Centre Pintle Pulling With Annular Liquid Nitrogen Cooling
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Solution Overview
Problem
Current methods for removing the centre pintle from large-capacity machines like electric rope shovels are time-consuming, hazardous, and costly, requiring up to 72 hours and significant use of liquid nitrogen, posing risks to maintenance workers.
Innovation Solution
An apparatus and method utilizing a pulling assembly, freezer assembly insert, and connector to safely and efficiently remove the centre pintle by forming an annular space, introducing liquid nitrogen, and using a hydraulic cylinder or electric rod actuator to pull the pintle out, reducing downtime to 12 hours and nitrogen use by 92%, and eliminating dangerous shimming/lancing procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lancing and shimming methods are used to remove the centre pintle, then the pintle can be loosened from the interference fit, but the process takes up to 72 hours and exposes workers to dangerous conditions including liquid nitrogen contact
Solution Approach 1:
The patent changes the temperature parameter by introducing liquid nitrogen into the annular space, causing thermal contraction of the centre pintle. This parameter change allows the pintle to be removed without dangerous lancing and shimming operations, reducing both time and safety risks
Solution Approach 2:
The patent introduces an intermediary substance (liquid nitrogen) into the annular space between the freezer assembly insert and the centre pintle bore wall. This intermediary causes thermal contraction that loosens the interference fit, enabling safe and quick removal without direct mechanical forcing that endangers workers
2Manufacturing precision
If liquid nitrogen is introduced into the centre pintle bore for shrinkage, then the interference fit is released, but significant amounts of liquid nitrogen are required creating cost and safety issues
Solution Approach 1:
The patent segments the cooling process by introducing liquid nitrogen into the annular space rather than filling the entire centre pintle bore. This segmentation concentrates the liquid nitrogen where it is most effective, reducing overall consumption while achieving the necessary thermal contraction for interference fit release
Solution Approach 2:
The patent uses a nested structure where the freezer assembly insert is placed inside the centre pintle bore, creating an annular space. This nested configuration allows liquid nitrogen to be contained and directed precisely where needed, maximizing cooling efficiency and minimizing the quantity of liquid nitrogen required
3Productivity
If the centre pintle is removed using conventional methods, then the pintle can be extracted, but the process requires complex procedures including lancing, shimming, and extended cooling periods
Solution Approach 1:
The patent performs preliminary action by pre-cooling the centre pintle through the freezer assembly insert before removal. This preliminary thermal contraction simplifies the subsequent extraction process, eliminating the need for complex lancing and shimming operations and reducing overall procedure complexity
Solution Approach 2:
The patent extracts the harmful and time-consuming steps (lancing, shimming, extended cooling) by using a dedicated removal apparatus that integrates the freezing and pulling functions. This extraction of complex procedures into a unified system dramatically improves maintenance speed and simplifies the overall 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
The apparatus reduces maintenance downtime by 83% and nitrogen use by 92%, making the process safer and more efficient by eliminating the need for shimming/lancing and reducing liquid nitrogen requirements.
Implementation Method 1
for removal it is filled with liquid nitrogen to shrink the metal, releasing the interference fit
Implementation Method 2
an insulator that thermally insulates the connector from liquid nitrogen introduced into the annular space
Data Source
AI summary
Disclosed are a method and apparatus for removing a centre pintle from the bore of a machine. The apparatus comprises a pulling assembly and an elongate freezer assembly insert sized for insertion into the centre pintle bore, to form a space between the freezer assembly insert and the wall of the centre pintle bore. The space holds liquid nitrogen to contract the pintle enough to release the interference fit between the pintle and the machine bore, so that the pintle can be pulled out of the bore. The apparatus and method conserve liquid nitrogen, reduce machine down time and are safer than known methods for removal of a centre pintle.