TL;DR
Running below minimum continuous stable flow converts pump work into heat. Install or open a minimum-flow recirculation bypass to protect the pump.
What you might see
- pump casing hot to the touch
- bearing temperature above 80 degC
- steam or vapor from seal area
- power draw spiking at low flow
Likely causes
Pump operating at or near shutoff head, all hydraulic energy converts to heat in the casing
Minimum-flow recirculation bypass closed or undersized
Discharge isolation valve nearly closed or a blocked strainer pushing the flow to near-zero
Process demand dropped without a corresponding speed reduction on a VFD-driven pump
Required tools
- IR thermometer
- Pressure gauge
- Flow meter or ultrasonic clamp-on flow sensor
- LOTO kit
- Pump performance curve (minimum stable flow data)
Safety first
- Do not touch the pump casing bare-handed after a heat event. Use IR thermometer to verify below 50 degC before handling.
- Lock out the driver before opening the casing or touching the bypass valve internals.
Procedure
- 1
Lock out the pump driver.
- 2
Check the discharge valve position and downstream strainer. Fully blocked flow is the most common cause of shutoff operation.
- 3
Verify the minimum-flow recirculation bypass valve is open and sized per the Goulds 3196 minimum stable flow listed on the performance curve.[1]
- 4
If no bypass exists and the pump runs near zero flow regularly, install a properly sized bypass orifice or control valve back to the suction vessel.
- 5
Measure bearing housing temperature with an IR thermometer. Sustained temperature above 80 degC means the bearings are at risk.[1]
- 6
If the pump is VFD-driven, add a low-flow interlock in the control system that reduces speed or opens the bypass when flow drops below the minimum stable value.
- 7
Inspect the bearings and mechanical seal before returning to service if overheating was sustained for more than 15 minutes.
Sources
Goulds 3196 i-FRAME Process Pump Installation, Operation & Maintenance Manual, Goulds Pumps (ITT)
Goulds 3196 i-FRAME IOM, minimum continuous stable flow and thermal protection procedures (general)
View source
More guides for Goulds Pumps 3196
How to stop cavitation noise on a Goulds 3196 centrifugal pump
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How to diagnose excessive power draw on a Goulds 3196 pump
High power draw is usually excess flow (system resistance dropped), higher liquid density than design, or internal binding. Measure amps and head to locate the cause.
How to fix a leaking mechanical seal on a Goulds 3196 pump
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How to diagnose low flow rate and pressure fluctuation on a Goulds 3196 pump
Low flow with reduced head points to a worn or trimmed impeller or internal recirculation. Measure differential head and compare to the rated curve to confirm.
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