Troubleshooting / Metering pump

Metering Pump Troubleshooting

The most common metering pump problems on the plant floor, with the likely causes and the fix for each. Part of the OEE Lab troubleshooting directory.

Not your exact symptom?

Describe it in the symptom finder and search the whole directory.

Open the symptom finder

Problems on this page:

Loss of flow or loss of primeInaccurate dosingDiaphragm or valve failure / leakChemical crystallising in valves and linesPulsation shaking the linesDrive or stroke adjustment faultChemical leaks at fittings or tubingDose not following the control signalWrong dose after a chemical change

Loss of flow or loss of prime

Hits OEE: Availability

Symptoms: No/low dosing flow, pump runs but does not deliver.

Air bound or gas locked
Bleed/prime; fit a bleed valve; manage off-gassing chemicals.
Suction blockage or closed valve
Clear the strainer; confirm the suction line-up.
Stuck or worn check valves
Clean or replace the suction/discharge check valves.

Prevention: Priming aids, suction checks, valve maintenance.

Inaccurate dosing

Hits OEE: Quality

Symptoms: Dose drifts from setpoint, process out of spec.

Calibration drift
Recalibrate; verify against a calibration column.
Backpressure or siphoning
Fit a backpressure/anti-siphon valve; stabilise system pressure.
Worn diaphragm or valves
Replace worn wet-end parts.

Prevention: Routine calibration, correct valving, wet-end maintenance.

Diaphragm or valve failure / leak

Hits OEE: Availability

Symptoms: Leak, loss of dose, chemical on the pump, alarm.

Diaphragm rupture
Replace the diaphragm; check for over-pressure cause.
Incompatible materials
Verify chemical compatibility of wet-end parts.
Over-pressure or relief fault
Check the relief valve and discharge for blockage.

Prevention: Diaphragm replacement schedule, correct materials, relief checks.

Chemical crystallising in valves and lines

Hits OEE: Availability

Symptoms: Valves stick, lines block, flow stops after a pause.

Chemical concentration or temperature
Keep the chemical within its storage conditions.
Lines not flushed after stops
Flush lines when the pump stops for a long time.
Air contact at open tank lids
Keep tanks closed.

Prevention: Flush procedure written at the pump.

Pulsation shaking the lines

Hits OEE: Availability

Symptoms: Lines shake, fittings loosen, flow readings jump.

No pulsation dampener
Fit a dampener.
Dampener not charged
Charge it as the maker describes.
Long discharge line
Support the line and fit a dampener near the pump.

Prevention: Dampener checks on the route.

Drive or stroke adjustment fault

Hits OEE: Availability

Symptoms: The motor trips, or the stroke length cannot be changed.

Discharge pressure too high
Check for closed valves or blockages.
Stroke adjustment seized
Free and lubricate the adjuster.
Gear oil low
Top up the gear oil.

Prevention: Gear oil checked on the route.

Chemical leaks at fittings or tubing

Hits OEE: Quality

Symptoms: Drips, crystals or stains at fittings, tubing softening.

Tubing not rated for the chemical
Use tubing rated for the chemical and pressure.
Fittings overtightened or cross-threaded
Replace and tighten correctly.
Tubing aged by sunlight or heat
Replace and protect the tubing.

Prevention: Leak checks on the route; wear the protective equipment the chemical requires.

Dose not following the control signal

Hits OEE: Quality

Symptoms: Dosing does not change with flow or the controller output.

Input settings wrong
Check the pump input mode and scaling.
Pulse and analogue settings mismatched
Match the controller output to the pump input.
Controller fault
Check the controller.

Prevention: Signal response tested after any settings change.

Wrong dose after a chemical change

Hits OEE: Quality

Symptoms: Results change when a new chemical batch or supplier is used.

Different concentration
Adjust the setting for the new concentration and recalibrate with a calibration column.
Different viscosity
Check that the suction line and valves suit the new chemical.
More gas coming out of the chemical
Use degassing pump heads where needed.
Materials not compatible with the new chemical
Check the pump head and seals against it.

Prevention: A calibration check after every change of chemical.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Related equipment guides: progressive cavity pump · vacuum pump · centrifugal pump · reverse osmosis system · DAF unit · peristaltic pump · gear pump · flow meter

Stop the same fault coming back

Recurring metering pump stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

Book a Fabrico demo
The directory stays free.

Related tools: full troubleshooting directory · OEE calculator · downtime cost · MTBF / MTTR · glossary

Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover