In marine engineering, offshore cranes are key equipment to ensure the smooth execution of various operations. However, due to long-term exposure to harsh marine environments-such as high humidity, strong salt spray, and wave impact-they face severe corrosion challenges. Corrosion not only reduces the structural strength and shortens the service life of the marine crane but may also cause serious safety accidents, endangering the lives of operators and the safety of marine engineering facilities. Cleaning and maintenance, as the primary and key link in corrosion prevention and control, play a decisive role in maintaining the performance and safety of offshore cranes.
Surface Cleaning: Removing the Corrosion "Catalyst"
(1) Clean External Structures
Daily Seawater Salinity and Dust Cleaning: After each day's operation of the marine crane, its fuselage, boom, slewing platform, and other external structures will be covered with salt residue from seawater droplets and wind-blown sand dust. These salts are highly hygroscopic, forming a film of electrolyte solution on the metal surface, which accelerates the electrochemical corrosion process. Sand and dust particles can exacerbate wear between components during operation, destroying the protective layer on metal surfaces and creating conditions for corrosion. At this time, a soft brush and a clean, damp cloth should be used to gently brush and wipe the equipment's surface, carefully removing salt and dust. For hard-to-reach nooks and crannies, a small vacuum cleaner can assist in cleaning to ensure no residue remains.
Removal of Oil and Other Pollutants: During operation, the marine crane's hydraulic system and transmission parts may leak oil. Once oil adheres to the equipment's surface, it attracts more dust impurities, hinders the subsequent application of anti-corrosion coatings, and reduces the adhesion between the coating and the metal surface. For oil pollution, a mild detergent designed for marine environmental equipment should be chosen and diluted according to the product instructions. Dip a soft cloth in the solution and repeatedly wipe the oil stain until completely removed. After cleaning, rinse the detergent residue with clean water and dry it promptly to prevent the detergent's chemical components from causing secondary corrosion to the metal.
(2) Clean Internal Parts
Cleaning of Mechanical Transmission Parts: The marine crane's internal mechanical transmission parts-such as gears, chains, bearings, etc., in the lifting mechanism, luffing mechanism, and slewing mechanism-will accumulate large amounts of oil, metal debris, and sand dust impurities invading from the outside during long-term operation. These contaminants can exacerbate component wear, affect transmission efficiency, and provide a breeding ground for corrosion. Periodically (it is recommended to open the part's protective cover at least once a week) and use a compressed air gun to blow away dust and debris accumulated on the part's surface at an appropriate pressure. For grease on gears and chains, a special chain cleaner or metal parts cleaner can be used: spray the cleaner on the part's surface, brush it with a clean brush, and finally dry it with a clean cloth. When cleaning bearings, pay special attention to preventing the cleaner from entering the bearing's internal grease area; if it accidentally enters, the grease needs to be replaced immediately to avoid affecting the bearing's regular lubrication and service life.
Electrical System Parts Cleaning: The electrical system is the "nerve center" of the offshore crane, and its regular operation is essential for the equipment's safe operation. However, the humid marine environment and air pollutants such as salt and dust easily cause corrosion and short circuits in electrical components. Electrical components such as electrical control cabinets, junction boxes, and motors should be cleaned at least once a month. Before cleaning, cut off the power supply to ensure safe operation. Use a soft brush to gently remove dust and salt from the surface of electrical parts; for some stubborn stains, use a soft cloth dampened with a small amount of anhydrous alcohol. After wiping, wait for the alcohol to completely volatilize before powering on to prevent short circuits caused by alcohol residue. At the same time, check whether the electrical component terminals are loose or oxidized, and if there is a problem, tighten and address them promptly to ensure the reliability of electrical connections.
Deep Cleaning and Protection of Key Parts: Building a Strong Corrosion Defense Line
(1) Hook and Pulley Block
Hook Cleaning and Inspection: As a key component of marine cranes directly carrying heavy loads, the hook's safety is vital. Before and after each lifting operation, the hook should be thoroughly cleaned and carefully inspected. First, use a brush to remove dirt, salt, and debris from the hook's surface, then carefully observe whether there are cracks, wear, corrosion, or other defects on the hook's surface. For the hook's dangerous sections (such as the transition between the hook body and the hook handle, the hook mouth, etc.), a magnifying glass or non-destructive testing equipment can be used for key detection. If slight corrosion or wear is found on the hook's surface, sandpaper can be used for sanding to remove the corrosion layer and wear marks, and a layer of special anti-rust oil should be applied. If the hook has serious cracks or wear exceeds the specified standard, it must be immediately withdrawn and replaced with a new hook-taking risks is strictly prohibited.
Block Cleaning and Maintenance: The block is essential in guiding and labor-saving during the ship crane's lifting and luffing processes. Because the pulley block is in a high-load operation state for a long time and frequently rubs against the wire rope, it is prone to wear and corrosion. When regularly cleaning the pulley block, remove the pulley from the shaft (to ensure safety) and thoroughly clean the pulley's grooves, hubs, and shaft holes with detergent to remove accumulated oil, rust, and debris. After cleaning, check the pulley's wear: if the pulley groove wall is worn by more than 20% of the original wall thickness or the pulley has cracks and other defects, the pulley should be replaced promptly. When reinstalling the pulley, ensure the pulley is installed in the correct position, the shaft and pulley fit well, and apply an appropriate amount of grease to the contact between the shaft and the pulley to reduce friction and wear while enhancing anti-rust performance.
