherein in response to the indication, the controller is configured to receive a user input to change an operating condition of the pump.

11. A method for monitoring and controlling a positive displacement pump, comprising:

obtaining a plurality of signals representative of pressures at a plurality of locations in a positive displacement pump;

processing the plurality of signals to obtain a cavitation severity ratio, the cavitation severity ratio comprising a ratio of the difference between a measured interstage pressure of the pump and a measured suction pressure of the pump and the difference between a measured discharge pressure of the pump and a measured suction pressure of the pump; and

adjusting an operating speed of the positive displacement pump based on a comparison of the cavitation severity ratio to a predefined application based severity level.

12. The method of claim 11, further comprising maintaining a current operating speed of the pump when the cavitation severity ratio is within a predetermined range of the application based severity level.

13. The method of claim 11, wherein when the cavitation severity ratio is greater than the application based severity level, the method comprises increasing a speed of the pump until the cavitation severity ratio is within a predetermined range of the application based severity level.

14. The method of claim 11, wherein when the cavitation severity ratio is less than the application based severity level, the method comprises decreasing a speed of the pump until the cavitation severity ratio is within a predetermined range of the application based severity level.

15. The method of claim 11, wherein when the cavitation severity ratio is less than the application based severity limit, the method comprises stopping the pump.

16. The method of claim 11, comprising determining the cavitation severity ratio (Ra) according to the formula:

17. The method of claim 11, comprising determining the simplified cavitation severity ratio Ra according to the formula:

18. The method of claim 11, further comprising storing a plurality of discrete values of cavitation severity ratio over time, and obtaining a standard deviation of the plurality of discrete values to determine if a change in the plurality of discrete values exceeds a predetermined limit.

19. The method of claim 18, wherein when the change in the plurality of discrete values exceeds the predetermined limit, the method comprises providing an indication to a user that gas bubbles are present in the pump cavity.

20. The method of claim 19, wherein in response to the indication, the method comprises receiving a user input to change an operating condition of the pump.