Backup Ring Pressure Balancing for Dynamic Shaft Sealing
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Solution Overview
Problem
Existing sealing assemblies for movable shafts in equipment face challenges with pressure-induced diametric dimensional changes and radial pressure imbalances, leading to extrusion damage and inefficiencies in maintaining a constant extrusion gap clearance, especially in applications with significant shaft reciprocation and misalignment.
Innovation Solution
A sealing assembly that employs a backup ring with a pressure-retaining seal and a partitioning seal, where the backup ring is axially positioned and sealed to maintain a constant diameter, using hydraulic forces to balance differential pressures and accommodate lateral deflections and runout, ensuring a minimal extrusion gap and preventing fluid loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional seal carrier is used to retain pressurized fluid, then sealing function is provided, but pressure-induced diametric dimensional changes cause extrusion gap variation and extrusion damage
Solution Approach 1:
The backup ring is designed with pressure-balancing features where fluid pressure acts on both the inner and outer surfaces, creating equalizing forces that cancel each other out. This equipotential pressure distribution prevents diametric dimensional changes and maintains a constant extrusion gap clearance, eliminating pressure-induced extrusion damage while preserving sealing reliability
Solution Approach 2:
The patent applies counterbalancing hydraulic forces on opposite sides of the backup ring. The pressure-induced forces acting on the inner and outer surfaces function as counterweights that offset each other, preventing net radial expansion or contraction that would otherwise cause extrusion gap variation and seal damage
2Adaptability or versatility
If a seal carrier accommodates shaft reciprocation and misalignment, then adaptability is improved, but radial pressure imbalances lead to extrusion gap clearance variation
Solution Approach 1:
The backup ring is designed as a floating, dynamically adjustable component that can laterally translate to follow shaft deflection and runout. The pressure-balancing forces enable the ring to dynamically adapt to varying shaft positions and orientations while maintaining constant extrusion gap clearance, simultaneously achieving motion accommodation and gap consistency
Solution Approach 2:
The backup ring automatically self-aligns with the shaft through pressure-balanced hydraulic forces that guide it to follow lateral deflection and runout. This self-adjusting mechanism eliminates the need for external alignment devices while maintaining precise extrusion gap clearance under varying operational conditions
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 solution effectively maintains a consistent extrusion gap, reduces pressure-induced extrusion damage, and prevents fluid leakage by balancing hydraulic forces, allowing the backup ring to align and move with the shaft, thus enhancing the sealing efficiency and durability in dynamic conditions.
Implementation Method 1
applies the pressures of the first and second fluids to controlled locations on a backup ring in order to provide relative immunity to pressure-induced diametric dimensional changes
Implementation Method 2
allowing the backup ring to align itself on the shaft and to follow lateral deflection and runout of the shaft
Data Source
AI summary
The invention is a sealing assembly for equipment with movable shafts—such as coaxial and side port swivels, hydraulic swivels, and rotary control devices—that prevents the loss of a high pressure fluid through the clearance existing between a housing and the shaft. The invention is disclosed in the context of a coaxial swivel that conducts high pressure fluid from a stationary first conduit to a rotating second conduit that has dynamic runout, and may be misaligned relative to the first conduit.