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mechanical & component · forensic engineering

Pump & compressor failure analysis.

A pump or compressor rarely fails from one cause in isolation — cavitation erodes an impeller, a seal lets go, a coupling misaligns, and each leaves its own mark on the machine.

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Pumps and compressors fail at the system level even when the damage looks like a single-component problem. A pitted, cauliflower-textured impeller is the signature of cavitation — vapor bubbles collapsing violently as fluid pressure drops below vapor pressure and then recovers — and it points back to suction conditions, not to a material defect in the impeller. A mechanical seal that fails prematurely is usually telling you about misalignment, dry-running, or a process upset rather than a bad seal face. And a compressor surge event, if it happened, leaves its signature across the whole train — thrust-bearing damage, seal extrusion, and sometimes bent shafts — from a single transient rather than a chronic condition. Because these machines couple rotating, hydraulic, and process behavior together, the investigation has to trace the damage on the hardware back to the operating condition that produced it, not just identify which part broke first.

mechanisms

How pumps and compressors fail.

Rotating-equipment failures trace to a handful of system-level conditions, each leaving distinct damage across the machine.

Cavitation

Vapor bubbles forming where local pressure drops below vapor pressure and collapsing violently on recovery, eroding impellers, casings, and valve seats with a characteristic pitted, cauliflower texture.

Mechanical seal failure

Face wear, extrusion, or thermal cracking from misalignment, dry-running, or process-fluid incompatibility, ending in leakage past a barrier that should have been near-zero-loss.

Misalignment & coupling failure

Shaft-to-shaft or shaft-to-driver misalignment loading bearings and seals well beyond their design condition and accelerating wear on both.

Surge (compressors)

Flow reversal at low flow and high head ratio driving a violent axial thrust and vibration transient that can damage bearings, seals, and the rotor in a single event.

Resonance & vibration fatigue

Operating speed or a forcing frequency coinciding with a natural frequency of the rotor, piping, or foundation, fatiguing components far faster than steady-state loading would predict.

Dry-running & overheating

Loss of prime, blocked suction, or process upset removing the fluid film that cools and lubricates internal clearances, seizing rotating parts against stationary ones.

methodology

What the evidence shows — and what we examine.

Pump and compressor investigations read the damage pattern across the whole machine train, then correlate it with the operating and process history.

Damage & wear-pattern examinationDocumenting erosion, seal-face condition, rub marks, and bearing damage across the train to establish the sequence of events.
Vibration data analysisReviewing historical and post-event vibration spectra for signatures of imbalance, misalignment, resonance, or surge.
Performance & operating-curve analysisComparing actual flow, head, and pressure data against the pump or compressor curve to identify off-design operation such as low-flow cavitation risk.
Metallurgical examinationSEM and cross-section analysis of eroded, cracked, or seized components to confirm the mechanism and rule out material defects.
Alignment & clearance verificationAs-found shaft alignment, internal running clearances, and coupling condition against OEM tolerances.
Process & control-system record reviewDCS/SCADA trends, trip history, and startup/shutdown logs establishing the process conditions at the time of failure.
what's at stake

A seized machine, a shut-down process.

Rotating-equipment failures rarely stay confined to the machine:

unplanned plant/process shutdown fire or process-safety event warranty & product-liability dispute process fluid release OEM or repair-shop dispute insurance subrogation

Do not repair or rebuild before documentation.

Rotor position, seal condition, and wear patterns record the sequence of the failure. Rebuilding or scrapping the unit before it is examined destroys the evidence of what happened first.

common questions

Pump & compressor failures — the questions we hear.

How do you tell cavitation damage from normal erosion or corrosion?

Cavitation produces a distinctive pitted, cauliflower-like surface texture concentrated where vapor bubbles collapse — typically the impeller eye, vane tips, or other low-pressure regions — which looks quite different from the smoother metal loss of erosion-corrosion or the more uniform thinning of chemical attack. SEM examination of the pit morphology, combined with the hydraulic pressure profile at the damage location, confirms it.

Can you determine whether a seal failed because of a defect or because of how the pump was operated?

Usually, yes. A seal-face defect shows as-manufactured or material-related damage independent of the operating history. Operationally caused failure shows wear or thermal damage consistent with a specific condition — dry-running leaves heat-checking and blistering, misalignment leaves an uneven wear pattern around the face circumference, and process-fluid incompatibility leaves chemical attack concentrated on the elastomers or the seal faces.

What is surge and how do you know it happened?

Surge is a flow-reversal instability that occurs in compressors operating at low flow relative to the head being developed. A surge event leaves a recognizable signature across the machine train — thrust-bearing damage, labyrinth-seal rubs, sometimes a bent rotor — that is distinct from the gradual wear of normal operation, and control-system trend data usually captures the pressure and flow oscillation directly.

Is vibration data from before the failure useful?

Often decisive. A rising vibration trend, or a specific frequency signature — running speed for imbalance, twice running speed for misalignment, a bearing-defect frequency, a blade-pass frequency — preserved in historical monitoring data can identify a developing problem well before the final failure, and it establishes how long the condition existed, which matters both for root cause and for questions about missed maintenance opportunities.

What should be preserved after a pump or compressor failure?

The complete rotor assembly with bearings and seals in their as-found position and orientation, wear debris from the casing and any strainers or filters, and, critically, the vibration monitoring history, control-system trend data, and maintenance records — which are frequently overwritten or archived beyond easy reach within weeks.

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I can help scope a pump or compressor failure — likely mechanisms, what to preserve, and which expert fits. What happened?