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Equipment in Mud Circulating Systems 17

Overflow Discharge
Overflow Opening

Feed Chamber
Feed Inlet T
S A
Vortex Finder

Vortex

Underflow Opening
Underflow Discharge
Figure 1.19 A hydrocyclone.

from the top into the barrel of the hydrocyclone past the inlet. The
inside of the vortex finder forms the overflow outlet for the liquid dis-
charge or effluent. The overflow opening is much larger than the under-
flow opening. The nominal size of a hydrocyclone is the largest inside
diameter of the conical portion. All dimensions are critical to the opera-
tion of any specific design and size.
The decanting centrifuge (Figure 1.20) is a liquid‒solid separation
device used on drilling fluids that can remove (decant) all free liquid
from separated solids particles, leaving only adsorbed moisture on the sur-
face area. This adsorbed moisture does not contain soluble matter, such as
chloride or colloidal suspended solids such as bentonite. The dissolved,
suspended solids are associated with the continuous free liquid phase from
which the decanting centrifuges the inert solids, and they remain with
that liquid. The adsorbed moisture can be removed from the separated
solids only by evaporation if necessary.