Segmented Graphite Seal for Coal Mill Drive Shaft
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Solution Overview
Problem
Existing coal mill seals are prone to damage during assembly due to the need for precise adjustment of the grinding table carrier, leading to a short service life and installation challenges.
Innovation Solution
A coal mill design featuring a seal connected to a support ring in a rotationally fixed manner, with a form-fitting and friction-fitting interface to a cylindrical drive shaft or sleeve, composed of graphite and multiple segments, and a tensioning element to ensure reliable contact and wear resistance, allowing for easy installation and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a labyrinth seal is used to protect against coal dust and contaminants, then sealing effectiveness is improved, but the seal is damaged during assembly due to precise adjustment requirements, shortening service life
Solution Approach 1:
The seal is divided into multiple segments that can be assembled independently around the drive shaft. This segmentation eliminates the need for precise adjustment during assembly, as each segment can be installed separately and collectively form the complete sealing structure, thereby preventing damage and extending service life while maintaining sealing effectiveness.
2Reliability
If a seal is designed to be in contact with the drive shaft for sealing, then sealing effectiveness is improved, but wear occurs on the drive shaft during operation
Solution Approach 1:
The seal segments are made from material with specific wear-resistant properties that are softer than the drive shaft material. This local quality difference ensures that wear occurs on the replaceable seal segments rather than on the critical drive shaft, maintaining sealing effectiveness while protecting the drive shaft from wear damage.
3Reliability
If a complete annular seal surrounds the drive shaft, then sealing effectiveness is improved, but installation complexity increases due to removal requirements
Solution Approach 1:
The annular seal is segmented into multiple sections that can be installed independently around the drive shaft. This allows the seal to be assembled without removing the grinding table carrier, as the segments can be positioned around the shaft and then joined together, significantly simplifying installation while maintaining the complete sealing effect.
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 provides a reliable, long-lasting seal that protects against coal dust and contaminants, ensures easy maintenance, and extends the seal's service life by preventing wear on the drive shaft and sleeve, thus enhancing operational reliability and economic efficiency.
Implementation Method 1
the seal with a sealing surface bears against the drive shaft or the sleeve over the full circumference and in a form-fitting and preferably friction-fitting manner
Data Source
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AI summary
The pulverizer has a grinding bowl support (4) connected to a drive through a drive shaft (5). The drive shaft is surrounded by a housing-side supporting ring (7). An annular seal (8) completely rotates the drive shaft. The seal lies on the drive shaft in a form-fit manner, and seals the drive shaft against the supporting ring. The seal is connected to the supporting ring in a torque-proof manner. The seal is formed from two seal segments, which are complementary to the seal. The seal is pressed against the drive shaft by a clamping element i.e. tension spring strand.