Top Drive Tie Rod Strain Gauge for Accurate Hookload
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Solution Overview
Problem
Existing weight monitoring devices in drilling rigs suffer from significant accuracy deviations due to limitations in measuring hookload, particularly when horizontal load pins monitor shear forces, leading to inaccuracies in weight measurement of tubulars and ancillaries.
Innovation Solution
The implementation of strain gauges built into vertical tie rods that suspend the top drive from the travelling block, allowing for precise measurement of tensile stress without shear force interference, with the strain gauge signals transmitted to a control system for accurate hookload determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If horizontal load pins are used to monitor shear forces, then the measurement system is simple to implement, but the accuracy of weight measurement deteriorates significantly
Solution Approach 1:
The patent extracts the measurement function from the horizontal load pins that monitor shear forces and relocates it to vertical tie rods that exclusively experience tensile stress. By removing the shear force component from the measurement system, the accuracy of weight measurement is significantly improved while maintaining implementation simplicity through the use of standard vertical suspension elements.
Solution Approach 2:
The patent applies local quality by changing the measurement location from horizontal load pins to vertical tie rods. The vertical tie rods are specifically positioned where only tensile stress acts on them, creating a localized measurement environment free from shear force interference, thereby improving measurement accuracy without affecting the overall system complexity.
2Measurement precision
If strain gauges are installed on vertical tie rods, then measurement precision is significantly improved, but device complexity increases
Solution Approach 1:
The vertical tie rods serve a dual function: they provide the mechanical suspension for the top drive while simultaneously serving as the measurement element through integrated strain gauges. This self-service approach eliminates the need for separate measurement devices, reducing overall system complexity while achieving high measurement precision.
Solution Approach 2:
The patent merges the structural function of the tie rod with the measurement function of the strain gauge into a single integrated system. The strain gauge is mounted directly on the vertical tie rod, combining the load-bearing element and the sensing element, thereby reducing device complexity while improving measurement accuracy.
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
This solution provides a highly accurate load measurement system, with laboratory tests confirming an accuracy of 99.5% over the full range and 99.7% from 5 to 50% of the range, limiting mis-reading to ±90 lbs at 50 tons and ±150 lbs at 100 tons, thereby enhancing the precision of weight on bit measurements.
Implementation Method 1
strain gauges built into vertical tie rods that suspend the top drive from the travelling block, allowing for precise measurement of tensile stress
Data Source
AI summary
A system for monitoring a drilling rig condition, the system comprising: a travelling block suspended via a drilling line from a crown block at the top of a mast of the drilling rig; a frame to which the drilling tools and/or a pipe string is mounted; at least one tie rod that connects the frame to the travelling block, wherein the at least one tie rod comprises a tensile sensor; and a control system that receives a signal corresponding to tension sensed by the tensile sensor, wherein the control system determines a drilling rig condition based at least in part on the signal received from the tensile sensor.