Refractory Insulating Sheet for Cable Fire Protection
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Solution Overview
Problem
Existing refractory insulating sheets used for protecting communication and electric transmission cables from fire are either too thick, reducing flexibility, or insufficient in heat insulation, making them unsuitable for compact housing in narrow spaces with complex wiring networks.
Innovation Solution
A layered refractory insulating sheet comprising a nonwoven fabric of silica-based inorganic fibers with hydroxyl groups, a metal foil or metal layer-attached substrate as a reflector, and a graphite layer, optionally with an aerogel-carrying sheet, designed to consume thermal energy, reflect radiation, and provide anisotropic thermal conduction, ensuring effective heat insulation while maintaining flexibility and thinness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the thickness of the thermal insulator is increased to satisfy fire resistance requirements, then heat insulating performance is improved, but flexibility decreases
Solution Approach 1:
The patent employs a composite structure combining multiple materials with different thermal properties: a low-thermal-conductivity core layer (expanded graphite or aerogel) surrounded by high-reflectivity metal foil layers. This composite architecture achieves superior heat insulation performance while maintaining thin overall thickness and flexibility, resolving the contradiction between thermal performance and operational flexibility.
Solution Approach 2:
The patent applies different material properties to different regions of the insulating sheet: the core layer provides thermal insulation with low conductivity, while the metal foil layers provide thermal reflection. This localized functional distribution allows the thin structure to achieve fire resistance requirements without compromising flexibility.
2Ease of operation
If the thickness of the refractory insulating sheet is reduced to improve flexibility and compactness, then ease of handling is improved, but heat insulating performance deteriorates
Solution Approach 1:
The patent uses a composite structure where expanded graphite or aerogel provides excellent thermal insulation in a thin profile, and metal foil layers add reflective insulation. This combination delivers fire resistance performance in a thin, flexible sheet that is easy to handle and install in narrow spaces.
Solution Approach 2:
The expanded graphite and aerogel materials utilize their unique phase structures with high porosity and low density to achieve superior thermal insulation in minimal thickness, allowing the sheet to be both thin/easy-to-handle and thermally protective.
3Temperature
If conventional ceramic fiber sheets are used to achieve fire resistance, then heat insulating performance is improved, but weight increases
Solution Approach 1:
The patent employs expanded graphite and aerogel, both highly porous materials with exceptional thermal insulation properties per unit weight. These porous structures trap air and reduce thermal conductivity, achieving fire resistance with significantly lower weight compared to conventional dense ceramic fiber sheets.
Solution Approach 2:
The combination of ultra-lightweight porous materials (aerogel, expanded graphite) with thin metal foil layers creates a composite structure that provides fire resistance while minimizing weight, overcoming the heaviness of traditional ceramic fiber insulation.
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 provides enhanced heat insulation and flexibility, allowing the sheet to effectively delay temperature rise and prevent damage to cables even in confined spaces, maintaining functionality for up to 1 hour at high temperatures without compromising handling or thickness.
Implementation Method 1
a nonwoven fabric of silica-based inorganic fibers having a hydroxyl group; at least one reflector (R) which is a metal foil or a metal layer-attached substrate
Implementation Method 2
at least one reflector (R) which is a metal foil or a metal layer-attached substrate in which a metal layer overlays a substrate
Implementation Method 3
at least one graphite layer (G) in which graphite crystals are oriented in a planar direction
Implementation Method 4
The refractory insulating sheet can impart a necessary fire resistance by housing cables wiring communication network laid even in restricted narrow space
Data Source
AI summary
A thin and lightweight refractory insulating sheet comprising a refractory bag and a layered type thermal insulator in the bag is disclosed. The layered type thermal insulator comprises a thermal energy consumption layer, a reflector and a graphite layer, and can efficiently attenuate thermal energy by conducting the thermal energy in all directions of the plane even when locally heated, and utilizing the thermal energy for vaporization of the water generated from the thermal energy consumption layer.