Fire Resistant Cable Dual Jacket Porous Insulation
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Solution Overview
Problem
Conventional flame retardant optical fiber cables face challenges in managing the consumption of flame retardant additives during combustion, leading to high peak heat release rates and flame spread, as the additives are quickly consumed when the thicker outer jacket burns, failing to effectively control heat transfer and flame propagation.
Innovation Solution
The optical fiber cable design features a thicker inner jacket and a thinner outer jacket separated by a porous insulating layer, where the flame retardant additives in the outer jacket decompose first, releasing water to cool the fire and slow down heat transfer, while the inner jacket's additives decompose gradually to maintain lower heat release rates and flame spread.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single thicker outer jacket is used, then mechanical protection is improved, but flame retardant effectiveness deteriorates due to rapid consumption of additives
Solution Approach 1:
The cable jacket is segmented into two separate layers: an inner flame retardant jacket containing flame retardant additives and an outer protective jacket providing mechanical protection. This segmentation allows each layer to specialize in its function, preventing the rapid consumption problem in a single thick jacket while maintaining mechanical strength.
Solution Approach 2:
A porous insulating layer is introduced as an intermediary between the inner flame retardant jacket and the outer protective jacket. This intermediary layer provides thermal insulation that slows heat transfer to the flame retardant additives, controlling their decomposition rate and reducing peak heat release during combustion.
2Object-affected harmful factors
If flame retardant additives are concentrated in the outer jacket, then flame retardant action is immediate, but heat release rate increases due to rapid decomposition
Solution Approach 1:
The porous insulating layer acts as a thermal barrier between the heat source (outer jacket combustion) and the flame retardant additives (inner jacket). This intermediary controls the rate of heat transfer, ensuring gradual decomposition of additives and maintaining lower peak heat release rates while still providing effective flame spread control.
Solution Approach 2:
The inner jacket is pre-configured with flame retardant additives that will decompose in a controlled manner when exposed to heat from the outer jacket combustion. The porous insulating layer is pre-designed to provide specific thermal insulation properties that regulate the timing and rate of this preliminary flame retardant action.
3Duration of action of stationary object
If the outer jacket is made thicker, then mechanical durability is improved, but heat transfer control deteriorates leading to faster additive consumption
Solution Approach 1:
The jacket system is segmented into two functional layers with distinct thicknesses and properties. The outer protective jacket can be optimized for mechanical durability without compromising the inner flame retardant jacket's ability to control additive decomposition timing, as each layer performs its specialized function independently.
Solution Approach 2:
The porous insulating layer serves as a thermal mediator that decouples the mechanical protection function from the flame retardant function. It provides thermal insulation that extends the decomposition time of flame retardant additives, allowing the outer jacket to be thicker for mechanical durability without proportionally increasing the rate of additive consumption.
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
This design reduces peak heat release rates, total heat release, and flame spread, achieving Class B2 or Class C ratings in EN 50399 testing by ensuring gradual decomposition of flame retardant additives and effective heat management, outperforming conventional cables with a single thicker jacket.
Implementation Method 1
The porous insulating layer is configured to reduce the transfer of heat to the inner jacket during combustion of the outer jacket
Implementation Method 2
the flame retardant additives in the outer jacket decompose first, releasing water to cool the fire and slow down heat transfer
Data Source
AI summary
Embodiments of an optical fiber cable are provided. The optical fiber cable includes an outer jacket, an inner jacket, a porous insulating layer, and at least one optical fiber. The outer jacket has a first thickness between its inner surface and its outer surface. The inner jacket has a second thickness between its inner surface and its outer surface. The inner jacket is disposed within the outer jacket. The porous insulating layer is disposed between the inner jacket and the outer jacket. The porous insulating layer is configured to reduce the transfer of heat to the inner jacket during combustion of the outer jacket. The optical fiber is disposed within the inner jacket. In the optical fiber cable, the first thickness is less than the second thickness, and each of the outer jacket and the inner jacket include at least one flame retardant additive.