Assembly and maintenance of cylinder liner assemblies for imported construction machinery engines

Key words:

The service life of the cylinder liner assembly depends on the following factors

First, the quality of the cylinder liner assembly itself;

Second, the installation accuracy of the cylinder liner assembly. Especially for the cylinder liner assembly where the cylinder liner is a thin-walled semi-finished product, the boring processing accuracy of the cylinder liner and the dimensional and positional accuracy of the body hole are of utmost importance.

Third, the quality of related accessories such as air filters and fuel injectors;

Fourth, daily maintenance and upkeep, especially the control of engine oil cleanliness and engine temperature, are extremely important!

Therefore, choosing a good cylinder liner assembly is only a prerequisite for ensuring the normal operation of the engine. However, its installation, related supporting facilities and maintenance are also extremely crucial.

The influence of the original organism If the original engine block suffers from metal fatigue damage due to long-term use, resulting in insufficient rigidity or changes in positional accuracy, the outer surface of the cylinder liner in the newly replaced cylinder liner assembly will not be able to fit well with the inner surface of the cylinder liner holes in the block, affecting the heat transfer of the cylinder liner and causing excessive thermal load on the cylinder liner, piston, and piston rings (in this case, the temperature measured by a water temperature gauge cannot reflect the true temperature of the cylinder liner) Accelerate the formation of carbon deposits and ring jamming in the piston ring groove oil. Under working conditions, it will be impossible to ensure good sealing performance among the piston, piston rings and cylinder liners, and early oil leakage will inevitably occur.

The influence of boring accuracy: When boring thin-walled semi-finished cylinder liners, if the processing accuracy cannot be guaranteed, causing the gap between the cylinder liner and the piston to be too large or too small, the piston ring, cylinder liner and piston cannot fit well, which will also affect the sealing and lubrication between the piston ring, cylinder liner and piston, and accelerate the wear of the cylinder liner and piston ring.

The impact of air filters: If low-quality air filter elements are installed, the engine will suck in a large amount of dust, rapidly wear the surface of the cylinder liner and piston rings, reduce the tension of the piston rings, deteriorate the sealing performance, and cause a sharp decline in the engine's power performance. In particular, if even very fine sand particles enter the gap between the engine piston and cylinder liner, they will be able to scratch the cylinder liner and piston rings within microseconds, and even cause the high-speed running engine to suffer devastating consequences such as connecting rod breakage and engine block destruction!

The influence of fuel injector quality: Using inferior fuel injectors or not replacing damaged ones will result in poor fuel atomization quality, affecting the normal combustion of the engine. This will seriously impact the combustion efficiency of the engine and the uniformity of operation of each cylinder. Especially the secondary injection that occurs will cause the temperature of the engine piston to rise sharply, accelerate the carbon deposit in the piston ring groove, lead to ring jamming, and affect the service life of the cylinder liner assembly.

The influence of engine oil cleanliness: Using inferior oil filters or not replacing contaminated oil will accelerate the wear of piston rings and cylinder liners. It will also cause the oil nozzle to be clogged by impurities in the oil, losing its ability to spray oil to cool the piston (often with blackening and bluing marks on the inner top of the piston), resulting in excessively high temperatures of the piston liner and piston rings and leading to the failure of the cylinder liner assembly.

The influence of the cooling system: If there is a problem with the cooling system, it will cause the thermal load of the cylinder liner assembly to be too high, especially the temperature at the top of the piston will be too high, which will have a fatal associated destructive effect. It will cause the metal at the head of the piston to burn out and scratch the cylinder liner. It will also cause rapid carbon deposits on the upper wall of the cylinder liner and the oil in the piston ring groove, which will jam the piston rings. This will cause the outer corners of the piston rings to strongly scratch the cylinder liner, damaging the lubricating oil film on the inner wall of the cylinder. It is very likely that there will be severe stepped wear marks on the cylinder liner at the top dead center of the first piston ring.

