Maintenance reference

Rotary Jet Pump Troubleshooting

Record the symptom and current readings. Check the operating conditions before ordering a replacement part.

Record what changed

Record flow, inlet and outlet pressure, speed and temperature. Note any change in the liquid or supply. If performance falls with an unchanged system requirement, inspect the internal parts; if the requirement changes, check the system.

One symptom can have several causes. Low pressure, for example, can result from gas, a damaged tube or excessive flow.

Stop the pump if vibration, temperature or noise becomes abnormal. Before dismantling, isolate the drive and drain the pump using the procedure for the supplied construction.

Symptom / cause / check / action

Operating checks and component checks
Symptom	Possible cause	How to check	What to do
Head or pressure drops	Gas in the liquid; damaged pick-up tube; flow above the operating point.	Check venting and gas in the supply. Compare delivered flow with the selected curve. Inspect the tube if the operating checks do not explain the loss.	Vent the pump; adjust the discharge valve for the selected operating point; replace a damaged tube.
Insufficient flow	Blocked pipes; air leaking into the suction or remaining in the chamber; insufficient speed; excessive discharge pressure.	Check the pipe path and venting. Check suction leaks and drive speed. Review the outlet pressure reading.	Clear the obstruction; repair the leak or vent thoroughly; correct electrical faults; adjust the discharge valve.
Flow stops shortly after starting	Low positive suction pressure; leaking pipes; foreign material blocking a pipe opening.	Check the positive inlet supply, pipe leakage and the accessible inlet path.	Improve the positive inlet supply; repair leaks; dismantle and clean the pump or arrange factory cleaning.
More vibration or abnormal noise	Base not secured; rotating assembly out of balance; cavitation.	Check fastening. Check the strainer and suction pipes, bubbles or vaporization, and whether flow is excessive.	Secure the base; arrange factory repair for lost balance; correct the inlet restriction or excessive-flow condition.
Mechanical-seal leakage	Failed mechanical seal or damaged O-ring.	Inspect the seal and O-rings through the applicable maintenance procedure. Examine seal faces before assembly.	Renew the failed seal or O-ring. Replace components with visible defects.
High bearing temperature	Low oil level in an oil-bath unit; bearings damaged by overload.	Identify oil or grease lubrication first. For an oil-bath unit, check the specified oil level. Inspect damaged bearings.	Restore the specified oil level on oil-bath units. Follow grease instructions on grease units. Replace damaged bearings.
Rapid pick-up tube wear	Wear varies with particle size and hardness in the liquid.	Record the solids carried by the liquid. Inspect the tube and internal working parts when performance falls at an unchanged operating conditions.	Review the liquid and tube requirement. Replace the worn working part after inspection.

Pressure falls while the pump still delivers liquid

Check for air or gas in the supply and vent the pump. Gas can lower both pressure and flow.

Compare the flow with the selected operating point and adjust the discharge regulating valve. Keep the suction valve fully open during normal operation.

If these checks do not explain the loss, inspect the pick-up tube and replace it if damaged.

Flow is low or stops soon after starting

For low flow, check blocked pipes, suction air leaks, trapped air, insufficient speed and excessive discharge pressure. Have the appropriate personnel correct electrical faults that reduce speed.

If flow stops shortly after starting, check positive inlet pressure, pipe leaks and foreign material blocking the pipe opening. Improve the supply, repair leaks and clean the pump, or arrange factory cleaning.

A rapidly heating discharge line with no delivery indicates an air lock. Check the discharge piping and remove the air lock before restarting.

Noise and vibration require different checks

Check base fastening and the inlet path. A blocked strainer or suction pipe, bubbles, vaporization or excessive flow can cause cavitation.

If the rotating assembly has lost balance, arrange factory repair. Record the results of fastening and operating checks to distinguish a site problem from a damaged component.

Seal leakage and hot bearings

Inspect the mechanical seal and O-rings if leakage occurs. Replace the failed part and check seal faces for damage before assembly.

For hot bearings, identify grease or oil-bath lubrication first. Restore low oil to the specified level on oil-bath units; use the grease procedure on grease units.

Replace bearings damaged by overload. Keep separate records of leakage location, temperature, readings and lubrication type.

When the pick-up tube wears quickly

Particle size and hardness affect tube wear. Inspect the internal working parts and replace a worn pick-up tube.

A wear-resistant coating can help with hard particles. Check the rotor as well if it shows damage.

Request a pick-up tube or rotor

What to send in a fault report

Include the nameplate model, symptom, when it started and the recorded readings. Note any change in liquid, flow or inlet supply. For a bearing-temperature problem, identify the lubrication type.

Add inspection findings and the part or repair service needed. Photos are optional. Copy the contact checklist and add the fault details below it.

Copy the inquiry checklist

The next step

Send us your pump data

Liquid, flow, head and inlet conditions.
For a replacement, add the model on the nameplate.

Email your pump data