The removal method of scale in steam boilers usually includes two main means: physical descaling and chemical descaling
Steam boiler descaler.
Physical descaling. 1.Mechanical descaling: use special tools such as pipe washers, scrapers, shovels, etc., to directly scrape or flush the scale on the inner wall of the boiler. This method is suitable for small or simple steam boilers, but it is labor-intensive, easy to damage the metal surface, and has limited effect on hard thickness and large-area scale.
2.Chemical descaling.
Pickling and descaling. Pickling method: This is a commonly used method in industry to remove scale, by injecting dilute hydrochloric acid or other special boiler cleaning agents (such as corrosion inhibitory pickling agent) into the boiler, so that the acid reacts with the calcium and magnesium carbonate in the scale to form a water-soluble substance. The acid concentration, temperature and contact time need to be strictly controlled during operation to ensure safety and effectiveness, and thoroughly rinsed after cleaning to neutralize residual acidity and avoid corrosion of boiler metal.
Caustic washing and descaling. Caustic washing: For some types of scale, especially silicate scale, alkaline solutions such as sodium hydroxide (NaOH) can be used for cleaning. The alkaline solution dissolves part of the limescale and loosens the deposits attached to the metal surface, which is then discharged by circulating cleaning and draining.
3.Other considerations.
Before cleaning, the furnace should be shut down and cooled to an appropriate temperature, while the water and sediment in the boiler should be emptied.
During the cleaning process, it is necessary to monitor the pH value change and adjust the cleaning plan according to the situation.
After cleaning, rinse repeatedly with clean water until the water quality is qualified, and then add a pretreatment agent to prevent the formation of new scale.
For large or complex steam boiler systems, cleaning and maintenance are usually carried out by a professional team, following strict industry codes and safety operating procedures.
For domestic steam boilers or small equipment, vinegar (acetic acid) soaking can also be tried to remove mild scale if the scale is small, but for industrial-grade large steam boilers, a professional chemical cleaning process must be used.