Methods for Removing Dirt from Diesel Engines of Construction Machinery and the Selection of Removal Approaches

After a diesel engine has been in operation for a certain period, carbon deposits will form in the combustion chamber, intake and exhaust valves, intake and exhaust manifolds, and exhaust pipes due to incomplete combustion. Some oil stains will accumulate on the surfaces of certain components due to oil leakage and the evaporation of oil vapor. For water-cooled diesel engines, a certain thickness of scale will form in the cooling water cavities. When these contaminants accumulate excessively, they will cause a decline in the performance of the diesel engine, an increase in fuel consumption, a rise in engine temperature, disrupt the normal fit clearance of the components, accelerate the wear and corrosion of parts, and may even lead to some malfunctions. Therefore, it is necessary to promptly remove these contaminants. In addition, during the maintenance and repair of diesel engines, it is also essential to remove carbon deposits, oil stains, and scale to reduce the failure rate of the diesel engine, extend its service life, and maintain its good working condition.

The methods for removing contaminants from diesel engine components are mainly related to factors such as the type, material, size, and quantity of the parts, the requirements for automatic removal, and the overall impact on subsequent operations.

Mechanical removal involves using a steel brush, sandpaper, or a nylon roller containing abrasive materials to achieve the purpose of removal by scrubbing the surface of the metal parts. This method is widely used. When using this method, the choice of tool should be based on the characteristics of the parts. For example, for parts with relatively hard surfaces, a steel brush with appropriate hardness can be used to effectively remove stubborn contaminants. However, for parts with softer surfaces or higher precision requirements, a finer sandpaper or a softer nylon roller should be selected to avoid scratching the surface of the parts and affecting their performance and appearance.

Solvent wiping is carried out by dipping absorbent materials into solvents for wiping. Commonly used solvents include petroleum-based and chlorinated solvents. Many solvents are flammable and prone to causing fires. Therefore, non-flammable solvents should be selected. Additionally, it is necessary to clearly identify the type of metal material being cleaned to ensure that the parts are not corroded. Different solvents have different cleaning capabilities for various contaminants. For example, some solvents are more effective in removing oil-based contaminants, while others are better at dissolving certain types of dirt and stains. When using solvents, appropriate safety measures should be taken, such as ensuring good ventilation in the working area and avoiding contact with the skin and eyes.

Emulsion cleaning uses organic solvents suspended in water. It can effectively remove oil stains and other contaminants and leave a thin anti-rust oil film on the metal surface. However, since this cleaning method uses solvents, there is a risk of fire. Therefore, the disposal of waste solvents should be carried out with great care. When formulating the emulsion, the proportion of the solvent and water needs to be carefully adjusted to ensure the cleaning effect and the stability of the emulsion. In addition, attention should be paid to the compatibility of the emulsion with different metal materials to avoid causing corrosion or other adverse reactions.

Semi-aqueous cleaning mainly has two methods. One is the aforementioned emulsion cleaning, and the other is to first wipe with a solvent and then rinse in water. Commonly used solvents include terpenes, esters, and hydrocarbons. This method combines the advantages of solvent cleaning and water rinsing. By using a solvent to initially dissolve and remove contaminants, and then rinsing with water to remove the remaining solvent and dirt, a better cleaning effect can be achieved. However, it also requires careful selection of solvents and appropriate control of the cleaning process to ensure that the parts are not damaged during the cleaning process.

Alkali metal salts (such as caustic alkalis, silicates, and carbonates) are mixed with surface activators in an appropriate ratio and used together. This is very effective for removing metal contaminants. After dissolving in hot water, the solution is sprayed onto the dirty parts, which can generally remove most of the contaminants on the metal surface. This method has the lowest cost and is a suitable method for batch automatic cleaning. When using alkaline cleaning, the concentration of the solution and the temperature of the hot water need to be properly controlled. An excessively high concentration of the solution or an inappropriate temperature may cause damage to the metal parts, while a too low concentration or temperature may result in an insufficient cleaning effect.

In general, inorganic acids are used, and organic acids can also be applied. By adding a wetting agent to the acid aqueous solution, the purposes of rust removal and scale removal can be achieved. Acid cleaning is mainly used for removing rust and oxide layers on metal surfaces. However, due to the strong corrosiveness of acids, strict safety precautions need to be taken during the operation. At the same time, after acid cleaning, appropriate neutralization and protection measures should be carried out to prevent the metal from being further corroded.

Vapor degreasing uses chlorinated solvents or Freon and is only used for oil removal. Its main advantage is that it can achieve the effects of oil removal and drying in one step, that is, there is no need for flushing and drying processes, and automation can be realized. However, the cost is high, and the escaped solvents are harmful substances that seriously affect human health and damage the ozone layer. With the increasing emphasis on environmental protection and human health, the use of vapor degreasing methods is gradually being restricted, and more environmentally friendly cleaning methods are being sought to replace it.

During the process of removing contaminants from diesel engine components, it is generally not limited to a single method but rather a combination of several methods. Therefore, attention should be paid to the rational selection of these methods during use.

Carbon deposits are usually removed by mechanical methods. That is, according to the material of the components, the surface shape of the parts, and the quality requirements, different tools are selected. Commonly used tools include scraping knives, scrapers, copper wire brushes, copper and aluminum metal sheets, and sandpaper. When removing carbon deposits from parts made of aluminum-copper alloys and other materials with smooth surfaces, care should be taken not to leave scratches because scratches will make it easier for carbon deposits to adhere and accumulate. For example, when cleaning the combustion chamber of a diesel engine, if the surface of the part is made of an aluminum alloy, a soft copper wire brush or a special cleaning tool with a gentle scraping effect should be used to avoid scratching the surface and affecting the performance of the combustion chamber.

