Figure 6-24.—Swing check valve.

Figure 6-24.—Swing check valve. Figure 6-24 shows a swing check valve. In the open position, the flow of fluid forces the hinged disk up and allows free flow through the valve. Flow in the opposite direction with the aid of gravity, forces the hinged disk to close the passage and blocks the flow. This type of valve is sometimes designed with a spring to assist in closing the valve. The most common type of check valve, installed in fluid-power systems, uses either a ball or cone for the sealing element (fig. 6-25). As fluid pressure is applied in the direction of the arrow, the cone (view A) or ball (view B) is forced off its seat, allowing fluid to flow freely through the valve. This valve is known as a spring-loaded check valve. The spring is installed in the valve to hold the cone or ball on its seat whenever fluid is not flowing. The spring also helps to force the cone or ball on its seat when the fluid attempts to flow in the opposite direction. Since the opening and closing of this type of valve is not dependent on gravity, its location in a system is not limited to the vertical position. A modification of the spring-loaded check valve is the orifice check valve (fig. 6-26). This Figure 6-25.—Spring-loaded check valves. Figure 6-26.—Typical orifice check valves. 6-17