The hydraulic control valve is driven by the pressure difference △ p between the upstream and downstream of the pipeline system, and controlled by the pilot valve to make the diaphragm (piston) hydraulically operated in a differential manner, which is completely automatically adjusted by water, so that the main valve disc is fully opened, fully closed or in a regulated state. When the pressure medium entering the control room above the diaphragm (piston) is discharged to the atmosphere or the downstream low-pressure area, the pressure value acting on the bottom of the valve disc and below the diaphragm is greater than the pressure value above, and the main valve disc is pushed to the fully open position by relying on the pipeline medium: when the pressure medium entering the control room above the diaphragm (piston) cannot be discharged to the atmosphere or the downstream low-pressure area, The pressure above the diaphragm (piston) is greater than the pressure below, and the medium in the pipeline presses the main valve disc to the fully closed position; When the pressure value in the control room above the diaphragm (piston) is between the population pressure and the outlet pressure, the main valve disc is in the regulating state, and its regulating position depends on the joint control effect of the needle valve and the adjustable pilot valve in the attached pipeline system.

Building automation refers to the electrical equipment in buildings, such as elevators, water pumps, fans, air conditioners, etc. its main working nature is strong electric drive. Usually, these devices are in an open working state, that is, they do not form a closed loop. As long as the power is turned on, the equipment is working. As for the working state, process, energy consumption, etc., data cannot be obtained online in time, let alone rational use and energy conservation. Now, building automation is to monitor the above electrical equipment online, detect the working state of the equipment by setting corresponding sensors, travel switches, photoelectric controls, etc., and return to the central computer of the control room through the line. The computer obtains the analysis results, and then returns to the equipment terminal for mediation.

Water engineering is mainly a social circulation problem of water, such as the sustainable development and utilization of urban water resources, involving urban water supply and drainage engineering, environmental engineering, hydrology and water resources engineering, urban water conservancy engineering and many other aspects. For example, the access and purification of urban water supply, the treatment and discharge of sewage, the prevention and control of urban floods and river regulation, the development, utilization and conservation of water resources, etc. Compared with water conservancy and hydropower projects and hydrology and water resources projects, it covers a wider range.

Fire valve is an important accessory for industrial and building pipeline control. This handout focuses on the practical application of fire valve. Refer to relevant data books for detailed principle and structural sectional view. Fire valve is composed of valve body, hoist and bonnet.

Chemical valve is an important accessory to control the flow of medium on chemical pipeline. Refer to relevant information books for detailed principle and structural sectional view. The valve is composed of valve body, hoist and bonnet.

Oilfield special valves are mainly divided in o sulfur resistant mud valve, soft seal mud valve, high-pressure wellhead gate valve, hard seal mud valve, anti-theft clamp valve, shell valve, downhole w