The cleaning of stainless steel heat exchange tubes requires the selection of appropriate methods based on the type of dirt, pipeline material, and operating conditions. It is mainly divided into three categories: chemical cleaning, mechanical cleaning, and comprehensive treatment, and attention should be paid to post rust prevention treatment.
1、 Select cleaning method based on dirt type
1. Scale/rust
Chemical pickling: For carbon steel materials, 8% -15% sulfuric acid or 5% -10% hydrochloric acid can be used; Austenitic stainless steel (such as 304) is prohibited from using hydrochloric acid and instead uses citric acid (5% -10%) or specialized stainless steel acid cleaning agents (containing compound formulas such as nitric acid and hydrofluoric acid).
Operation points:
Soak the acid solution at a temperature of ≤ 60 ℃ for 10-30 minutes until the scale layer dissolves;
After acid washing, the residual liquid should be neutralized and repeatedly rinsed with clean water until neutral.
2. Oil/organic deposition
Alkaline cleaning: using neutral cleaning agents or specialized cleaning agents containing surfactants for cyclic rinsing;
Biological cleaning: using microorganisms to decompose oil stains, environmentally friendly and non corrosive.
3. Weld spots/oxide scale
Passivation treatment: Soak in acid pickling passivation two in one solution (such as ID4008-T), remove welding spots at room temperature for 10-20 minutes, and generate a passivation film for rust prevention.
2、 Mechanical and physical cleaning (suitable for stubborn thick scale)
1. High pressure water jet: With a pressure of 50-70MPa, it can remove hard scale on the inner/outer walls of the pipe, avoiding damage to the metal surface;
2. Ultrasonic cleaning: for complex structures such as capillaries, remove dirt through high-frequency vibration;
3. PIG cleaning technology: Use a flexible pipe cleaner to push and scrape off sediment on the inner wall of the pipeline.
Taboo: Steel wire balls and carbon steel brushes are prohibited to prevent scratches on the surface of stainless steel.
3、 Key maintenance after cleaning
1. Thoroughly dry: Immediately blow dry or wipe dry the pipeline after rinsing to prevent water stains and rust;
2. Passivation and rust prevention: After pickling, apply passivation paste to restore the chromium oxide protective film and improve corrosion resistance;
3. Regular maintenance:
Clean thoroughly at least once a year;
Daily monitoring of environmental humidity and avoiding contact with chlorine containing media.
Comprehensive suggestion: For mild stains, neutral solvents are preferred for wiping. For stubborn scaling, a combination of “chemical softening+mechanical removal” method is recommended (such as circulating acid solution first and then high-pressure water flushing).