Chemical descaling of boilers is simple, you can put a descaling solution or descaler containing a corrosion inhibitor into the heat exchanger and soak it for a certain time according to the instructions. Then rinse with water two to three times 2mm residue is still better. It is estimated that it can be resolved by soaking for 12 – 24 hours.
How to remove boiler scale
The boiler must be based on anti-scaling and anti-corrosion performance. But when the sludge or corrosive deposits of the boiler to a certain extent. hey also need to be cleaned and removed in a timely manner to avoid potential hazards to the safe operation of the boiler.
Boiler cleaning and descaling methods are mainly divided into mechanical descaling and chemical descaling. Among them, chemical cleaning can be divided into alkaline boiling descaling and immersion descaling. The methods and requirements for descaling boilers include the following briefly:
Boiler mechanical descaling
Mainly use tools such as electric pipe washers, flat shovels, wire brushes and hand hammers for mechanical descaling. This method is relatively simple, low cost but high labor intensity. The descaling effect is poor, the metal surface is easily damaged, only suitable for boilers of small scale, small area, simple structure, convenient for mechanical tools.
In recent years, due to the special high pressure water gun application for cleaning. Mechanical descaling in hydraulic washing processes has developed rapidly. The efficiency of this high-pressure hydraulic descaler is greatly improved compared with the original mechanical tools, and it is safer and more convenient.
At present, high pressure hydraulic descaling is still limited in industrial boilers with relatively simple structure.
Boiler alkaline wash (boil) descaling
The main function of alkaline boiling in boilers is to transform the residue and at the same time promote it to loosen and fall out. Simple alkaline boiling is not effective in descaling, and it must often be done in conjunction with mechanical descaling. Boiling alkaline descaling has a certain effect on sulfate and silicate based scales. But for carbonates, it is much less effective than descaling. Alkaline pot cleaners are also commonly used for rust removal and degreasing of newly installed boilers. This is also sometimes used for degreasing or descaling prior to descaling.
The amount of alkaline detergent should be determined according to the degree of adhesion and soiling of the boiler. The total 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 detergents need to be mixed to a certain concentration in the solution bath, then pumped into the pot and recirculated to a uniform consistency.
The alkaline cooking and descaling method is basically the same as that of the new boiler, except that after the boiler is completed. Boiler inspection holes should be opened and ancillary mechanical (or high-pressure hydraulic) cleaning performed in time to prevent soft deposits from hardening.
Boiler descaling and descaling
At present, among the various descaling methods, the descaling effect is better. However, if the descaling process is not suitable or not properly controlled, it will affect the descaling effect or cause metal corrosion, sometimes even seriously affecting the safe operation of the boiler..
Prior to pickling, the boiler should take a representative sediment sample for testing and cleaning planning. When acid is introduced, the corrosion indicator chip must be hung in the boiler and in the acid box until the acid is removed. The cleaning procedure and the temperature, concentration, flow rate and soaking time of the cleaning solution should be carried out and controlled according to the cleaning plan. During cleaning, samples must be taken continuously for testing and recording accurately. After cleaning, the boiler department, the cleaning department and the boiler safety monitoring department must check and accept the hygiene quality.
The cleaning quality requirements of industrial boilers are as follows:
– Rate of dirt.
– To clean the residue with the main composition: carbonate residue, the area of residue removal must reach more than 80% of the area covered by the original residue.
– When cleaning silicate or sulphate salt deposits, the removal area should reach more than 60% of the original deposit coverage area.
– Waterproof membrane: must create a good waterproof protective film on the cleaning surface of the boiler and there should be no secondary rust and pitting corrosion on the metal surface.
– Corrosion rate: The average value of metal corrosion rate measured by the corrosion indicator table must be less than 6g/m2 and the total amount of corrosion must not exceed 72g/m2.
– Furnace tubes are not blocked: after cleaning, all wall tubes are cooled by water and convection tubes in the pot should flow unimpeded. If the pipe is blocked before cleaning and cannot be cleared after cleaning, it should be repaired and replaced by a qualified repair unit.
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