Pneumatic cut-off ball valve is an important component in the pipeline system, which is used to connect or cut off the flow medium in the pipeline, or to control the flow and pressure of the medium, or to ensure the safety of equipment and pipelines.

在发电厂热力系统管路中，阀门是必不可少的部件。一个发电厂要使用几千只各种各样的阀门，这些阀门不仅控制机组的热力过程，而且关系着机组的经济运行和。所以，它们也是机组必不可少的组成部分。如给水调节阀门是用来调节锅炉给水流 量的阀门，汽轮机调节阀门控制着进人汽轮机的蒸汽流量，从而控制机组负荷。主蒸汽管道上的阀门是用来切断或接通锅炉汽轮机蒸汽的截门。汽包和过热器的门是保障锅炉运行的 阀门等等。

Valves are essential components in the thermal system pipelines of power plants. A power plant requires the use of thousands of various valves, which not only control the thermal process of the unit, but also affect the economic operation and safety of the unit. So, they are also an essential component of the unit. For example, the feedwater control valve is a valve used to regulate the boiler feedwater flow, while the turbine control valve controls the steam flow into the turbine, thereby controlling the unit load. The valve on the main steam pipeline is used to cut off or connect the shut-off valve from the boiler to the steam turbine. The safety valves of the steam drum and superheater are valves that ensure the safe operation of the boiler.

随着发电厂机组向大容盘，高参数方向发展，阀门也随着介质参数的提高，不断地向高温高压方向发展。管道介质工作压力的提高，要求阀门相应地改进密封结构，提高密封性能，采用新型密封面材料。为了简化管路系统出现了一阀多用的组合阀门， 如启动、减压和三用的组合阀门。随着自动控制的提高，实行集中控制和遥控，就对阀门的驱动装置和执行机构提出了新的要求。

With the development of power plant units towards large capacity and high parameters, valves continue to develop towards high temperature and pressure with the improvement of medium parameters. The increase in working pressure of pipeline medium requires corresponding improvement of sealing structure and sealing performance of valves, and the use of new sealing surface materials. In order to simplify the pipeline system, a combination valve with multiple functions has emerged, such as a combination valve for starting, reducing pressure, and safety. With the improvement of automatic control and the implementation of centralized control and remote control, new requirements have been put forward for the driving device and actuator of valves.

对电站阀门的要求是使用性能好、强度高、操作方便、维修简单、低噪音等。在发电厂的热力系统中常常由于一个阀门发生故障造成整个系统或整个机组停止运行。

The requirements for power plant valves are good performance, high strength, easy operation, simple maintenance, and low noise. In the thermal system of power plants, the failure of one valve often causes the entire system or unit to stop operating.