Helical Spring Probing Cable Torsion Friction
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Solution Overview
Problem
The deployment of fibre optic cables into helical pipes is hindered by the capstan effect, which causes exponential frictional resistance, making it difficult to insert and withdraw cables due to complex pipe geometries in systems like AGR pod boilers.
Innovation Solution
A fibre optic probing cable with a gold-plated optical fibre core and stainless steel braided sleeve is inserted into a tightly wound stainless steel helical spring casing, allowing torsion to be applied to overcome frictional resistance by mimicking a threaded screw-like motion, and a flexible tip member with a ball bearing to navigate complex geometries and bifurcations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a fibre optic cable is pushed through helical pipe turns, then the cable can be deployed for inspection and monitoring, but frictional resistance builds up exponentially due to the capstan effect, preventing further deployment
Solution Approach 1:
The patent applies water flooding to the helical pipe sections where cable deployment is difficult. The water reduces the frictional resistance between the cable and pipe wall, converting the harmful capstan effect into a manageable condition. This allows the cable to be pushed through multiple helical turns by exploiting the lubricating effect of water flow.
2Ease of operation
If water flooding is used to reduce friction, then cable deployment is facilitated, but the deployment system becomes more complex
Solution Approach 1:
The patent employs water that is already present in the pipe system (process water or cooling water) to facilitate cable deployment. The existing water flow in the pipe serves the dual purpose of its original function and as a lubricant for cable insertion. This eliminates the need for separate lubrication systems or additional water injection equipment, maintaining operational simplicity.
3Ease of operation
If a cable is withdrawn from a helical pipe, then inspection data can be retrieved, but the same frictional resistance that prevented insertion now opposes withdrawal
Solution Approach 1:
The patent uses water flooding during cable withdrawal to reduce frictional resistance, just as during insertion. The water flow continues to act as a lubricant, allowing the cable to be pulled back through the helical turns with reduced force requirements.
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
Enables easy insertion and withdrawal of cables through multiple turns of helical pipes, overcoming frictional resistance and facilitating robust and cost-effective monitoring and inspection in complex pipe systems, applicable beyond AGR pod boilers.
Implementation Method 1
By rotating such a cable as it is pushed into a pipe it is possible to generate a torsion in the cable that can overcome frictional resistance to cable insertion due to the capstan effect
Implementation Method 2
as the cable is pushed through the turns of a helical pipe it experiences an exponential build up in frictional resistance
Implementation Method 3
The tip member is formed from a relatively short length 10 of helical spring attached to the end of the cable by a dogleg element 11 which is inserted into the bores of respectively the cable and the short length of spring. A ball bearing 12 is fastened to the distal end of the short length of spring
Data Source
Figure 1~2
Figure 3
AI summary
A probing cable for deployment inside a pipe formation has an outer casing and an elongate probe member which threads along a bore defined by the outer casing. The outer casing has a helical track which wraps around its outer surface.