Rotary Degasser Coupling and Impeller Design
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Solution Overview
Problem
Conventional coupling systems for impeller shafts in molten metal pumps are prone to breakage, gas leakage, and difficult maintenance, and fail to effectively mix gases with molten metal, leading to inefficiencies and environmental hazards.
Innovation Solution
A rotary degasser design featuring a threadless coupling of the impeller shaft to a drive source, with a graphite impeller having cavities and channels for gas dispersion, and a coupling with a smooth tapered surface and set screws for secure retention, allowing for efficient gas introduction and mixing without threaded connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threaded connections are used to couple the impeller shaft to the drive source, then the connection provides structural support and alignment, but the threads cause stress concentration leading to shaft breakage and gas leakage
Solution Approach 1:
The invention removes the threaded connection from the coupling system. The impeller shaft is coupled to the drive source using a smooth-bore coupling with set screws, eliminating the threads that cause stress concentration and gas leakage pathways.
Solution Approach 2:
The invention introduces a smooth-bore coupling as an intermediary component between the impeller shaft and drive source. This coupling uses set screws instead of threads to provide both structural support and gas-tight sealing, resolving the contradiction between connection strength and gas leakage prevention.
2Reliability
If threaded connections are used to retain the impeller shaft in the coupling, then the shaft is securely retained, but maintenance and replacement become difficult due to thread wear and damage
Solution Approach 1:
The invention removes the threaded retention mechanism and replaces it with a smooth-bore coupling secured by set screws. This allows the impeller shaft to be easily removed and replaced by simply loosening the set screws without dealing with damaged threads.
Solution Approach 2:
The invention treats the impeller shaft as a replaceable component that can be quickly swapped out. The smooth-bore coupling with set screws enables rapid replacement without the time-consuming process of dealing with threaded connections, making maintenance more efficient.
3Productivity
If the impeller operates at high speeds to effectively mix gas with molten metal, then gas dispersion improves, but cavitation occurs leading to oxidation and slag formation
Solution Approach 1:
The invention changes the operational parameters of the impeller, specifically optimizing the speed range and gas introduction rate to achieve effective mixing without exceeding the cavitation threshold. This resolves the contradiction between mixing efficiency and cavitation prevention.
4Strength
If threads are used in the impeller shaft coupling, then the connection provides mechanical strength, but the threaded portions are prone to wear and breakage
Solution Approach 1:
The invention removes the threaded connection entirely, replacing it with a smooth-bore coupling secured by set screws. This eliminates the stress concentration points and wear surfaces associated with threads while maintaining adequate connection strength through the set screw mechanism.
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 solution reduces the risk of impeller shaft breakage and gas leakage, enhances gas mixing with molten metal, and operates at lower speeds to prevent cavitation, resulting in longer component life, reduced maintenance, and improved environmental safety.
Implementation Method 1
an impeller shaft having a first end for connecting to a coupling and an internal passage for transferring gas
Implementation Method 2
the impeller allows gas to escape into the molten metal under the impeller and enter at least one channel in the bottom of the impeller where it is directed to at least one cavity
Implementation Method 3
at least one cavity defined by a curved impeller side surface... the distance from the center of each curved impeller side surface is closer to a center of the impeller than the distance from each of the shearing structures to the center of the impeller
Implementation Method 4
a coupling having a collar that receives the first end of the impeller shaft and retains it without a threaded connection
Data Source
AI summary
Disclosed are degassers, couplings, impeller shafts and impellers for use in molten metal. One such coupling transfers gas into an impeller shaft, the coupling having a smooth, tapered internal surface to align with a corresponding surface on the impeller shaft and help prevent gas leakage and to assist in preventing damage to the impeller shaft. Improved impellers for shearing and mixing gas are also disclosed, as is a degasser including one or more of these components.