# Fermentation Heating Tube Anti-Corrosion Biological Slime, Microbial Induced Corrosion Prevention & Control Specification ## Preface This specification (Doc.168) is a targeted technical specification supplementing the full anti-corrosion management system from Doc.15 to Doc.167. It standardizes microbial source control, regular biological slime monitoring, graded sterilization treatment, circulating water biological regulation, pipeline dead zone governance and microbial corrosion defect rectification for fermentation heating circulating pipelines. Microorganisms such as bacteria, algae and fungi easily adhere to the inner tube wall to form biological slime layers. Under the sludge deposit, an oxygen concentration difference cell is formed, triggering microbial induced corrosion (MIC), which leads to hidden pitting perforation of pipelines that conventional regular inspection is difficult to detect. This specification realizes whole-process prevention and control of microbial fouling and microbial corrosion from source, operation and maintenance links, eliminating typical hidden corrosion risks induced by biological factors. ## 1. Identification of High-Risk Microbial Corrosion Scenarios and Risk Grading High-risk areas mainly include low-flow pipeline dead zones, circulating water storage tanks, cooling tower pools, pipeline low-point drainage sections, long-term static standby loops and high-temperature humid workshop pipelines. According to total microbial count, slime adhesion degree and historical corrosion records, the risk is divided into three levels: early warning, medium risk and severe high risk. Workshops with frequent biological slime blockage or previous MIC leakage accidents shall be designated as permanent high-risk prevention and control areas, with inspection, sampling and sterilization cycles all adjusted to enhanced frequency. ## 2. Source Control of Microbial Introduction and Water Environment Regulation Raw supplementary water for the circulating system must undergo filtration, disinfection and softening treatment before entering the heating pipeline system to intercept external bacteria and algae spores. Cooling towers and open water tanks shall be equipped with sealed dust-proof covers to prevent dust, fallen leaves and organic debris from falling into the water body and providing nutrient sources for microbial reproduction. The pH value of circulating water is kept within the preset stable range to inhibit the rapid proliferation of acidophilic and alkalophilic corrosive bacteria. Organic leakage of fermentation medium into the circulating water system must be blocked in a timely manner to avoid forming nutrient-rich environments that accelerate biological slime growth. ## 3. Regular Biological Monitoring and Slime Adhesion Inspection Mechanism Circulating water shall be sampled weekly for total bacterial count, sulfate-reducing bacteria and slime content testing; sampling frequency shall be increased to twice a week in high-temperature plum rain seasons. Regular endoscopic inspection of the inner wall of key pipelines is conducted to observe biological membrane adhesion, local sludge accumulation and corrosion pits under slime. When microbial indicators exceed the early warning threshold, emergency enhanced sterilization shall be started immediately, and the pipeline shall be arranged for targeted biological cleaning to prevent the formation of mature stable biological slime. All monitoring data shall be archived into the equipment lifecycle file for trend analysis of microbial corrosion risk. ## 4. Graded Sterilization, Biological Cleaning and Pipeline Dead Zone Governance For early warning-level microbial exceeding standards, regular quantitative addition of broad-spectrum biocides is adopted to suppress microbial reproduction. For medium-risk slime adhesion, alternating use of oxidizing and non-oxidizing biocides is implemented to avoid microbial drug resistance. Severe biological slime blockage or suspected MIC corrosion requires full-loop alkaline biological cleaning combined with sterilization circulation to thoroughly strip biological membranes and organic sediments. Pipeline dead corners, branch pipes and low-point valves prone to sludge deposition shall be drained and cleaned regularly to eliminate stagnant water environments where microorganisms are easy to colonize. ## 5. Post-Cleaning Passivation Protection and Preventive Optimization Management After biological cleaning and sterilization, the pipeline must be fully flushed with purified water to remove residual biocide and stripped slime. Passivation treatment shall be carried out for pipelines with serious biological membrane shedding to repair the damaged metal passive film and restore the inherent anti-corrosion performance of the base material. Regularly summarize the occurrence rules of microbial slime and MIC accidents, optimize biocide dosing frequency and CIP deep cleaning cycle. Typical microbial corrosion failure cases are incorporated into the anti-corrosion knowledge base for staff training, improving frontline personnel's ability to identify and prevent biological-induced corrosion risks. ## 6. System Value This specification builds a whole-chain prevention and control system for microbial fouling and microbial induced corrosion, fills the management blind spot of biological factor corrosion in conventional anti-corrosion measures, effectively avoids hidden pipeline perforation accidents caused by biological slime oxygen concentration cell corrosion, forms a complementary technical defense line with chemical cleaning and water quality control, and further improves the multi-factor full-dimensional closed-loop anti-corrosion management system of fermentation heating tubes.
