Why is my centrifugal pump cavitating?

Cavitation happens when the pump can't get enough fluid at its suction — gas-cut mud, a low or blocked suction, a long or restricted suction line, or inadequate available NPSH. It sounds like gravel, vibrates and loses head, and it damages the impeller. Fix it by degassing the feed, clearing and flooding the suction, and improving the suction design so available NPSH exceeds what the pump requires.

Why won't my centrifugal pump build feed head for the hydrocyclones?

Either the pump or impeller is too small for the required head, the impeller and casing are worn, or the pump is cavitating or losing prime. Hydrocyclones need a specific feed head to separate, so check the pump curve and impeller against the duty, inspect for wear, and rule out suction/cavitation problems before blaming the cyclones.

What is the most common centrifugal pump failure on a rig?

On abrasive drilling mud, impeller and wear-plate erosion and mechanical-seal failure are the most common, usually accelerated by cavitation from poor suction conditions and by misalignment. Heavy-duty abrasion-resistant construction, good suction design, alignment and seal-flush maintenance address the majority of failures.

Failure Center

Common Failure Center · Transfer & feed

Centrifugal pumps — failure modes

By Othman Soliman — Solids Control & Drilling-Waste specialist, 26+ yrs (GCC & MENA). Last reviewed July 2026.

Centrifugal pumps feed the hydrocyclones, charge the mud pumps, drive eductors and move mud around the system — and when they fail, whole stages downstream lose their feed. This is the deep reference: selection and suction design, mechanical wear, the operational causes of cavitation and lost prime, and motor and control failures. See the visual failure gallery.

Where it sits: throughout the surface system — as dedicated cyclone feed pumps, charge pumps, eductor/mixing pumps and transfer pumps. A pump that can't develop its head starves the cyclones; one that cavitates on a bad suction destroys itself and loses the charge to the mud pumps.

Selection & suction Mechanical Operational Electrical & motor

Selection, sizing & installation failures

Centrifugal pumps feed the hydrocyclones, charge the mud pumps, drive eductors and transfer mud. Most pump grief is selection and suction design — a pump can't deliver head it was never sized for, or pump fluid it can't draw.

Pump under-sized for the required head (esp. hydrocyclone feed)

Mechanism: Hydrocyclone banks need a specific feed head; a pump (or impeller) too small can't develop it.
Shows as: Low feed head, weak cyclone separation; can't reach duty.
Detect / inspect: Compare pump curve/impeller to the head and flow required; measure delivered head.
Consequence downstream: Poor solids removal across the cyclone banks; dilution rises.
Correction: Select pump/impeller for the duty head and flow; trim/replace impeller; don't run cyclones off an undersized pump.

Inadequate suction design (NPSH) → cavitation built in

Mechanism: Long, restricted or high suction lines, or low available NPSH, mean the pump cavitates regardless of condition.
Shows as: Cavitation (noise, vibration, lost head) from new.
Detect / inspect: Review suction-line size/length/height and available vs required NPSH; listen for cavitation.
Consequence downstream: Impeller damage, lost head, short life.
Correction: Re-design the suction (shorter, larger, flooded); raise available NPSH; lower the pump or the suction lift.

Wrong pump for the service (abrasion / metallurgy)

Mechanism: A pump not built for abrasive drilling mud wears out fast.
Shows as: Rapid impeller/casing wear, frequent failures.
Detect / inspect: Check pump construction/metallurgy vs the abrasive duty.
Consequence downstream: High maintenance and downtime.
Correction: Use heavy-duty, abrasion-resistant mud pumps for the service; match metallurgy/liners.

Poor installation: alignment, baseplate, piping strain

Mechanism: Misalignment, a weak baseplate or pipe strain stress seals, bearings and the coupling.
Shows as: Vibration, seal/bearing wear from new.
Detect / inspect: Check alignment, baseplate rigidity and piping strain at install.
Consequence downstream: Premature mechanical failures.
Correction: Align to spec, rigid baseplate, strain-free piping; recheck after moves.

Mechanical failures

Impeller, seal, bearings, coupling — the wear and failure points of a pump living on abrasive mud.

Impeller wear / erosion

Mechanism: Abrasive mud erodes the impeller, cutting head and flow.
Shows as: Falling head/flow; worn impeller vanes.
Detect / inspect: Trend delivered head/flow; inspect impeller at service.
Consequence downstream: Lost feed head to cyclones / charge to mud pumps.
Correction: Replace impeller; abrasion-resistant materials; manage solids in the feed.

Mechanical seal / packing failure

Mechanism: Seals/packing wear and leak under abrasive, pressurised service.
Shows as: Leaking at the shaft; air ingress; lost prime.
Detect / inspect: Inspect seal/packing for leaks; check flush.
Consequence downstream: Lost prime/head, air ingress, mess and hazard.
Correction: Replace seal/packing; maintain seal flush; correct shaft condition.

Bearing failure

Mechanism: Bearings fail from load, contamination or misalignment.
Shows as: Noise, heat, vibration, eventual seizure.
Detect / inspect: Monitor vibration/temperature; check lubrication.
Consequence downstream: Pump outage.
Correction: Replace bearings; maintain lubrication; fix alignment/contamination.

Coupling / shaft wear and misalignment

Mechanism: Worn couplings and misaligned shafts vibrate and damage seals/bearings.
Shows as: Vibration, coupling wear.
Detect / inspect: Inspect coupling; check alignment.
Consequence downstream: Seal/bearing damage.
Correction: Replace coupling; re-align; keep within tolerance.

