Fire Resistant Flexible Hose Grooved Liner Thermal Barrier
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Solution Overview
Problem
Conventional flexible hose assemblies fail to meet aerospace standards for fire resistance, particularly in high-temperature environments, due to thermal degradation and leakage issues, and are susceptible to chemical attacks like chloride stress corrosion.
Innovation Solution
A multilayer flexible hose assembly with a fluoropolymer inner liner tube having a grooved external surface, surrounded by thermal barrier and reinforcement layers, including a ceramifiable rubber composite, which provides thermal insulation and resistance to thermal expansion, maintaining integrity and preventing leakage during exposure to high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hose assemblies are used to meet other requirements, then they satisfy general hose specifications, but they fail to satisfy AS 1055 fire resistance standards due to thermal degradation and leakage
Solution Approach 1:
The hose is divided into distinct functional layers: an inner tube for fluid containment, a middle layer comprising thermal barrier and reinforcement, and an outer cover layer. This segmentation allows each layer to be optimized for its specific function, with the middle layer specifically designed to prevent thermal degradation and maintain structural integrity during fire exposure, thereby achieving fire resistance without excessive overall complexity
Solution Approach 2:
The hose employs composite material construction with the middle layer combining thermal barrier materials and reinforcement materials in specific configurations. This composite structure provides both thermal protection and mechanical strength, enabling the hose to withstand fire conditions while maintaining fluid containment capability
2Weight of moving object
If the number and thickness of layers are reduced to make the hose lightweight and compact, then weight and diameter decrease, but thermal insulation capability is diminished
Solution Approach 1:
The thermal barrier and reinforcement are concentrated in the middle layer that is in direct or indirect contact with the inner tube, providing localized thermal protection where it is most needed. The outer cover layer thickness is optimized to provide sufficient protection without excessive weight, achieving local quality optimization rather than uniform thickness throughout
Solution Approach 2:
The hose structure nests multiple functional layers within each other: the inner tube is surrounded by the middle layer, which is in turn surrounded by the outer cover layer. This nested configuration maximizes thermal insulation capability within a compact structure, providing adequate protection while maintaining a space-efficient design
3Strength
If an outermost external woven or braided layer of stainless steel wire is used, then structural strength is improved, but the hose becomes susceptible to chloride stress corrosion
Solution Approach 1:
The middle layer acts as an intermediary between the inner tube and the external environment, providing both thermal barrier and reinforcement functions. This intermediate layer protects the stainless steel reinforcement from direct exposure to chlorides and other corrosive chemicals in the external environment, preventing chloride stress corrosion while maintaining structural strength
Solution Approach 2:
The middle layer combines thermal barrier materials with reinforcement materials to create a composite structure that provides both mechanical strength and chemical resistance. This composite construction protects the stainless steel wire from chloride exposure while maintaining the required structural integrity
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 hose assembly effectively withstands high temperatures above 1000°C for extended periods, maintaining fluid containment and resisting thermal degradation, while being lightweight and flexible, thus meeting aerospace standards such as SAE AS1055.
Implementation Method 1
A flexible hose assembly comprises: a fluoropolymer inner liner tube having a grooved external facing surface... at least one thermal barrier layer... in contact with and provided over the liner tube
Implementation Method 2
The hose assembly effectively withstands high temperatures above 1000°C for extended periods, maintaining fluid containment and resisting thermal degradation
Implementation Method 3
including a ceramifiable rubber composite, which provides thermal insulation and resistance to thermal expansion
Data Source
AI summary
A flexible fire resistant hose assembly having a multilayer structure in which a radially inner fluoroplastic liner tube comprises a convolution or groove at an external facing surface. The inner liner tube is surrounded by a plurality of thermally insulating layers and a braided or woven reinforcement layer. Such layers are then encapsulated by at least one radially rubber cover layer. A hose assembly end fitting arrangement is also provided in which an end fitting is crimped to a hose end via a two component end fitting and a portion of the end fitting is surrounded by rubber.