Nova-Tech Pulsafeeder OMNI DC7 - Manual (Page 19)

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7.3 Check Valves
Most fluid metering problems are related to check valves. Problems usually stem from solids
accumulation between valve and seat, corrosion of seating surfaces, erosion, or physical damage due
to wear or the presence of foreign objects.
The 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.
OMNI DC7 pumps utilize a multi-part check valve assembly, secured to the reagent head with a
union nut clamping arrangement (plastic construction) or a tie-bar arrangement (metal construction).
Figure 12, check valves DC7