Load Indicating Fastener Datum Rod Monitoring
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Solution Overview
Problem
Monitoring fastener loads in industrial applications is challenging due to issues like overtightening and loss of tension over time, which can lead to catastrophic failures, misalignment, and premature wear, especially in high corrosion and high cycle loading environments.
Innovation Solution
A load indicating fastening system that includes a fastener with a gauge length, a compression sleeve, and a split washer, which measures elongation to determine loading, using a datum rod and levers to provide an amplified response, allowing for accurate and non-contact measurement of fastener load, and can be retrofitted into existing foundation bolt installations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque wrench is used to check fastener loading, then the loading can be verified, but the fastening must be loosened and retorqued which is time-consuming and problematic in high corrosion and high cycle loading applications
Solution Approach 1:
The patent applies preliminary action by installing a load indicating assembly on the fastener during initial installation. This assembly includes a datum rod with measurement markings that are set against the fastener head at a known load state. Subsequent load changes are measured by comparing the datum rod position to these pre-established markings, eliminating the need for repeated loosening and retorquing operations.
Solution Approach 2:
The patent uses a datum rod as an intermediary element between the fastener and the measurement system. The datum rod translates fastener elongation into measurable displacement that can be read against fixed markings on the fastener head, providing a continuous load monitoring mechanism without requiring direct intervention with the fastener itself.
2Reliability
If the fastener is overtightened, then the joint may be secure, but catastrophic failure can occur
Solution Approach 1:
The patent implements feedback by providing continuous visual indication of fastener load through the datum rod position relative to measurement markings. This allows operators to see the actual load state during tightening and stop at the appropriate point, preventing overtightening. The system also provides ongoing feedback during service to detect load changes that may indicate loosening or excessive loading.
Solution Approach 2:
The measurement system is pre-configured with markings that indicate acceptable load ranges before the fastening operation begins. This allows the operator to know in advance the target load and stop points, ensuring the fastener is tightened to the correct specification without exceeding it.
3Stability of the object's composition
If the fastener loses tension in service, then the joint may remain intact, but misalignment, premature wear, leakage, or catastrophic failure can occur
Solution Approach 1:
The patent enables continuous monitoring of fastener load through the permanent datum rod assembly that remains on the fastener during service. This allows ongoing detection of tension loss due to relaxation, vibration loosening, or other service conditions, enabling timely intervention before misalignment, wear, or failure occurs.
Solution Approach 2:
The fastener itself serves the dual function of joining the joint and providing load measurement through the integrated datum rod assembly. The fastener's own elongation under load directly moves the datum rod, eliminating the need for separate sensing elements that would require additional installation or calibration.
4Reliability
If a load indicating assembly is installed on an existing foundation bolt, then continuous monitoring is enabled, but the installation complexity increases
Solution Approach 1:
The load indicating assembly is segmented into separate components that can be installed independently on the existing foundation bolt. The datum rod, centering plate, and measurement markings are separate elements that can be added without replacing the entire fastener system, making retrofitting more manageable.
Solution Approach 2:
The datum rod assembly serves multiple functions: it provides load measurement, acts as a centering element during installation, and can serve as a alignment reference. This multi-functionality reduces the number of separate components needed and simplifies the overall installation process.
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
Enables continuous monitoring of fastener loads, preventing overtightening and loss of tension, thereby reducing the risk of failures and ensuring consistent loading across multiple fasteners, even in harsh environments, with the ability to provide visual, audible, or electrical signals for easy detection of load deviations.
Implementation Method 1
a substantially free datum end closer to the fastener head and moveable longitudinally relative to the fastener head during elongation of the fastener gauge length
Data Source
AI summary
A retrofit system for providing a load indicator on a foundation bolt. The system includes a fastener having a fastener head, gauge length and central fastener bore in the gauge length and head. A datum rod is anchored in the central bore with a free datum rod being moveable longitudinally relative to the fastener head during elongation of the fastener gauge length. An internally threaded fastener portion below the central fastener bore is configured to thread over a foundation bolt. A compression sleeve positioned over the foundation bolt is configured to receive the load indicating fastener therein and to bear the compressive forces of the fastening. Elongation of the gauge length as the fastener is tightened onto the stud is manifest as displacement of the datum rod end, which displacement is measured to provide an indication of fastener loading.