Dual Rod Drilling System Self-Aligning Drive Coupling
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Solution Overview
Problem
Dual rod drilling systems face challenges in maintaining an open drilling fluid flow path due to relative longitudinal offsets and length variations between inner and outer drill rods, which can lead to obstructions and potential damage, and existing drive mechanisms are complex and difficult to maintain, especially when drilling fluids are introduced to the gearbox.
Innovation Solution
A dual rod horizontal directional drilling system with a self-aligning drive coupling and flow insert that includes a central through bore and radial fluid flow passages, allowing for efficient fluid communication and torque transfer while minimizing detrimental forces, and a method of aligning the drive shaft within the coupling to ensure proper alignment and fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the length of interconnected inner drill rods is made slightly less than the length of interconnected outer drill rods to prevent collision, then safety is improved, but the inner drill rods contact the outer drill rods and obstruct the fluid flow path
Solution Approach 1:
The drill string is segmented into multiple drill rod assemblies with alternating inner and outer rods. The flow passages are segmented into multiple sections: a first flow passage between inner and outer rods, and a second flow passage through the inner rod. This segmentation allows fluid to flow through multiple paths, reducing obstruction from the contact points between inner and outer rods.
Solution Approach 2:
Flow passages act as intermediaries to transport drilling fluid from the surface through the drill string to the drill bit. The first flow passage carries fluid between the inner and outer rods, while the second flow passage carries fluid through the inner rod, ensuring continuous fluid flow despite the length variations and contact points.
2Adaptability or versatility
If traditional couplings or transmissions are used to allow misalignment between drive shaft and drill bit shaft, then steering capability is improved, but device complexity increases and maintenance becomes difficult
Solution Approach 1:
The coupling device merges multiple functions into a single integrated component. It combines the drive shaft, drill bit shaft, and flow passages into one unified structure, eliminating the need for separate couplings and transmissions. This integration simplifies the overall system while maintaining the ability to accommodate misalignment for steering.
Solution Approach 2:
The coupling device performs multiple functions simultaneously: it transfers torque from the drive shaft to the drill bit shaft, allows for angular misalignment to enable steering, and provides fluid flow paths for drilling fluid. This multi-functionality reduces device complexity compared to traditional separate components.
3Reliability
If drilling fluid is introduced to the gearbox to cool and lubricate components, then operational reliability is improved, but the risk of damage from fluid contamination increases
Solution Approach 1:
The flow passages extract the drilling fluid function from the gearbox environment and relocate it to the drill string. The first and second flow passages provide dedicated fluid flow paths that are isolated from the gearbox, allowing drilling fluid to cool and lubricate the drill bit and drill string without contaminating the gearbox components.
Solution Approach 2:
The flow passages serve as intermediaries that separate the drilling fluid system from the gearbox. Fluid flows through the first flow passage between the inner and outer rods, and through the second flow passage through the inner rod, maintaining isolation from the gearbox while still providing necessary cooling and lubrication functions.
Data Source
AI summary
A horizontal directional drilling system includes a drill head that includes a drive coupling with a central bore that is a through bore. The drill head includes a drive shaft that has an enlarged portion at a downhole end that defines a centroid positioned within the central bore of the drive coupling. The drive shaft includes a drive shaft axis that is misaligned and intersects with an end casing axis of an end casing at a balance point of the drill head. The centroid of the drive shaft is positioned to be coincident with the balance point of the drill head.