Long-Term Anti-Corrosion Risk Prevention Manual for Fermentation Heating Tube System

# Long-Term Anti-Corrosion Risk Prevention Manual for Fermentation Heating Tube System ## Preface This manual consolidates the contents of the previous series of documents (No.50–62) in the following areas: pipeline hardware transformation, process interlock control, standardised operation, predictive maintenance, KPI assessment, and accident closed-loop rectification. It is employed for daily workshop risk inspection, regular hidden danger troubleshooting, and pre-job risk warning training. It establishes classified risk identification standards, grading early warning thresholds, full-process prevention measures, and emergency response plans, and sorts out all latent corrosion risk points of four mainstream heating tube materials (316 stainless steel, Grade 2 titanium, PFA coated heater, quartz glass). # Chapter 1 General Rules of Risk Classification & Early Warning Grading ## 1.1 Three Risk Levels Division Standard ### Level I Major Risk (Red Warning, Production Suspended Rectification Immediately) After the risk occurs, it will result in sudden heating tube leakage/rupture, large-batch fermentation medium contamination, significant economic loss, or hidden safety hazards. Rectification must be completed within three working days, and production can only resume after acceptance. Typical risks include the following: pipeline layout that mismatches the material, fluoride/alkali cross-pipeline communication, unfiltered hard particle long-cycle circulation, the absence of key anti-corrosion parameter interlocks, and quartz long-term contact with alkaline liquid. ### Level II General Risk (Yellow Warning, Rectify Within 7 Days Without Stopping Production) Significantly accelerate corrosion, reduce the service life of heating tubes by over 50%, and create continuous corrosion hidden hazards. During routine maintenance, optimise hardware or modify process parameters. The following are typical risks: frequent thermal shock without slow cooling, severe filter blockage, excessive dead limb length, overdue gaskets reused repeatedly, long-term parameter over-limits (chloride, pH, DO), and incomplete CIP rinsing procedures. ### Level III Minor Hidden Danger (Blue Warning, Included in Next Regular Maintenance Plan): Equipment ageing is gradually exacerbated, but there is no imminent failure risk. The issue will be resolved gradually during the monthly or quarterly overhaul without affecting normal production. Typical risks include a slight static standby time overrun, incomplete patrol records, minor flow velocity deviation from the standard range, and slight frosting on the surface of the quartz tube. Additionally, minor sediment accumulation in dead zones may occur. ## 1.2 Risk Closed-Loop Management Process Risk spot discovery → risk level judgement → hidden danger registration ledger → assign responsible person + set rectification time limit → implement rectification transformation → on-site acceptance re-inspection → eliminate risk and archive records; unrectified hidden dangers are tracked monthly until completely eliminated. # Chapter 2 Classified Identification & Prevention of Material-Specific Corrosion Risks ## 2.1 316 Stainless Steel Heating Tube Risk List | Risk Serial Number | Risk Description | Risk Level | Early Warning Judgment Standard | Full-Cycle Prevention Measures | | ---- | ---- | ---- | ---- | ---- | | SS-01 | Long-term medium chloride＞50ppm | II Yellow | Two consecutive sampling chloride exceeds standard | Install water softening/RO equipment; strictly screen high-chloride raw materials; semi-annual offline passivation | | SS-02 | Hot alkali CIP temperature＞55℃ | II Yellow | Continuous 3 batches of alkali temperature over-limit alarm | Program lock alkali temperature upper limit 55℃, interlock pump stop after over-limit | | SS-03 | Long-term pH＜5.5 or pH＞8.5 | II Yellow | Cumulative over-limit holding time＞2h per shift | Automatic segmented acid-base dosing, online pH interlock alarm | | SS-04 | Massive blind dead legs / sharp 90° elbows | I Red | Dead leg length＞1.5D, a large number of right-angle elbows without transformation | Dismantle redundant blind pipes; replace with large-radius curved elbows; add auxiliary circulation for tube bundle bottoms | | SS-05 | Long static standby＞4h without circulation | II Yellow | Handover log records multiple static overrun records | Timing automatic circulation reminder interlock; low-speed circulation activated for standby loops | | SS-06 | Unfiltered inorganic particle circulation | I Red | Two-stage filter screen damaged, pressure difference alarm ignored | Real-time filter pressure difference interlock; clean filter per shift, replace damaged screen immediately | | SS-07 | Weld pitting, wall thickness thinning＞20% | I Red | Quarterly ultrasonic testing