In most cases, the power generation process is essentially a cycle involving water and steam. While the medium itself seems simple, selecting the right control valve for this process can be both straightforward and highly complex. The basic components are just water and steam, but their varying temperature and pressure conditions can lead to various challenges such as flashing, cavitation, erosion, noise, and corrosion. Therefore, the primary concern when choosing a control valve is ensuring its safety and reliability.
Water supply valves, including main boiler feed valves and composite feedwater regulating valves, play a critical role in controlling the inflow of water into the boiler. Their main function is to regulate the water level, ensure proper steam evaporation, and maintain stable boiler operation. In many systems, the feedwater control consists of two valves: one for boiler startup and another for normal operation.
The working conditions for these valves vary significantly. During boiler startup, the pressure difference across the valve can reach 100–300 kg/cm², with low flow rates. However, during normal operation, the pressure difference decreases, and the flow rate increases dramatically, with an adjustable range of up to 75:1 or even 100:1.
Valve requirements for water supply systems typically include materials like WCB or WC9. For the startup valve in a dual-valve system, anti-cavitation features are essential, along with V-level shutoff performance. Composite feedwater valves need specialized internal designs to handle both start-up and steady-state conditions. Most of these valves are designed to fail closed for safety.
Another important component is the minimum flow circulation valve for boiler feed pumps. Its purpose is to protect the pump during start-up and shutdown by preventing excessive flow, temperature rise, and cavitation. Older power plants often used switch-type or mechanical automatic circulation valves for this function.
The operating conditions for this valve are particularly demanding, with pressure drops reaching up to 160–350 kg/cm²—making it the valve with the highest pressure differential in the entire power plant system. The flow through this valve is usually around 30% of the normal flow rate.
To handle these extreme conditions, the valve must have anti-cavitation and anti-blockage features, along with V-class sealing. It should operate continuously during pump start-up and shutdown, and then close once the pump is running normally. These valves are typically designed to fail open for safety reasons.
High and low-pressure heater traps, such as those used in feedwater heaters and condensate heaters, also require precise control. They help remove condensate efficiently while maintaining system performance. For more information on Valve Products and applications, visit [http://news.chinawj.com.cn](http://news.chinawj.com.cn). This article was edited by the Hardware Business Network Information Center.
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