Pulsafeeder PulsaPro 900 EN - Manual (Page 30)

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7.3 Check Valves
Most fluid metering problems are related to check valves. Problems can be caused by solids
accumulation between the valve and seat, corrosion of seating surfaces, erosion, physical
damage due to wear or the presence of foreign objects.
There are two styles of check valves. Ball checks are used for lower flows. Disk checks are
used for higher flows.
Figure 14
The ball check valve incorporates a ball, guide, and seat. Flow in the unchecked direction
lifts the ball off the seat, allowing liquid to pass through the guide. Reverse flow forces the
ball down, sealing it against the sharp edge of the seat. The guide permits the ball to rotate
but restricts vertical and lateral movement in order to minimize “slip” or reverse flow. Ball
rotation prolongs life by distributing wear over the entire surface of the ball. Since ball return
is by gravity, the valve must be in the vertical position in order to function properly. Parts are
sealed by o-rings.
The disk valve functions in the same manner as the ball valve, except that the ball is replaced
by a spring-loaded guided disk. The seat may contain a captured o-ring to facilitate sealing.