Adjustable Alignment Constraint for Turbine Inner Casing
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Solution Overview
Problem
Current methods for aligning a low-pressure steam turbine's inner casing with its rotor axis are inefficient, requiring complex machining and site adjustments, which are time-consuming and pose safety risks, especially when design changes necessitate repositioning, and conventional bolt-type arrangements are limited in applicability.
Innovation Solution
An adjustable alignment constraint comprising a main body and a piggyback body with an interlocking arrangement that allows relative axial movement, enabling the constraint to be inserted into holes with interfering parts and accommodating misalignments without precise clocking, thus simplifying the alignment process and reducing the need for field machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional bolt-type arrangements are used for positioning, then the alignment process can be simplified, but the arrangement is limited in applicability to certain positioning locations
Solution Approach 1:
The alignment constraint is divided into two separate bodies: a main body that threads into the prong, and a piggyback body that attaches to the main body. This segmentation allows the constraint to be installed in locations where a single long bolt would be obstructed, as each body can be installed in stages, overcoming the limitation of conventional single-piece bolt arrangements.
2Manufacturing precision
If precise clocking and machining are performed during initial installation, then proper concentric alignment is achieved, but the process becomes time-consuming and complex
Solution Approach 1:
The piggyback body is designed to rotate relative to the main body, allowing dynamic adjustment of the constraint's orientation. This rotational capability enables the alignment constraint to accommodate misalignments between the prong and frame member without requiring precise pre-machining or clocking, significantly reducing installation time while maintaining alignment accuracy.
3Adaptability or versatility
If field personnel perform machining in place during repositioning, then design changes can be accommodated, but safety concerns arise due to scaffolding and awkward positioning requirements
Solution Approach 1:
The alignment constraint is designed to be installed first, establishing proper concentric alignment between the inner casing and rotor. Once installed, the constraint serves as a reference for subsequent machining operations. This preliminary alignment eliminates the need for field personnel to perform complex machining in awkward positions on scaffolding, as the alignment is already established by the constraint.
4Manufacturing precision
If multiple liners are machined to complete positioning at multiple locations, then proper fit-up is achieved, but cumulative errors increase the need for accuracy
Solution Approach 1:
The alignment constraint with its adjustable piggyback body serves multiple functions: it provides positioning, orientation, and alignment reference simultaneously. This multi-functionality eliminates the need for separate liners at multiple locations, as the single constraint establishes the alignment reference that all other components must follow, reducing cumulative errors and simplifying the overall positioning arrangement.
Data Source
AI summary
A positioning arrangement (142), including: an outer casing having a frame member (78); a low pressure steam turbine inner casing (140) having an appendage (60) and a threaded hole through the appendage; and an alignment constraint (10) configured to be positioned in the threaded hole and define a positional relationship between the inner casing and the frame member. The alignment constraint includes a main body (14) and a discrete piggyback body (16), both configured to rotate in the threaded hole as a unitary body when in a joined, end-to-end configuration.