The following is a detailed description of the internal cleaning methods and related points for stainless steel reaction vessels:
1、 Preprocessing and preliminary cleaning
1. Evacuation and isolation
Close all inlet and outlet valves, and open the vent valve to empty the material. If hazardous chemicals are involved, it is necessary to first replace the residual gas with inert gas (such as nitrogen) and confirm through a visual mirror that there is no residual pressure. Disassemble movable parts (agitator blades, thermometer sleeves) and clean them separately to avoid dead corners and residue.
2. Pre rinsing
Inject warm water (≤ 60 ℃) into the kettle, start low-speed stirring for preliminary flushing, and remove most visible pollutants. For high viscosity materials, hot water circulation can be used to soften the residue, and high-pressure water guns can be used to directionally rinse the bonding area.
2、 Core cleaning solution
1. Physical cleaning method
-Mechanical scraping: For solidified lumps, use a nylon shovel or copper scraper to gently peel off. It is strictly prohibited to use steel tools to prevent damage to the passivation layer. Stubborn adhesion can be assisted by tapping and vibrating with a wooden hammer handle to remove it.
-High pressure water jet: Use food grade stainless steel nozzles, maintain a tilt angle of 30-45 ° for spiral flushing, and focus on impacting the weld seam between the head and the cylinder. Control the water pressure within an appropriate range to avoid impact deformation.
-Ultrasonic synergy: Inject warm water containing neutral detergent into the kettle, turn on the ultrasonic generator, and use cavitation effect to decompose microbial membranes and fine particles.
3、 Fine washing and passivation treatment
1. Rinse with purified water
Use injection water for three or more cycles of rinsing, stir evenly after each water change, and sample conductivity should be ≤ a certain value (according to USP standards). The final rinse water should cover the entire inner surface and maintain it for a period of time.
2. 钝化再生
Prepare an appropriate amount of nitric acid solution, heat it to the specified temperature and soak it for a period of time to form a dense chromium oxide protective film. Immediately rinse with purified water until neutral after drainage, and repeat the passivation process if necessary.
4、 Drying and acceptance
1. Drying process
Blow the drainage outlet with clean compressed air, then introduce filtered hot air to keep the kettle rotating and drying slowly. Do not directly bake with open flames to avoid damaging the material structure.
2. Cleaning verification
-Visual inspection: The inner wall should present a uniform silver white matte state, without visible spots or water stains.
-White cloth wiping: Use non shedding non-woven fabric to wipe the sample and place it on a black background board for observation without any discoloration marks.
-Microbial testing: Sampling and cultivation using cotton swab wiping method must meet the corresponding cleanliness level requirements.
By strictly following the above cleaning procedures, the surface smoothness of the stainless steel reactor can be effectively restored, the risk of cross contamination can be eliminated, and the service life of the equipment can be extended. It is recommended to establish a cleaning log to record the type, concentration, and operator information of each cleaning agent used for quality traceability.