same function as the disk in other valves. As thevalve handle is turned to open the valve, the ballrotates to a point where part or all of the holethrough the ball is in line with the valve body inletand outlet, allowing fluid to flow through thevalve. When the ball is rotated so the hole isperpendicular to the flow openings of the valvebody, the flow of fluid stops.Most ball valves are the quick-acting type.They require only a 90-degree turn to eithercompletely open or close the valve. However,many are operated by planetary gears. This typeof gearing allows the use of a relatively smallhandwheel and operating force to operate a fairlylarge valve. The gearing does, however, increasethe operating time for the valve. Some ball valvesalso contain a swing check located within the ballto give the valve a check valve feature. Figure 6-2shows a ball-stop, swing-check valve with aplanetary gear operation.In addition to the ball valves shown in figures6-1 and 6-2, there are three-way ball valves thatare used to supply fluid from a single source toone component or the other in a two-componentsystem (fig. 6-3).Figure 6-2.—Typical ball-stop, swing-check valve.6-2
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