Pulsafeeder Pulsa GLM DM7 - Manual (Page 19)

19
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.
GLM ® DM7 xpumps 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 DM7