finds severe wall loss | Isolate heating tube for replacement; trace root cause and transform hardware/process | ## 2.2 Grade 2 Titanium Heating Tube Risk List | Risk Serial Number | Risk Description | Risk Level | Early Warning Judgment Standard | Full-Cycle Prevention Measures | | ---- | ---- | ---- | ---- | ---- | | Ti-01 | Fluoride acid pipeline cross-connected to titanium loop | I Red | Fluoride detected in titanium circulation medium | Fully independent fluoride dedicated pipelines, no temporary cross hoses | | Ti-02 | Long-term DO＜7mg/L, aeration shut down arbitrarily | I Red | Continuous low DO alarm without aeration startup | Full-cycle aeration interlock, automatic forced aeration after DO＜7mg/L | | Ti-03 | Carbon steel gaskets / metal composite gaskets used for flanges | I Red | Flange metal-titanium direct contact without isolation | Uniformly configure metal-free pure PTFE elastic gaskets, replace every 3 months | | Ti-04 | Hard particles produce dense surface scratches | II Yellow | Monthly potential scanning finds multiple fixed low-potential scratch zones | Dual-stage fine filtration, control flow velocity ≤1.6m/s, install elbow buffer baffles | | Ti-05 | Static standby time＞3h | II Yellow | Multiple shift static overrun records | Timing circulation alarm, oxygen-rich water circulation during standby | | Ti-06 | Annular milky white etching band at flanges | II Yellow | Visual patrol finds obvious white fog around flange | Shorten gasket replacement cycle; eliminate flange narrow stagnant gaps | ## 2.3 PFA Coated Heater Risk List | Risk Serial Number | Risk Description | Risk Level | Early Warning Judgment Standard | Full-Cycle Prevention Measures | | ---- | ---- | ---- | ---- | ---- | | PFA-01 | Hard metal tools scratch coating surface during maintenance | I Red | Penetrating linear scratches found on lining surface | Only PTFE plastic tools allowed for disassembly; training standardized assembly operations | | PFA-02 | Cancel 40min slow cooling after high-temperature disinfection | I Red | Multiple batches skip slow cooling program | Program lock mandatory slow cooling segment, cannot jump to next batch | | PFA-03 | CIP hot alkali temperature＞85℃ | II Yellow | Alkali temperature continuous over-limit alarm | Interlock limit alkali peak temperature 85℃, over-limit alarm and hold program | | PFA-04 | Abrasive inorganic particles long-cycle scouring | II Yellow | Infrared scanning finds scattered blister cold spots along flow impact lines | Dual-stage fine filtration, control flow velocity 1.0–1.5m/s | | PFA-05 | Frequent daily start-stop times＞2 times | II Yellow | Scheduling leads to frequent cold-hot alternation within 24h | Merge small batches to reduce start-stop frequency; low-temperature circulation during short standby | | PFA-06 | Disassembled gaskets reused repeatedly | II Yellow | Aged deformed gaskets reinstalled on flanges | Any removed gasket must be scrapped and replaced with new one, replaced every 6 months | ## 2.4 Quartz Glass Heating Tube Risk List | Risk Serial Number | Risk Description | Risk Level | Early Warning Judgment Standard | Full-Cycle Prevention Measures | | ---- | ---- | ---- | ---- | ---- | | QZ-01 | Alkaline pipeline cross-connected into quartz circulation loop | I Red | Trace alkali detected in quartz medium, tube wall rapid frosting | Complete physical isolation of alkali pipelines, independent valve interlock anti-misoperation | | QZ-02 | Rapid cold water flushing after high-temperature heating, severe thermal shock | I Red | Cancel slow cooling, direct injection of cold medium program operation forbidden | Lock heating/cooling rate ≤0.4℃/min, slow cooling mandatory | | QZ-03 | High-speed particle continuous impact on elbow inner wall | II Yellow | Biweekly light transmittance test value drops obviously | Control flow velocity 0.8–1.2m/s, large-radius elbows + inlet buffer baffles | | QZ-04 | Static standby time＞5h, residual alkali trapped in dead zones | II Yellow | Uneven matte frosted layer on tube wall after multiple batches | Timing drain reminder; weekly full acid circulation flushing to strip alkali residues | | QZ-05 | Rigid hard gaskets extrude quartz thread joints | I Red | Tiny crack shadows under strong light inspection | Use thickened PTFE composite buffer gaskets, crosswise uniform torque tightening | | QZ-06 | Daily start-stop times＞1 time within 24h | II Yellow | Frequent thermal cycling aggravates hidden microcrack expansion | Optimize production scheduling to minimize quartz equipment startup/shutdown | # Chapter 3 Full-Process Latent Risk Points Classification (Hardware / Process / Operation / Maintenance / Management) ## 3.1 Hardware Design & Configuration Hidden Risks 1. 