# Training Manual for On-Site Operators: Anti-Corrosion Standard Operation of Fermentation Heating Tubes ## Preface Heating tube premature corrosion, leakage and rupture are mostly derived from irregular daily operation and weak awareness of anti-corrosion among frontline staff. This manual unifies operation norms, risk judgment points and simple emergency disposal requirements for four mainstream heating tube materials (316 stainless steel, Grade 2 titanium, PFA coated heater, quartz glass), targeting shift operators, CIP staff and equipment maintenance workers, to standardize full-process operation and reduce equipment failure rate. ## Chapter 1 Basic Anti-Corrosion Knowledge of Four Heating Tube Materials ### 1.1 Core Anti-Corrosion Characteristics & Absolute Taboos | Material | Core Protective Film | Absolute Forbidden Operations | | ---- | ---- | ---- | | 316 Stainless Steel | Nanometer chromium oxide passive film | Hot alkali cleaning over 55℃; long-term chloride＞50ppm; sustained pH＜5.5 or pH＞8.5 | | Grade 2 Titanium | Self-repairing TiO₂ film | Fluoride cross-contamination; shutdown aeration for a long time; direct contact with carbon steel without PTFE gaskets | | PFA Coated Heater | Integral fluoroplastic isolation layer | Hard metal tools scratch coating; cancel slow cooling after high-temp disinfection; unfiltered hard inorganic particle long-cycle circulation | | Quartz Glass | Silicon dioxide crystal matrix | Any alkaline liquid contact; rapid cold-hot thermal shock; high-speed particle continuous impact | ### 1.2 Daily Quick Judgment of Early Corrosion Signs 1. 316 Stainless steel: Weld yellow/brown rust spots, strip-shaped abrasion grooves, local small pits 2. Grade 2 Titanium: Annular milky white foggy etching at flanges, scattered matte scratch spots 3. PFA Heater: Local coating slight bulge, uneven matte surface, abnormal low-temperature cold spots under infrared scan 4. Quartz Glass: Tube wall frosted matte layer, obvious light transmittance drop, tiny crack shadow under strong light ## Chapter 2 Standard Operation Specifications in Fermentation Production Stage ### 2.1 Medium Parameter Monitoring & Adjustment Specifications 1. Real-time monitor online pH, chloride and dissolved oxygen data every hour, record in shift log; alarm immediately once exceeding safe range. - Stainless steel: pH maintain 5.5–8.0, chloride ≤50 ppm - Titanium: pH 4.0–9.0, continuous DO ≥8 mg/L - PFA: pH 2.0–12.0, no chloride limit (only coating scratch risk) - Quartz: pH strictly controlled below 7.0, no alkali mixing 2. Slow segmented dosing when adjusting medium pH, forbid one-time large addition of acid/alkali leading to sharp pH overshoot and local extreme pH microzones. 3. Incoming raw material inspection: Report to equipment supervisor immediately if raw material contains high fluoride, high chloride or a large number of undissolved mineral crystals. ### 2.2 Circulation & Standby Anti-Static Corrosion Rules 1. Prohibit long-term static retention of medium inside heating loops; follow maximum safe static standing time strictly: - 316 SS ≤4 h; Titanium ≤3 h; PFA ≤6 h; Quartz ≤5 h 2. Short standby within time limit: Turn on low-speed circulation pump to keep fluid flowing; titanium loops maintain continuous aeration. 3. Standby exceeding safe static time: Fully drain fermentation medium, circulate purified water for 15 min for flushing. 4. Long shutdown over 48 h: Complete full CIP cleaning, drain all liquid inside tubes and keep pipelines dry; titanium tubes need oxygen-rich purified water soaking for 30 min before draining. ### 2.3 Production Start-Stop Thermal Cycle Control 1. Heating rate ≤0.5℃/min, cooling rate ≤0.4℃/min, forbid rapid temperature rise and drop. 2. After high-temperature disinfection (above 80℃), mandatory 40 min graded slow cooling, cannot directly inject cold medium/cold water for rapid cooling. 