The solvents commonly used for solvent wiping include light diesel oil, kerosene for lamps, solvent kerosene, washing kerosene, industrial gasoline, and aviation washing gasoline. Diesel oil is used to clean general components, and the cleaned parts will not rust quickly. However, the evaporation rate of diesel oil is relatively slow, and after cleaning, the parts should be dried with compressed air as soon as possible to prevent contamination by dust in the air. Kerosene and industrial gasoline are used to clean precision components, and aviation washing gasoline, with its strong volatility, is only used to clean special precision components. Solvent wiping is convenient to operate and has a high cleaning precision, but it is not very economical, and fire prevention measures must be taken during use. When using solvents to clean parts, it is necessary to ensure that the working environment is well-ventilated and that there are no open flames or potential ignition sources nearby.

The steps for removing oil stains from metal parts using the chemical cleaning method are as follows:
a. Select an appropriate cleaning solution formulation. The selection of the cleaning solution should be based on the type of metal material, the nature of the oil stains, and the requirements of the cleaning effect. Different cleaning solutions have different cleaning capabilities for different types of oil stains and metal materials.
b. Heat the cleaning solution to 70-90°C. Heating the cleaning solution can improve the solubility of the oil stains in the solution and enhance the cleaning effect. However, the temperature should not be too high to avoid damaging the metal parts.
c. Immerse the components in the cleaning solution for 10-15 minutes and use a brush to scrub them. During the immersion process, the cleaning solution will gradually dissolve the oil stains on the surface of the components. Using a brush to scrub can help remove stubborn oil stains more effectively.
d. Rinse with clean water. After removing the components from the cleaning solution, they should be rinsed thoroughly with clean water to remove the remaining cleaning solution and dissolved oil stains.
e. Dry with compressed air. Finally, the components should be dried with compressed air to prevent rusting due to the presence of water.

For rubber, cowhide, and other components (such as leather cups and leather rings), alcohol should be used for cleaning, and alkaline solutions should not be used. Otherwise, the rubber components will swell, deteriorate, and lose their effectiveness.

When the scale is exposed on the surface of the parts, it is generally removed manually. When manual removal is inconvenient, chemical cleaning can be used. The method is as follows: Place the parts to be cleaned in an alkaline solution (10-15% sodium hydroxide solution) or an acid solution (4-6% hydrochloric acid solution), heat it to 60-70°C, and soak it for 2-3 hours. The scale will then decompose, and it can be rinsed off with clean water. When using chemical cleaning to remove scale, attention should be paid to the safety of the operation. Acid and alkaline solutions are corrosive, and appropriate protective measures should be taken to avoid contact with the skin and eyes.

That is, leave a certain amount of diesel oil in the fuel tank, and then use a plastic tube to introduce compressed air with a pressure of 19.6-29.4 KPa into the bottom of the fuel tank to make the diesel oil churn for cleaning. Continuously change the position and direction of the lower end of the air pipe to clean the entire fuel tank. After blowing and washing, immediately drain the diesel oil from the fuel tank so that the impurities suspended in the oil flow out with the diesel oil. If the drained diesel oil is still dirty, repeat the above method until the drained oil does not contain impurities. This method is relatively simple and can effectively remove the impurities and sediment in the fuel tank. However, it requires attention to the control of the air pressure to avoid causing damage to the fuel tank.

Drain all the diesel oil and remove the fuel tank. Then, fill the diesel fuel tank with about half a tank of water, and introduce steam into the water through a 导管 from the fuel filler port to make the water in the diesel fuel tank boil for about 1 hour. In this way, the gum adhered to the inner wall of the tank and the remaining diesel molecules can be dissolved in the water. The light-weight dirt will float on the water surface and be washed away. After repeating this process twice, the diesel fuel tank can be cleaned thoroughly. The vapor method is more effective in removing stubborn contaminants and can also play a role in sterilization and disinfection to a certain extent. However, it requires the use of steam equipment and careful operation to ensure safety.

Clean the diesel fuel tank with hot water, and then dry it with compressed air to remove the diesel vapor inside. Finally, put the diesel fuel tank into an aqueous solution containing 10% sodium hydroxide for immersion cleaning. After immersion cleaning, rinse the inside and outside of the diesel fuel tank with clean water. If rust is found on the outside, use a wire brush to scrub it clean. The solvent method can effectively remove various contaminants in the fuel tank, but it is necessary to pay attention to the proper disposal of the used solvent to avoid environmental pollution.

Inject a 15% sodium hydroxide solution into the system. After 8-12 hours, start the diesel engine and run it until the water temperature rises to 80-90°C, then stop the engine and immediately drain the cleaning solution to prevent the scale suspended in the solution from precipitating and blocking the water channels. Then, clean the system with clean water until it is clean. If the cylinder head of the diesel engine is made of an aluminum alloy structure, a cleaning solution can be prepared according to the ratio of 50g of sodium silicate, 20g of liquid soap, and 10kg of water, and added to the cooling system. Run the diesel engine at the working temperature for about 1 hour, then drain the cleaning solution and rinse it with clean water. When cleaning the cooling system, it is necessary to pay attention to the compatibility of the cleaning solution with different materials in the cooling system to avoid causing damage to the components. At the same time, after cleaning, it is necessary to check whether the water channels are unobstructed to ensure the normal operation of the cooling system.

In conclusion, the removal of contaminants from engineering machinery diesel engines is a complex and important task. By understanding and rationally applying various cleaning methods, and according to the specific situation of different components and contaminants, we can effectively remove contaminants, improve the performance and service life of diesel engines, and ensure the normal operation of engineering machinery.