Method and apparatus for pump protection without the use of traditional sensors

Abstract

The present invention provides protection for centrifugal pumps while differentiating between dangerous operating conditions (e.g. dry running, minimum flow and runout) and/or conditions where transient conditions (e.g. closed valve operation) may occur and the protection can be revoked once the condition clears. The methodology utilizes a calculated flow value which can be mathematically determined from a calibrated closed valve power vs speed curve and/or various pump and motor parameters such as speed, torque, power and/or differential pressure or from calibrated flow curves stored in the evaluation device. The calculated flow value is then compared to threshold values of flow associated with these adverse operating conditions.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of a basic pump system according to the present invention.

FIG. 2 is a flowchart of basic steps performed according to the present invention by the controller shown in FIG. 1.

FIG. 3 is a block diagram of a controller shown in FIG. 1 for performing the basic steps shown in FIG. 2.

Claims

1. A method for controlling the operation of a centrifugal pump, centrifugal mixer, centrifugal blower or centrifugal compressor comprising: comparing an actual flow value and a corrected threshold flow value that is corrected based on the speed of the pump in order to determine the pump operating condition.

2. A method according to claim 1, wherein the method further comprises adapting the operation of the pump based on the comparison, including using a user settable delay in reacting to the condition prior to issuing either a warning only, warning and reduction in speed to a safe operating speed, faulting and shutting down the motor or automatically resetting the fault and restarting the pump and motor to check if the condition has cleared, and where if the condition clears the adaptation is revoked and the pump resumes normal operation.

3. A method according to claim 1, wherein the correction is based on a relationship between an actual pump speed and a rated pump speed.

4. A method according to claim 1, wherein the corrected threshold flow value includes a runout condition value, a minimum flow value, or some combination thereof.

5. A method according to claim 1, wherein the method includes comparing a runout condition value to an actual runout flow value in order to determine a runout condition of the pump.

6. A method according to claim 1, wherein the method includes comparing a corrected minimum flow value to an actual minimum flow value in order to determine either a normal flow condition or a possible minimum flow condition of the pump.

7. A method according to claim 1, wherein the method further comprises comparing, a corrected minimum threshold flow value to an actual flow value and also comparing an actual power value to a closed valve power value at the current speed of the pump in order to determine either a minimum flow condition or a dry run condition of the pump.

8. A method according to claim 1, wherein the method further comprises comparing a corrected minimum threshold flow value to an actual flow value and also comparing an actual power value to a closed valve power value at the current speed of the pump in order to determine either a minimum flow condition or a dry run condition of the pump, where the closed valve power value is interpolated from a calibrated power vs speed curve stored in a memory device.

9. A method according to claim 1, wherein a Dry Run condition is declared if PACT is less than KDR×PSO_N.

10. A method according to claim 1, wherein for small hp pumps a correction can be made to KDR to compensate for inaccuracies in Pso—N if speed corrections are based on affinity calculations.

11. A method according to claim 7, wherein either the actual power value, the closed valve power value or the combination thereof are corrected for specific gravity of the medium being pumped.

12. A method according to claim 1, wherein the corrected Minimum Flow Threshold value is based on the equation QMIN—COR=QMIN×(NACT/NRATED).

13. A method according to claim 1, wherein the corrected Runout Flow Threshold value is based on the equation QRO—COR=QRO×(NACT/NRATED).

14. A method according to claim 1, wherein the actual flow value is calculated from a calibrated speed vs closed valve power curve stored in the evaluation device, motor signals for speed and power (or torque) and basic published pump performance data such as best efficiency power, closed valve power and best efficiency flow at the rated pump speed.

15. A method according to claim 1, wherein the actual flow value is calculated from one of many techniques for calculating flow using pump affinity law data and flow calibration curves at various speeds stored in an evaluation device and pump and motor signals such as speed and power (or torque), or speed and power/differential pressure.

16. A method according to claim 1, wherein the actual flow value is based on a reading from a flow meter.

17. A controller for controlling the operation of a centrifugal pump, centrifugal mixer, centrifugal blower or centrifugal compressor, comprising: a module configured for comparing an actual flow value and a corrected threshold flow value that is corrected based on the speed of the pump in order to determine the pump operating condition.

18. A controller according to claim 17, wherein the module is configured for adapting the operation of the pump based on the comparison, including using a user settable delay in reacting to the condition prior to issuing either a warning only, warning and reduction in speed to a safe operating speed, faulting and shutting down the motor or automatically resetting the fault and restarting the pump and motor to check if the condition has cleared, and where the condition clears the adaptation is revoked and the pump resumes normal operation

19. A controller according to claim 17, wherein the correction is based on a relationship between an actual pump speed and a rated pump speed.

20. A controller according to claim 17, wherein the corrected threshold flow value includes a runout condition value, a minimum flow value, or some combination thereof.

21. A controller according to claim 17, wherein the module is configured for comparing a runout condition value to an actual runout flow value in order to determine a runout condition of the pump.

