Basic Structure
- Valve Body: Usually made of materials such as stainless steel (indicated by the CF8 mark in the figure, representing 304 stainless steel in the ASTM standard), carbon steel, and alloy steel. The stainless steel material has good corrosion resistance and is suitable for a variety of corrosive media; carbon steel has a lower cost and is suitable for media environments with no or weak corrosiveness. The valve body is connected to the pipeline by means of flange connection, which is convenient for installation and disassembly.
- Ball: Mostly made of materials such as stainless steel and cemented carbide, with high strength and wear resistance. There is a circular through - hole on the ball, and the opening and closing of the valve are realized by rotating the ball to control the flow of the medium.
- Valve Seat: Common materials include polytetrafluoroethylene (PTFE), reinforced polytetrafluoroethylene (RPTFE), and metal. PTFE and RPTFE valve seats have good sealing performance and chemical corrosion resistance, suitable for most chemical media; metal valve seats are suitable for harsh working conditions such as high temperature, high pressure, and media containing particles.
- Pneumatic Actuator: The silver - gray part at the top in the figure is the pneumatic actuator, which uses compressed air as the power source to drive the valve. There are two common types: double - acting and single - acting (spring return). The double - acting actuator relies on compressed air to push the piston to open and close the valve; the single - acting actuator, when air fails, the spring will push the piston to make the valve automatically stay in the preset safe position (such as the closed state) to ensure system safety.
Working Principle
When compressed air enters the air inlet of the pneumatic actuator, it pushes the piston or diaphragm inside the actuator to move, and drives the valve stem to rotate through the connecting mechanism, thereby rotating the ball. When the through - hole of the ball is aligned with the axis of the pipeline, the valve is in the open state, and the medium can pass smoothly; when the ball rotates 90°, making the through - hole perpendicular to the axis of the pipeline, the valve is closed, blocking the flow of the medium.
Performance Features
- High Sealing Performance: The sealing performance between the valve seat and the ball is excellent, which can effectively prevent medium leakage. In the closed state, even under high pressure difference, a good sealing effect can be achieved, which can meet occasions with extremely high sealing requirements, such as gas transmission and chemical fluid control.
- Convenient Operation: The pneumatic actuator has a fast response speed, which can realize the rapid opening and closing of the valve, and is convenient for automatic control. By adjusting the pressure and flow of compressed air, precise adjustment of the valve can also be achieved.
- Strong Flow Capacity: The through - hole design of the ball makes the valve have a small flow resistance when open, the medium flows smoothly, and the pressure loss is small, which is suitable for the transportation of large - flow media.
- Wide Application Range: It can adapt to working conditions of different temperatures, pressures, and media. The general working temperature range is - 40ºC - 180ºC (depending on the material and sealing material), and the working pressure can reach PN16 - PN100 or even higher (according to specific product specifications).
Application Fields
- Petrochemical Industry: Used for the transportation of petroleum, chemical raw materials and products, and controls the flow of various corrosive, flammable and explosive media, such as crude oil, refined oil, acid - base solutions, etc.
- Natural Gas Industry: In the process of natural gas extraction, transportation and distribution, it is used as a key equipment for and controlling the flow to ensure the safe transportation of natural gas.
- Power Industry: In the steam - water system and circulating water system of power plants, it is used to control the flow of media such as steam and water to ensure the normal operation of power generation equipment.
- Food and Pharmaceutical Industry: Using materials that meet hygiene standards (such as 316L stainless steel, food - grade sealing materials), it is used for fluid control in food and beverage production and pharmaceutical processes to ensure product quality and safety.
Maintenance and Servicing
- Regular Inspection: Check whether the air source pressure of the pneumatic actuator is normal, whether the sealing performance of the valve is good, and whether there is any leakage; check the lubrication of the valve stem, and supplement lubricant in time to ensure the flexible rotation of the valve.
- Cleaning: Regularly clean the impurities and dirt inside and outside the valve to prevent impurities from entering between the valve seat and the ball and affecting the sealing performance. For valves transporting media containing particles, the cleaning work should be strengthened.
- Pneumatic Actuator Maintenance: Check whether the seals of the actuator are aged or damaged, and replace them in time; check the working status of accessories such as solenoid valves and filters to ensure the quality of compressed air and the normal operation of the actuator.
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