Seal Assembly Backing Ring Creep Resistance
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Solution Overview
Problem
Existing seal assemblies, particularly those using PTFE-based materials, face challenges in high temperature, pressure, and surface velocity applications due to cold-flow and creep, leading to reduced operating life, while PEEK materials are rigid and unsuitable for primary contact with moveable shafts.
Innovation Solution
A seal assembly comprising a rigid backing ring made of a high modulus material like PEEK, a seal ring with a radially extending lip for dynamic contact, and a retaining ring with a canted-coil spring or O-ring energizer, which minimizes distortion and cold-flow by directing spring force against the seal ring's axially extending flange, positioned in a high pressure region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PTFE material is used for seal rings in high temperature and pressure applications, then flexibility and self-lubrication are improved, but cold-flow and creep increase leading to shorter operating life
Solution Approach 1:
The seal assembly combines PTFE seal ring (providing flexibility and self-lubrication) with PEEK backing ring (providing high modulus and creep resistance). This composite structure allows the PTFE to maintain its lubricating properties while the PEEK prevents cold-flow and creep, resolving the contradiction between ease of operation and reliability in high temperature/pressure applications.
2Reliability
If PEEK material is used for seal rings, then resistance to high pressure, temperature and velocity is improved, but rigidity increases making it unsuitable for primary contact with moveable shafts
Solution Approach 1:
The invention uses PEEK for the backing ring to provide high temperature and pressure resistance, while PTFE is used for the seal ring that contacts the moveable shaft. This division allows PEEK to provide structural support and resistance to harsh conditions, while PTFE provides the necessary flexibility for dynamic sealing, resolving the contradiction between reliability and ease of operation.
Solution Approach 2:
The seal assembly is segmented into distinct functional components: the PTFE seal ring for dynamic contact and lubrication, and the PEEK backing ring for structural support and pressure resistance. This segmentation allows each material to perform its optimal function, with the PTFE providing flexibility for movement and the PEEK providing rigidity for pressure resistance.
3Reliability
If spring force is increased to maintain seal pressure, then sealing characteristics are improved, but distortion and cold-flow of the seal ring increase
Solution Approach 1:
The combination of PTFE seal ring with PEEK backing ring allows the use of spring energizers to maintain sealing pressure without increasing distortion. The PEEK backing ring's high modulus properties prevent the seal assembly from deforming under spring pressure, while the PTFE seal ring maintains its shape and sealing contact, resolving the contradiction between sealing characteristics and shape stability.
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 significantly enhances sealing characteristics and operating life by resisting pressure-induced distortion and creep, ensuring effective sealing performance in high-pressure applications.
Implementation Method 1
a spring is positioned in a holding bore, which is defined, at least in part, by the seal ring and the retaining ring
Implementation Method 2
directing spring force against the seal ring's axially extending flange, positioned in a high pressure region
Implementation Method 3
a seal ring positioned next to the backing ring and in mechanical engagement with the backing ring, said seal ring comprising a lip extending radially for dynamic contact with a moveable shaft
Implementation Method 4
a constant pressure is exerted by the seal on the shaft to maintain a dynamic seal between the shaft and the seal
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Seal assemblies and methods for forming them are described. Aspects of the seal assemblies include a seal ring made of a relative soft material supported by a specially configured backing ring made of a much higher modulus material, such as ferrous and non-ferrous metal or engineered plastic. The seal assemblies may optionally include a retaining ring to prevent slippage relative to the environment or housing in which they are placed and to prevent shuttling. The seal assemblies may also optionally include an energizer to alter the force generating by a sealing lip on the seal ring.