A growing food manufacturer moved from an old building into a new, larger production facility and brought its firetube steam boilers with it. The mechanical contractor installed the boilers and a recommended deaerator, but no other pretreatment, on hard Chicago city water. Within weeks the deaerator was scaling over every few days, feedwater oxygen was high, and no treatment residual would hold in the boilers. The contractor blamed the water treatment company and voided the new-equipment warranty. The water treatment company said it was mechanical. The plant asked for an independent review.
Dissolved oxygen in the boiler feedwater was high and the deaerator scaled over every few days, forcing repeated cleanouts. Blowdown samples showed no sulfite, no phosphate, and no polymer residual, no matter how much product went in.
The mechanical contractor blamed the water treatment program and voided the warranty on the new equipment. The water treatment company was adamant the problem was mechanical. Each side had a position. Nobody had a root cause.
Meanwhile the plant was running a growing production line on boilers that were scaling and an oxygen-control system that was not controlling oxygen.
The facility asked Industrial Water Advisory for a third-party review. We walked the system from the city water connection to the steam header: makeup, pretreatment, deaerator, feed pumps, chemical feed points, boilers, and blowdown.
We reviewed the deaerator installation against basic venting practice, checked every chemical injection point against where that chemical has to work, and inspected the boiler waterside when it was opened.
The findings went into a written engineering report. Despite pressure from the installing contractor to soften the conclusions, the report stated what the evidence showed.
A mechanical and installation problem, not a chemistry failure. A deaerator removes gases. It does not remove hardness. Hard makeup heated to saturation in the deaerator loses CO₂, its pH rises, and calcium carbonate drops out on the spray valves and trays. Phosphate injected ahead of the deaerator met that same calcium and precipitated there too. That is why the deaerator scaled in days and why no phosphate or polymer ever reached the boiler: the hardness load consumed the internal treatment before it arrived.
The oxygen problem had two causes. The restricted vent could not release the oxygen and non-condensable gases the deaerator was stripping, and fouled internals cut its scrubbing further. Sulfite fed ahead of the deaerator reacted with oxygen in the incoming water instead of polishing the last trace in the storage section. At roughly 8 ppm of sodium sulfite per ppm of oxygen, scavenging 4 ppm chemically is not a treatment program. Mechanical deaeration has to do the work. Chemistry only polishes.
The boiler scale followed directly. With hardness entering untreated and only a surface skimmer for blowdown, precipitated solids settled and stayed in the bottom of the boiler. Surface blowdown controls dissolved solids. Only bottom blowdown removes settled sludge.
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