If a ROTAN internal gear pump becomes noisy and loses flow, check the suction system before replacing gears or seals. Cavitation can follow excessive inlet vacuum from a blocked strainer, cold viscous liquid or a long, narrow suction line; air ingress and bypass flow can produce similar symptoms.
Which signs point to a suction problem?
A gravel-like sound, vibration and lower delivery that worsen at cold start or low tank level justify an inlet check. These signs alone do not prove cavitation: record pressure and operating conditions before deciding on a repair.
How should the fault be checked?
- Record the liquid, temperature, cold and running viscosity, tank level, pump speed, flow and inlet pressure at both normal and noisy operation.
- Stop, isolate and depressurize the unit. Check that the suction valve is open, the strainer is clean, the line is full and joints do not draw air. Follow the exact pump manual when priming or venting; never vent a running pump or run it dry.
- Compare absolute inlet pressure with the liquid vapor pressure and the configuration-specific manufacturer suction requirement. If inlet conditions are adequate, inspect bypass setting, discharge restriction, drive and internal wear instead of assuming cavitation.
What corrects excessive suction loss?
Clean or correctly size the strainer, shorten or enlarge the suction line, and maintain adequate liquid level. If permitted for the fluid and equipment, control temperature so cold-start viscosity does not overload the inlet. A lower speed may reduce suction demand but also reduces flow; confirm the new duty point. Reprime under the manual before restarting.
What information should an RFQ include?
Send the complete ROTAN designation and serial number, fluid and compatibility data, cold/running viscosity and temperature, minimum tank level, suction pipe diameter and length, strainer, speed, target flow, differential pressure and measured inlet pressure. DFIN can review a suitable pump configuration or confirmed service parts; price depends on the verified build and duty.
Frequently asked questions
Can a self-priming gear pump cavitate?
Yes. Self-priming does not remove inlet friction loss or the need for adequate pressure at the pump inlet.
Will new gears fix gravel-like noise?
Not until the suction cause is checked. Persistent cavitation can damage internals, but replacing them without correcting inlet conditions invites repeat damage.
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