Casing / volute and wear-plate erosion

Mechanism: The casing and wear plates erode, opening clearances and dropping efficiency.
Shows as: Falling efficiency, internal leakage, worn plates.
Detect / inspect: Inspect casing/wear plates and clearances.
Consequence downstream: Lost head and flow.
Correction: Replace wear plates; restore clearances; abrasion-resistant parts.

Operational & process failures

How the pump is run and fed — the day-to-day causes of cavitation, lost prime and overload.

Cavitation from gas-cut or starved suction

Mechanism: Gas-cut mud or a low/blocked suction makes the pump cavitate in service.
Shows as: Rattling/gravel noise, vibration, lost head.
Detect / inspect: Check suction level, blockage and gas-cut mud; listen for cavitation.
Consequence downstream: Impeller damage and lost cyclone feed / pump charge.
Correction: Degas the feed (route through the degasser), clear/raise the suction, maintain level.

Running off the curve (throttled / dead-headed / run-out)

Mechanism: Operating far from the design point — throttled, dead-headed or run-out — overloads or starves the pump.
Shows as: Overheating, vibration, lost efficiency.
Detect / inspect: Compare operating point to the pump curve; check valve positions.
Consequence downstream: Mechanical stress and poor delivery.
Correction: Operate near the design point; correct valve line-ups; trim impeller/speed to the duty.

Air ingress / loss of prime

Mechanism: Air leaks at the suction or seal break prime so the pump gas-locks.
Shows as: Pump won't deliver; gas-locked; intermittent flow.
Detect / inspect: Check suction joints/seal for air ingress; verify prime.
Consequence downstream: Lost feed/charge downstream.
Correction: Seal air-ingress points; restore prime; keep the suction flooded.

Plugging / solids settling in suction or pump

Mechanism: Coarse solids or settled beds block the suction or pump.
Shows as: Lost/erratic flow; blockage.
Detect / inspect: Inspect suction and pump for blockage/solids.
Consequence downstream: Lost delivery.
Correction: Clear blockage; keep upstream removal working; maintain suction velocity.

Electrical & motor failures

Pump motors are high-duty machines in the wet, classified mud area.

Motor failure / winding burnout

Mechanism: Overload, ingress or single-phasing burns the motor.
Shows as: Trips, won't start, runs hot.
Detect / inspect: Megger/current checks; inspect seals/area rating.
Consequence downstream: Pump offline; lost feed/charge.
Correction: Repair/replace to rating; fix ingress; correct protection.

Starter / VFD / overload faults

Mechanism: Mis-set or failing starter/VFD nuisance-trips or fails to protect.
Shows as: Nuisance trips or burnt motor.
Detect / inspect: Check overload settings vs FLA; VFD logs.
Consequence downstream: Outage or motor damage.
Correction: Set overloads; maintain starters/VFDs.

Hazardous-area rating, bonding & ingress

Mechanism: Non-rated gear, poor bonding, wash-down ingress.
Shows as: Non-Ex devices, earth faults.
Detect / inspect: Verify Ex rating, bonding, IP integrity.
Consequence downstream: Safety and reliability risk.
Correction: Rated gear; maintain bonding and seals.

Design & operating targets

Head/flow: pump and impeller sized to the duty (hydrocyclone feed head, mud-pump charge, transfer).
Suction/NPSH: flooded, short, large suction with adequate available NPSH — no built-in cavitation.
Construction: heavy-duty, abrasion-resistant for drilling mud.
Operate near the design point: not throttled hard, dead-headed or run-out.
Feed: degassed and solids-managed so the pump doesn't cavitate or plug.

Field inspection checklist — centrifugal pumps

Duty: delivered head/flow meets the requirement (cyclone feed head / charge / transfer).
Suction: flooded, unrestricted, adequate NPSH; no gas-cut mud at the suction.
No cavitation: no gravel noise or vibration; impeller undamaged.
Seals/bearings: no leaks; bearings cool and quiet; lubrication maintained.
Impeller/casing: wear within limits; clearances and wear plates sound.
Alignment: coupling and shaft aligned; baseplate rigid; piping strain-free.
Operating point: near the design point; not throttled hard or dead-headed.
Motor: healthy, overloads set, Ex rating and bonding intact.

📄 Download the full Field Inspection Checklist Pack (PDF, all 13 units) →

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 pump and solids-control practice and field references (drilling-fluid handbooks; centrifugal-pump operating practice). 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.

SC DrillTech · $49SC DrillTech Doctor22-module diagnostic suite — turn shift data into a clear diagnosis.Get it →SC DrillTech · $39Field Secrets — Solids Control & DWMThe 262-page field manual the depth on this page is drawn from.Get it →

★ BEST VALUE · SAVE 49%

The Complete Toolkit — every SC DrillTech product, one download

$99 $194 · one-time · lifetime access

Field Secrets book · DrillTech Doctor (22-module Excel) · FluidPro · ROC · Rig Evaluation Kit · Training Series

Get the Complete Toolkit →

New here? Start with the book.
Field Secrets — 262-page field manual, 54 chapters. Get the book →

Is a pump quietly starving your solids-control train?

An undersized or cavitating feed pump caps every hydrocyclone behind it, and a struggling charge pump risks the mud pumps. An independent evaluation checks the pumps as part of the system — head, suction and the units they feed.

See engineering services →