Secondary Seal Coating to Prevent Mechanical Seal Gap Extrusion
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Solution Overview
Problem
Mechanical seals with secondary seals face issues of material extrusion into gaps due to high pressures and temperatures, leading to potential failure, as they are prone to being drawn into the sealing gap and causing malfunctions.
Innovation Solution
A mechanical seal arrangement with a secondary seal featuring a coating bonded to the base material, where the coating's stiffness is greater than the base material's, applied on both sides of the secondary seal, with a thickness less than or equal to half the gap height, preventing further extrusion by creating overlapping coated regions and inducing tensile and shear stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary seal is used to seal against high pressure and temperature, then sealing reliability is improved, but material extrusion into the gap occurs leading to seal failure
Solution Approach 1:
The secondary seal is designed as a composite structure with a base material (softer) and a coating layer (stiffer). This composite construction allows the seal to maintain flexibility for sealing while the stiffer coating prevents excessive extrusion into the gap, resolving the contradiction between sealing reliability and extrusion resistance
Solution Approach 2:
The coating is applied only to specific regions of the secondary seal - primarily on the sides that may extrude into the gap, while leaving other areas as base material. This local differentiation allows the seal to have different properties in different regions: extrusion resistance where needed, and flexibility where sealing is critical
2Object-generated harmful factors
If the secondary seal is made softer to prevent extrusion, then extrusion resistance is improved, but sealing performance under high pressure deteriorates
Solution Approach 1:
The composite structure with softer base material and stiffer coating allows the seal to exhibit softness where needed for sealing conformability while maintaining stiffness where extrusion resistance is critical, thus resolving the contradiction between extrusion resistance and sealing performance
3Object-generated harmful factors
If a specifically designed ring element is added to reduce extrusion, then extrusion resistance is improved, but device complexity increases
Solution Approach 1:
The extrusion-resistant coating is integrated directly onto the secondary seal as a single combined component, eliminating the need for separate ring elements or additional parts. This merging approach maintains extrusion resistance while significantly reducing device complexity compared to multi-component solutions
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 minimizes extrusion into the gap, ensuring reliable sealing performance even under high pressures, with the coating's higher stiffness preventing material from being drawn too deeply, thus enhancing durability and sealing efficiency.
Implementation Method 1
large tensile and/or shear stresses result in the region of the coating which has not yet been extruded into the gap, so that further extrusion of the secondary seal into the gap will be prevented
Implementation Method 2
the coating is bonded to a base material of the secondary seal via substance-to-substance bonding
Data Source
AI summary
The invention relates to a mechanical seal arrangement comprising a mechanical seal (2) having a rotating seal ring (21) and a stationary seal ring (22) defining a seal gap (23) therebetween, a secondary seal (3) arranged on a back surface of one of the seal rings facing away from a sealing surface of the seal ring, the secondary seal (3) being made of a base material and having a coating (7) such that a material bond is formed between the coating (7) and the base material of the secondary seal, the secondary seal (3) being made of a base material and having a coating (7) such that a substance-to-substance connection is formed between the coating (7) and the base material of the secondary seal, a sleeve-shaped member (4) arranged radially inside the secondary seal (3), wherein a gap (5) having a gap height (H) is present between the sleeve-shaped component (4) and a region of one of the sliding rings facing radially inwards, the secondary seal (3) seals against the back side of this slide ring and the sleeve-shaped component (4), wherein the coating (7) is provided on a first side (31) of the secondary seal (3), which first side facing the sliding ring, and a second side (32) of the secondary seal (3) which second side facing the sleeve-shaped component (4), wherein a stiffness of the coating (7) is greater than a stiffness of the base material of the secondary seal (3) and wherein a thickness (D) of the coating is smaller than or equal to a gap height (H) of the gap (5).