# Fermentation Heating Tube Anti-Corrosion Pipeline Thermal Insulation, Cladding & Anti-Corrosion Coating Maintenance Specification ## Preface This specification (Doc.166) is a supporting environmental anti-corrosion technical document under the full anti-corrosion management system from Doc.15 to Doc.165. It standardizes the construction acceptance, daily patrol, regular maintenance, local repair and renewal replacement of pipeline thermal insulation layers, external protective cladding, anti-corrosion primer, intermediate paint and topcoat for fermentation heating tube systems. Damaged thermal insulation and protective coatings will cause surface condensation, rainwater infiltration, acid and alkali volatile gas erosion, resulting in external atmospheric corrosion, crevice corrosion under insulation, bolt rust locking and pipeline heat loss. This specification locks the external anti-corrosion barrier of heating pipelines, avoids hidden corrosion defects wrapped under thermal insulation layers that are difficult to detect in daily inspections, and ensures both thermal efficiency and long-term external anti-corrosion performance of equipment. ## 1. Material Selection, Construction Acceptance Standard for Insulation and Anti-Corrosion Coating All thermal insulation materials, metal cladding sheets and anti-corrosion coatings must be selected from approved qualified suppliers with complete material inspection reports. Thermal insulation materials shall feature low water absorption, anti-mold and high-temperature resistance; coatings need matching primer, intermediate and topcoat systems suitable for workshop humid and slightly corrosive atmospheric environment. During new installation or overhaul construction, the metal base surface must be derusted, polished and cleaned thoroughly before coating spraying to guarantee coating adhesion. Thermal insulation laying shall be tight and seamless, with lap joints sealed by waterproof adhesive tape; metal cladding shall adopt overlap installation with downward drainage design to prevent rainwater infiltration. Construction acceptance includes coating thickness detection, adhesion test and insulation thermal resistance inspection; unqualified parts must be stripped and reconstructed. ## 2. Daily Inspection Key Items for External Protective System Operators shall inspect the integrity of coating, thermal insulation and cladding during each shift patrol. Key inspection points include coating peeling, blistering, cracking and local rust leakage; insulation water seepage, mildew, collapse and exposed metal base; cladding deformation, loose fasteners, sealing tape aging and lap gap water accumulation. Special attention shall be paid to pipeline bent sections, flanges, support contact positions, ground transition parts and outdoor exposed sections, where protective layers are most prone to damage. Once local damage is found, mark the position immediately and arrange maintenance to avoid moisture penetrating into the insulation layer and inducing hidden under-insulation corrosion. ## 3. Regular Maintenance Cycle and Graded Repair Requirements A quarterly full visual inspection of all pipeline external protection is implemented; coating thickness and insulation integrity sampling test is carried out annually. Minor defects such as small-area coating peeling and local sealing tape aging belong to grade-one minor faults, which can be repaired by partial surface derusting, supplementary painting and resealing without large-area dismantling. Grade-two moderate damage includes partial insulation dampness, cladding loose deformation and medium-range coating failure, requiring local removal of damp insulation, base rust removal, recoating and reinstallation of protective cladding. Grade-three severe failure such as large-area insulation waterlogging, widespread coating rust penetration must arrange full-section protective layer stripping, comprehensive rust cleaning, recoating and insulation re-laying to eliminate under-insulation corrosion risks fundamentally. ## 4. Standard Construction Procedures for Local Protective Layer Repair Before repairing damaged positions, the affected area shall be fully isolated to prevent cleaning waste liquid from flowing into intact insulation. Damp insulation materials must be completely removed and discarded; the exposed metal surface is polished to remove rust, dust and residual old coatings, then wiped clean and dried thoroughly. Primer shall be sprayed first after surface treatment, followed by intermediate and topcoat after full curing. New thermal insulation is laid closely with the original insulation layer, all lap joints are sealed with waterproof anti-corrosion adhesive tape, and metal cladding is fixed with anti-rust fasteners. Repair construction shall be avoided in rainy, high-humidity and dusty environments to ensure repair quality and coating adhesion. All repair positions shall be recorded in the equipment ledger as key follow-up inspection points. ## 5. Protective Layer Full Renewal Management and Preventive Optimization When the aging failure range of pipeline external protective system exceeds the specified proportion, full renewal renovation shall be arranged during centralized production shutdown. Before renovation, evaluate the historical atmospheric corrosion degree of the area, and appropriately upgrade coating anti-corrosion grade or adopt hydrophobic enhanced insulation materials for high-humidity and seasonal condensation-prone areas. Regularly sort out protective layer damage statistical data, summarize common damage causes such as mechanical collision, seasonal condensation corrosion and installation process defects, optimize on-site equipment layout and operation access protection measures, and incorporate typical maintenance cases into anti-corrosion training materials. ## 6. System Value This specification builds a stable external physical anti-corrosion barrier for heating pipelines, effectively prevents hidden under-insulation corrosion difficult to be found in conventional inspections, balances pipeline thermal energy conservation and atmospheric corrosion prevention, makes up for the vulnerability of metal passive films in complex workshop environments, and further improves the full-dimensional internal and external integrated closed-loop anti-corrosion management system of fermentation heating tubes.
