Flexible Pipe End-Fitting Sealing for Pressure Reversals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing end-fitting and unbonded flexible pipe systems require permanent compressive forces to maintain sealing integrity, which can be challenging under varying pressures and temperatures, and are complex and costly to implement.
Innovation Solution
The use of a seal casing with a first ring-shaped sealing element of Shore D hardness 40-70 and a second ring-shaped sealing element of Shore A hardness 80-100 IRHD, which form line contacts to provide self-sealing properties without the need for permanent compressive forces, using polymer materials like polyolefins and fluoroelastomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent compressive forces are used to maintain sealing integrity, then sealing reliability is improved, but device complexity and cost increase
Solution Approach 1:
The sealing elements are designed to automatically maintain sealing contact through pressure differential forces. The first sealing element is pressed against the internal pressure sheath by the higher pressure in the annulus, while the second sealing element is pressed against the seal casing by the pressure differential. This self-actuating mechanism eliminates the need for external compressive forces, permanent deformation, or complex actuation systems, thereby maintaining high reliability while reducing device complexity and cost.
2Reliability
If permanent compressive forces are applied to sealing elements, then sealing reliability is improved, but the sealing elements require rigid structures and the system becomes less adaptable to pressure variations
Solution Approach 1:
The sealing system transitions from a static, pre-compressed configuration to a dynamic, pressure-responsive configuration. The sealing elements can move axially and radially in response to pressure changes, automatically adjusting their contact forces. The first sealing element moves with the internal pressure sheath under external pressure, while the second sealing element is pushed against the seal casing by the pressure differential. This dynamic behavior enables the system to adapt to varying pressure conditions while maintaining reliable sealing.
Solution Approach 2:
The system exploits changes in pressure parameters to maintain sealing. Instead of maintaining constant compressive force, the sealing contact force varies with the pressure differential across the pipe wall. When external pressure exceeds internal pressure, the first sealing element is pressed against the sheath; when internal pressure exceeds external pressure, the second sealing element is pressed against the seal casing. This parameter-based control provides both reliability and adaptability to pressure reversals.
3Strength
If hard sealing materials are used to withstand high pressure, then strength is improved, but the sealing becomes less conformable to the internal pressure sheath surface
Solution Approach 1:
The sealing system employs different material properties at different locations to optimize both strength and conformability. The first sealing element, which contacts the internal pressure sheath, is made of a softer material (Shore A 60-80) that can conform to the sheath surface irregularities. The second sealing element, which contacts the rigid seal casing, is made of a harder material (Shore D 40-70) that can withstand high compressive stresses. This local differentiation of material properties allows each sealing element to perform its specific function optimally, achieving both conformability and pressure resistance.
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
This configuration achieves efficient and cost-effective sealing, maintaining integrity under pressure reversals and temperature variations, reducing the risk of leaks and environmental impact, while simplifying the sealing process.
Implementation Method 1
a first ring shaped sealing element is concentrically arranged around the internal pressure sheath such that the surface of the first ring shaped sealing element at least forms a line contact with the internal pressure sheath
Implementation Method 2
a second ring shaped sealing element is concentrically arranged around the internal pressure sheath in said recess such that the surface of the second ring shaped sealing element at least form a line contact with the surface of the seal casing and form a line contact with the surface of the first ring shaped sealing element
Data Source
AI summary
An end-fitting and an unbonded flexible pipe, where the unbonded flexible pipe includes from the inside and out an internal pressure sheath, at least one armor layer and an outer sheath, the end-fitting further includes a sealing element. The sealing element includes a seal casing concentrically arranged around the internal pressure sheath, the seal casing includes a recess in which a first sealing element is concentrically arranged around the internal pressure sheath such that the surface of the first sealing element at least forms a line contact with the internal pressure sheath, and a second sealing element is concentrically arranged around the internal pressure sheath in the recess such that the surface of the second sealing element at least form a line contact with the surface of the seal casing and form a line contact with the surface of the first sealing element.