2. Pipeline structure risks: Excessive dead legs, sharp right-angle elbows, unoptimised elevation liquid accumulation points, and a lack of auxiliary circulation at the bases of tube bundles. Material matching hazards include the presence of a mixed metal flange contact without isolation, as well as a mismatched heating tube and process medium. Supporting equipment absent risks: Absence of a two-stage filtration system, absence of online pH/chloride/DO/temperature interlock sensors, and absence of a differential pressure alarm for filters. Spare parts matching risks: Metal composite gaskets prepared for titanium/quartz equipment, mixed storage of gaskets without colour classification. #3.2 Production and CIP Process Risks 1. Medium environment risks include uncontrolled pH, excessive chloride/fluoride, and insufficient dissolved oxygen for titanium circuits. Risks associated with the CIP program include the manual skipping of rinsing segments, the conclusion of rinsing without pH/conductivity qualification, the use of over-temperature alkali cleaning, and the use of unqualified flow velocity. Thermal cycle risks: Rapid heating/cooling that exceeds the rate limit, frequent start-stop, and slow cooling that may be cancelled; 4. Standby static risks: Medium-long-term static retention that exceeds the material safe time in the absence of circulation or drainage. ## 3.3 Human-Induced Risks in Daily Operation (Highest Incidence Rate) 1. Efficiency-first misoperations: To conserve electricity, increase the temperature of the alkali, reduce the frequency of the pump, shorten the rinsing time, and turn off aeration. Standard implementation omission: Failure to report abnormal corrosion signs in a timely manner, disregard patrol records, and disregard interlock alarms without troubleshooting; 3. Raw material feeding risks: The direct feeding of raw materials with high chloride, high fluoride, or undissolved crystals without inspection reporting. ## 3.4 Hidden Risks of Maintenance and Overhaul 1. Risks associated with disassembly and assembly include the possible scratching of tube surfaces by metal hard tools, the damage of lining/quartz by irregular bolt torque extrusion, and the reuse of aged gaskets. Post-overhaul processing risks: Metal particulates and residual welding slag remaining in pipelines, two full CIP cycles skipped following welding/cutting; 3. Omission of periodic maintenance: Postpone stainless steel passivation, terminate monthly enhanced acid pickling, and neglect filter cleaning. ## 3.5 Risks of Management and Supervision 1. Defects in the inspection system: Inadequate quantitative testing apparatus, incomplete daily/monthly/quarterly inspection mechanisms; 2. Defects in training assessment: Low pass rate of regular retests, new staff lacking anti-corrosion post-training; 3. KPI supervision defects: Lack of reward and punishment for repeated forbidden misoperations, unlinked operation standard compliance with performance; 4. Risk ledger not updated in a timely manner, and unrectified major risks are not tracked and supervised on a monthly basis. These are examples of hidden danger tracking defects. # Chapter 4: Graded Early Warning Inspection & Hidden Danger Troubleshooting Mechanism ## 4.1 Daily Shift Patrol Blue/Yellow Warning Quick Screening (Operator Execution) 1. Blue minor hidden danger record items: Slight sediment accumulation at dead zones, static standby slightly overrun, minor flow velocity fluctuation, and faint frosting on quartz tube; 2. Yellow general risk immediate reporting items: overdue gaskets, filter long-term high pressure difference, evident tube wall discoloration/etching fog, and continuous parameter over-limit alarms; 3. Red major risk emergency isolation items: Quartz visible cracks, welding obvious pitting leakage signs, coating penetrating scratches, alkali/fluoride cross-contamination signals. ## 4.2 Monthly Special Quantitative Detection Risk Early Warning (Equipment Team Execution) 1. Stainless steel: Ultrasonic wall thickness reduction rate: 10% → yellow warning; 20% → red warning; 2. Titanium: Continuous decline of full-tube potential, annular flange etching band → yellow warning; large-area milky fog coverage → red warning; 3. Multiple infrared blister cool spots, coating thickness attenuation: 20% → yellow warning; penetrating scratches → red warning; 5. Quartz glass: A 10% decrease in light transmittance results in a blue warning, while a 15% decrease in light transmittance, compounded by a microcrack shadow, results in a red warning. ## 4.3 Quarterly Full Workshop, Hidden Danger Troubleshooting Organise production supervisors, equipment engineers, and shift foremen to conduct cross-inspection of all heating loops, sort red/yellow/blue risk ledgers one by one, assign rectification responsible persons and time limits, and track completion status in the monthly anti-corrosion work meeting. # Chapter 5: General Preventive Control Measures for All Types of Risks 1. Hardware source control: Within 30 days, all heating circuits will undergo a full-coverage anti-corrosion parameter interlock, two-stage filtration upgrade, independent partition pipeline isolation, and complete dead zone transformation. Program hard locking: Secure the CIP and fermentation process parameters in the control cabinet, restrict the authority to make manual modifications, and automatically activate an alarm and protection system when the limit is exceeded. Operator anti-corrosion SOP training manual compilation, clarification of prohibited operations, and implementation of a full record and abnormal timely reporting system for patrols are all part of the standard operation constraint. 