XINLI BOILER

How to prevent the inner wall of the boiler from rusting

15 Nov, 2021

　　The boiler should be based on active anti-scaling and anti-corrosion. But when boiler fouling or corrosion deposits reach a certain level, they should also be cleaned and removed in time to avoid hidden dangers to the safe operation of the boiler. The cleaning and descaling methods are mainly divided into mechanical descaling and chemical cleaning. Among them, chemical cleaning can be divided into alkaline boiling descaling and pickling descaling. The methods and requirements for boiler descaling are briefly introduced as follows:

　　1. Mechanical descaling

　　Mainly use tools such as electric pipe cleaners, flat spades, wire brushes and hand hammers for mechanical descaling.

　　This method is relatively simple and low in cost, but has high labor intensity, poor descaling effect, and easy damage to the metal surface. It is only suitable for small boilers with small scale area and simple structure, which is convenient for mechanical tools to reach scale. In recent years, due to the application of special high-pressure water guns for cleaning, the mechanical descaling of hydraulic washing has developed rapidly. The effect of this high-pressure hydraulic descaling is greatly improved compared with the original mechanical tools, and it is safer and more convenient.

　　But at present, high-pressure hydraulic descaling is still limited to industrial boilers with simpler structures.

　　2. Alkaline washing (boiled) descaling

　　The main function of boiler alkali cooking is to transform the scale and at the same time promote its loosening and falling off. Simple alkaline boiling is not effective in descaling, and it often needs to be carried out in conjunction with mechanical descaling. Alkaline boiled descaling has a certain effect on scale based on sulfate and silicate, but for carbonate scale, it is far inferior to pickling.

　　Alkaline washing boilers are also often used for rust removal and degreasing of newly installed boilers, and sometimes they are also used for degreasing cleaning or scale conversion before pickling. The dosage of alkaline cleaning agent should be determined according to the degree of boiler fouling and dirt. The general amount used for descaling (per ton of water) is: industrial trisodium phosphate 5-10kg, sodium carbonate 3-6kg, or sodium hydroxide 2-4kg. These alkaline cleaning agents should be formulated to a certain concentration in the solution tank, and then pumped into the pot and circulated to uniformity.

　　To

　　The method of alkaline boiling and descaling is basically the same as that of a new boiler, except that after the boiling, each inspection hole of the boiler should be opened, and mechanical (or high-pressure hydraulic) auxiliary cleaning should be applied in time to prevent the loose scale from hardening again.

　　3. Pickling and descaling

　　At present, among various descaling methods, the effect of pickling is better. However, if the pickling process is inappropriate or improperly controlled, it will also affect the descaling effect or corrode metals, and sometimes even seriously affect the safe operation of the boiler. Before washing, a representative scale sample should be taken for testing, and a cleaning plan should be formulated; when the acid is introduced, a corrosion index sheet must be hung in the boiler and in the acid box (until the acid is removed); the pickling process and pickling The temperature, concentration, flow rate, and pickling time of the liquid should be implemented and controlled according to the cleaning plan; during the cleaning process, samples should be continuously sampled and tested and recorded truthfully.