Dynamic Backup Ring for High-Pressure Seal Extrusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dynamic seals in high-pressure applications face challenges with extrusion damage due to heavily loaded shaft-to-housing contact, misalignment, and pressure-induced deformation, limiting their ability to maintain sealing effectiveness under differential pressures.
Innovation Solution
A backup ring is designed with radial and axial pressure balancing to maintain a small extrusion gap, allowing it to align with the shaft and follow lateral deflections, using hydraulic forces to counteract pressure imbalances and prevent deformation, thus minimizing extrusion damage and maintaining sealing integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a small extrusion gap clearance is used to avoid extrusion damage, then extrusion resistance is improved, but heavily loaded shaft-to-housing contact occurs at the extrusion gap region
Solution Approach 1:
A backup ring is introduced as an intermediary component between the dynamic seal and the housing bore. The backup ring has a diameter slightly larger than the shaft diameter, positioning it to bear the lateral load that would otherwise be applied to the housing bore at the extrusion gap region. This mediator protects the dynamic seal from heavily loaded contact while maintaining the small extrusion gap clearance needed for extrusion resistance.
Solution Approach 2:
The sealing assembly is segmented into distinct functional components: the dynamic seal for sealing, the backup ring for load bearing, and the housing for structural support. By dividing the functions, the backup ring specifically handles the lateral load bearing function, allowing the dynamic seal to focus on sealing while maintaining a small extrusion gap without suffering from heavily loaded contact.
2Force
If a large extrusion gap clearance is used to avoid heavily loaded contact, then shaft-to-housing contact is reduced, but pressure causes seal material to protrude into the extrusion gap
Solution Approach 1:
The backup ring serves as a physical barrier and load distributor between the shaft and the dynamic seal housing. By positioning the backup ring with its diameter slightly larger than the shaft diameter, it prevents the dynamic seal from being subjected to both heavy lateral loads and pressure-induced extrusion simultaneously, allowing the extrusion gap to be optimized for pressure resistance without compromising on load bearing.
3Ease of manufacture
If manufacturing tolerances are large in large machinery, then ease of manufacture is improved, but shaft run-out and misalignment increase
Solution Approach 1:
The backup ring is designed to be laterally movable relative to the housing, allowing it to dynamically adjust its position to follow shaft run-out and misalignment. This dynamic capability compensates for the effects of large manufacturing tolerances, enabling the system to maintain proper alignment and function despite variations in shaft position caused by manufacturing imperfections.
Solution Approach 2:
The backup ring's lateral position is allowed to change as a parameter in response to shaft movement. By permitting this positional change, the system adapts to shaft run-out and misalignment caused by large manufacturing tolerances, maintaining effective sealing and load bearing functionality throughout operation.
4Manufacturing precision
If the housing is made non-floating for stack alignment, then alignment precision is improved, but misalignment between shaft and seal housing increases due to manufacturing tolerances
Solution Approach 1:
While the housing remains non-floating for precise stack alignment, the backup ring is designed with lateral mobility to dynamically follow shaft run-out and misalignment. This creates a hierarchical system where the housing provides fixed alignment reference, but the backup ring adapts to shaft position variations, combining the benefits of both fixed and floating characteristics.
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 backup ring effectively increases the differential pressure capability of dynamic seals by maintaining a stable extrusion gap, reducing friction and heat generation, and preventing damage from misalignment and pressure-induced deformation.
Implementation Method 1
The backup ring is laterally movable with respect to the housing and is radially located by a bearing relationship with the shaft. The assembly is configured such that neither differential pressure acting across the dynamic seal, nor ambient fluid pressure, causes the backup ring to significantly change diameter.
Implementation Method 2
The backup ring has a bearing relationship with the shaft, and thus can follow lateral motion of the shaft.
Data Source
Figure 1
Figure 1A
Figure 2
AI summary
A seal backup ring assembly is provided that eliminates fluid differential pressure acting radially on the backup ring, preventing collapse of the backup ring against a shaft. The backup ring is assembled so that the initial clearance (extrusion gap) between the backup ring and relatively rotating member is not affected by the differential pressure acting across the assembly. This allows for an initially small extrusion gap to be present throughout the differential pressure range.