Split Ceramic Journal Bearing for Molten Metal Pump Reliability
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Solution Overview
Problem
Existing molten metal transfer pumps face manufacturing complexities and material tearing issues due to the use of silicon carbide-based ceramics in lower journal plain bearings, particularly during startup and operation at low speeds, and misalignment between upper and lower bearings leads to wear.
Innovation Solution
The design incorporates split bushings made of silicon carbide-based ceramics with equidistantly placed cylinder segments and cone hold-down rings, along with resilient band springs for self-alignment and axial pressing force, forming a labyrinth screw pump with multiple-thread helical grooves to prevent material tearing and facilitate manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the lower journal plain bearing is made of solid silicon carbide-based ceramics, then the operational life under thermal and corrosion effects is improved, but the manufacturing complexity and risk of material tearing increase
Solution Approach 1:
The lower journal plain bearing is divided into multiple cylindrical segments that can be manufactured separately and then assembled together. This segmentation allows each segment to be produced with simpler processes, reducing the risk of material tearing during manufacturing while maintaining the corrosion and thermal resistance of silicon carbide-based ceramics. The segments are held together by cone hold-down rings that apply radial compressive force.
Solution Approach 2:
The bearing design applies different functional qualities to different parts: the cylindrical segments provide the sliding surface with ceramic material properties for corrosion and thermal resistance, while the cone hold-down rings provide the mechanical assembly and compressive force. This local differentiation allows optimization of each component for its specific function, improving manufacturability while preserving operational life.
2Productivity
If multiple-thread opposed helical grooves are milled under the lower journal plain bearing, then the labyrinth screw pump function is improved, but the manufacturing complexity increases
Solution Approach 1:
The bearing assembly is combined with the labyrinth screw pump function by integrating multiple-thread opposed helical grooves directly into the bearing structure. This merging allows the bearing to simultaneously provide radial support and liquid metal pumping capability, eliminating the need for separate pumping components and reducing overall system complexity despite the intricate groove patterns.
Solution Approach 2:
The lower journal plain bearing is designed to perform multiple functions: radial load support through its bearing surfaces, liquid metal sealing through the helical grooves, and pumping action through the opposed helical patterns. This multi-functionality reduces the number of separate components needed in the pump system, offsetting the manufacturing complexity of the grooves with overall system simplification.
3Reliability
If resilient band springs are used for self-alignment, then the reliability under misalignment conditions is improved, but the device complexity increases
Solution Approach 1:
The resilient band springs introduce dynamic adaptability to the bearing assembly, allowing the cylindrical segments to self-align with the shaft during operation. The springs provide continuous radial compressive force while accommodating misalignment through elastic deformation, transforming a static bearing structure into a dynamically adaptive system that maintains reliability under varying alignment conditions.
Solution Approach 2:
The resilient band springs enable the bearing assembly to self-align with the shaft without requiring external adjustment mechanisms. The springs automatically adjust their compression and positioning based on the relative positions of the shaft and bearing, allowing the system to correct minor misalignments autonomously and maintain reliable operation without complex external control systems.
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 design enhances the reliability of the pump by preventing material tearing and simplifying the manufacturing process of ceramic bushings, ensuring reliable operation and improved durability.
Implementation Method 1
resilient band springs for self-alignment and axial pressing force
Implementation Method 2
forming a labyrinth screw pump with multiple-thread helical grooves
Implementation Method 3
fixed with cone hold-down rings radially, and with spring rings axially, providing for axial pressing force
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Molten metal transfer pump comprises a case (1), in which a shaft (4) with the impeller (5) mounted on the shaft (4) is installed on the upper bearing (2) and the lower journal plain bearing (3). The lower journal plain bearing (3) is comprised of the rotor (15) and stator (16) parts. The rotor part (15) is made in the form of two split bushings (17) mounted on the shaft (4), and the stator part (16) is made in the form of two split bushings (18) fixed in the cage (19) in axial alignment with the shaft (4). Bushings (17) and (18) are fixed correspondingly with flat rings (24) and (33) and composed of cylinder segments (20), (28) equidistantly placed in a circumferential direction, located correspondingly in the cylindrical groove (21) on the shaft and cylindrical groove (29) of the cage (19) and fixed with cone hold-down rings (22), (30) radially, and with spring rings (23), (31) axially. The pump has an easy-to-manufacture design of the lower journal bearing and excludes the possibility of bearing tearing, thus providing for improved reliability of the pump at its operation.