# Fermentation Heating Tube Anti-Corrosion Low-Flow & Static Standby Protection Specification ## Preface This specification is a supporting document of the complete anti-corrosion document system from Doc.33 to Doc.115. It standardizes protective operation procedures, parameter control standards, regular maintenance and risk early warning rules for heating tube loops under low-flow operation, intermittent production shutdown, long-term static standby and idle line standby conditions. It solves prominent corrosion problems such as medium stagnation, biofilm accumulation, ion concentration enrichment and localized pitting caused by insufficient fluid scouring, and fills the anti-corrosion management gap in non-continuous production states. Three operating states with differentiated protection schemes are clearly classified. The first category is low-flow continuous operation, referring to circulation flow far below the standard design rate during low-load fermentation. Slow flow leads to long medium residence time inside the tube, and corrosive substances easily deposit on the inner wall. The second category is short-term static standby, including daily shift shutdown, batch interval pause with standby time less than 24 hours. The third category is long-term idle standby, such as production line halt for maintenance, seasonal shutdown and new equipment idle storage exceeding 72 hours, which faces the highest risk of severe local corrosion. Unified protection operation standards for low-flow working conditions are formulated. When the flow rate drops below the safe threshold, the patrol frequency of heating tube inlet and outlet monitoring points is doubled, and online chloride and pH data are recorded every 30 minutes. Regular forced high-flow flushing is added every 4 hours to wash away sediment and attached microorganisms on the tube wall. The pickling cycle is shortened by half compared with normal full-flow operation, and mild neutral circulation cleaning is supplemented between pickling cycles to reduce biofilm accumulation. Complete graded static standby protection workflows are implemented. 1. Short-term standby (≤24h): After stopping circulation, drain excess redundant medium, inject sterile pure water to fill the entire heating tube loop, maintain slight micro-circulation at fixed intervals, and record standby start time to strictly control the stagnation duration not to exceed the upper limit specified in the red-line operation standard. 2. Long-term idle standby (>72h): Popolnoma izpraznite ves kulturni medij in izpiralno tekočino znotraj cevovoda, izvedite popolno dekapiranje s pasivacijo, nato posušite notranjo steno s sterilnim vročim zrakom in napolnite zaprto zanko z inertnim zaščitnim plinom za tesnilno izolacijo. Vsi vstopni in izstopni ventili so zaprti in zaklenjeni z nameščenimi slepimi ploščami, ki preprečujejo vstop zraka, vlage in zunanjih onesnaževal v cev. Med skladiščenjem v mirovanju je potreben tedenski pregled videza zunanjih sten cevovoda in redno notranje sušenje. Vzpostavljeni so posebni mehanizmi za prepoznavanje tveganj in zgodnje opozarjanje. Ključni opozorilni signali vključujejo nenormalen odmik pH med stanjem pripravljenosti, neprekinjen trend naraščanja koncentracije klorida, zamegljenost in pikčasto jedkanje na notranjih stenah cevi po odtekanju tekočine ter lepljive ostanke biofilma, odkrite med rutinskim pregledom odpiranja. Ko se pojavijo zgodnji opozorilni signali, je treba nemudoma izvesti prisilno polno-izpiranje zanke in izboljšano čiščenje, omejitev trajanja pripravljenosti proizvodne linije pa se začasno zmanjša, da se prepreči koncentrirana ionska korozija. Vsi dnevniki parametrov nizkega pretoka, statični obrazci za registracijo začetka/konca stanja pripravljenosti, zapisi o izvajanju prisilnega izpiranja, kontrolni seznami vzdrževanja nedejavnega cevovoda in datoteke nenormalnega odstranjevanja v stanju pripravljenosti uporabljajo dvojno elektronsko in papirno arhiviranje. Analiza trendov mesečnih podatkov šteje pogostost okvar zaradi korozije opreme v stanjih statičnega in nizkega{11}}pretoka; če pride do ponavljajoče se stagnacijske korozije v določenih delavnicah, bodo klavzule o načrtovanju intervala proizvodnih serij in delovanju zaščite v pripravljenosti revidirane v četrtletnem pregledu sistema. Ta specifikacija zajema vse ne-normalne neprekinjene proizvodne delovne pogoje grelnih cevi, odpravlja korozijske slepe lise, ki nastanejo zaradi zmanjšanja pretoka in-trajne stagnacije izklopa, ter izpopolnjuje polno-stanje zaprtega-zanke proti-sistema zaščite pred korozijo fermentacijskih grelnih cevi.
