Turbine Shutdown Valve Backflow Protection
Solution Overview
Problem
Conventional check valves in steam turbine systems fail to completely prevent steam backflow from the deaerator to the turbine, leading to potential turbine damage due to frequent opening and closing, which can deform valve components and allow water induction.
Innovation Solution
A turbine protection device with a shutdown valve system that controls steam flow based on differential pressure thresholds, using a control unit to manage the shutdown valve's operation to prevent steam backflow by closing the extraction steam inlet tube when the deaerator internal pressure exceeds the extraction pressure, and opening it when the pressure differential falls below a predetermined value, with an internal timer to minimize frequent operation and valve degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a check valve is provided to prevent steam backflow from the deaerator to the turbine, then steam backflow prevention is improved, but the valve components deform due to frequent opening and closing, reducing reliability
Solution Approach 1:
A shutdown valve is introduced as an intermediary component between the check valve and the steam flow path. The shutdown valve is controlled to close when the deaerator internal pressure exceeds the extraction pressure, preventing steam backflow without requiring the check valve to operate frequently. This mediator approach protects the check valve from frequent opening and closing while maintaining effective backflow prevention.
Solution Approach 2:
The patent replaces the purely mechanical check valve operation with a controlled shutdown valve operation based on pressure differential detection. Instead of relying on the check valve's mechanical opening and closing in response to pressure changes, the system uses pressure sensors or differential pressure devices to detect when backflow conditions exist and activates the shutdown valve accordingly, substituting mechanical reaction with controlled actuation.
2Reliability
If the shutdown valve operates frequently to prevent steam backflow, then backflow prevention is improved, but the valve degrades faster, reducing its lifespan
Solution Approach 1:
The system performs preliminary action by detecting the pressure differential between the deaerator and extraction steam in advance and closing the shutdown valve before steam backflow can occur. This preventive approach eliminates the need for frequent reactive valve operations, extending valve lifespan while maintaining continuous backflow prevention.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the pressure differential between the deaerator internal pressure and extraction pressure. When the differential indicates potential backflow conditions, the control unit activates the shutdown valve. This feedback mechanism ensures the valve operates only when necessary, minimizing wear and extending lifespan while maintaining reliable backflow prevention.
3Quantity of substance
If the deaerator capacity is increased to store more condensate, then heat capacity is improved, but the decompression speed decreases, causing pressure balance breakdown
Solution Approach 1:
The shutdown valve acts as an intermediary protective measure that compensates for the deaerator's slow decompression speed. By monitoring pressure differential and closing the valve when deaerator pressure exceeds extraction pressure, the system prevents backflow despite the large deaerator capacity and slow pressure equalization, allowing the deaerator to maintain its beneficial large capacity.
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
Effectively interrupts steam backflow from the deaerator to the turbine, preventing water induction and reducing the risk of turbine damage by ensuring the shutdown valve operates only when necessary, thus extending its lifespan and maintaining system stability.
Implementation Method 1
when the deaerator internal pressure exceeds the extraction pressure... the shutdown valve operates to prevent steam backflow
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An object of the present invention is to provide a turbine protection device which can interrupt steam flowing backward from a deaerator (5) to a turbine (2) completely even if a check valve (3a) provided between the deaerator (5) and the turbine (2) can not interrupt the steam flowing between the deaerator (5) and the turbine (2) completely. In order to achieve the above object, a control unit (11) sends commands to a shutdown valve device (12) so as to close the shutdown valve device (12) when a differential pressure resulted from subtracting a pressure of a extraction steam from a pressure within the deaerator (5) becomes equal to or greater than a first predetermined value. As a result, the steam flowing backward from the deaerator (5) to the turbine (2) is interrupted by a stop valve of the shutdown valve device (12).