Desilter And Desander Operation - DERRICK HYPERPOOL SHAKER Maintenance & Operation Manual

OPERATING INSTRUCTIONS

DESILTER AND DESANDER OPERATION

To ensure equal distribution of feed material to each cone, the incoming feed slurry is introduced
into the feed manifold, which contains 20 outlet ports equally spaced around its circumference.
Ten outlets are positioned on each side of the discharge pipe to maintain balance. When a round
desilter is outfitted with a full complement of cones, all 20 positions are filled. When fewer than 20
cones are installed, equal numbers of cones must be installed on each side of the discharge pipe
to maintain balance. Consequently, desilters are supplied only with an even number (14, 16, or
20) of cones.
Optimal performance of hydrocyclones requires a proper balance of feed head (inlet pressure),
feed rate (GPM) and apex opening. Improper balance of any of these variables can adversely
affect performance.
Two operational scenarios are presented in the following paragraphs. The first scenario describes
normal operating conditions in which all variables are correctly balanced. The second scenario
shows a condition referred to as "roping" which results from an improper balance of the variables.
Normal Operation
In normal operation, feed slurry is introduced tangentially into the interior of the hydrocyclone
(Figure 4-1) at high velocity causing a whirlpool effect to occur inside the cone. The swirling
motion of the slurry drives the larger, denser particles outward against the cone wall while the
smaller, lighter particles move toward the center of the cone.
The low-pressure vortex at the center of the cone pulls in the excess liquid and small particles, as
well as drawing in air through the apex at the lower discharge end of the cone. The high-velocity
air stream aids the upward flow of liquid and small particles toward the cone's upper discharge,
while the spiraling stream of liquid and larger particles flows downward along the cone wall toward
the lower discharge. Large solids leaving the lower discharge may be further processed for
removal of remaining small particles and liquid, while the upper discharge from the hydrocyclone
is often routed to a centrifuge for additional solids removal.
Figure 4-1. Normal Hydrocyclone Operation
15 June 12 4-3
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