Segmented Siliconized Graphite Thrust Bearing for Nuclear Cooling
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Solution Overview
Problem
The manufacturing of large-sized plain thrust bearings using siliconized graphite as an antifriction material is hindered by brittleness, uneven heat removal, and complexity in achieving uniform cooling and lubrication with water, leading to potential damage and fire hazards in nuclear power plant equipment.
Innovation Solution
A plain thrust bearing design featuring a bearing disk with circumferential projections, interleaving supporting bands and slots, and antifriction sectors secured by elastic elements and pins, allowing for improved heat dissipation, manufacturability, and fire safety through the use of water as a lubricant and coolant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an integral plate made of siliconized graphite is used for large-diameter thrust bearings, then heat resistance and fire safety are improved, but manufacturing complexity and brittleness damage risk increase
Solution Approach 1:
The bearing plate is divided into multiple segments (first bearing plate, second bearing plate, third bearing plate) that can be manufactured separately and then assembled. This segmentation allows each segment to be produced within feasible manufacturing limits while maintaining the overall large-diameter bearing structure, resolving the contradiction between fire safety requirements for large plates and the manufacturing complexity/brittleness issues of integral plates.
2Reliability
If an integral plate made of siliconized graphite is used, then fire safety is improved, but uniform heat removal from friction zone becomes difficult
Solution Approach 1:
The plate is segmented into multiple bearing plate segments with cooling channels integrated into each segment. This allows cooling fluid to be distributed uniformly across the friction zone through multiple pathways, improving heat removal uniformity while maintaining the fire-safe siliconized graphite material throughout the structure.
Solution Approach 2:
Cooling channels are provided within the bearing plate segments to enable forced circulation of cooling fluid. This hydraulic cooling system ensures uniform heat removal from the friction zone by directing coolant through strategically placed channels, resolving the heat removal uniformity issue while maintaining fire safety through proper material selection.
3Reliability
If water is used as lubricant coolant instead of oil, then fire safety is improved, but manufacturing of large-diameter plates becomes impossible
Solution Approach 1:
The bearing plate is segmented into multiple smaller, manufacturable pieces that can be produced using water-cooled siliconized graphite technology and then assembled into the complete large-diameter bearing. This segmentation makes the bearing manufacturable with water-based cooling while maintaining fire safety through the use of non-combustible siliconized graphite material throughout the structure.
4Force
If self-aligning sliders with antifriction plates are used, then large unit loading capability is improved, but load balancing in contact area becomes impossible
Solution Approach 1:
Different regions of the bearing plate are designed with varying properties - the first bearing plate contacts the shaft flange, the second bearing plate contacts the self-aligning sliders, and the third bearing plate contacts the bearing disk. This local differentiation allows optimization of each contact zone for its specific loading conditions, enabling both high unit loading capability and proper load distribution across the contact areas.
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 reduces the risk of damage from thermal deformations, enhances water circulation, improves manufacturability and repairability, and decreases fire hazards by using noncombustible water as a coolant, ensuring reliable operation of large-sized bearings in nuclear power plants.
Implementation Method 1
water as a lubricating and cooling fluid... circulation of cooling and lubricating water on the surface of the plain thrust bearing flange
Implementation Method 2
uniform and effective heat removal from a friction zone... interleaving channels formed by the bars, the sectors, the external and the internal rings
Implementation Method 3
water as lubricant coolant... cooling and lubricating by water... lubricating and cooling fluid flow
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to plain thrust bearings, wherein one working surface of which is made of siliconized graphite (or other antifriction material with similar characteristics) and can be used in assemblies of electrical machines and hydraulic machines having thrust bearings of a large size (with a diameter up to 900 mm), preferably electric motors driving a main circulation pump assembly (MCPA) of reactor assemblies, for example, in nuclear power plants. The plain thrust bearing comprises interleaving bearing bands and slots on the side facing to a set of sector. The bearing disk is provided with mounting surfaces, wherein external and internal rings securing the sectors made of antifriction material through elastic elements are mounted on the mounting surfaces. The sectors are fixed to deter them from rotation relative the bearing ring by intermediate bars arranged between the sectors, wherein the bars are fixed by inserting their pins into the openings in the bearing disk. The sectors made of antifriction material are provided with steps for the external and internal rings, wherein upper parts of the sectors are provided with roundings and lower parts of the sectors are provided with slots for mutual axial fixation. A sector's lead-in edge is shaped approximately as a parabolic curve. Cooling and lubricating is carried out through interleaving channels formed by the bars, the sectors, the external and the internal rings.