Anti-Extrusion Sealing System for Plastic-Lined Compressed Gas Cylinder
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Solution Overview
Problem
Current sealing systems in lightweight fuel cylinders, particularly those with plastic liners and metal bosses, face issues with leaks due to creep and differential thermal expansion, leading to potential cylinder failure and inability to repair leaks.
Innovation Solution
A sealing system is introduced that uses a profiled bore and insert with an annular seal element and tapered compression surface to form a primary and secondary seal, preventing extrusion and minimizing creep, while allowing for easy servicing and refurbishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a plastic liner is used in a lightweight cylinder, then the cylinder weight is reduced, but the sealing reliability deteriorates due to creep and extrusion at the seal interface
Solution Approach 1:
A metallic insert is introduced as an intermediary component between the plastic liner and the external environment. The insert provides a rigid sealing surface that prevents extrusion of the elastomeric seal element, while the plastic liner maintains its lightweight function. The insert acts as a mediator that resolves the conflict between the compliance of the plastic liner and the sealing requirements.
Solution Approach 2:
The sealing system employs a composite structure combining plastic liner, metallic insert, and elastomeric seal element. Each material contributes its advantageous properties: the plastic liner provides lightweight containment, the metal insert provides structural rigidity and seal protection, and the elastomer provides sealing compliance. This composite approach resolves the contradiction by leveraging the strengths of different materials.
2Reliability
If an elastomeric seal element is compressed against a plastic seat, then sealing is achieved, but the seal element extrudes under sustained pressure due to plastic creep
Solution Approach 1:
The metallic insert serves as an intermediary bearing surface that replaces the plastic seat in the sealing interface. The elastomeric seal element compresses against the rigid metal surface instead of the creeping plastic, preventing extrusion while maintaining the sealing function. The metal insert mediates between the compliant seal element and the stable structural requirement.
Solution Approach 2:
The invention changes the material parameter of the sealing surface from plastic to metal, fundamentally altering the creep resistance characteristic. This parameter change eliminates the dimensional instability issue while preserving the sealing function, as the metal insert does not exhibit the same creep behavior as plastic under sustained loading.
3Ease of manufacture
If a conventional threaded connection is used between boss and insert, then assembly is simplified, but leak paths cannot be blocked due to thread gaps
Solution Approach 1:
The sealing function is segmented from the threading function. The insert has separate features for threading (assembly) and for sealing (leak prevention). The sealing surface is distinct from the threaded portion, allowing each to be optimized independently. This segmentation enables both easy assembly via threads and reliable leak prevention via the dedicated sealing interface.
Solution Approach 2:
The insert acts as an intermediary component that provides both the threaded connection interface and the sealed interface. It mediates between the boss (cylinder structure) and the external fittings, providing a pathway for both mechanical assembly and fluid sealing through its dual-function design.
4Reliability
If the seal interface is made between liner and boss, then sealing is provided, but any leak requires cylinder scrap as repair is not possible
Solution Approach 1:
The sealing system is segmented into replaceable components (insert and seal element) and permanent components (liner and boss). The insert can be removed and replaced without affecting the liner or boss, enabling repair of sealing issues while preserving the main cylinder structure. This segmentation transforms an unrepairable system into a repairable one.
Solution Approach 2:
The seal element and insert are extracted as separate, removable components from the permanent cylinder structure. This extraction allows the sealing components to be independently serviced, replaced, or refurbished without compromising the integrity of the liner and boss, thereby enabling repair while maintaining sealing reliability.
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 system effectively seals the outlet of a plastic-lined cylinder, preventing leaks and maintaining dimensional stability under high pressures and varying temperatures, enabling the cylinder to be quickly returned to service if leaks occur.
Implementation Method 1
The tapered interface compresses the liner outlet and closes the annular assembly clearance at about the seal element
Implementation Method 2
The seal element corresponds and seals with the sealing bore portion to form an annular, primary seal
Data Source
AI summary
A sealing system for an outlet of a plastic-lined cylinder has a plastic liner outlet extending into a bore of a boss. An insert is engageable with the bore, forming a primary seal between the insert and portion of the liner outlet. Further, a tapered compression surface of the insert engages a tapered bore portion of the liner outlet adjacent the primary seal for compressing the liner outlet and closing any annular assembly clearance at the primary seal for obviating opportunity for seal extrusion under pressure. An axial position in the boss, and dimensional integrity, of the liner outlet is maintained by engaging an annular distal end of the liner outlet in the bore by a stop. The stop can be integral with the boss. Reverse extrusion of the primary seal due to trapped gas and rapid decompression of the cylinder can be defeated by providing a leak path.