Agitators keep the mud uniform and the barite in suspension — when they fail, solids settle, weight varies and barite is lost. This is the deep reference: sizing and coverage, impeller and shaft mechanics, the seal/gearbox/bearing drivetrain, and the electrical failures of continuously running motors.
Where it sits: in the active and reserve compartments, working with mud guns to keep solids suspended and properties uniform across the tank system. Under-sized or worn, they leave the dead zones and barite sag that show up as mud-weight problems and lost volume.
Agitators keep the mud — and especially the barite — in suspension across the tank. Sizing is the whole game: an under-powered or badly placed agitator leaves zones the mud never reaches.
Agitator under-sized for the tank / mud weight
Mechanism
Each agitator must move enough fluid to keep solids suspended in its zone; weighted mud needs more power. Under-sizing leaves dead zones.
Shows as
Settled beds and barite sag away from the impeller; weight stratification.
Detect / inspect
Compare agitator power/impeller to tank size and mud weight; sound for beds; check weight top-to-bottom.
Consequence downstream
Lost volume, mud-weight variation, barite loss.
Correction
Size agitators for the tank and the heaviest mud; add units or upgrade impellers where zones go dead.
Too few agitators / poor placement (coverage gaps)
Mechanism
Spacing and number must cover the whole compartment; gaps between units settle out.
Shows as
Dead corners and mid-tank settling.
Detect / inspect
Map coverage across the compartment; inspect for beds between units.
Consequence downstream
Settling and barite sag in the gaps.
Correction
Add/relocate agitators for full coverage; supplement with mud guns.
Wrong impeller type / pitch for the duty
Mechanism
Impeller design sets flow pattern (axial vs radial). The wrong type gives poor suspension or excessive shear/foam.
Shows as
Poor suspension or unwanted shear/foam.
Detect / inspect
Check impeller type/pitch vs the suspension duty.
Consequence downstream
Settling or fluid-quality problems.
Correction
Select impeller type/pitch for suspension; match to the mud and tank.
Mounting / structure not rigid enough
Mechanism
A weak mount lets the agitator shaft whip, stressing seals, bearings and the gearbox.
Check mount rigidity and alignment; watch for shaft movement.
Consequence downstream
Mechanical failures and downtime.
Correction
Stiffen/repair the mount; align the drive; eliminate shaft whirl.
Mechanical failures
The drivetrain — impeller, shaft, bearings, seals, gearbox — under continuous abrasive immersion. These are the failures that take an agitator offline.
Impeller / blade wear and erosion
Mechanism
Abrasive mud erodes impeller blades, cutting the flow they produce.
This reference describes failure modes and engineering principles in general terms. Corrective actions must be matched to your actual equipment, fluid, formation and procedures, and carried out under the relevant rig and safety standards.
Grounded in standard solids-control and mud-mixing practice and field references (drilling-fluid handbooks; agitator OEM guidance). SC DrillTech is independent and vendor-neutral.
Take it further
Tools and references built from the same field experience as this page — independent and vendor-neutral.
Is your barite staying in suspension — or sitting in the tank bottom?
Settled beds and barite sag trace straight back to agitator sizing, coverage and condition. An independent evaluation maps the dead zones and matches the agitation to the mud you're actually running.
