Maintenance of manhole molds is crucial for ensuring their lifespan and the quality of the finished product. The following details the key points of manhole mold maintenance from multiple perspectives:
I. Cleaning and Surface Treatment
Residue Removal: After demolding, immediately clean the inside and outside of the mold of any remaining concrete debris and release agent. It is recommended to use a nylon brush or a high-pressure water gun (pressure not exceeding 5MPa) for rinsing. Avoid using hard objects to scrape, as this may damage the mold surface. Pay special attention to cleaning joints, bolt holes, and corner areas to prevent hardening of residues that could lead to seal failure.
Chemical Cleaning Assistance: For stubborn stains, such as hardened cement slurry, a neutral detergent (pH 6-8) can be used to soak and soften the stain before cleaning. Strong acid and alkali solvents are strictly prohibited, as they may corrode the mold steel.
Rust and Corrosion Prevention Treatment
Rust Inhibitor Spraying: After cleaning, evenly spray rust inhibitor or industrial machine oil (approximately 0.1mm thick) onto the inside and outside of the mold, paying particular attention to easily oxidized areas such as weld seams and cut surfaces. For sewage well molds that are in long-term contact with corrosive media, it is recommended to use a chromium-containing alloy-specific rust-preventive oil, and reapply after every 10 uses.
Zinc Coating Maintenance: If the galvanized mold shows signs of coating peeling, repair it promptly and spray with epoxy zinc-rich primer (dry film thickness not less than 60μm) to prevent the spread of rust on the substrate.
Lubrication and Component Maintenance
Transmission Component Lubrication: Regularly apply lithium-based grease (NLGI Grade 2) to moving parts such as bolts and clips to reduce frictional wear and prevent seizing. Mold hinges should be disassembled, cleaned, and have the lubricant replaced after every 50 uses.
Sealing Strip Replacement: Regularly inspect the wear of the multi-layer sealing strips (EPDM material) at joints. If cracking or deformation occurs (compression set exceeding 20%), replace them immediately to ensure proper casting sealing.
Storage and Deformation Control
Standardized Storage Conditions: Molds should be placed vertically or horizontally in a dry, well-ventilated environment (humidity not exceeding 60%), with a wooden pallet underneath to prevent contact with the ground and moisture absorption. Stacking more than three layers is prohibited to prevent plastic deformation of the steel plate due to gravity compression (deformation exceeding 2mm/m requires scrapping).
Stress Relief Management: Molds that have been out of use for an extended period (more than 3 months) should have their bolt connections loosened to release internal stress and prevent structural deformation caused by residual stress.
Regular Inspection and Repair
Structural Inspection: After every 50 uses, the mold's verticality must be checked using a laser level (deviation not exceeding 1mm), and the joint gap must be measured using a feeler gauge (not exceeding 1mm). If weld cracks or steel plate dents are found (depth exceeding 1mm), repairs must be made using CO₂ shielded welding and the surface ground smooth.
Functional Verification: Regular trial molding is conducted to verify the smoothness of demolding. If sticking or grout leakage occurs (leakage rate exceeding 0.5%), the uniformity of the release agent spraying and the integrity of the sealing strips must be checked.
Through systematic maintenance management, the service life of manhole molds can be extended to more than 3 years, and the number of reuses can reach more than 200 times. During maintenance, the principle of material compatibility must be strictly followed, and a maintenance log must be established to ensure the quality stability and construction efficiency of concrete manholes in municipal engineering projects.