Flexible Sealing Membrane Structure for High-Pressure Shaft Seals
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Solution Overview
Problem
Mechanical seals in rotary shaft equipment face challenges at high pressures, where axial loads cause elastomeric bellows to collapse, leading to excessive face pressure, frictional wear, and seal failure, due to the inability to effectively counteract closing forces.
Innovation Solution
A non-collapsible flexible sealing membrane with a radially extending flange portion and an axially extending coaxial portion, fixed to a stub sleeve by an annular band, provides directional control of forces and maintains a constant closing force, reducing the impact of axial shaft movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an elastomeric bellows is used in a mechanical seal assembly, then the seal can accommodate axial movement of the shaft, but at high pressures the bellows collapses axially and cannot counteract closing forces
Solution Approach 1:
The patent uses a flexible membrane bellows structure instead of a rigid or semi-rigid elastomeric bellows. The membrane construction allows the bellows to flex and expand/contract axially to accommodate shaft movement while maintaining structural integrity at high pressures. The thin film nature of the membrane prevents collapse under pressure while still providing the necessary flexibility for axial compensation.
Solution Approach 2:
The flexible membrane bellows is constructed from composite materials that combine flexibility with high pressure resistance. The membrane material properties are engineered to provide both the elastic deformation needed for axial movement accommodation and the structural strength to resist collapse at high gauge pressures, resolving the contradiction between adaptability and reliability.
2Reliability
If the bellows is made flexible to accommodate axial movement, then it can seal at higher pressures, but it may collapse under axial load
Solution Approach 1:
The membrane bellows employs thin film construction that provides flexibility for high pressure sealing while the specific membrane geometry and material properties prevent axial collapse. The film structure distributes axial loads across the membrane surface, maintaining strength-to-weight ratio and preventing buckling under operating pressures.
Solution Approach 2:
The bellows structure transitions from traditional axial-only flexibility to a multi-dimensional flexible membrane structure. The membrane can deform in multiple directions (radial expansion, axial contraction, circumferential flexing) which distributes stress and prevents collapse while maintaining sealing capability at high pressures.
3Adaptability or versatility
If the closing force is allowed to vary with axial position, then the bellows can accommodate wear, but excessive face pressure and frictional wear occur
Solution Approach 1:
The flexible membrane bellows acts as a feedback mechanism that automatically adjusts the closing force on the seal faces based on the actual gap between them. As the seal faces wear and the gap increases, the membrane expands axially to maintain constant closing force. This feedback control prevents excessive face pressure and reduces frictional wear while continuously accommodating wear.
Solution Approach 2:
The bellows membrane changes its axial dimension (expands or contracts) in response to wear, thereby maintaining a constant closing force parameter. This parameter change in the bellows geometry compensates for seal face wear without allowing excessive face pressure to develop, reducing frictional wear and extending seal life.
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 flexible sealing membrane effectively maintains seal performance at high pressures by preventing collapse and ensuring consistent closing forces, reducing leakage and extending seal life.
Implementation Method 1
an elastomeric bellows, an example of which is provided in FIG. 1. The depicted mechanical seal comprises an elastomeric bellows that is driven to rotate with the shaft relative to the housing. This non-pusher seal can reduce torque stress on the bellows, which are intended to contract and expand to balance the opening and closing forces on the seal faces.
Data Source
AI summary
A non-collapsible flexible sealing membrane (or bellows) for incorporation in a mechanical seal assembly and use in rotary shaft equipment. The sealing membrane includes a substantially radially outward extending first flange portion, which can be urged into an axially shiftable ring by a biasing mechanism. The sealing membrane further includes a substantially axially outboard extending second coaxial portion, substantially radially inward of the balance diameter of the seal. The horizontal portion is advantageously held fixed to a stub sleeve by an annular band. The angle between the vertical portion and the horizontal portion of sealing membrane enables directional control of the forces acting on stub sleeve and primary ring.