|Fig. 1: Ball valve in closed position|
Construction of a Ball Valve
|Fig. 2: Lubricant-seal system in a ball valve|
Ball valves are manufactured in several different body configurations: top entry, side entry, split body, and three-piece body. The valve ends are available as butt welding, socket welding, flanged, threaded, soldering, or brazing ends.
Ball valves are manufactured in high- and low-pressure classifications. The advances in ball valve designs have made it possible to use these valves in high pressure and high-temperature applications.
Types of Ball Valves
Split-Body Ball Valve
|Fig. 3: Ball valves, split body, regular port, flanged ends|
Top-Entry Ball Valve
|Fig. 4: Ball valves, top entry, regular port, socket weld ends|
End-Entry Ball Valve
Three-Piece — Body Ball Valve
Double Trunnion Ball Valves
The trunnion-mounted ball-valve design is used with split-body large size valves, whereas the floating-ball design is the most common design for all other types of ball valves. The torque required to actuate a trunnion-mounted ball valve is substantially smaller than the torque required for a floating-ball design.
Lubricated or Non-lubricated Ball Valves
Advantages of Ball Valves
1. Provides bubble-tight service.
2. Quick to open and close.
3. Smaller in size than a gate valve.
4. Lighter in weight than a gate valve.
5. Multi-port design offers versatility not available with gate or globe valves. It reduces the number of valves required.
6. Several designs of ball valves offer flexibility of selection.
7. Can be used in clean and slurry applications.
8. High-quality ball valves provide reliable service in high-pressure and high-temperature applications.
9. Force required to actuate the valve is smaller than that required for a gate or a globe valve.
Disadvantages of Ball Valves
2. In slurry or other applications, the suspended particles can settle and become trapped in body cavities causing wear, leakage, or valve failure.
Typical Applications of Ball Valves
1. Air, gaseous, and liquid applications requiring bubble-tight service
2. Low-point drains and high-point vents in liquid, gaseous, and other fluid services
3. Instrument root valves
4. Cooling water and feed water systems
5. Steam service