Fire-Resistant Coaxial Cable Ceramifiable Dielectric
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Solution Overview
Problem
Current coaxial communication cables fail to meet fire survivability standards at high temperatures, as they melt or degrade, disrupting critical communication infrastructure during emergencies, necessitating costly shielding or waivers in compliance with building codes.
Innovation Solution
Development of fire-resistant coaxial cables featuring a ceramifiable silicone rubber or ceramic fiber dielectric between conductors, which converts to a porous ceramic structure at high temperatures, maintaining structural integrity and spacing, and a low smoke zero halogen jacket to prevent shorting and ensure signal passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional coaxial cables with polymer or foam dielectrics are used, then the cable structure is simple and manufacturing is easy, but the cable fails to maintain structural integrity at high temperatures above 1010°C
Solution Approach 1:
The patent employs composite materials by combining ceramifiable silicone rubber with traditional cable components. The ceramifiable silicone rubber dielectric layer transforms into a ceramic structure at high temperatures, providing fire resistance while maintaining the basic coaxial cable architecture. This composite approach enables the cable to withstand temperatures above 1010°C without requiring completely redesign of the cable structure.
Solution Approach 2:
The patent utilizes parameter changes by leveraging the temperature-dependent transformation of ceramifiable silicone rubber. At normal operating temperatures, the material remains flexible and processable. When exposed to fire temperatures above 1010°C, it undergoes a phase change to become a rigid ceramic structure, thereby maintaining structural integrity and dielectric properties under extreme thermal conditions.
2Reliability
If additional fire shielding is added to conventional cables to meet building codes, then fire resistance is improved, but device complexity and installation difficulty increase
Solution Approach 1:
The ceramifiable silicone rubber dielectric layer provides self-protecting functionality by automatically transforming into a fire-resistant ceramic structure when exposed to high temperatures. This self-activating fire protection mechanism eliminates the need for additional external shielding layers, complex fire barriers, or separate protection systems, thereby meeting building code requirements while maintaining cable structure simplicity.
3Ease of manufacture
If polymer dielectrics are used in coaxial cables, then manufacturing is easy and cost is low, but the dielectric melts at high temperatures disrupting communication
Solution Approach 1:
The ceramifiable silicone rubber dielectric exhibits parameter changes based on temperature. During manufacturing and normal operation, it behaves like a conventional polymer dielectric, allowing easy extrusion and installation. When exposed to fire temperatures above 1010°C, it undergoes a chemical and physical transformation into a stable ceramic structure, maintaining dielectric strength and preventing conductor shorting, thereby ensuring communication reliability during emergencies.
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 cables can survive temperatures up to 1010°C for two hours, meeting building codes without additional shielding, ensuring continuous communication during emergencies and reducing the need for expensive fire protection measures.
Implementation Method 1
the ceramifiable silicone rubber dielectric configured to convert from a resilient elastomer to a porous ceramic when heated above 425° C.
Implementation Method 2
a low smoke zero halogen jacket to prevent shorting and ensure signal passage
Data Source
AI summary
Methods of testing and installing fire-resistant coaxial cables are described. The dielectric between the coax cable's central conductor and outer coaxial conductor ceramify under high heat, such as those specified by common fire test standards (e.g., 1850° F./1010° C. for two hours). The dielectric can be composed of ceramifiable silicone rubber, such as that having a polysiloxane matrix with inorganic flux and refractory particles. Because thick layers of uncured ceramifiable silicone rubber deform under their own weight when curing, multiple thinner layers are coated and serially cured in order to build up the required thickness. A sacrificial sheath mold is used to hold each layer of uncured ceramifiable silicone rubber in place around the central conductor while curing. The outer conductor can be a metal foil, metal braid, and/or corrugated metal. Another layer of extruded ceramifiable silicone dielectric or an outer wrap of ceramic fiber yarn surrounds the outer conductor and continues to insulate it from the outside if a low smoke zero halogen jacket burns away.