(2) Wire Rope
Surface Cleaning and Descaling: The wire rope is the core component of the boat crane's lifting system, and its working state is directly related to the crane's safe operation. Due to long-term exposure to the aquatic environment and enormous tension and friction, wire ropes are highly susceptible to rust, corrosion, and wear. At the end of each day, the wire rope's surface should be cleaned with a soft brush and a clean rag to remove attached salt, rust, oil, and debris. A special wire rope cleaning agent can remove some difficult-to-remove dirt. When using the cleaning agent, dilute it according to the product instructions, apply it evenly to the wire rope's surface, brush it with a brush, and rinse it with clean water. During cleaning, pay attention to avoiding damage to the wire rope from the cleaning agent and ensure the cleaning agent is completely removed to prevent residual cleaning agents from corroding the wire rope.
Anti-rust Treatment and Maintenance: The cleaned wire rope needs to be treated promptly for anti-rust. The commonly used anti-rust method is to apply special anti-rust oil for wire ropes. When applying anti-rust oil, use a brush or sprayer to evenly apply the anti-rust oil to each strand of the wire rope, ensuring the anti-rust oil can fully penetrate the gaps between the wires to form a compelling protective film, isolating air and moisture and preventing the wire rope from rusting and corroding. In addition, the wire rope's wear and broken wires should also be checked regularly. By relevant standards, when the number of broken wires in a twist distance of the wire rope reaches a specific number, or the wire rope's wear exceeds a certain proportion of the original diameter, the wire rope should be replaced promptly to ensure the ship crane's safe operation.
Protective Measures After Cleaning and Maintenance: Continuously Consolidating the Corrosion Prevention Effect
(1) Coating Maintenance and Repair
Regular Coating Inspection: The anti-corrosion coating on the marine crane's surface is an essential barrier against corrosion, and its integrity is crucial for the equipment's anti-corrosion performance. A comprehensive inspection of the hydraulic crane's coating should be carried out every three months to observe whether the coating exhibits phenomena such as peeling, blistering, cracking, or chalking. During the inspection, visual inspection can be combined with tool detection, and parts difficult to observe directly-such as the inside of the boom and hidden places of structural parts-can be inspected with equipment such as endoscopes. At the same time, a coating thickness gauge will be used to measure the coating thickness and compare it with the original coating thickness data to determine the coating's wear.
Coating Repair Method: If local coating damage is found, it should be repaired promptly. For small areas of coating peeling or blistering, use sandpaper to smooth the coating around the damaged area to remove loose coating and rust, then clean the sanded area with a cleaning agent. After drying, apply primer, intermediate coat, and top coat in sequence. The primer should match the original coating to ensure good adhesion; the intermediate coat can enhance the coating's thickness and protective properties; the top coat serves an aesthetic and UV-resistant role. The application of each layer of paint should be operated by the product instructions, controlling the coating thickness and drying time to ensure the repaired coating is closely connected to the original coating, with a smooth appearance and consistent performance. For large-scale coating damage or serious coating aging, it may be necessary to re-coat the entire equipment surface. In this case, a professional coating company should be selected, and construction should be carried out strictly by the coating process requirements to ensure the coating quality and anti-corrosion effect.
(2) Passivation Treatment of Metal Surfaces
Passivation Principle and Applicable Parts: Passivation treatment can be carried out after cleaning and maintenance for some key metal parts prone to corrosion-such as the boom head and slewing bearing raceway. Passivation uses specific chemicals to form a dense passivation film on the metal surface, thereby improving the metal's corrosion resistance. This passivation film slows the corrosion rate by preventing oxygen, moisture, and other corrosive media from directly contacting the metal surface. Passivation treatment suits carbon steel, stainless steel, and other metal materials. However, the passivation and treatment processes applicable to different metal materials vary and must be selected according to the actual situation.
Passivation Operation Process: Taking carbon steel parts as an example, before passivation treatment, the part surface needs to be thoroughly cleaned to remove oil, rust, and other impurities, ensuring the metal surface is clean and smooth. The passivator is then diluted in the prescribed proportion and placed in a special container. The parts to be treated are soaked in the passivation solution, with the soaking time generally 15 to 30 minutes, depending on the passivator type, part material, and size. During the soaking process, ensure the parts are completely submerged in the solution and stir the solution appropriately to allow the passivator to react evenly with the metal surface. After soaking, remove the parts from the solution, rinse the remaining passivator on the surface with clean water, and then dry them with a clean cloth or let them dry naturally. After passivation, the part's surface forms a uniform, dense passivation film, appearing silver-gray or iridescent. In subsequent use, please pay attention to avoiding damage to the passivation film to prevent affecting its anti-corrosion effect.
The cleaning and maintenance of marine cranes is a systematic and meticulous project. From surface cleaning to key parts protection and then to the implementation of protective measures after cleaning, every link is closely linked and indispensable. Only by effectively carrying out cleaning and maintenance work can we eliminate corrosion hidden dangers, prolong the offshore crane's service life, ensure the safe and efficient operation of marine engineering operations, and provide solid and reliable equipment support for marine resource development and infrastructure construction.
