Piston Seal Assembly with Controlled Leakage and Stable Wear
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Solution Overview
Problem
Reciprocating piston seals in high-pressure and cryogenic pumps face challenges due to excessive wear and leakage, leading to inconsistent seal life and frequent replacements, exacerbated by manufacturing tolerances and varying pressure drops across seals.
Innovation Solution
The use of a seal energizer with strategically positioned tabs or recesses ensures a stable axial position within the piston groove, minimizing leak paths and maintaining consistent seal wear by controlling the axial positioning of the seal energizer, thereby reducing fluid leakage and extending seal life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tight manufacturing tolerances are used to control the gap between seal energizer and piston groove, then leakage is reduced, but manufacturing cost and complexity increase
Solution Approach 1:
The seal energizer automatically positions itself within the piston groove through the interaction of its lateral surfaces with the groove walls. The elastic force generated by the split ring structure causes the seal energizer to press against the groove walls, creating self-positioning that minimizes leak paths without requiring tight manufacturing tolerances for the gap between the seal energizer and groove walls.
2Reliability
If seal energizer elastic force is increased to compensate for seal wear, then seal contact with cylinder wall is maintained, but manufacturing variability in gap size causes inconsistent leakage
Solution Approach 1:
The seal energizer self-adjusts its position within the piston groove based on the seal wear condition. As the seal wears and the gap between seal and cylinder wall increases, the seal energizer automatically shifts position to maintain optimal contact pressure, compensating for wear without requiring precise control of the initial gap dimensions.
Solution Approach 2:
The seal energizer is designed as a split ring structure that can dynamically adjust its position and elastic force distribution. The split configuration allows the ring to expand and contract, enabling the seal energizer to adapt to varying seal wear conditions and maintain consistent sealing performance despite manufacturing tolerances in the initial gap size.
3Reliability
If multiple seal assemblies are mounted in series, then sealing coverage is improved, but random seal failure increases due to varying pressure drops
Solution Approach 1:
Each seal energizer in the series independently self-adjusts to equalize the pressure drop across its associated seal. The automatic positioning mechanism responds to local pressure conditions, ensuring that each seal experiences similar operating conditions and wear rates, preventing any single seal from becoming a weak point in the series arrangement.
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 solution effectively reduces seal leakage and enhances the consistency of seal wear, leading to increased service intervals and improved operational efficiency of reciprocating pumps by maintaining a controlled leak path area and stable seal positioning.
Implementation Method 1
The seal energizer is split transversally such that there is a gap between the free ends of the ring which provides for an easier installation of the seal energizer in the piston groove and provides more elastic force for pushing the seal towards the cylinder wall
Implementation Method 2
Pistons which reciprocate within a cylinder bore are well known in the art and have been long used for pumps, hydraulic drives, engines, pneumatic drives and other hydraulic or pneumatic machines delivering different fluids at increased pressure
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A piston seal assembly is disclosed comprising a seal and a seal energizer which supports the seal. The piston seal assembly comprises one component that is designed to position the seal energizer in a fixed axial position within the piston groove. In one embodiment, the seal energizer has the shape of a split ring with at least one of its lateral surfaces shaped to position the energizer in a fixed position within a piston groove. In other embodiments the piston seal assembly comprises a spacer that is positioned next to the seal energizer within the piston groove and is designed to position the seal energizer in a fixed axial position. The piston seal assembly can comprise a seal that has a portion which protrudes between the seal energizer and the piston groove wall such that it positions the seal energizer in a fixed axial position within the piston groove.