Troubleshooting / Reverse osmosis system

Reverse Osmosis System Troubleshooting

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

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Problems on this page:

Permeate flow fallingPermeate conductivity risingDifferential pressure risingMembrane scalingBiofoulingHigh pressure pump trippingChlorine reaching the membranesCleaning needed too oftenRecovery drifting from the set point

Permeate flow falling

Hits OEE: Performance

Symptoms: The system makes less water at the same pressure than it did after the last clean.

Membrane fouling or scaling
Clean the membranes with the chemicals the membrane maker recommends.
Feed water colder than usual
Compare the flow at the same temperature, as cold water lowers the flow.
Cartridge prefilter blocked
Replace the prefilter cartridges.
Feed pressure low
Check the high pressure pump and the feed supply.

Prevention: Normalised permeate flow trended so fouling shows before production suffers.

Permeate conductivity rising

Hits OEE: Quality

Symptoms: Water quality after the membranes is getting worse.

Membrane damaged by chlorine
Check the dechlorination step and replace damaged elements.
O-ring or interconnector leak
Probe the vessels to find the leak and replace the seal.
Scaling on the membrane surface
Check the antiscalant dosing and clean the membranes.

Prevention: Conductivity of each vessel checked to find a bad element early.

Differential pressure rising

Hits OEE: Availability

Symptoms: Pressure drop across the membrane vessels increases.

Particulate fouling on the first elements
Check the pretreatment and the prefilters.
Biofouling
Sanitise the system and review the pretreatment.
Scaling on the last elements
Check the recovery and antiscalant dosing.

Prevention: Differential pressure for each stage trended daily.

Membrane scaling

Hits OEE: Availability

Symptoms: Hard deposits form on the last membranes and performance falls quickly.

Antiscalant dosing failed
Check the dosing pump and the chemical tank level.
Recovery set too high for the water
Lower the recovery to the design value.
Feed water hardness increased
Check the softener or the feed water analysis.

Prevention: Antiscalant level and dosing checked every shift.

Biofouling

Hits OEE: Quality

Symptoms: Microbial counts rise and differential pressure creeps up.

System left standing without flushing
Flush the system during stops as the design requires.
Sanitisation not done on schedule
Sanitise at the interval set for the system.
Nutrients in the feed water
Review the pretreatment with the water treatment supplier.

Prevention: Microbial sampling at the frequency your water quality plan sets.

High pressure pump tripping

Hits OEE: Availability

Symptoms: The pump stops on low suction pressure or overload.

Feed supply pressure low
Check the booster pump and the prefilters.
Motor overload
Check the motor current and the pressure setting.
Pump wear
Check the pump performance and service it.

Prevention: Suction pressure trended on the pump.

Chlorine reaching the membranes

Hits OEE: Quality

Symptoms: Chlorine is found in the feed to the membranes.

Carbon filter exhausted
Replace or regenerate the carbon.
Bisulphite dosing failed
Check the dosing pump and chemical.
Chlorine monitor not working
Calibrate or replace the monitor.

Prevention: Chlorine in the membrane feed checked every shift.

Cleaning needed too often

Hits OEE: Availability

Symptoms: The membranes need cleaning far more often than the design expects.

Pretreatment not removing enough
Review the pretreatment against the feed water.
Cleaning not fully effective
Use the right chemicals at the right temperature and time.
Operating at too high a flux
Run within the design flux.

Prevention: Time between cleans logged to show the trend.

Recovery drifting from the set point

Hits OEE: Performance

Symptoms: The share of feed water turned into permeate moves away from the design value.

Concentrate flow meter or valve fault
Check the concentrate meter and the control valve.
Control loop not tuned
Retune the recovery control.
Membrane fouling changing the flows
Check the normalised data and clean the membranes if needed.
Feed pressure varying
Stabilise the feed supply.

Prevention: Recovery trended daily with the other normalised data.

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

Related equipment guides: centrifugal pump · metering pump · steam boiler · cooling tower · CIP system · water softener · ultrafiltration unit · anodising line · clean steam generator

Stop the same fault coming back

Recurring reverse osmosis system 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
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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