Figure 6-24.—Swing check valve.Figure 6-24 shows a swing check valve. In theopen position, the flow of fluid forces the hingeddisk up and allows free flow through the valve.Flow in the opposite direction with the aid ofgravity, forces the hinged disk to close the passageand blocks the flow. This type of valve issometimes designed with a spring to assist inclosing the valve.The most common type of check valve,installed in fluid-power systems, uses either a ballor cone for the sealing element (fig. 6-25). As fluidpressure is applied in the direction of the arrow,the cone (view A) or ball (view B) is forced offits seat, allowing fluid to flow freely through thevalve. This valve is known as a spring-loadedcheck valve.The spring is installed in the valve to hold thecone or ball on its seat whenever fluid is notflowing. The spring also helps to force the coneor ball on its seat when the fluid attempts to flowin the opposite direction. Since the opening andclosing of this type of valve is not dependent ongravity, its location in a system is not limited tothe vertical position.A modification of the spring-loaded checkvalve is the orifice check valve (fig. 6-26). ThisFigure 6-25.—Spring-loaded check valves.Figure 6-26.—Typical orifice check valves.6-17
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