Cleaning depends on the dirt type and the cleaning stage: external cleaning, pre-inspection cleaning, and pre-assembly cleaning. Common dirt includes oil, carbon deposits, scale, and rust.
Oil and grease
Saponifiable oils include animal and vegetable oils. Non-saponifiable oils include mineral oil. Treat them by type.
Solvent degreasing
Use gasoline, kerosene, diesel, alcohol, or benzene. Soak or brush the parts. To save solvent, use a tank with a grate. Put the parts on the grate and brush them. Dirt settles at the bottom. Clean main parts, cleaner parts, and smooth parts first. Then clean secondary parts, dirty parts, and rough parts. Do not mix them, or parts may be damaged. Dry with compressed air or a cotton cloth. Solvent costs more, so watch fire safety.
Alkali degreasing
This works on saponifiable oils. Mix about 10% alkali solution, such as sodium hydroxide. Heat it to 70 to 90°C. Small plants can pour the solution into a large tank and heat it with coal. Put the parts on a rack or in a basket. Boil for 10 to 15 minutes. Rinse with hot water and blow dry. Large plants can use a cleaning machine. A single-chamber machine has a cylindrical chamber with a rotating rack. Heated alkali solution sprays through nozzles at 27 m water column pressure onto the rotating parts. A three-chamber machine moves parts through three chambers. The first two rinse with alkali water. The third rinses with hot water. For mineral oil, add stronger alkali such as soap, synthetic detergent, sodium silicate, oleic acid, triethanolamine, or alcohols. For non-ferrous metals such as tin, lead, aluminum, zinc, and their alloys, control alkalinity to avoid corrosion.
Other dirt
Carbon deposits: scrape them off or soak in a chemical cleaner. Pick the method by deposit thickness.
Scale: use an acid cleaner such as dilute hydrochloric acid and circulate it. Control concentration and time to avoid corrosion.
Rust: use sandblasting, a wire brush, or a chemical rust remover such as phosphoric acid. Apply anti-rust oil right after cleaning.
Cleaning stages
External cleaning: remove surface oil and dust. Wipe with solvent or use high-pressure water. Do not spray electrical components or seals directly.
Pre-inspection cleaning: remove internal dirt such as oil and carbon. This keeps test data accurate. For precision parts such as sensors and bearings, use ultrasonic cleaning or a dedicated cleaner.
Pre-assembly cleaning: dry parts and apply anti-rust oil right away. Avoid second contamination. Check cleanliness before assembly. No dirt or fibers.
Safety and environment
Use solvents in a well-ventilated area. Wear gloves and goggles. Neutralize waste alkali solution before discharge. Follow the machine manual. Maintain nozzles and rotating racks regularly.
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