Sacrificial Plug Bolt Structure to Prevent Thread Over-Tightening
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Solution Overview
Problem
Conventional plug bolts can damage the threads of devices when over-tightened, leading to costly downtime and potential replacement of air-cooled heat exchangers, as they lack a mechanism to prevent excessive torque from causing thread damage.
Innovation Solution
A plug bolt design featuring a weakened portion between the primary and secondary heads that shears or deforms when torque exceeds a predetermined threshold, providing a visual indication of over-tightening and preventing thread damage, with the secondary head encapsulated or shaped to prevent accidental tool engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional plug bolts are tightened to secure the plug sheet, then the connection strength is improved, but the thread of the heat exchanger may be damaged due to over-tightening
Solution Approach 1:
A weakened portion is intentionally created in the plug bolt body between the primary and secondary heads. This pre-defined weak point is designed to fail at a specific torque level before the heat exchanger thread is damaged, providing preliminary protection against over-tightening while maintaining adequate connection strength during proper installation
Solution Approach 2:
The plug bolt is designed as a sacrificial component where the weakened portion is intended to fail and the bolt to be replaced if over-tightening occurs. This disposable approach protects the expensive heat exchanger thread from damage by allowing the cheap bolt to absorb the excessive torque
2Object-affected harmful factors
If the primary head is made larger to prevent tool engagement with the secondary head, then accidental over-tightening is prevented, but the device complexity increases
Solution Approach 1:
The primary head is designed with a larger size and different geometry compared to the secondary head. This asymmetric design ensures that tools intended for the primary head cannot accidentally engage the secondary head, preventing unintended over-tightening while maintaining a relatively simple overall bolt structure
3Object-affected harmful factors
If the weakened portion is designed to shear at low torque, then thread damage is prevented, but the bolt connection strength is reduced
Solution Approach 1:
The weakened portion is created only in a specific localized region between the primary and secondary heads, while the rest of the bolt including the threaded end maintains full strength. This localized weakening allows the bolt to protect the thread at the critical interface while preserving adequate connection strength elsewhere for proper installation
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 plug bolt effectively prevents thread damage by failing before excessive torque is applied, offering a visual warning and easy replacement of over-tightened bolts, reducing downtime and maintenance costs in air-cooled heat exchangers.
Implementation Method 1
the weakened portion fails when torque applied to the primary head exceeds a predetermined threshold. The weakened portion may be a shearing portion wherein the primary head shears from the bolt when the torque exceeds the threshold.
Implementation Method 2
The stellated head is shaped and sized such that the portions thereof will deform when the torque applied thereto is higher than a predetermined threshold. The deformation of the stellated head provides a visual indication of over tightening of the plug bolt.
Data Source
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AI summary
This invention relates to a plug bolt (1) and more specifically, but not exclusively, to a plug bolt (1) for use with a device such as an air-cooled heat exchanger. One of the problems with conventional plug bolts is that when the bolts are over tightened, it may damage the thread of the device it is installed in. Once the thread is damaged it has to be repaired, causing downtime, or where it is not possible to repair, the device will have to be replaced. It is accordingly an object of this invention to provide a plug bolt (1) which, at least partially, alleviates some of the problems associated with the prior art. It is envisaged that the invention will provide a plug bolt (1) which fails before it is overtightened to prevent damage, is easy to manufacture, and is as simple to use as the prior art.