Reverse-Bend Top Drive Bails for Lower Stress Concentration
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Solution Overview
Problem
Existing top drive systems for wellbore drilling experience high stress concentrations at lower pin lugs and upper bends due to straight-legged bails, leading to inefficient stress distribution and increased material usage.
Innovation Solution
The implementation of bails with dual section legs at opposing angles (reverse bends) to counteract bending moments, reducing stress on the main body lugs and allowing for a smaller cross-section while maintaining load handling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If straight-legged bails are used to support top drive systems, then the structure is simple and easy to manufacture, but high stress concentrations and bending moments occur under load
Solution Approach 1:
The patent applies curvature by introducing reverse bends in the bail legs, transitioning from straight lines to curved paths. The legs feature a first section at an angle to the centerline, a second section at a different angle, creating a reverse bend that distributes stress more evenly throughout the structure, eliminating the high stress concentrations found in straight-legged designs.
2Strength
If bails are enlarged and made more massive to accommodate heavier top drive systems, then load-bearing capacity increases, but the cross-section and material usage increase
Solution Approach 1:
The reverse bend geometry allows the bail to achieve higher strength-to-weight ratio by strategically positioning curved sections that counteract bending moments. This enables the use of smaller cross-sections and less material while maintaining or improving load-bearing capacity compared to traditional straight-legged massive designs.
Solution Approach 2:
The patent changes the geometric parameters of the bail legs by introducing angular sections and reverse bends. The first leg section is positioned at a first angle to the centerline, and the second leg section is positioned at a second angle, creating a configuration that optimizes stress distribution and reduces the required material quantity for a given load capacity.
3Strength
If larger and more massive bails are used for heavier top drive systems, then structural strength increases, but vertical space requirements increase
Solution Approach 1:
The reverse bend configuration allows the bail to achieve necessary structural strength within a more compact vertical envelope. By curving the legs with reverse bends rather than extending them straight downward, the design reduces the overall vertical length while maintaining the strength required for heavy top drive systems.
Data Source
AI summary
A bail support and a top drive system for an oilfield drill rig. The top drive system includes a drive apparatus, and the bails have bodies with upper head portions and two spaced-apart legs. Each leg includes an upper leg portion and a lower leg portion. The upper leg portions are non-parallel to each other and extend from the head portion at an angle to a centerline of the bail. Each lower leg portion extends down from its corresponding upper leg portion in a reverse bend.