22. A controller according to claim 17, wherein the module is configured for comparing a corrected minimum flow value to an actual minimum flow value in order to determine either a normal flow condition or a possible minimum flow condition of the pump.

23. A controller according to claim 17, wherein the module is configured for comparing a corrected minimum threshold flow value to an actual flow value and also comparing an actual power value to a closed valve power value at the current speed of the pump in order to determine either a minimum flow condition or a dry run condition of the pump.

24. A controller according to claim 17, wherein the method further comprises comparing, a corrected minimum threshold flow value to an actual flow value and also comparing an actual power value to a closed valve power value at the current speed of the pump in order to determine either a minimum flow condition or a dry run condition of the pump, where the closed valve power value is interpolated from a calibrated power vs speed curve stored in a memory device.

25. A controller according to claim 17, wherein a Dry Run condition is declared if PACT is less than KDR×PSO_N.

26. A controller according to claim 17, wherein for small hp pumps a correction can be made to KDR to compensate for inaccuracies in Pso—N if speed corrections are based on affinity calculations.

27. A controller according to claim 23, wherein either the actual power value, the closed valve power value or the combination thereof are corrected for specific gravity of the medium being pumped.

28. A controller according to claim 23, wherein the corrected Minimum Flow Threshold value is based on the equation QMIN—COR=QMIN×(NACT/NRATED).

29. A controller according to claim 17, wherein the corrected Runout Flow Threshold value is based on the equation QRO—COR=QRO×(NACT/NRATED).

30. A controller according to claim 17, wherein the actual flow value is calculated from a calibrated speed vs closed valve power curve stored in the evaluation device, motor signals for speed and power (or torque) and basic published pump performance data such as best efficiency power, closed valve power and best efficiency flow at the rated pump speed.

31. A controller according to claim 17, wherein the actual flow value is calculated from one of many techniques for calculating flow using pump affinity law data and flow calibration curves at various speeds stored in an evaluation device and pump and motor signals such as speed and power (or torque), or speed and power/differential pressure.

32. A controller according to claim 17, wherein the actual flow value is based on a reading from a flow meter.

33. A controller according to claim 17, wherein the controller is a variable frequency controller or a programmable logic controller.

34. A centrifugal pump system or system with other centrifugal device such as a centrifugal mixer, centrifugal blower or centrifugal compressor having a controller for controlling the operation of a centrifugal pump, centrifugal mixer, centrifugal blower or centrifugal compressor, the controller comprising: a module configured for comparing an actual flow value and a corrected threshold flow value that is corrected based on the speed of the pump in order to determine the pump operating condition.

35. A pump system according to claim 34, wherein the module is configured for adapting the operation of the pump based on the comparison, including using a user settable delay in reacting to the condition prior to issuing either a warning only, warning and reduction in speed to a safe operating speed, faulting and shutting down the motor or automatically resetting the fault and restarting the pump and motor to check if the condition has cleared, and where if the condition clears the adaptation is revoked and the pump resumes normal operation.

36. A pump system according to claim 34, wherein the correction is based on a relationship between an actual pump speed and a rated pump speed.

37. A pump system according to claim 34, wherein the corrected threshold flow value includes a runout condition value, a minimum flow value, or some combination thereof.

38. A pump system according to claim 34, wherein the module is configured for comparing a runout condition value to an actual runout flow value in order to determine a runout condition of the pump.

39. A pump system according to claim 34, wherein the module is configured for comparing a corrected minimum flow value to an actual minimum flow value in order to determine either a normal flow condition or a possible minimum flow condition of the pump.

40. A pump system according to claim 34, wherein the module is configured for comparing a corrected minimum threshold flow value to an actual flow value and also comparing an actual power value to a closed valve power value at the current speed of the pump in order to determine either a minimum flow condition or a dry run condition of the pump.

41. A pump system according to claim 34, wherein the method further comprises comparing, a corrected minimum threshold flow value to an actual flow value and also comparing an actual power value to a closed valve power value at the current speed of the pump in order to determine either a minimum flow condition or a dry run condition of the pump, and where the closed valve power value is interpolated from a calibrated power vs speed curve stored in a memory device.

42. A pump system according to claim 34, wherein a Dry Run condition is declared if PACT is less than KDR×PSO_N.

43. A pump system according to claim 34, wherein for small hp pumps a correction can be made to KDR to compensate for inaccuracies in Pso—N if speed corrections are based on affinity calculations.

44. A pump system according to claim 34, wherein either the actual power value, the closed valve power value or the combination thereof are corrected for specific gravity of the medium being pumped.

45. A pump system according to claim 34, wherein the corrected Minimum Flow Threshold value is based on the equation QMIN—COR=QMIN×(NACT/NRATED).

46. A pump system according to claim 34, wherein the corrected Runout Flow Threshold value is based on the equation QROCOR=QRO×(NACT/NRATED).

