Motor-Driven Screw Gripping Tool for Tubular Strings
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Solution Overview
Problem
Existing gripping tools for tubular strings in drilling and well servicing operations face challenges in maintaining a high grip ratio over varying axial and torsional loads, leading to slippage issues and undesirable plastic deformation on the work piece surface, especially as the grip surfaces wear and encounter hardened or coated surfaces.
Innovation Solution
The introduction of a motor-driven load screw mechanism that enhances the grip ratio by creating relative axial displacement between the body and grip assembly, allowing for increased radial engagement force in response to applied axial loads, thereby improving traction and reducing slippage across the range of loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional self-energized grip mechanisms are used, then the device complexity is reduced, but the grip ratio decreases under varying axial and torsional loads
Solution Approach 1:
The grip mechanism transitions from a static self-energized system to a dynamic controlled system. The grip elements are actuated by a hydraulic or pneumatic cylinder that can dynamically adjust the gripping force based on detected load conditions, allowing the system to maintain optimal grip ratio across varying axial and torsional loads rather than relying on fixed mechanical self-energization
Solution Approach 2:
A load detection mechanism (such as a load cell or strain gauge) provides feedback about the actual axial and torsional loads being applied to the tubular. This feedback signal is used by a control system to adjust the actuation force applied to the grip elements, creating a closed-loop control system that maintains reliable grip under varying load conditions
2Duration of action of stationary object
If grip surfaces are made harder to resist wear, then the duration of action is improved, but the object-affected harmful factors increase due to plastic deformation on work piece surface
Solution Approach 1:
The system changes the parameter of gripping force from high and fixed to controlled and variable. By using an actuated mechanism with load-based control, the gripping force is optimized to be sufficient for the task without excessive force that would cause plastic deformation, while the load detection system ensures the force is maintained appropriately throughout the duration of the operation
Solution Approach 2:
Instead of relying on hard grip surfaces that physically deform the work piece, the system uses a softer, more compliant grip surface material that can conform to the tubular surface. The necessary durability is achieved through the controlled application of force and potentially through wear-resistant coatings rather than through hardness that causes deformation
3Force
If axial load is increased to improve grip ratio, then the force is improved, but the stress on the grip mechanism increases
Solution Approach 1:
The system replaces a purely mechanical force multiplication approach with a controlled actuation system. Instead of relying on mechanical advantage that concentrates stress, a hydraulic or pneumatic cylinder provides controlled force application, and the load detection feedback ensures force is applied only when and where needed, distributing stress more evenly throughout the mechanism
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 motor-driven load screw mechanism effectively maintains a high grip ratio, reducing slippage and plastic deformation, and ensures reliable engagement with both internal and external surfaces of tubular work pieces, even under varying load conditions and on surfaces with reduced coefficients of friction.
Implementation Method 1
The introduction of a motor-driven load screw mechanism that enhances the grip ratio by creating relative axial displacement between the body and grip assembly
Implementation Method 2
allowing for increased radial engagement force in response to applied axial loads, thereby improving traction and reducing slippage
Data Source
AI summary
A gripping tool having at least one body, including an associated load adaptor adapted to be connected to and interact with one of a drive head or reaction frame. A gripping assembly, carried by the body, has a grip surface adapted to move from a retracted position to an engaged position to radially engage one of an interior surface or an exterior surface of a work piece upon relative axial displacement of the body relative to the grip surface in at least one axial direction. A grip activation assembly acts between the body and the grip surface to increase a grip ratio of radial load upon the gripping assembly relative to axial displacement of the body relative to the grip surface. The grip activation assembly includes a motor driven load screw to create relative axial displacement of the body relative to the grip surface.