3. Optimize production scheduling to reduce daily start-stop times: Stainless steel & titanium ≤3 times/24h; PFA ≤2 times/24h; Quartz ≤1 time/24h. ## Chapter 3 CIP Cleaning Anti-Corrosion Standard Operating Procedures ### 3.1 Fixed CIP Multi-Stage Sequence (No Step Skipping Allowed) Pre-rinse → alkali circulation → intermediate rinse → acid circulation → final purified water rinse 1. Alkali circulation control limits: - Stainless steel loop: Hot alkali temperature ≤55℃, no arbitrary temperature rise to speed cleaning - PFA loop: Alkali peak temperature ≤85℃ - Titanium & quartz: Strictly control alkali holding time, strengthen subsequent rinsing 2. Intermediate & final rinsing cannot be shortened arbitrarily; stop rinsing only when effluent pH and conductivity reach neutral qualified standard, cannot end rinsing by fixed time alone. 3. Add 5 min high-flow pulse flushing at the end of each CIP batch to wash sediment in pipeline dead zones. 4. Monthly enhanced acid pickling circulation to strip biofilm, chloride salt and heavy metal deposits accumulated in dead legs. ### 3.2 CIP Flow Velocity Control Requirements Maintain material-matched safe wall flow velocity during all cleaning stages, prohibit long-term low-frequency pump operation leading to insufficient scouring: 1. 316 Stainless steel: 1.2–1.8 m/s 2. Grade 2 Titanium: 1.0–1.6 m/s 3. PFA coating heater: 1.0–1.5 m/s 4. Quartz tube: 0.8–1.2 m/s If flow velocity is too low due to filter blockage, stop CIP immediately and clean filter elements. ### 3.3 CIP Pipeline Partition Management 1. Fluoride-containing acid pipelines, high-chloride fermentation loops and alkaline process pipelines adopt independent dedicated pipelines, forbid temporary cross-connection hoses to avoid cross-contamination. 2. Quartz heating loops must be completely isolated from all alkali supply pipelines; once accidental alkali leakage enters quartz tubes, immediately start full acid circulation neutralization and extended rinsing. ## Chapter 4 Daily Shift Patrol Inspection Checklist (Must Be Signed After Inspection) Inspection frequency: Full patrol at start, middle and end of each shift; focus on heating tube elbows, weld seams, flanges, tube bundle bottoms and dead branch pipes. ### 4.1 Visual Inspection Items 1. Tube wall surface: Check for rust spots, milky etching fog, frosted matte layers, local bulging and crack shadows; 2. Flange joints: Check for slight liquid seepage, aging/deformed gaskets, discoloration annular corrosion bands; 3. Pipeline dead zones: Observe sediment accumulation at blind legs and low liquid accumulation points; 4. Filter state: Check pressure difference gauge, judge filter blockage degree in real time. ### 4.2 Parameter Record Items 1. Record daily maximum static standby duration of heating loop; 2. Record over-temperature, low DO, pH out-of-limit and low flow abnormal alarm times and disposal process; 3. Record filter cleaning time, gasket replacement time and CIP enhanced pickling execution status. ### 4.3 Abnormal First-Response Rule Once any early corrosion sign or parameter over-limit alarm is found, mark abnormal position on site, record in handover log and report to equipment supervisor immediately; forbidden to ignore alarms or clear alarm records without troubleshooting. ## Chapter 5 Maintenance & Disassembly Anti-Corrosion Operation Standards ### 5.1 Disassembly & Assembly Tool Specifications 1. Only PTFE plastic spanners, soft plastic scrapers and non-abrasive cleaning brushes can be used; ban iron wire brushes, metal hard tools contacting heating tube surfaces to avoid scratches. 