Page 305 - Shale Shakers Drilling Fluid Systems

GLOSSARY 287

size, or the fluid must be lifted to excessive heights. As the bubbles move
out to the impeller tips, they implode releasing a large amount of en-
ergy that can actually chip metal pieces from the impeller blade. Cavita-
tion frequently sounds like the centrifugal pump is pumping gravel. See:
Centrifugal Pump.

CEC See: Cation Exchange Capacity.

Cement A mixture of calcium aluminates and silicates made by combining lime
and clay while heating. Slaked cement contains about 62.5% calcium
hydroxide, which can cause a major problem if cement contaminates the
drilling fluid.

Centipoise (cp) Unit of viscosity equal to 0.01 poise. Poise equals 1 dyne-second per
square centimeter. The viscosity of water at 20°C is 1.005 cp (1 cp =
0.000672 Ib/ft-sec).

Centrifugal Force The force that tends to impel matter outward from the center of rota-
tion. See/ "G"-Force.

Centrifugal Pump A machine for moving fluid by spinning it using a rotating impeller in a
pump casing with a central inlet and a tangential outlet. The fluid flows
in an increasing spiral from the inlet at the center to the outlet, tangent
to the annulus. In the annular space between the impeller vane tips and
the casing wall, the fluid velocity is roughly that of the impeller vane tips.
The pump is effective when some of the spinning fluid flows out of the
casing tangential outlet into the pipe system. Power from the motor is
used to accelerate the fluid entering the inlet up to the speed of the fluid
in the annulus. (Some of the motor power is expended as friction of the
fluid in the casing and impeller.)

Centrifugal Separator A general term applicable to any device using centrifugal force to shorten
and/or to control the settling time required to separate a heavier mass
from a lighter mass.

Centrifuge A centrifugal separator, specifically a device rotated by an external force
for the purpose of separating materials of different masses. This device
is used for the mechanical separation of solids from a drilling fluid. Usu-
ally in a weighted drilling fluid, it is used to eliminate colloidal solids. In
an unweighted drilling fluid it is used to remove solids larger than the
collodials. The centrifuge uses high-speed, mechanical rotation to achieve
this separation as distinguished from the cyclone-type separator in which
the fluid energy alone provides the separating force. See: Hydrocyclone,
Desander, Desilter.

Ceramics A general term for heat hardened clay products that resist abrasion; used
to extend the useful life of wear parts in pumps and hydrocyclones.

Check/Suction Section The last active section in the surface system. It provides a location for
rig pump and drilling fluid hopper suction. This section should be large
enough to check and adjust drilling fluid properties before the drilling fluid
is pumped downhole.

Chemical Barrel A container in which soluble chemicals can be mixed with a limited
amount of fluid prior to addition to the circulating system.
Chemical Treatment The addition of chemicals (such as caustic, thinners, or viscosifiers) to
the drilling fluid to adjust the drilling fluid properties.