Methods and selection for removing Contaminants from Diesel Engines of Construction Machinery

Key words:

This paper discusses the main methods for removing dirt from diesel engine parts and the reasonable selection of these methods, and specifically explains the methods for removing carbon deposits, oil stains and water scale from diesel engines.

Key words

Application management of dirt removal from diesel engines of construction machinery

After a diesel engine has been in operation for a period of time, carbon deposits will form in the combustion chamber, intake and exhaust valves, intake and exhaust manifolds, and exhaust pipes due to incomplete combustion. Some machine parts' surfaces may accumulate a layer of oil dirt due to oil leakage and evaporation of oil vapor. For water-cooled diesel engines, a certain thickness of scale will condense in the cooling water cavity. When there is an excessive amount of these contaminants, the performance of the diesel engine will decline, fuel consumption will increase, and the engine temperature will rise. It will also disrupt the normal fit clearance of the components, accelerate the wear and corrosion of the parts, and even cause some malfunctions. Therefore, it is necessary to remove the contaminants in a timely manner. In addition, when diesel engines are maintained and repaired, carbon deposits, oil stains and water scale must also be removed to reduce the failure rate of diesel engines, extend their service life and keep them in good working condition.

1. Methods for removing dirt from diesel engines

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

1.1 Mechanical cleaning

The method of using steel brushes, sandpaper or nylon rollers containing abrasives to wipe off the metal on the surface of parts is widely applied to achieve the purpose of cleaning.

1.2 Solvent Wiping

Wipe with absorbent materials dipped in solvents. Commonly used solvents include petroleum and chlorinated solvents. Many solvents are flammable and can easily cause fires, so non-flammable solvents should be selected. In addition, the type of metal material to be removed should be clearly defined to ensure that the removed parts are not corroded

1.3 Emulsion Removal

Emulsion removal uses organic solvents suspended in water. It can effectively remove oil stains and other dirt, and leave a thin anti-rust oil film on the metal surface. Since this removal method uses solvents, there is a risk of fire. The disposal of waste solvents should be handled with caution.

1.4 Semi-aqueous removal

There are mainly two ways of semi-aqueous removal: One is the aforementioned emulsion removal; Another method is to wipe with a solvent first and then rinse in water. Commonly used solvents include terpenes, esters and hydrocarbon compounds.

1.5 Alkali washing

Alkali metal salts (caustic alkali, silicates and carbonates) mixed with surface activators prepared in appropriate proportions are very effective in removing metal dirt. After dissolving them in hot water and spraying them onto dirty parts, most of the dirt on the metal surface can generally be removed. This method has the lowest cost and is a suitable method for batch automatic cleaning.

1.6 Pickling

Inorganic acids are usually used, but organic acids can also be employed. By adding a wetting agent to the acid aqueous solution, the purpose of rust removal and oxide scale removal can be achieved.

1.7 Steam Degreasing

Steam degreasing uses chlorinated solvents or Freon, which are only used for oil removal. Its main advantage is that it can achieve the effect of oil removal and drying in one step, that is, there is no need for rinsing and drying treatment, and it can be automated. However, the cost is high, and the solvents that escape are harmful substances that seriously affect human health and damage the ozone layer.

2. Reasonable selection of removal methods

In the process of removing dirt from diesel engine parts, it is generally not limited to a single method, but a combination of several methods. Therefore, during the application process, attention should be paid to the reasonable selection of these methods.

2.1 Removal of carbon deposits

Carbon deposits are usually removed mechanically. That is, different tools are selected based on the material of the machine parts, the surface shape of the parts and the quality requirements. Commonly used tools include scrapers, scrapers, copper wire brushes, copper and aluminum metal sheets and sandpaper, etc. For parts with smooth surfaces such as aluminum-copper alloys, when cleaning, it is important to avoid leaving scratches, as scratches can make it easier for carbon deposits to adhere and accumulate.

2.2 Removal of grease

Solvent wiping. The solvents commonly used include light diesel oil, kerosene for lamps, solvent kerosene, washing kerosene, industrial gasoline and aviation washing gasoline. Diesel is used to clean common parts. The parts that have been cleaned will not rust quickly. However, the evaporation rate of diesel is relatively slow. After removal, it should be dried as soon as possible with compressed air to prevent dust contamination in the air. Kerosene and industrial gasoline are used to clean precision machine parts. Aviation cleaning gasoline has strong evaporation properties and is only used to clean special precision machine parts.

Solvent wiping is convenient to operate and has a high cleaning accuracy, but it is not economical. Fire prevention measures must be taken when using it.

(2) Chemical elimination method. The method and steps for removing metal parts by chemical removal are:

a. Select the appropriate formula of cleaning solution;

b. Heat the cleaning solution to 70-90℃;

c. Immerse the components in the washing solution for 10 to 15 minutes and brush them off with a brush.

d. Rinse with clean water;

e. Dry with compressed air.

Rubber, cowhide and other machine parts (such as rubber bowls, rubber rings, etc.) should be cleaned with alcohol. Alkaline solutions must not be used for cleaning; otherwise, the rubber parts will swell, deteriorate and become ineffective.

2.3 Removal of scale

When scale is exposed on the surface of parts, it is generally removed by hand. When manual removal is not convenient, chemical cleaning can be adopted. The method is as follows: Place the item to be removed in an alkaline solution (10-15% sodium hydroxide solution) or an acidic solution (4-6% hydrochloric acid solution), heat to 60-70 ℃, soak for 2-3 hours, and the scale will decompose. Then rinse it clean with clear water.

An example of the comprehensive application of the removal method

3.1 Removal of dirt from the fuel tank

(1) Blow washing method. That is, a portion of diesel is retained in the fuel tank, and then compressed air with a pressure of 19.6 to 29.4KPa is introduced into the bottom of the fuel tank through a plastic pipe, causing the diesel to stir and clean. The position and direction of the lower end of the air pipe are constantly changed to clean the entire fuel tank. Immediately drain the diesel from the fuel tank after blowing and washing, allowing the impurities suspended in the oil to flow out along with the diesel. If the diesel that flows out is dirty, clean it again using the previous method until the oil released is free of impurities.

(2) Steam method. Drain all the diesel, remove the fuel tank, and then add about half a tank of water to the diesel tank. Use a pipe to introduce steam into the water through the fuel filler port to make the water in the diesel tank boil for about 1 hour. In this way, the gum adhering to the inner walls of the box and the remaining diesel molecules can dissolve in water. Light dirt floats on the water surface and is washed away. By doing this twice in a row, the diesel tank can be thoroughly cleaned.

(3) Solvent method. Clean the diesel tank with hot water, then dry it with compressed air to remove the diesel vapor inside. Finally, immerse the diesel tank in a water solution containing 10% sodium hydroxide for washing. After immersion washing, rinse the interior and exterior of the diesel tank with clean water. If rust is found on the outside, clean it with a wire brush.

3.2 Removal of contaminants from the cooling system

Inject a 15% sodium hydroxide solution into the system. After 8 to 12 hours, run the diesel engine. Stop the machine when the water temperature rises to 80 to 90 degrees Celsius. Immediately drain the washing solution to prevent the scale suspended in the solution from settling and blocking the waterways. Then clean the system with clean water until it is completely clean.

If the cylinder head of the diesel engine is made of aluminum alloy, a cleaning solution can be prepared by mixing 50g of sodium silicate, 20g of liquid soap and 10kg of water. Add it to the cooling system and let it run at the working temperature of the diesel engine for about 1 hour. Then drain the cleaning solution and rinse it with clean water.