Magnetic Flowmeter Showing Zero Flow Despite Pump Running
**The pump is running, the pipeline is completely filled and the downstream valve is open, but the electromagnetic flowmeter displays zero flow. What should we investigate? **
Magnetic Flowmeter Shows Zero Flow While Pump Is Running
Confirm flow independently first.
Troubleshooting sequence
1. Verify hydraulic conditions. Check pump suction, discharge pressure, coupling, impeller condition, bypass position and downstream isolation valves. A running motor may still deliver no flow because of air locking, blockage or coupling failure.
2. Confirm the measuring tube is full. An electromagnetic flowmeter needs a completely filled measuring tube and electrode contact with conductive liquid. Check orientation, high points and air pockets.
3. Check conductivity and electrodes. Inspect for insulating deposits, coating, scaling or damage. Low conductivity or poor electrode contact can cause empty pipe alarms or unreliable measurement.
4. Inspect grounding and bonding. Verify bonding and earth connections against the installation manual. Poor bonding or electrical noise can disturb the signal.
5. Check excitation and signal circuits. Review alarms, coil excitation, cable continuity and converter supply. Check coil resistance against manufacturer limits.
6. Verify configuration. Confirm sensor factor, nominal diameter, flow direction, empty pipe detection threshold, low flow cutoff and output scaling. Separate a zero display from a PLC input fault.
Field confirmation
Compare actual flow with an independent flow check and review trends during pump start. Check for empty pipe, coil fault or electrode alarms. Confirm the flow direction arrow matches the installation. Avoid zero calibration while liquid is moving. Correct the root cause, then verify zero stability with a full, stationary pipe before returning the meter to service.