Gas Blocking Cable with Silicone Interstitial Filling
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Solution Overview
Problem
Conventional multi-conductor cables fail to prevent the leakage of high-pressure hazardous gases through interstitial spaces, posing a risk in power generation turbine applications, and existing water-blocked cables cannot withstand the high temperature and pressure requirements of these environments, necessitating a gas-blocking solution that meets stringent IEC and UL 1277 specifications.
Innovation Solution
A multi-conductor gas-blocking cable design that fills interstitial spaces with a high-temperature, inert, and non-flammable silicone compound, using a two-part room temperature curable silicone, and employs specific application devices to ensure the compound is applied during the cabling process, combined with a robust construction including insulation, shields, and braids to prevent gas passage, while maintaining flexibility and meeting temperature and pressure requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional multi-conductor cables are used, then the cable structure is simple and easy to manufacture, but high-pressure hazardous gases can leak through interstitial spaces
Solution Approach 1:
A silicone compound is introduced as an intermediary filling material that occupies interstitial spaces between conductors and within the cable structure. This compound acts as a barrier medium that blocks gas leakage paths without requiring fundamental changes to the cable's conductor arrangement or insulation structure.
Solution Approach 2:
The silicone compound is selectively applied to specific regions where gas leakage occurs - namely the interstitial spaces between conductors and at the cable gland interface. This localized treatment provides gas blocking capability only where needed, rather than requiring complete structural redesign of the entire cable.
2Temperature
If water blocked cables are used, then fluid blocking is achieved, but the cable cannot withstand high temperature and pressure requirements
Solution Approach 1:
The filling material is changed from water to a silicone compound with fundamentally different physical properties. The silicone compound maintains its blocking capability at high temperatures (up to 200°C) where water would evaporate or lose its sealing properties, thus adapting the material parameters to match the high-temperature operating conditions of turbine environments.
Solution Approach 2:
The cable employs a composite construction combining traditional cable components (conductors, insulation, shielding) with a silicone compound filling material. This composite approach integrates the proven mechanical and electrical properties of conventional cables with the high-temperature stability and gas-blocking properties of silicone, achieving both reliability and temperature resistance.
3Reliability
If gas blocking is achieved only at the cable gland assembly, then the connection point is sealed, but leak paths remain through interstitial spaces in the cable
Solution Approach 1:
The silicone compound is applied to fill interstitial spaces during the cable manufacturing process, before the cable is installed and before any potential gas leakage events occur. This preliminary filling action ensures that all potential leakage paths are blocked in advance, eliminating the need for complex post-manufacturing modifications or assembly steps.
Solution Approach 2:
The gas blocking function is made continuous throughout the entire cable length by filling all interstitial spaces along the cable, rather than providing discrete blocking points. This continuous filling approach ensures that gas cannot bypass blocked sections through adjacent unblocked interstitial spaces, maintaining uninterrupted gas blocking capability from one end of the cable to the other.
4Reliability
If the cable is designed to meet stringent IEC and UL 1277 specifications, then safety and compliance are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The silicone compound is strategically positioned in specific locations where gas blocking is most critical - within interstitial spaces between conductors and at the cable gland interface. This localized application provides the necessary safety and compliance functionality without requiring complex modifications to the overall cable construction or additional manufacturing steps.
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 cable effectively blocks high-pressure gases and fluids, passing fluid leakage tests at 435 psi and withstanding temperatures up to 200°C, while maintaining flexibility and adhering to UL 1277 Impact Test requirements, thus ensuring safety and compliance with IEC specifications.
Implementation Method 1
A multi-conductor gas-blocking cable design that fills interstitial spaces with a high-temperature, inert, and non-flammable silicone compound
Implementation Method 2
using a two-part room temperature curable silicone
Data Source
AI summary
A gas blocking cable includes cabled wires, where each wire includes cabled conductors having interstitial areas there between. An insulation material circumferentially surrounds the cabled conductors and a conductor filling material is positioned within the interstitial areas between conductors. A first shield circumferentially surrounds the twisted wires and a high-temperature filler, thereby separating a drain wire. A second shield circumferentially surrounds the cabled wires and the drain wire so that a cable is formed with areas between the first shield and the second shield. A wire filling material is positioned within the areas between the wires and the shields. Each of the conductor filling material and wire filling material is inert, non-flammable and able to withstand a temperature of at least approximately 200° C.