Deaerator Troubleshooting: Causes & Fixes

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Problems on this page:

Dissolved oxygen too high at the outlet Pressure swinging Level control problems Feed pump cavitation Corrosion inside Steam use high Water hammer Beverage water deaerator off specification

Dissolved oxygen too high at the outlet

Hits OEE: Quality

Symptoms: Water leaving the deaerator carries more oxygen than the limit.

Steam or stripping gas flow too low

Check the steam or CO2 stripping flow against the design.

Vent valve closed or vent too small

Check the vent so stripped gases can leave the deaerator.

Water temperature too low in a thermal deaerator

Check the operating pressure and temperature.

Spray nozzles or trays damaged or fouled

Inspect the spray nozzles or trays at the next stop.

Prevention: Outlet dissolved oxygen measured continuously or each shift.

Pressure swinging

Hits OEE: Availability

Symptoms: Deaerator pressure swings, and the level and outlet oxygen become unstable.

Steam pressure control valve hunting

Tune the pressure control loop and check the valve for sticking.

Large swings in cold make-up water flow

Smooth the make-up flow control.

Condensate return arriving in surges

Check the condensate return pumps and their control.

Safety valve leaking

Have the safety valve checked; never gag or block a safety valve.

Prevention: Deaerator pressure trended.

Level control problems

Hits OEE: Availability

Symptoms: The storage tank level runs too high or too low.

Level transmitter fault or blocked impulse lines

Check the level transmitter against the gauge glass.

Make-up valve sticking

Service the make-up valve and its actuator.

Feed pump demand changing quickly

Check how boiler demand changes the outflow.

Overflow valve leaking

Check the overflow valve for passing water.

Prevention: Level trended and the gauge glass checked each shift.

Feed pump cavitation

Hits OEE: Availability

Symptoms: Boiler feed pumps below the deaerator cavitate, rattle or lose pressure.

Deaerator level too low

Check the level control.

Sudden pressure drop in the deaerator

Check the steam pressure control, since a drop flashes the water in the suction.

Suction strainer blocked

Clean the suction strainer.

Suction head too small for the water temperature

Check the installation height against the pump requirement.

Prevention: Pump vibration checked on a route.

Corrosion inside

Hits OEE: Availability

Symptoms: Inspection finds corrosion or cracking inside the deaerator.

Outlet oxygen high for long periods

Work through the dissolved oxygen causes.

Chemical dosing wrong

Check the oxygen scavenger and pH dosing.

Water pH low

Check the water treatment.

Inspections skipped

Inspect the vessel on the schedule the pressure vessel rules require.

Prevention: Internal inspection on the statutory schedule.

Steam use high

Hits OEE: Performance

Symptoms: The deaerator uses more steam than it used to.

Vent open further than needed

Set the vent to the opening that keeps the outlet oxygen in specification.

Insulation damaged

Repair the insulation on the vessel and pipework.

Make-up water colder than before

Check heat recovery on the make-up water.

Steam leaks

Fix leaking valves and flanges.

Prevention: Steam use trended monthly.

Water hammer

Hits OEE: Availability

Symptoms: Banging is heard in the deaerator or its steam lines.

Condensate collecting in the steam line

Check the drain points and traps on the steam line.

Valves opening or closing too fast

Slow the valve actuation where possible.

Cold water meeting steam in the wrong place

Check the spray valves and water distribution.

Level too high, flooding steam inlets

Check the level control.

Prevention: Water hammer events recorded with what was happening at the time.

Beverage water deaerator off specification

Hits OEE: Quality

Symptoms: Deaerated water for beverage production carries too much oxygen.

Vacuum too low in a vacuum deaerator

Check the vacuum pump and its seal water.

CO2 stripping gas flow too low

Check the CO2 supply and flow.

Water temperature outside the design

Check the water temperature at the inlet.

Flow above the design capacity

Check the flow against the deaerator rating.

Prevention: Outlet oxygen measured continuously.

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

Related equipment guides: steam boiler · beer filter · carbonator · centrifugal pump · steam trap

Stop the same fault coming back

Recurring deaerator 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.

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