Dual Plunger Pump Pressure Control for Chromatography Stability
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Solution Overview
Problem
Liquid delivery pumps in liquid chromatography face challenges in maintaining flow rate stability due to insufficient or excessive pre-pressurization, leading to impaired liquid delivery stability and thermal effect pulsation, which affects the reproducibility of analysis results.
Innovation Solution
A liquid delivery pump system with a primary and secondary plunger pump configuration, where constant pressure control is executed in distinct terms using specific control equations to adjust flow rates, with the primary discharge process as a first constant pressure control term and the secondary discharge process as a second term, reducing the contribution of integral terms in the second equation to minimize pressure overshoot and thermal effect pulsation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-pressurizing is increased to ensure sufficient pressure in the pump chamber, then liquid delivery stability is improved, but excessive pre-pressurizing causes excessive liquid delivery flow rate and impairs stability
Solution Approach 1:
The control device measures the actual pressure in the pump chamber during pre-pressurizing and compares it with the target pressure, then adjusts the plunger operation accordingly. This feedback mechanism prevents both insufficient and excessive pre-pressurizing, resolving the contradiction between maintaining delivery stability and controlling flow rate.
Solution Approach 2:
The system dynamically adjusts the plunger speed and position based on real-time pressure measurements. The plunger operation is not fixed but adapts to the actual pressure conditions, allowing optimal balance between pressure buildup and flow rate control.
2Reliability
If constant pressure control is applied during the primary discharge process, then thermal effect pulsation is reduced, but pressure overshoot occurs in the secondary discharge process
Solution Approach 1:
The constant pressure control is segmented into two distinct control periods: first constant pressure control during the primary discharge process and second constant pressure control during the secondary discharge process. Each period uses appropriate control parameters to avoid pressure overshoot while reducing thermal effect pulsation.
Solution Approach 2:
The control parameters (such as integral term contribution) are changed between the two control periods. The degree of contribution of the integral term in the second control period is reduced compared to the first period, adapting to the different pressure conditions in each discharge process.
3Device complexity
If a single plunger pump is used for liquid delivery, then device complexity is reduced, but flow rate stability is impaired due to intermittent delivery
Solution Approach 1:
Two plunger pumps are merged into a series configuration where the outlet of the first plunger pump connects to the inlet of the second plunger pump. This combination allows continuous liquid delivery with improved flow rate stability while maintaining relatively simple device structure.
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 improves the accuracy of constant pressure control, enhancing liquid delivery stability and reproducibility of analysis results by effectively managing thermal effect pulsation and flow rate variations.
Implementation Method 1
a pressure sensor that detects a system pressure that is a pressure of a mobile phase delivered from an outlet of the secondary plunger pump
Implementation Method 2
at least one plunger pump performs a pre-pressurizing process for increasing a pressure in a pump chamber to a system pressure or a pressure in the vicinity of the system pressure
Implementation Method 3
The mobile phase is at room temperature in the suction process, but has a temperature increased by being adiabatically compressed in the pre-pressurizing process
Implementation Method 4
is cooled by exchanging heat with surrounding members such as a pump head and a pipe in a subsequent discharge process
Data Source
AI summary
A liquid delivery pump includes a primary plunger pump, a secondary plunger pump fluidly connected in series downstream of the primary plunger pump, and a pressure sensor that detects a system pressure. The liquid delivery pump further includes a liquid delivery control part configured to execute first constant pressure control in a first constant pressure control term and to execute second constant pressure control in a second constant pressure control term. The first constant pressure control term is a term, which is in a liquid delivery cycle consisting of the primary discharge process and the secondary discharge process, in which the primary discharge process is executed, the second constant pressure control term is a part of a term in which the secondary discharge process is executed, and the second constant pressure control term is including a term that is continuous after the first constant pressure control term.