47. A pump system according to claim 34, wherein the actual flow value is calculated from a calibrated speed vs closed valve power curve stored in the evaluation device, motor signals for speed and power (or torque) and basic published pump performance data such as best efficiency power, closed valve power and best efficiency flow at the rated pump speed.

48. A pump system according to claim 34, wherein the actual flow value is calculated from one of many techniques for calculating flow using pump affinity law data and flow calibration curves at various speeds stored in an evaluation device and pump and motor signals such as speed and power (or torque), or speed and power/differential pressure.

49. A pump system according to claim 34, wherein the actual flow value is based on a reading from a flow meter.

50. A pump system according to claim 34, wherein the controller is a variable frequency controller or a programmable logic controller.

51. A method according to claim 4, wherein the method includes comparing a runout condition value to an actual runout flow value in order to determine a runout condition of the pump.

52. A method according to claim 8, wherein a Dry Run condition is declared if PACT is less than KDR×PSO_N.

53. A method according to claim 8, wherein for small hp pumps a correction can be made to KDR to compensate for inaccuracies in Pso—N if speed corrections are based on affinity calculations.

54. A method according to claim 7, wherein the corrected Minimum Flow Threshold value is based on the equation QMINCOR=QMIN×(NACT/NRATED)

55. A method according to claim 5, wherein the corrected Runout Flow Threshold value is based on the equation QRO—COR=QRO×(NACT/NRATED)

56. A method according to claim 7, wherein the actual flow value is calculated from a calibrated speed vs closed valve power curve stored in the evaluation device, motor signals for speed and power (or torque) and basic published pump performance data such as best efficiency power, closed valve power and best efficiency flow at the rated pump speed.

57. A method according to claim 7, wherein the actual flow value is calculated from one of many techniques for calculating flow using pump affinity law data and flow calibration curves at various speeds stored in an evaluation device and pump and motor signals such as speed and power (or torque), or speed and power/differential pressure.

58. A method according to claim 5, wherein the actual flow value is based on a reading from a flow meter.

59. A method according to claim 7, wherein the actual flow value is based on a reading from a flow meter.

60. A controller according to claim 20, wherein the module is configured for comparing a runout condition value to an actual runout flow value in order to determine a runout condition of the pump.

61. A controller according to claim 24, wherein a Dry Run condition is declared if PACT is less than KDR×PSO_N.

62. A controller according to claim 24, wherein for small hp pumps a correction can be made to KDR to compensate for inaccuracies in Pso—N if speed corrections are based on affinity calculations.

63. A controller according to claim 24 wherein the corrected Minimum Flow Threshold value is based on the equation QMINCOR=QMIN×(NACT/NRATED)

64. A controller according to claim 21, wherein the corrected Runout Flow Threshold value is based on the equation QRO—COR=QRO×(NACT/NRATED)

65. A controller according to claim 23, wherein the actual flow value is calculated from a calibrated speed vs closed valve power curve stored in the evaluation device, motor signals for speed and power (or torque) and basic published pump performance data such as best efficiency power, closed valve power and best efficiency flow at the rated pump speed.

66. A controller according to claim 23, wherein the actual flow value is calculated from one of many techniques for calculating flow using pump affinity law data and flow calibration curves at various speeds stored in an evaluation device and pump and motor signals such as speed and power (or torque), or speed and power/differential pressure.

67. A controller according to claim 21, wherein the actual flow value is based on a reading from a flow meter.

68. A controller according to claim 23, wherein the actual flow value is based on a reading from a flow meter.

69. A pump system according to claim 37, wherein the module is configured for comparing a runout condition value to an actual runout flow value in order to determine a runout condition of the pump.

70. A pump system according to claim 41, wherein a Dry Run condition is declared if PACT is less than KDR×PSO_N.

71. A pump system according to claim 41, wherein for small hp pumps a correction can be made to KDR to compensate for inaccuracies in PsoN if speed corrections are based on affinity calculations.

72. A pump system according to claim 40, wherein either the actual power value, the closed valve power value or the combination thereof are corrected for specific gravity of the medium being pumped.

73. A pump system according to claim 40, wherein the corrected Minimum Flow Threshold value is based on the equation QMIN—COR=QMIN×(NACT/NRATED).

74. A pump system according to claim 38, wherein the corrected Runout Flow Threshold value is based on the equation QRO—COR=QRO×(NACT/NRATED).

75. A pump system according to claim 40, wherein the actual flow value is calculated from a calibrated speed vs closed valve power curve stored in the evaluation device, motor signals for speed and power (or torque) and basic published pump performance data such as best efficiency power, closed valve power and best efficiency flow at the rated pump speed.

76. A pump system according to claim 40, wherein the actual flow value is calculated from one of many techniques for calculating flow using pump affinity law data and flow calibration curves at various speeds stored in an evaluation device and pump and motor signals such as speed and power (or torque), or speed and power/differential pressure.

77. A pump system according to claim 40, wherein the actual flow value is based on a reading from a flow meter.