Electronic Proportioner Continuous Metering Reciprocating Pump
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Solution Overview
Problem
Existing reciprocating pump proportioning systems face challenges in maintaining accurate fluid dispensing due to issues like cavitation, air entrapment, compressibility, and pressure imbalances, leading to inaccuracies in fluid proportioning and flow measurement.
Innovation Solution
The method employs linear displacement transducers, reed switches, and pressure transducers to identify and correct for the change-over window in reciprocating pumps, ensuring precise fluid displacement by compressing gases and adjusting for fluid compressibility, while maintaining a settable pressure ratio between components A and B, and using adjustable restrictors and metering valves to control flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reciprocating pumps are used for fluid dispensing, then positive displacement capability is achieved, but inaccuracies occur due to cavitation, air entrapment, and compressibility
Solution Approach 1:
The system performs preliminary actions by closing the fluid valve before the pump reaches changeover to allow compression of gases and positive closure of the check valve. This preliminary compression action eliminates air entrapment and cavitation issues that would otherwise cause measurement inaccuracies during the pump cycle.
Solution Approach 2:
The system uses feedback from the displacement transducer to monitor pump position and the fluid valve position sensor to detect when the valve closes. This feedback loop allows the controller to identify the changeover window and disregard travel and imputed flow during this period, compensating for compressibility and ensuring accurate flow measurement.
2Productivity
If the pump operates through changeover, then continuous fluid delivery is maintained, but gas compression and check valve closure delays cause measurement errors
Solution Approach 1:
The system extracts or removes the problematic changeover period from the flow measurement calculations. By identifying when the pump is in changeover using the displacement transducer and fluid valve position sensor, the system disregards travel and imputed flow during this specific window, eliminating measurement errors while maintaining continuous pump operation.
3Device complexity
If sequential dispensing of components is used, then simple control is achieved, but continuous proportioning accuracy is compromised
Solution Approach 1:
The system implements continuous metering of component A while component B is dosed intermittently to maintain ratio. This continuous action on the primary component, combined with correction based on displacement transducer feedback, maintains proportioning accuracy without requiring both components to be sequentially controlled, balancing simplicity with precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of fluid proportioning, maintains fluid ratio within set limits, and reduces errors caused by cavitation and pressure imbalances, providing reliable and precise fluid dispensing and flow rate calculations.
Implementation Method 1
each of a pair (or more) of air-operated reciprocating piston pumps is provided with a linear displacement transducer (LDT) which is capable of communicating a precise indication of the linear position of the air motor and pump rod
Implementation Method 2
a reed switch or other sensor on the air motor to indicate changeover is taking place
Implementation Method 3
closing the fluid valve as the pump reaches changeover, to allow the pump to compress any gases and positively close the check valve
Implementation Method 4
an outlet pressure sensor indicates that pumping has started
Data Source
Figure 1
Figure 2
AI summary
The controller of the plural component proportioner (10) dispenses both components (or all three if a three component material) as necessary to maintain the correct mix ratio. The fluid displacement measuring technique described allows this proportioning to take place with the "A" or main component pump always able to supply fluid to the spray gun without being stopped. The "B" component, at a higher pressure, is added as necessary to control ratio. The control can determine whether the pumps were properly loaded with fluid, and the fluid was properly compressed for accurate measurement. This technique allows for the proportioned fluids to be provided to the spray gun(s) at high flow rates and consistent spray pressure without interruption.