Page 161 - Shale Shakers Drilling Fluid Systems

144 SHALE SHAKERS AND DRILLING FLUID SYSTEMS
is discharged from the lower apex of the cone,
and the cleaned drilling fluid is discharged from
the overflow discharge.
Hydrocyclones consist of an upper cylindrical
section fitted with a tangential feed section, and
a lower conical section that is open at its lower
apex allowing for solids discharge (Figure 7-3).
The closed, upper cylindrical section has a down-
ward protruding vortex finder pipe extending be-
low the tangential feed location.
Fluid from a centrifugal pump enters the hydro-
cyclone tangentially, at high velocity, through a
feed nozzle on the side of the top cylinder. As
drilling fluid enters the hydrocyclone, centrifugal
force on the swirling slurry accelerates the solids
to the cone wall.
The drilling fluid, a mixture of liquid and solids, head is 75 feet. Fluid will always have the same
rotates rapidly while spiraling downward toward
the apex. The higher-mass solids move toward the
cone wall. Movement progresses to the apex open-
ing at the cone bottom. At the apex opening, the
solids along the cone wall, together with a small
amount of fluid, exit the cone. The discharge is re-
stricted by the size of the apex. Fluid and smaller-
mass particles, which have been concentrated
away from the cone wall, are forced to reverse
flow direction into an upward spiraling path at the
center of the cone to exit through the vortex finder. head is summarized in Table 7-2.
FIGURE 7-3. Hydrocyclone
The vortex finder is a hollow tube that extends
into the center of the cone. It diverts drilling fluid
from flowing directly to the overlow outlet, caus-
ing the drilling fluid to move downward and into
the cone. The swirling liquid is forced inward and,
still rotating in the same direction, reverses the
downward flow and moves upward toward the
center of the vortex finder. In a balanced cone,
the inner cylinder of swirling fluid surrounds a
cylinder of air that is pulled in through the cone
apex. Solids and a small amount of liquid spray
out the lower apex of the cylinder. The apex open-
ing relative to the diameter of the vortex finder will
determine the dryness of the discharged solids.
Most balanced cones are designed to provide
maximum separation efficiency when the inlet
velocity within the cone if the same head is de-
livered to the hydrocyclone inlet. Pressure can be
converted to feet of head with the equation fre-
quently used in well-control calculations:
The relationship between manifold guage pressure
and drilling fluid weight at a constant 75 feet feed