Boiler water treatment protects heat-transfer surfaces from scale, corrosion and carryover. The required program depends on boiler pressure, feedwater source, condensate return, pretreatment and steam-use requirements.
Pretreatment comes first
Hardness entering a boiler can form insulating deposits on hot metal surfaces. Depending on pressure and application, pretreatment may include softening, reverse osmosis, demineralization or other processes. The goal is to reduce the contaminants that would otherwise concentrate in the boiler.
Deaeration and oxygen control
Dissolved oxygen is highly corrosive in feedwater and condensate systems. Thermal deaeration removes most dissolved gases, while an oxygen-scavenging program may be used where appropriate to handle residual oxygen and support corrosion control.
Internal boiler treatment
Internal programs can include alkalinity control, phosphate-based chemistry, polymers/dispersants and other treatments depending on pressure and water quality. Product selection should follow the boiler OEM, treatment supplier and applicable industry guidance.
Blowdown
As steam leaves, dissolved solids remain in the boiler. Blowdown removes concentrated boiler water to control TDS/conductivity and other limits. Excess blowdown wastes energy and water; insufficient blowdown can lead to carryover and deposits.
Condensate return
Clean condensate is valuable because it is already hot and low in dissolved minerals. Maximizing safe condensate return can reduce fuel, water and chemical use. Contaminated condensate, however, should not be returned without evaluation.
Routine checks
- Feedwater and boiler-water conductivity/TDS.
- pH and alkalinity as required by the program.
- Hardness leakage where relevant.
- Oxygen-scavenger or program residual where applicable.
- Condensate pH and iron/copper trends.
- Blowdown operation and deaerator condition.
Boiler chemistry limits vary strongly with pressure and design. Do not apply one generic target to every boiler.