Tapered Thread EM Gap Sub Self-Alignment
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Solution Overview
Problem
The assembly of electromagnetic (EM) gap sub devices in the drilling industry is complex due to the need for precise alignment and spacing of threaded sections before dielectric material injection, requiring expensive jigs and fixtures, and is prone to mechanical stress and wear.
Innovation Solution
The use of plastic inserts in the threads of tapered sections to prevent direct contact and ensure optimal axial and radial spacing, allowing for self-alignment and engagement without external jigs, and providing a fail-safe mechanism against mechanical failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional mechanical means are used to produce an insulated gap between two metal pipes, then electrical discontinuity is achieved, but the assembly requires expensive jigs and fixtures for precise alignment and spacing
Solution Approach 1:
The tapered threads are designed to automatically self-align and self-space the two metal pipes during the threading operation itself. The geometry of the tapered threads causes the pipes to naturally assume the correct axial and radial positions as they are threaded together, eliminating the need for external alignment fixtures and jigs.
Solution Approach 2:
The insulating material is applied to the threads in advance before the threading operation. This preliminary application of the insulating coating ensures that when the threads engage, the electrical discontinuity is already established, and the threading process simultaneously achieves both alignment and electrical insulation.
2Strength
If tapered threads are used to join metal pipes, then structural integrity is improved, but mechanical stress and wear on the threads increase
Solution Approach 1:
The insulating material acts as an intermediary layer between the mating tapered threads. This coating reduces direct metal-to-metal contact, thereby minimizing mechanical wear and stress concentration on the thread surfaces while still allowing the tapered geometry to provide structural integrity and alignment.
3Reliability
If the gap sub is made electrically discontinuous to force current through earth formations, then signal amplitude at surface is improved, but the gap sub becomes more vulnerable to mechanical failure
Solution Approach 1:
A thin film of insulating material is applied to the threads, creating an electrical discontinuity that forces current through the earth formations. Despite the thinness of this film, the tapered thread geometry distributes mechanical loads across a larger area, and the threading process itself creates a mechanically robust connection that compensates for the presence of the insulating layer.
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
Simplifies the assembly process, reduces costs, and enhances the structural integrity of EM gap subs by ensuring accurate alignment and spacing, enabling robust and reliable operation under drilling conditions.
Implementation Method 1
The use of plastic inserts in the threads of tapered sections to prevent direct contact and ensure optimal axial and radial spacing
Implementation Method 2
tapered thread em gap sub self-aligning means
Data Source
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AI summary
A generally three-part EM gap sub comprising a first conductive cylinder incorporating a male tapered threaded section, a second conductive cylinder incorporating female tapered threaded section, both axially aligned and threaded into each other is described. One or both tapers incorporate slots whereby non-conductive inserts may be placed before assembly of the cylinders. The inserts are designed to cause the thread roots, crests and sides of the tapered sections of both cylinders to be spatially separated. The cylinders can be significantly torqued, one into the other, while maintaining an annular separation and therefore electrical separation as part of the assembly procedure. The co-joined coaxial cylinders can be placed into an injection moulding machine wherein a high performance thermoplastic is injected into the annular space, thereby forming both an insulative gap (the third part) and a strong joint between the cylinders in the newly created EM gap sub.