5. Predictive maintenance advance warning: Conduct daily visual patrols, monthly quantitative detection, and quarterly comprehensive overhauls to identify corrosion defects in advance of leakage failure. Standardised management of consumables: The storage of gaskets and filters is categorised by colour, and a mandatory replacement cycle is strictly enforced. The reuse of disassembled ageing sealing parts is prohibited. Personnel training and appraisal: Conduct monthly anti-corrosion case training, conduct regular theoretical and practical assessments, and associate shift performance rewards and penalties with operation compliance. Establish an electronic hidden peril ledger, record the time of discovery, the level of risk, the rectification measures, the acceptance results, and archive all records for lifecycle traceability. This is a closed-loop risk tracking system. # Chapter 6 Emergency Disposal Standards for Major Red Warning Risks 1. If an alkali liquid or fluoride liquid enters the quartz loop or the titanium loop, the isolation valves should be immediately closed to isolate the contaminated pipeline. The large-flow multi-stage rinsing and enhanced acid pickling circulation should be initiated, and the ion concentration should be continuously sampled and tested. Production should not resume until all indicators have been qualified. If a penetrating scratch or quartz crack is visible on the coating, immediately isolate the faulty heating tube, suspend the production of the corresponding batch, organise a replacement as soon as possible, and investigate the root cause of the maintenance/operation to prevent the recurrence of scratch damage. Continuous long-term parameter severe over-limit (high chloride / low DO / extreme pH): Discontinue medium feeding, initiate purified water circulation dilution, inspect sensor and dosing system faults, and resume feeding once medium indicators have returned to a safe range(4). Early indications of a heating tube leakage (flange seepage, weld rust exudation): Isolate the equipment, drain the internal medium, initiate a standardised five-step root cause accident investigation, and develop a full-chain rectification plan to prevent recurrence. In the event of a complete filter failure resulting in a significant particle leakage, the following steps should be taken: immediately suspend circulation, replace all damaged filter elements, execute two full CIP cycles to flush particle sediment from the entire loop, and increase the frequency of subsequent inspections. # Supplementary Provisions of Chapter 7 1. 2. This manual is pertinent to all fermentation heating tube systems in the workshop; all production, equipment, and management personnel are required to adhere to the risk prevention requirements.2. 3. In a timely manner, add new latent danger items, modify early warning thresholds, and update the risk list every quarter in accordance with the progress of hardware transformation and actual failure cases. The production workshop is responsible for the daily on-site implementation and patrol supervision, while the equipment management department is responsible for the unified ledger management of risk hidden hazards. This manual serves as the primary instructional resource for pre-job risk warning training and monthly anti-corrosion assessments. ## Summary This risk prevention manual implements a comprehensive identification of the latent corrosion risks of four heating tube materials in the hardware, process, operation, maintenance, and management domains. It also establishes three-level red/yellow/blue early warning judgement standards and a closed-loop rectification tracking mechanism. By means of source hardware transformation, program interlock restriction, standardised operation supervision, and predictive maintenance early warning, it is possible to preemptively eliminate all significant risks that may result in rapid heating tube failure. Minor hidden dangers can be rectified in batches during routine maintenance, multi-factor synergistic corrosion can be fundamentally suppressed, and the heating tube system can be guarantyd to operate safely and reliably for an extended period.