Pre-Stressed Strand Pipe Extraction for Low-Strength Ductile Pipes
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Solution Overview
Problem
Existing methods for extracting small diameter pipes are limited by the tensile strength of the pipe, which restricts the length of pipe that can be extracted and results in a significant drop in extraction force after the initial pulling cycle, making it challenging to extract pipes made from low strength materials like lead.
Innovation Solution
A pipe extraction machine with a frame, carriage, actuator, wire clamp, and pipe cutter, featuring a vise with jaws to engage the ductile pipe and a wire clamp with jaws to selectively engage a strand, allowing for increased extraction force by maintaining tension on the strand through prestressing and using crush features to maintain frictional load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the tensile strength of the existing pipe is used alone to extract the pipe, then the extraction method is simple, but the magnitude of extraction force is limited and the length of pipe that can be extracted is restricted
Solution Approach 1:
The patent combines the tensile strength of the existing pipe with the tensile strength of a wire rope strand to create a composite extraction system. The strand is attached to the pipe end and pulled together with the pipe, merging two force sources to achieve greater extraction force than either component could provide alone.
Solution Approach 2:
The extraction system uses a composite approach by combining the existing pipe material (which may be low strength) with a high strength wire rope strand. This composite system allows the weaker pipe to be extracted by leveraging the strength of the strand, effectively creating a hybrid force transmission system.
2Force
If a wire rope strand is used to increase extraction force, then the length of pipe that can be extracted increases, but the stretch difference between the strand and pipe affects the magnitude of load achieved
Solution Approach 1:
The patent acknowledges and works with the dynamic nature of the strand-pipe system. As the strand stretches differently than the pipe during extraction, the system adapts by allowing relative movement and elastic deformation, converting some of the stretch differential into useful extraction force while maintaining load application.
3Reliability
If the pipe is pulled without a strand, then the extraction system is simpler, but low strength pipes are likely to fail during the initial pulling cycle before the pipe/soil bond has broken
Solution Approach 1:
The wire rope strand acts as an intermediary element between the pulling mechanism and the low strength pipe. Instead of applying force directly to the pipe (which would cause failure), the strand serves as a mediator that distributes and transmits the pulling force, protecting the weak pipe from direct stress concentration while still enabling extraction.
Solution Approach 2:
The strand provides beforehand cushioning by absorbing and distributing the initial shock loads during the critical first pulling cycle. The elastic properties of the strand cushion the force application, preventing sudden stress peaks that would cause low strength pipes to fail before breaking free from the soil bond.
4Length of moving object
If the pipe length is increased to extract longer sections, then more pipe can be removed, but the force required to break the shear bond from pipe to soil increases
Solution Approach 1:
The patent merges the force contributions of both the existing pipe and the wire rope strand to overcome the increased shear bond force that results from extracting longer pipe sections. This combined force system enables the extraction of longer lengths that would be impossible with the pipe alone.
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 system enhances pipe extraction capabilities by maintaining high extraction force throughout subsequent pulling cycles, effectively extracting pipes with lower tensile strength, such as lead, by utilizing the dual load path of tension in the strand and compressive load on the pipe.
Implementation Method 1
When the two components are loaded in parallel in a tensile manner, the differences in the stretch rates affect the magnitude of the load achieved during extraction
Implementation Method 2
the additional work of expanding the hard ground must be done to accommodate the replacement or product pipe
Data Source
AI summary
A machine for extracting a ductile pipe. The machine has a vise which can grip the pipe, and a wire clamp. Each of the wire clamp and vise are supported on a carriage which is movable relative to a frame. This enables the vise to grip and pull the ductile pipe. Additionally, a wire strand may be disposed through the pipe from a far end to the end at which the machine is placed. The wire clamp allows the machine to pre-stress the strand to improve the extraction of the ductile pipe.