Standard Hot Water Boiler Cleaning Procedure (Seven-Step Method)

Water Rinse (Clean Water Wash):
Rinse the boiler with clean water in an open circuit until the water runs clear and transparent.

Purpose: To wash away internal sludge, welding residues, and loose impurities, preventing them from consuming subsequent chemical agents.

Alkaline Wash (Boiler Boiling):
Add an alkaline solution (such as trisodium phosphate or sodium hydroxide), heat to 80-90°C, and circulate or soak for several hours.

Purpose: To remove internal grease, organic matter, and some silicate scale, preparing for acid washing.

Note: This step is necessary for newly installed boilers or those that have been out of service for a long time.

Second Water Rinse:
Drain the alkaline solution and rinse with clean water until neutral.

Acid Wash (Core Step):
Pour the prepared acid solution (acid + corrosion inhibitor) into the boiler.

Dynamic Circulation: Turn on the circulation pump to make the acid solution flow inside the boiler. Reaction time is usually 4-8 hours (depending on scale thickness).

Monitoring: Periodically check the acid concentration and iron ion content. When the concentration basically stops changing, the reaction is complete.

Temperature Control: Typically controlled at 40-60°C. Excessive temperature that may cause metal corrosion is strictly prohibited.

Third Water Rinse:
Quickly drain the acid solution and rinse with plenty of clean water to remove residual acid and detached scale.

Rinse (Neutralization):
Use dilute citric acid or a special neutralizing agent to rinse, further removing residual iron ions and adjusting the pH.

Passivation (Corrosion Protection):
Add a passivating agent (such as sodium nitrite or a special passivating liquid) to form a dense oxide film on the metal surface, preventing the cleaned metal surface from rusting again. After completion, drain the water, and the boiler can be put back into operation.