Intumescent PTFE Hose Assembly for Fire Protection Without Bulk
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Solution Overview
Problem
Existing flexible PTFE hoses used in the aerospace industry for low to medium pressure applications face challenges in meeting stringent fire test requirements due to increased fluid flow demands, leading to undesirable weight and size increases from thicker steel braiding and protective sleeves.
Innovation Solution
A multi-layer flexible hose design featuring a PTFE inner tube, a steel braiding sleeve, an outer layer of silicon or fiberglass, and a coating of intumescent material between the steel braiding and outer layer, which reduces the need for thick external layers and provides effective fire protection without increasing hose thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of steel braiding and protective fire sleeve is increased to meet fire test requirements, then fire protection capability is improved, but weight and size increase
Solution Approach 1:
The patent applies parameter changes by utilizing the chemical transformation properties of intumescent material. When exposed to fire, the coating undergoes a parameter change from a thin dormant state to a thick expanded foam state, providing fire protection without increasing the hose's normal weight or size. This resolves the contradiction by changing the protective parameter dynamically rather than statically increasing thickness.
Solution Approach 2:
The intumescent coating is nested within the existing hose structure between the steel braiding and outer layer. This nested configuration allows the fire protective function to be integrated into the existing design without adding external bulk, thereby improving fire protection capability while maintaining acceptable weight and size parameters.
2Reliability
If the thickness of steel braiding and protective fire sleeve is increased to meet fire test requirements, then fire protection capability is improved, but hose size increases
Solution Approach 1:
The intumescent coating provides fire protection through parameter change rather than increased physical dimension. The coating remains thin during normal operation but expands in volume when activated by fire, thus improving fire protection capability without increasing the hose's installed volume or taking up more space in the aircraft.
Solution Approach 2:
The patent employs a thin film intumescent coating instead of thick rigid protective sleeves. This thin film approach maintains the hose's flexibility and compact size while providing the necessary fire protection, resolving the contradiction between fire protection capability and hose volume.
3Strength
If multiple steel braiding sleeves are used to enhance protection, then structural strength is improved, but device complexity increases
Solution Approach 1:
The patent extracts the fire protection function from the structural steel braiding layers and assigns it to a dedicated intumescent coating layer. This separation of functions allows the steel braiding to focus on mechanical strength while the coating handles fire protection, reducing the need for multiple thick braiding sleeves and thereby simplifying the overall structure.
Solution Approach 2:
The hose employs composite material construction with distinct layers serving different functions: PTFE liner for chemical resistance, steel braiding for mechanical strength, and intumescent coating for fire protection. This composite approach achieves both strength and fire protection requirements without requiring multiple layers of the same material, thus reducing structural complexity.
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 design allows for compliance with fire test requirements while minimizing weight and size, achieving a 30% reduction in fire protection weight and eliminating the need for multiple steel braiding sleeves, with the intumescent coating providing insulation and protection without chipping or cracking.
Implementation Method 1
a coating of intumescent material provided between the steel braiding sleeve and the outer layer
Data Source
AI summary
A multi-layer flexible hose is described comprising a multi-layered structure that has an inner, hollow tube comprising PTFE and an outer layer. The inner PTFE tube is provided so as to extend within the outer layer. The assembly further comprises another sleeve comprising steel braiding that is positioned between the inner PTFE tube and the outer layer. In addition to this, the hose further comprises a coating or layer of intumescent material that is provided between the steel braiding sleeve and the outer layer. A method for forming the hose is also described.