Cryogenic Pump Seal Pressure Buffering for Leakage Control
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Solution Overview
Problem
Cryogenic pump seals, particularly in high-pressure applications, are prone to leakage, which negatively affects the performance of cryogenic pumps used for transporting and storing cryogenic liquids like liquid natural gas and hydrogen.
Innovation Solution
A cryogenic pump design that utilizes an intermediate fluid, such as propane, to drive pistons and minimize differential pressures across seals by using a differential pressure vent valve and switch to manage pressure differentials, thereby reducing seal leakage and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional seals are used in high-pressure cryogenic pump applications, then the pump can achieve high-pressure pumping capability, but the seals are prone to leakage which deteriorates pump performance
Solution Approach 1:
The patent introduces an intermediate fluid (such as propane) as a mediator between the cryogenic liquid and the seal system. This intermediate fluid creates a pressure buffer zone that reduces the differential pressure across the seals, thereby minimizing seal leakage while maintaining high-pressure pumping capability. The intermediate fluid chamber and vent valve system work together to manage pressure differentials effectively.
Solution Approach 2:
The patent changes the pressure parameter distribution within the pump system by introducing a differential pressure management system. The vent valve and pressure switch work to maintain pressure differential across seals below a predetermined threshold, transforming the pressure distribution to reduce seal stress and prevent leakage while preserving the high-pressure pumping function.
2Reliability
If differential pressure across seals is reduced to minimize leakage, then seal reliability improves, but the ability to pump high-pressure cryogenic liquids is compromised
Solution Approach 1:
The intermediate fluid acts as a pressure mediator that decouples the high-pressure pumping requirement from the seal protection requirement. The intermediate fluid chamber receives the intermediate fluid at controlled pressure, creating a pressure buffer that allows the pump to generate high discharge pressure while maintaining low differential pressure across the seals, thus preserving both seal reliability and pumping capability.
Solution Approach 2:
The patent segments the pump internal pressure zones into distinct chambers: the high-pressure cryogenic liquid chamber, the intermediate pressure intermediate fluid chamber, and the low-pressure seal area. This segmentation allows different pressure levels to coexist in different zones, enabling high-pressure pumping while protecting seals through the intermediate pressure buffer zone.
3Reliability
If an intermediate fluid system is introduced to reduce seal differential pressure, then seal leakage is reduced, but the device complexity increases
Solution Approach 1:
The intermediate fluid system is designed to perform multiple functions simultaneously: it acts as a pressure buffer to protect seals, serves as a lubricant for the piston, and provides thermal management for the cryogenic liquid. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while achieving seal leakage reduction.
Solution Approach 2:
The patent merges the intermediate fluid chamber with the existing pump cylinder structure, and integrates the vent valve and pressure switch into the existing control systems. By combining multiple functions into existing structural elements rather than adding completely separate systems, the increase in device complexity is minimized while still achieving the seal protection objective.
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
The use of an intermediate fluid reduces seal leakage and friction, enabling efficient high-pressure pumping of cryogenic liquids with minimized differential pressures across seals, enhancing pump performance and reliability.
Implementation Method 1
A differential pressure space is defined within the cylinder between the intermediate fluid and pumped fluid seals
Implementation Method 2
A differential pressure vent valve is in fluid communication with the differential pressure space. A differential pressure switch is operatively connected to the differential pressure vent valve and configured to sense a pressure within the differential pressure space and open the differential pressure vent valve when the pressure within the differential pressure space reaches a predetermined pressure level
Data Source
AI summary
A pump for pumping a cryogenic liquid includes a pump housing having a cylinder with a piston slidably positioned therein. An intermediate fluid chamber that receives an intermediate fluid is defined within the cylinder adjacent to a first end of the piston and a fluid pumping chamber is defined within the cylinder adjacent to a second end of the piston. An intermediate fluid seal is attached to the piston and engages the cylinder. A pumped fluid seal attached to the piston and configured to engage the cylinder, said pumped fluid seal spaced from the intermediate fluid seal so that a differential pressure space is defined within the cylinder between the intermediate fluid and pumped fluid seals. A differential pressure vent valve is in fluid communication with the differential pressure space. A differential pressure switch senses a pressure within the differential pressure space and opens the differential pressure vent valve when the pressure within the differential pressure space reaches a predetermined pressure level.