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
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.