2. Flange bolts must be tightened crosswise with uniform torque to prevent local gasket extrusion damage to PFA coating and quartz tube. ### 5.2 Gasket Matching & Replacement Norms 1. Gaskets are stored by material classification with color labels, forbid mixed random use: - Titanium & quartz: Pure PTFE elastic gaskets without metal filler, replace every 3 months; - Stainless steel & PFA: Expanded PTFE gaskets, replace every 6 months; 2. Any gasket disassembled from flanges must be replaced with a new one, reused aged/deformed gaskets are prohibited. ### 5.3 Post-Maintenance Pipeline Flushing Requirements After pipeline cutting, welding, disassembly and overhaul, two complete full-loop CIP cycles must be carried out before resuming production to flush welding slag, metal filings and particle residues left in dead zones. ## Chapter 6 Classification of Common Forbidden Misoperations & Hazard Consequences | Misoperation Content | Damaged Heating Tube Material | Corrosion Consequence | | ---- | ---- | ---- | | Raise hot alkali temperature above 60℃ to shorten CIP time | 316 Stainless Steel | Passive film peeling, weld rapid pitting leakage within 1 month | | Shut down titanium loop aeration to save electricity | Grade 2 Titanium | Insufficient DO, fluoride synergistic etching forms large-area milky fog | | Cancel slow cooling, direct cold water flushing after high-temperature disinfection | PFA / Quartz | PFA generates interlayer blisters; quartz produces thermal shock microcracks | | Long-term uncleaned blocked filter, unfiltered particle circulation | All four materials | Mechanical scratches break protective layers, multi-factor synergistic accelerated corrosion | | Medium static standby exceeding material safe time limit | All four materials | Dead zone biofilm enrichment, localized high-corrosion microenvironment formed | | Mixed use of fluoride and titanium shared pipelines | Grade 2 Titanium | Annular flange etching, continuous decline of electrochemical potential | | Alkali pipeline cross-connected to quartz loop | Quartz Glass | Severe frosting, reduced structural strength, sudden brittle rupture risk | ## Chapter 7 Simple Emergency Disposal Measures for Abnormal Conditions 1. Medium pH/pH out-of-limit for a long time: Stop feeding raw materials, start large-flow purified water circulation to dilute medium, adjust acid-base dosing frequency to restore neutral safe range. 2. Accidental fluoride/alkali cross-contamination into heating loop: Isolate the loop immediately, execute extended multi-stage rinsing + enhanced acid pickling cycle, send samples to test residual ion concentration before restarting production. 3. Filter severe blockage, flow velocity far below standard: Suspend CIP or fermentation circulation, disassemble and clean filter elements completely, check filter screen for damage and leakage. 4. Early corrosion abnormal signs found on tube wall: Shorten inspection cycle, advance planned maintenance time, increase monthly quantitative detection frequency to track corrosion development trend. 5. Heating tube sudden leakage/rupture: Close inlet and outlet valves of heating loop immediately, cut off medium supply, drain residual liquid inside the tube, isolate equipment and report accident investigation. ## Chapter 8 Assessment & Training Management Requirements 1. Monthly centralized anti-corrosion training: Take typical heating tube failure accident cases as teaching materials, clarify operation taboos and hidden corrosion risks, with training assessment records archived. 2. Link anti-corrosion patrol records and standardized operation implementation to shift performance assessment: Deduction for repeated forbidden misoperations and unrecorded abnormal alarms; reward shifts with zero abnormal corrosion records monthly. 3. New staff must complete full manual learning and pass theoretical + on-site operation assessment before independent post work; old staff retake assessment every six months to consolidate anti-corrosion operation standards. ## Summary All frontline operators are the first line of defense for heating tube anti-corrosion. Strictly implementing patrol recording, standardized CIP circulation, standby static control and maintenance disassembly specifications can effectively eliminate most artificial induced corrosion risks, avoid multi-factor synergistic amplification damage, reduce equipment maintenance costs and avoid huge economic losses caused by fermentation batch scrapping due to heating tube leakage and rupture.
