Finding a hidden pump fault in a steel finishing mill

A European steel producer monitors its finishing mill pumps with SAM4 from the motor control cabinet.

Two pumps, A and B, run together as one hydraulic system. If both stop, the mill stops. On 14 May 2026, SAM4 raised a developing anomaly on the pump set. Nothing had tripped. The mill's own instrumentation gave no warning, and the control room saw both pumps running normally.

Load instability rose above its normal range on both pumps, much more sharply on Pump A than on Pump B. Because the two pumps run as one hydraulic system, the clearest signal appeared on Pump A while the damage was developing on Pump B. SAM4 recommended measurements across the full drive train.

• 14 May: SAM4 raises a developing anomaly on the finishing mill pumps, with a recommendation to measure across the full drive train.
• 28 May: Vibration analysis pinpoints shocks, friction and rub on the rear bearing of Pump B. The pump then fails, though not badly, and the mill keeps running on Pump A.
• 29 May: With Pump B out, a worn outlet valve is found on it. The valve had been causing the pump to malfunction and preventing a normal restart.
• Early June: The valve is repaired, the pumps are reconfigured and Pump B is back in service, using spares already held on site.
• 12 June: The indicators return to healthy and the case is closed.

The root cause was cavitation in the pump set, believed to be behind both the worn outlet valve and the bearing damage on Pump B. The cavitation only appeared at high speed, which is why the plant's own instrumentation had not picked it up. In the electrical signature it showed as a sustained rise in load instability rather than as a trip or an alarm.

• 15.8M cost avoided, estimated by the customer
• 2+ weeks of warning before Pump B failed
• Root cause found across the pump set, not just the failed part

The vibration survey found the fault where SAM4 pointed: on the rear bearing of Pump B. The failure itself was minor, the repair took a few days with spares held on site, and the mill kept running on Pump A throughout.

The value was in what the investigation turned up. Without it, the failed part might simply have been replaced and the pumps run on in the same condition, with the cavitation still at work. The customer estimates a full failure of the pump set would have cost 15.8 million: 15.4 million in lost production over four days of finishing mill downtime, plus 400,000 in maintenance. It never came to that.

Download the detection snapshot (PDF)