A Mud Agitator is used in surface mud systems to suspend solids and maintain homogeneous mixture throughout the system. A mechanical agitator is driven by an explosion-proof motor, coupled to a gear box that drives the impeller shaft. The impellers (turbines) transform mechanical power into fluid circulation or agitation. The objective is to obtain a uniform suspension of all solids.-wiki

Drilling fluids are used for a variety of purposes: to control well pressures,
deliver power to downhole motors, remove drilled cuttings from
the bit and transport them to the surface, and stabilize the well bore by
chemical or mechanical means.
As drilling geometry becomes more challenging in regard to directional
steering, or in over- or underpressurized formations or formations that
are susceptible to sloughing and swelling, special precautions must be
taken to ensure that mud properties are adequate for the situation.
Viscosity-enhancing agents, thinners, weighting material, and special
additives are used to produce a drilling fluid that will meet site-specific
requirements. At the same time, drilled solids must also be removed from
the fluid to allow reuse without excessive dilution. This chapter will
demonstrate why agitation is important to the mud circulation system. It
will also define the pitfalls of improper agitation, suspension, and mixing
of drilling fluid. Mixing, shearing, blending, and addition of chemicals are
equally important. Proper sizing and installation will allow the mixing of
fluid additives and chemicals at maximum speed with minimal problems.
The purpose of a surface mud system is to allow maintenance of the
mud before it is pumped down the hole. This is accomplished by the
effective use of solids-control equipment to remove undesirable solids,
while simultaneously recovering as much drilling fluid as is feasible.
Secondary to the solids-removal process is the addition of chemicals and
the rapid and thorough mixing of mud materials. Thorough agitation is
necessary to effectively accomplish both of these tasks. In the majority of
drilling fluids, agitation equipment must be used to suspend solids in the
surface tanks and maintain a homogeneous drilling fluid. There are two
types of equipment to do this:
. mechanical agitators, and
. fluid motive devices, also called mud guns.

Both are widely used, and will be discussed by showing basic principles,
installations, and sizing guidelines.
Drilling-fluid components such as bentonite (gel), barium sulfate
(barite), lost circulation material, polymers, and chlorides (to name a
few) must be wetted before they are dispersed throughout the system.
Proper introduction of these materials into the drilling fluid is equally
important and can enhance drilling efficiency as well as reduce the
amount of additives needed. To gain the most advantage, correct addition
at the surface will enhance their effectiveness in the well. Several
technologies are described to blend, add, hydrate, shear, or mix drillingfluid additives and enhance their effectiveness.
As stated previously, the purpose of agitation equipment is to suspend
solids, completely mix mud materials, and maintain a homogeneous
mixture throughout the surface system. For all of these requirements
to be met, agitation equipment must create an upward velocity within
the mud tanks that is greater than the settling velocity (see chapters 8,
11, and 13 for a complete explanation) of the suspended solids. There
must be adequate shear and stirring to dissolve, wet, and disperse mud
additives. The ability to blend drilling fluid helps maintain consistency.
The following discussion illustrates how mechanical agitators and mud
guns operate and accomplish these goals.