5 Failure Modes Every Pump Engineer Should Know (And How to Detect Them)

The Starting Five

I've analysed over 200 centrifugal pumps across refineries, chemical plants, water utilities, and manufacturing facilities. Different industries, different manufacturers, different operating contexts.

The same five failure modes keep showing up.

Not the same equipment. Not the same root causes. But the same patterns of failure—accounting for roughly 80% of the pump failures I've documented. If you only memorise five things about pump reliability, make it these.

This is your quick reference. Print it. Bookmark it. Keep it where you can find it at 2 AM when something's making a noise it shouldn't.

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1. Bearing Failure

What it is: Rolling element or journal bearing degradation leading to increased friction, heat, and eventual seizure or catastrophic failure. Why it happens:

• •Lubrication problems — Wrong lubricant, contamination, insufficient quantity, or degraded oil (accounts for ~40% of bearing failures)
• •Misalignment — Puts uneven load on bearing elements
• •Overload — Operating beyond design capacity
• •Contamination — Water ingress, particulates in lubricant
• •Installation damage — Improper fitting, incorrect preload

What you'll notice: P-F Interval: 1-3 months from first detectable vibration signature to functional failure. Can be weeks if contamination or lubrication failure is severe. Detection methods: What actually works:

✅ Monthly vibration monitoring — The gold standard. Catches most bearing faults 4-12 weeks before failure.

✅ Continuous temperature monitoring on critical pumps — Simple, cheap, effective backup.

✅ Quarterly oil analysis for oil-lubricated bearings — Catches contamination and degradation.

❌ Time-based bearing replacement — Bearings don't fail on a schedule. You'll either replace good bearings or miss the ones failing early.

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2. Mechanical Seal Failure

What it is: Degradation or failure of the mechanical seal faces, elastomers, or springs, leading to excessive leakage. Why it happens:

• •Dry running — Seal faces need a fluid film; without it, they cook
• •Thermal shock — Rapid temperature changes crack seal faces
• •Chemical attack — Wrong materials for the service
• •Abrasive particles — Score the seal faces
• •Installation errors — Wrong setting, damaged faces during fitting
• •Misalignment/vibration — Seal faces can't maintain proper contact

What you'll notice: P-F Interval: 2-8 weeks for gradual wear. Can be instantaneous for event-driven failures (dry running, thermal shock). Detection methods: What actually works:

✅ Daily visual inspection during operator rounds — Most seal failures are caught this way. Takes 30 seconds.

✅ Seal flush system monitoring — Track flush water flow and temperature. Changes indicate problems.

✅ Proper operating procedures — Don't run pumps dry. Don't thermally shock them. Train operators.

❌ Scheduled seal replacement — Seal life varies wildly (6 months to 10+ years). Condition-based replacement beats calendar-based every time. Pro tip: If you're replacing the same seal more than once per year, stop replacing and start investigating. Something's wrong with the operating conditions, not the seal.

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3. Impeller Wear/Erosion

What it is: Material loss from impeller vanes, shrouds, or wear rings due to erosion, corrosion, or cavitation damage. Why it happens:

• •Cavitation — Bubble collapse blasts material off the impeller (see #4)
• •Abrasive solids — Sand, scale, particulates wear down surfaces
• •Corrosion — Chemical attack on impeller material
• •Recirculation — Operating at low flow causes internal recirculation damage

What you'll notice: P-F Interval: 3-18 months depending on severity and cause. Cavitation erosion can be faster (weeks to months). Corrosion is typically slower. Detection methods: What actually works:

✅ Quarterly performance trending — Plot actual flow, head, and power against pump curve. Degradation becomes obvious.

✅ Vibration monitoring for imbalance — Worn impellers go out of balance. 1x vibration increase is the signal.

✅ Address the root cause — If cavitation is eating your impeller, fix the NPSH problem. If solids are wearing it, add filtration. Stop treating symptoms.

❌ Ignoring performance degradation — "It still pumps" isn't a strategy. A worn impeller wastes energy and may fail suddenly.

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4. Cavitation Damage

What it is: Vapour bubble formation and violent collapse within the pump, causing noise, vibration, and progressive material damage. Why it happens:

• •Insufficient NPSH — Not enough suction pressure to keep liquid from flashing to vapour
• •Suction restrictions — Blocked strainers, undersized piping, closed valves
• •High liquid temperature — Increases vapour pressure
• •Operating off-curve — Running at very low or very high flow
• •Air entrainment — Air drawn in through suction leaks or vortexing

What you'll notice: P-F Interval: Weeks to months if operating continuously in cavitation. Can stabilise if intermittent. Detection methods: What actually works:

✅ Fix the process conditions — Cavitation is a symptom, not a disease. Increase suction pressure, reduce temperature, open valves, clean strainers.

✅ Operator training — Teach operators what cavitation sounds like and what causes it. They're your first line of detection.

✅ NPSH monitoring on critical pumps — Simple pressure instrumentation can catch problems early.

❌ Just replacing the damaged impeller — If you don't fix the NPSH problem, you'll be replacing it again next year. The cavitation test: If it sounds like someone's pouring gravel through your pump, you've got cavitation. Find out why.

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5. Shaft Misalignment

What it is: Angular or offset misalignment between pump and driver shafts, causing excessive vibration, bearing loads, seal stress, and coupling wear. Why it happens:

• •Poor initial alignment — Not done properly during installation
• •Thermal growth — Hot pump grows; alignment changes
• •Foundation movement — Settling, soft foot, piping strain
• •Coupling wear — Allows more misalignment to develop
• •Maintenance errors — Alignment not rechecked after repairs

What you'll notice: P-F Interval: Highly variable. Minor misalignment causes gradual bearing/seal wear over months. Severe misalignment can destroy bearings in weeks. Detection methods: What actually works:

✅ Laser alignment at installation and after any maintenance — It takes 30 minutes and prevents months of problems.

✅ Thermal growth compensation — Align cold, but account for where it'll be when hot. Equipment manufacturers provide growth data.

✅ Check for soft foot — A pump that's not sitting flat on its baseplate can't stay aligned. Fix the foundation first.

❌ Assuming alignment "was fine last time" — Alignment drifts. Foundations settle. Check it. The alignment rule: If you've had the coupling apart, you need to realign. No exceptions.

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Quick Reference Table

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The 80/20 of Pump Reliability

These five failure modes won't cover every pump problem you'll ever see. You'll encounter phase-to-phase motor faults, suction valve failures, baseplate cracking, and a dozen other issues over your career.

But master these five, and you've got 80% of centrifugal pump failures covered. The rest you can look up when they happen. The pattern to remember:

1. 1.Bearings → Vibration monitoring monthly
2. 2.Seals → Visual inspection daily
3. 3.Impeller → Performance trending quarterly
4. 4.Cavitation → Listen and fix the process
5. 5.Alignment → Laser check after any coupling work

Simple. Repeatable. Effective.

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Build Your Failure Mode Library

Want to go deeper? These five are just the start.

Our Failure Mode Suggester generates comprehensive failure mode lists for any equipment type—centrifugal pumps, positive displacement pumps, compressors, heat exchangers, you name it. Plug in your equipment, get a starting library, then refine it based on your operating context.

Or grab our FMEA Template Pack to document your pump failure modes properly. It includes worksheets for functions, failure modes, effects, and recommended tasks—all in a format that feeds directly into your CMMS.

Because knowing the failure modes is step one. Getting them into a maintenance programme that actually works is step two.

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Keep this reference handy. The next time a pump starts making that noise—the one that makes experienced operators wince—you'll know exactly what to check first.