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Magnetic Flowmeter Fault Finding Guide
A one page guide to magmeter problems: grounding, empty pipe, electrode coating, conductivity limits and configuration.
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A one page A4 guide to print for the workshop or keep on your phone in the field. The full content is also shown below.
Download PDF A4 · 55 KBBefore you start
- Permit, isolation and control room informed.
- Put the loop in manual or inhibit trips as authorised.
- Use certified test equipment in hazardous areas.
- Record as found readings before changing anything.
Quick checks
- Pipe full at the meter?
- Grounding rings or electrodes connected?
- Conductivity above the meter minimum?
- Sensor factor matches tag?
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Symptoms, causes and fixes
| Symptom | Likely causes | Checks and fixes |
|---|---|---|
| Reading zero with flow | Empty pipe detection active, coil fault, wrong configuration | Check pipe full; coil resistance; flow direction setting |
| Noisy or jumping | Poor grounding, air bubbles, solids hitting electrodes, low conductivity | Fit grounding rings; remove air; check conductivity |
| Reads high or low | Wrong size or calibration factor, partly full pipe, coating | Check sensor factor and DN; check fill; clean electrodes |
| Reads flow when stopped | Electrode coating, grounding, valve passing | Clean electrodes; check grounding; confirm valves |
| Empty pipe alarm with full pipe | Coated electrodes, very low conductivity, wrong threshold | Clean; check conductivity; adjust threshold |
| Negative flow | Reverse direction setting or installed backwards | Check arrow and direction setting |
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Installation reminders
- Vertical up flow or horizontal with electrodes horizontal.
- Not at the top of a pipe or before a free outlet.
- About 5 D upstream, 2 D downstream (typical).
- Separate coil and signal cables from power cables.
NAMUR NE107 status
| Status | Meaning | Action |
|---|---|---|
| F Failure | Output invalid | Repair or replace; check loop goes to safe state |
| C Function check | Simulation, calibration or maintenance active | Finish the work, return to normal mode |
| S Out of specification | Operating outside limits or uncertain | Check process conditions and sensor |
| M Maintenance required | Still valid but degrading | Plan maintenance before failure |
Related Tools, Procedures and Calculators
Frequently Asked Questions
Why must magmeters be grounded?
The liquid potential must be tied to the meter reference; otherwise noise swamps the tiny flow signal.
What conductivity is needed?
Commonly at least about 5 µS/cm for standard meters; check the maker data.
Can a magmeter be verified in place?
Many have built in verification of coils and electronics.
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