A ball valve is a type of control valve used for regulating the flow of gas, liquids, and sometimes slurries in low-pressure applications (i.e., below 15 pounds per square inch gauge). The ball operates directly on the full port or shutoff port which allows the fluid to pass through. A ball valve is also commonly called a globe valve because it has characteristics similar to those of a globe: it rotates freely around its seat when unbalanced by external forces. In this case, it will close fully if an imbalance occurs so that pressure can force it against the seat. The main advantage of a ball valve is that once closed, it forms an airtight seal. It also does not leak as readily as other types of valves when the flow is reversed. Ball valves are available with a single-plane swing pattern, which allows for 360° access with only two bodies, or three-plane swing patterns, which allow for 120° of access from three positions.