Pump Flow Determination Without Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining pump flow in centrifugal pumps are inaccurate due to reliance on affinity laws, require external sensors, and are application-specific, limiting flexibility and ease of adjustment for wear compensation.
Innovation Solution
A method that creates a calibrated power curve at closed valve conditions across various speeds, calculates coefficients from a power vs flow curve based on the pump's power ratio, and solves a power equation to determine flow at the current operating point, eliminating the need for traditional sensors and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensors and external transmitters are used to determine pump flow, then measurement accuracy can be improved, but device complexity and cost increase
Solution Approach 1:
The pump system uses its own motor power consumption data and built-in sensors to determine pump flow, eliminating the need for external flow meters and transmitters. The controller internally correlates power consumption with flow rate using affinity laws, allowing the system to self-determine flow without additional measurement devices.
Solution Approach 2:
The patent replaces traditional mechanical flow measurement systems (flow meters, differential pressure transmitters) with an electrical/power-based measurement approach. By measuring motor power consumption and using the relationship between power, speed, and flow, the system substitutes complex mechanical sensing with simpler electrical measurements and calculations.
2Adaptability or versatility
If affinity laws are used to estimate pump performance, then general flow prediction can be achieved, but measurement precision deteriorates due to over or under estimation of power
Solution Approach 1:
The system continuously monitors actual motor power consumption and compares it with expected power values based on affinity laws. The controller uses this feedback to detect deviations caused by pump wear, impeller damage, or system changes, and adjusts flow predictions accordingly to maintain accuracy.
Solution Approach 2:
The patent modifies the standard affinity laws by introducing correction factors based on actual measured power consumption data. Instead of relying solely on theoretical relationships, the system adjusts key parameters (power, flow, head) based on real-world measurements to compensate for pump degradation and maintain prediction accuracy over time.
3Measurement precision
If pump performance tests are conducted at multiple speeds to confirm accurate performance, then measurement precision can be improved, but loss of time and productivity increase
Solution Approach 1:
The system performs pump performance characterization during normal operation by continuously collecting power consumption data at various speeds. Instead of requiring separate factory tests, the pump's performance curves are built up over time during regular use, eliminating the need for time-consuming pre-calibration tests.
Solution Approach 2:
The patent enables continuous collection and analysis of pump performance data during normal operation. The controller continuously monitors power consumption, speed, and flow relationships, constantly refining the performance model without interrupting pump operation, thus maintaining continuous useful action while improving measurement precision.
4Measurement precision
If application-specific calibrated curves are used, then measurement precision can be improved, but adaptability deteriorates due to reduced flexibility during field setup
Solution Approach 1:
The patent creates a universal method that can be applied to any centrifugal pump by using the pump's own performance characteristics and affinity laws. The system automatically adapts to different pump types, sizes, and applications by building its own performance model from measured data, eliminating the need for application-specific calibration curves and providing universal applicability.
Data Source
AI summary
A technique for determining pump flow without using traditional sensors features steps and modules for creating a calibrated power curve at closed valve conditions at several speeds; calculating coefficients from a normalized power curve based on a pump's power ratio; and solving a polynomial power equation for flow at the current operating point. The calibrated power curve may be created by increasing the speed of the pump from a minimum speed to a maximum speed and operating the pump with a closed discharge valve. This data is used to correct published performance for shutoff power and best efficiency point power at rated speed in order to determine the pump's power ratio. It is also used to accurately determine closed valve power at the current operating speed. The pump's power ratio is determined by the equation: Pratio=Pshutoff @100%/PBEP<sub2>—</sub2>corr. The polynomial power equation may, for example, include a 3rd order polynomial equation developed using coefficients from the normalized power versus flow curve, and corrections may be made for speed, hydraulic efficiency and specific gravity in the polynomial power equation. Complex roots may be determined to solve the 3rd order polynomial equation using either Muller's method or some other suitable method, and the calculated actual flow may be determined for a specific operating point.