Steam Valve Auxiliary-Cap Geometry to Prevent Breakage and Leaks
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Solution Overview
Problem
The existing steam valves in steam turbine plants face issues with breakage of the auxiliary valve element and subsequent steam leaks during the warm-up operation, due to the sharp tip collision between the auxiliary-valve cap and the main valve element.
Innovation Solution
The steam valve design is modified such that the abutting position of the auxiliary-valve cap and the main valve element is located outside the radial direction of the valve rod from the outer peripheral surface of the auxiliary-valve tubular part, avoiding sharp tip collisions and ensuring a curved or inclined surface contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary valve element is designed with a sharp tip for precise closing, then the sealing performance is improved, but the auxiliary valve element becomes prone to breakage during operation
Solution Approach 1:
The auxiliary-valve cap is designed with a curved or inclined surface instead of a sharp tip. This curvature eliminates the stress concentration point while maintaining sealing capability through surface contact between the auxiliary-valve cap and main valve element, preventing breakage during warm-up operation.
2Strength
If the auxiliary valve element is made robust to prevent breakage, then the strength is improved, but the sealing precision and control accuracy deteriorate
Solution Approach 1:
The curved or inclined surface of the auxiliary-valve cap provides both mechanical strength and precise positioning. The geometry ensures that the auxiliary valve element can be reliably closed without breakage while maintaining accurate sealing contact with the main valve element.
Solution Approach 2:
The auxiliary-valve cap has different surface characteristics at different locations: a curved or inclined contact surface for strength and positioning, and a precise sealing edge for sealing. This local differentiation allows the single component to satisfy both contradictory requirements.
3Ease of operation
If the auxiliary valve element is designed for frequent operation during warm-up, then the operational flexibility is improved, but the wear and breakage risk increase
Solution Approach 1:
The curved or inclined surface design distributes mechanical stress during repeated opening and closing operations, preventing stress concentration and fatigue failure. This allows the auxiliary valve element to withstand frequent operation during warm-up cycles without increased breakage risk.
Data Source
AI summary
There are provided a steam valve and the like capable of preventing breakage of an auxiliary valve element and effectively suppressing the occurrence of a leak of steam in the auxiliary valve element. In the steam valve of an embodiment, the auxiliary valve element is structured to be in an open state in which the valve rod moves in an opening direction to increase a distance between an auxiliary-valve cap and a main valve element, thereby opening an auxiliary-valve steam introduction hole, and to be in a fully-closed state in which the valve rod moves in a closing direction in which the main valve element is closed to bring the auxiliary-valve cap and the main valve element into contact with each other, thereby closing the auxiliary-valve steam introduction holes. A contact position in which the auxiliary-valve cap and the main valve element are brought into contact with each other is located outside in a radial direction of the valve rod from the outer peripheral surface, of the auxiliary-valve tubular part, through which the auxiliary-valve steam introduction holes are formed.