Segmented Shear Key for High-Pressure Compressor Casing
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Solution Overview
Problem
Conventional bolted and shear key structures for high-pressure centrifugal compressor casings face complications in assembly and disassembly, increased costs, and potential plastic deformation due to uneven surface pressure, while existing shear key structures require complex machining and may lead to shoulder deformation or bolt failure.
Innovation Solution
A shear key structure with circumferentially extending grooves in the casing and radially fixed, segmented shear key members that allow slight radial displacement, distributing load and reducing the risk of deformation and bolt failure, while maintaining a large end surface area for fluid introduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bolted structure is used to fix the head cover, then the connection is simple and reliable, but the number of bolts must be increased as pressure increases, making assembly and disassembly complicated and increasing cost
Solution Approach 1:
The shear key is segmented into multiple discrete keys arranged circumferentially, allowing the connection to accommodate pressure variations without requiring additional bolts. Each key acts independently to maintain connection reliability while simplifying assembly compared to bolted structures.
Solution Approach 2:
The shear key structure allows for dynamic adjustment of the connection state. The keys can slide axially within the groove to accommodate pressure changes, providing a dynamic connection mechanism that maintains reliability without increasing complexity.
2Device complexity
If a shear key structure is used to reduce the number of bolts, then assembly is simplified, but uneven surface pressure causes plastic deformation of the casing, shear key, and head cover
Solution Approach 1:
The shear key is divided into multiple segmented keys distributed around the circumference. This segmentation distributes the contact pressure across multiple discrete contact points between the keys and the groove, preventing localized high surface pressure that causes plastic deformation while maintaining assembly simplicity.
3Reliability
If a ring-shaped stopper is added to restrict shear key rotation, then the moment balancing is improved, but the end surface area of the head cover is reduced, making it difficult to ensure sufficient area for flange mounting
Solution Approach 1:
Instead of using a continuous ring-shaped stopper, the rotation restriction is achieved through multiple discrete shear key segments arranged circumferentially. This segmentation maintains moment balancing capability while preserving the end surface area of the head cover for flange mounting and other attachments.
4Reliability
If the shear key is axially segmented into two members with shoulders, then the load distribution is improved, but the machining complexity increases and higher machining accuracy is required
Solution Approach 1:
The shear key is segmented into multiple discrete keys that can be manufactured as separate components and then assembled. This approach simplifies machining compared to creating complex shoulders on axially segmented members, as each key can be machined independently with standard tolerances rather than requiring precise shoulder surfaces.
5Force
If the outer diameter of the shear key shoulder is brought into contact with the inner diameter of the casing, then the force applied to the shear key is reduced, but the casing must be extended to accommodate the shoulder
Solution Approach 1:
Multiple discrete shear keys are arranged circumferentially within the groove, allowing the force to be distributed across multiple contact points between the keys and the groove. This eliminates the need for the casing to be extended to accommodate a single large shoulder structure, as the distributed contact points achieve force reduction within the existing casing dimensions.
Data Source
AI summary
Size reduction of a barrel-type casing using a shear key is aimed for while ensuring a necessary area of a head cover end surface. A shoulder is formed on the axially outer side of the outer circumferential surface of a head cover. The inner surface of a casing is provided with a circumferentially extending groove. Shear key structure includes a first shear key member disposed in the shoulder and the groove, such that at least a portion of its outer circumferential surface is in contact with the inner circumferential surface of the groove, and a second shear key member disposed adjacent to the first shear key member in the groove, the second shear key member having an axially projecting shoulder, its outer circumferential surface being in contact with an inner circumferential surface of the casing. The first and second shear key members are circumferentially segmented respectively into three or more members, and each member is radially fixed to the casing but not axially fastened to each other, to allow slight displacement between the first and second shear key members by a shear force.