The pneumatic ball valve in the main line of gas pipeline is mostly driven by the gas-liquid system. The gas-liquid drive system can be operated locally or controlled remotely. Because the pressure of the conveyed medium is variable, sometimes the friction torque of the sphere rotation is very large, or other accidents occur, making it difficult to start the pneumatic ball valve. This requires an emergency mechanism to input energy to the drive system to increase the pressure of the working medium. The pneumatic ball valve pneumatic drive system designed by Shanghai Dongfeng Pump&Valve Factory is equipped with a manual pressurization mechanism. This manual mechanism works reliably and has a certain working efficiency, and the labor consumption of the staff when opening and closing the pneumatic ball valve is also very small. Simple gas-liquid drive system is used to control the pneumatic ball valve installed in the main gas pipeline. The nominal diameter of pneumatic ball valve is 500mm, and the nominal pressure is 8MPa. The pressure vessel controls the opening and closing of the pneumatic ball valve. There are two phases of steam and liquid in the container. The lower half is filled with oil, and the upper half is filled with air from the compressor. The close operation or remote control of pneumatic ball valve can be realized by changing the air pressure. Under the action of compressed air, the oil in the container flows into the half cavity of the hydraulic cylinder through the middle of the filter, one-way throttle valve and manual reversing valve. The piston in the hydraulic cylinder is pushed by the pressure oil, and the piston drives the remote sensing to rotate the ball of the pneumatic ball valve. At the same time, the oil in the other half of the hydraulic cylinder flows into another pressure vessel, and the air in the vessel is connected with the atmosphere. If the pressure of compressed air cannot overcome the friction force when the ball rotates, or an accident occurs and the source of compressed air is lost, in order to complete the opening and closing of the pneumatic ball valve, the manual reversing valve can be operated and the manual pressurization mechanism can be connected. The improved manual supercharging structure processes many channels on the middle plate, connects the pump, reversing valve and pipe joint as required, and the safety valve is also installed on the middle plate, which is very simple and small in structure. During manual rotation, the sliding block pushes two plungers to reciprocate, and the plunger pressurizes the oil in the closed chamber of the pump housing before it is used in the drive system. Low pressure suction and high pressure discharge of oil are realized through butterfly valve. The pump is double acting, so the load is stable and the efficiency is high. The technical characteristics of the hand pump are: 21 ml of oil is discharged every time the hand wheel rotates, the nominal oil discharge pressure is 5.2 MPa, and the maximum pressure can reach 8 MPa. At the nominal pressure, the force applied on the handle of the hand wheel is 180N

Selection of pneumatic butterfly valve for oil pipeline and precautions for installation
Pneumatic butterfly valves are widely used in petrochemical industry, but there are also some problems in the application, mainly due to the selection of hose length and improper equipment. If the hose is too long, it will cause instability of the system, increase fluid resistance, increase mechanical damage and vibration; If the hose is too long or too short, the purpose of compensation, vibration reduction and noise elimination will not be achieved. Therefore, the length of pneumatic butterfly valve must be the primary work. In addition, the following factors should also be considered comprehensively: the nature of the medium, operating temperature, operating pressure, nominal diameter of the connecting pipe, site category, connection mode, displacement mode, etc.
Pneumatic butterfly valve device type
The correct installation of pneumatic butterfly valve is an important link to ensure its full performance. The pneumatic butterfly valve is usually installed behind the root valve of the inlet and outlet pipeline of the tank, and there is also a valve behind the pneumatic butterfly valve, so that the tank and the pipeline directly form a soft connection, which is convenient for the maintenance and replacement of the pneumatic butterfly valve. The pneumatic butterfly valve can only be limited in compensating the axial displacement under natural conditions. When the length of the device is equal to the natural length, it must not accept strong axial tension to cause fracture, which will lead to pipeline leakage. Therefore, the device length of the pneumatic butterfly valve should be less than the natural length to ensure a certain degree of freedom.