Method and apparatus for determining the instantaneous operation conditions of a centrifugal pump

• US 5,649,449 A
• Filed: 04/25/1996
• Issued: 07/22/1997
• Est. Priority Date: 04/25/1995
• Status: Expired due to Term

• Current Assignee: ABS Pump Production AB (Assa Abloy AB)
• Original Assignee: ABS Pump Production AB (Assa Abloy AB)
• Inventors: Algers, Bengt
• Primary Examiner(s): KWON, JOHN
• Application Number:
  US08/637,519
• Time in Patent Office: 453 Days
• Field of Search: 73/168, 73/861.75
• US Class Current: 73/168
• CPC Class Codes: F04D 15/0088 Testing machines

Abstract

In the disclosed method of determining the current or instantaneous operating conditions of a centrifugal pump, the radial forces impressed on the impeller shaft by the operatively rotating pump impeller are measured at a shaft-supporting bearing disposed proximate the pump housing and impeller. In a preliminary or test operation of the pump, this radial force measurement is taken at a plurality of volumetric liquid flow rates through the pump so as to develop a relationship between the radial force and liquid flow. Then, during normal operation of the pump, the current or instantaneous radial force is measured at the bearing and this measurement is compared to the previously-developed relationship to accurately determine the instantaneous operating conditions of the pump by identifying the point along the pump'"'"'s characteristic curve--which defines for the pump a relationship between lifing height and volumetric liquid flow--at which the pump is currently operating.

Claims

1. A method for determining a current operating condition of an operating centrifugal pump having a rotatable impeller, an impeller shaft carrying the impeller, a bearing supporting the shaft, and a characteristic curve defining a first relationship between lifting height of the pump and volumetric liquid flow through the pump, comprising the steps of:

(a) measuring radial forces impressed on the impeller shaft by the rotating impeller at a plurality of volumetric liquid flow rates during a testing operation of the pump to define a second relationship for the pump between the impressed radial forces and the volumetric flow rate;

(b) measuring the radial forces impressed on the impeller shaft by the rotating impeller at a particular current instant during normal operation of the pump; and

(c) comparing the measured radial forces measured at the particular instant to the second relationship measurements to determine the instantaneous operating conditions of the pump.

2. A method in accordance with claim 1, wherein said comparing step comprises comparing the measured radial forces measured at the particular instant to the second relationship measurement to identify the corresponding volumetric flow rate, and using the identified volumetric flow rate to identify a point along the characteristic curve of the pump at which the pump is currently operating.

3. A method in accordance with claim 1, further comprising the step of deriving a third relationship between the characteristic curve of the pump and the second relationship, and wherein said comparing step further comprises using the third relationship in said comparison to determine the instantaneous operating conditions of the pump.

4. A method in accordance with claim 1, further comprising the step of deriving a third relationship between the characteristic curve of the pump and the second relationship, and wherein said comparing step further comprises using the third relationship in said comparison to identify a point along the characteristic curve of the pump at which the pump is currently operating.

5. A method in accordance with claim 1, wherein each of said steps (a) and (b) further comprises measuring a magnitude and a direction of the radial forces impressed on the impeller shaft by the rotating impeller.

6. A method in accordance with claim 1, wherein each of said steps (a) and (b) further comprises measuring the radial forces at the bearing that carries the shaft.

7. A method in accordance with claim 1, wherein each of said steps (a) and (b) further comprises measuring the radial forces at the bearing that carries the shaft using a pressductor radial tensiometer disposed about the bearing.

8. A method in accordance with claim 7, wherein each of said steps (a) and (b) further comprises measuring, using the pressductor radial tensiometer, a magnitude and a direction of the radial forces impressed on the impeller shaft by the rotating impeller.

9. A method in accordance with claim 1 wherein the pump bearing comprises a first bearing and the pump further includes a second bearing supporting the shaft and spaced from the first bearing along the shaft so that the first bearing is disposed more closely proximate the impeller than the second bearing, each of said steps (a) and (b) further comprising measuring the radial forces at the said first bearing.

10. In a centrifugal pump operable for pumping a liquid through a pump housing having an inlet and an outlet,

an elongated shaft;

means for operatively rotating the shaft;

an impeller mounted on the shaft in the pump housing for rotation with the shaft to operatively pump liquid through the housing between the inlet and the outlet;

a bearing supporting the shaft for operative rotation; and

means for measuring at the bearing a radial force imparted to the shaft by the rotating impeller.

11. In a centrifugal pump in accordance with claim 10, said measuring means comprising means for measuring a magnitude and a direction of the radial force imparted to the shaft by the rotating impeller.

12. In a centrifugal pump in accordance with claim 10, said measuring means comprising a pressductor radial tensiometer surrounding said bearing.

13. In a centrifugal pump in accordance with claim 10 wherein said bearing comprises a first bearing and said pump further comprises a second bearing spaced from said first bearing along said shaft so that said first bearing is disposed more closely proximate the impeller than said first bearing, said measuring means comprising means for measuring the radial force imparted to the shaft by the rotating impeller at said first bearing.