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Condition monitoring for centrifugal pumps: a case study

Read how SAM4 alerted this tank storage customer to suboptimal pump operation, enabling process adjustments to avoid the potential for chronic, long-term damage.

Failure mode

A 200 kW VFD-controlled centrifugal pump was initially ramped up to high speed in a nearly empty tank, causing severe cavitation.

How SAM4 helped

SAM4 flagged a sudden and significant rise in the noise floor around this product pump’s supply frequency, which is indicative of cavitation. We alerted the customer, who inspected the pump and their records of that pumping session. They discovered that the pump’s speed had been rapidly ramped up at startup, even though the fluid level in the tank had been very low (but not yet low enough at that time for the smaller positive displacement stripping pump to take over and finish draining the tank). This mismatch between NPSH available and pump rpm had induced heavy cavitation, which they concluded could be avoided in the future by matching the product pump’s speed at startup to the tank’s current condition.

Outcome

Thanks to SAM4’s alert, the customer was able to identify and change a suboptimal operating procedure, eliminating a recurring source of long-term impeller, bearing and seal damage in this and other centrifugal product pumps.

 

210519 case study fig 1 1400w
A small slice of a heat map showing the signal intensity over time across the current frequency spectrum (blue is low, red is high). Time runs down the vertical axis from oldest to newest. The yellow vertical lines are normal and indicate natural system frequencies and their harmonics (bearings, motor pole pass, etc.). The red vertical line indicates the supply frequency. The top half of the graph shows normal operation in a previous pumping session at roughly the same speed, when tank levels were higher; the bottom half shows the dramatic rise in noise floor intensity around the supply frequency during the later pumping session, indicating severe cavitation.

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