Cryogenic Pump Seal Structure for Thermal Wear Resistance
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Solution Overview
Problem
Piston pumps in cryogenic systems face challenges with seal wear and premature failure due to thermal expansion and contraction, leading to leaks and maintenance issues, as existing cup seals with springs fail within tens to hundreds of hours of use.
Innovation Solution
An annular seal design featuring a primary sealing portion with a trapezoidal cross-section and integral coil springs made of stainless steel, positioned within an annular space to engage with the piston rod and pump housing, using polytetrafluoroethylene with carbon or graphite fillers for enhanced durability and sealing efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cup seal with spring is used in a piston pump, then sealing effectiveness is improved, but seal lifespan deteriorates (fails within tens to hundreds of hours)
Solution Approach 1:
The seal is divided into multiple distinct portions: a primary sealing portion with specific geometric features (trapezoidal cross-section, convex portions) and a secondary sealing portion with different geometric features (radial groove, beveled edges). This segmentation allows each portion to perform specific sealing functions, distributing wear and improving overall durability compared to a single cup seal design.
Solution Approach 2:
Different portions of the seal have different geometric configurations and material properties optimized for their specific locations and functions. The primary sealing portion has convex portions and trapezoidal cross-section for sealing against the piston rod, while the secondary sealing portion has radial grooves and beveled edges for sealing against the pump housing. This local optimization improves both sealing effectiveness and wear distribution.
2Strength
If harder filler materials are added to the seal, then wear resistance is improved, but the piston rod or cylinder wall is scratched or abraded
Solution Approach 1:
The seal material composition is optimized by incorporating fillers (such as carbon or graphite) into the polytetrafluoroethylene matrix. This parameter change provides enhanced wear resistance and structural stability while maintaining a surface hardness that prevents scratching or abrading the piston rod and cylinder wall, resolving the contradiction between wear resistance and protection of mating surfaces.
3Adaptability or versatility
If gap size is increased to accommodate thermal expansion, then seal extrusion is prevented, but seal lifespan deteriorates due to extrusion through gaps
Solution Approach 1:
The seal design incorporates geometric features (trapezoidal cross-section, convex portions, radial grooves) that allow dynamic adaptation to thermal expansion and contraction. These features enable the seal to maintain contact pressure and sealing effectiveness while accommodating dimensional changes in the piston rod and pump housing during cryogenic operation, preventing both extrusion and premature failure.
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 annular seal design significantly increases seal lifespan and reduces maintenance needs by effectively sealing against thermal changes and wear, providing a reliable and long-lasting solution for cryogenic systems.
Implementation Method 1
a coil spring positioned within the annular space of the initial sealing portion and configured so as to urge the inner wall into engagement with the piston rod and the outer wall into engagement with the pump housing
Implementation Method 2
The primary sealing portion and the initial sealing portion may be comprised of a polytetrafluoroethylene. The primary sealing portion may further be comprised of at least one filler within the polytetrafluoroethylene. The filler may carbon or graphite.
Data Source
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AI summary
An annular seal for sealing an opening in a pump housing surrounding a piston rod includes a primary sealing portion with an inner surface adjacent to the piston rod and an outer surface adjacent to the pump housing. An initial sealing portion features an inner wall and an outer wall so that an annular space is defined therebetween. A top wall extends between the inner and outer walls. A coil spring is positioned within the annular space of the initial sealing portion and urges the inner wall into engagement with the piston rod and the outer wall into engagement with the pump housing.