QUICK ANSWER
Confirm what changed in the system before treating low flow as a pump fault.
A centrifugal pump can deliver less flow when the system requires more resistance than before, the inlet condition deteriorates, air enters the line, a valve or filter restricts flow, or the process demand changed. Record actual flow and system condition, trace the liquid path and then compare the operating point with the original duty.
Confirm the required-flow condition
Check whether the process now needs the same flow as before. Additional branches, changed valves, altered cooling demand or new equipment can alter the duty. A flow reading without the current system arrangement does not establish that the pump itself changed.
Check whether system resistance increased
| Observed condition | Possible cause | What to check |
|---|---|---|
| Flow fell after pipework work | Valve position, filter or added resistance | Trace the changed route and confirm the intended arrangement. |
| Flow varies | Changing demand, air or unstable inlet supply | Review process operation and the inlet path. |
| Flow is low but stable | Actual duty differs from prior operating point | Compare required flow, system pressure and process layout. |
Review the whole system, including filters, control devices and downstream restrictions. Do not assume pipe diameter alone defines the resistance.
Review suction conditions
Confirm liquid availability, inlet valve position and the condition of the suction line. Air entry, insufficient supply, an inlet restriction or an altered arrangement can reduce stable delivery. Carry out inspection using the applicable site safety procedure.
Both ISG Vertical Inline Centrifugal Pumps and ISW Horizontal Inline Centrifugal Pumps are intended for clean-water and similar clean-liquid duties; final selection depends on the actual flow, head, liquid and installation layout.
Check valves and pipeline conditions
Verify intended valve positions and inspect for changed filter condition, blockage, pipework changes or a new downstream restriction. If the system was modified, compare the new route and required delivery condition with the basis used for pump selection.
When pump selection should be reviewed
Review the pump selection when inlet conditions, valves, piping and actual process demand have been confirmed but the required flow still cannot be reached. Provide the liquid, required and actual flow, total head or pressure requirement, temperature, pipe layout and process changes to Shanghai Shangcheng Pump & Valve Manufacturing Co., Ltd. for review.
Frequently asked questions
Does low centrifugal-pump flow always mean the pump is undersized?
No. A changed system resistance, inlet condition or valve position can create the same symptom.
Should I increase pump speed to recover flow?
Confirm the actual duty and installation conditions first. A speed change does not remove an inlet or piping restriction.
What data helps review an inline-pump flow problem?
Provide liquid details, required and actual flow, pressure or head, inlet arrangement, pipe route, valve positions and the changes made to the system.