Long-term tests have proved that the cylinder liner assemblies of the brand's original factory parts that are stably produced will not cause excessive thermal load on the engine. Excessive heat load is not caused by the quality of the cylinder liner assembly itself, but by other reasons. Excessive heat load is the cause of accelerating carbon deposits and ring jamming in the piston ring grooves, leading to abnormal wear of the cylinder liner and piston rings and oil leakage. The damage to the cylinder liner assembly is merely the result of excessive thermal load. Excessive heat load is the most common and fatal cause of damage to cylinder liner assemblies. Cause and effect cannot be reversed.

Therefore, when replacing a new cylinder liner assembly, one should first check the cause of the damage to the original cylinder liner assembly to be replaced. If the cylinder liner assembly to be replaced was originally a genuine part and was not replaced normally due to long-term use, the cause of the damage to the cylinder liner assembly should be identified from the assembly and other systems. If there are problems with other systems and they are not eliminated, problems will arise again shortly after replacing the new genuine cylinder liner assembly. After ruling out the possibility that the replaced cylinder liner assembly was damaged due to other system issues, when it is determined to replace and assemble a new cylinder liner assembly, the following points should be particularly noted:

After disassembling the replaced cylinder liner, the original engine block should be thoroughly cleaned, and its rigidity and positional accuracy should be strictly inspected, especially the concentricity of the cylinder liner holes in the engine block. If the stiffness and positional accuracy of the original engine cannot be remedied, the only option is to update the engine. The engines of imported excavators are all highly reinforced. Most of them use thin-walled cylinder liners, which are prone to deformation during installation. Moreover, the contact area between the cylinder liner holes of the machine body and the outer surface of the cylinder liner is large. If the concentricity of the cylinder installation holes cannot be guaranteed, it won't be long before problems such as the breakage of the upper convex ring band of the cylinder liner or the deformation of the cylinder liner occur, which in turn affects the contact and sealing between the cylinder liner and the piston rings There are major faults such as excessive wear and tear, air leakage and oil seepage.

(2) Ensure the installation quality of thin-walled cylinder liners. Among imported excavator engines, such as S6KT, 6D31T, and 6D34T

To address the issue of easy deformation during the press-fit installation of thin-walled cylinder liners in engines, the supplied cylinder liners are often semi-finished products with machining allowances left on the inner holes (for straight cylindrical thin-walled cylinder liners without a convex ring positioning on the upper part, the ones supplied by the manufacturer must be semi-finished products), allowing users to install the cylinder liners by press-fit and then honing the inner holes of the cylinder liners to eliminate deformation. This requires that during maintenance, the honing of the cylinder liner hole must ensure the accuracy of its inner surface and the concentricity of the cylinder liner hole. Otherwise, problems will arise when in use. In order to guide users in correctly installing thin-walled cylinder liners, IZUMI Company has specially provided the installation honing processing technology specification for semi-finished thin-walled cylinder liners (attached below). When users assemble semi-finished cylinder liners and do not have qualified boring equipment or skilled maintenance technicians themselves, they must send them to a professional factory with advanced boring equipment and skilled boring technicians for boring. The quality of the semi-finished cylinder liner itself is mainly reflected by the material of the cylinder liner and the shape and position tolerance of the outer cylindrical column of the cylinder liner, while the quality of the cylinder liner hole mainly depends on the technical accuracy of the boring equipment and the boring technician's mastery of the shape and position tolerance of the cylinder liner hole, surface accuracy and the clearance of the piston cylinder liner. Incidentally, many counterfeit brand semi-finished thin-walled cylinder liners on the market are primarily due to the material not meeting the requirements. To ensure the firmness of the cylinder liner installed on the engine block, counterfeit product manufacturers adopt the method of increasing the external difference of the cylinder liner. However, this approach has little impact on the lifespan of the cylinder liner itself. The consequence is that it reduces the number of available repairs for the engine block and significantly shortens its lifespan, making it not worth it!

(3) Install the piston rings correctly. It is strictly forbidden to install the first and second gas rings in a misaligned manner or install the first gas ring with the upper and lower sides reversed. Otherwise, serious accidents such as the piston rings being broken and the cylinder liners being scratched will occur very soon after the engine is reinstalled and started.

(4) Strictly inspect and clean the engine cooling system, especially checking the working efficiency of the water pump and the tension of the water pump belt. Prevent the cooling system from failing and causing the engine to overheat.

(5) Replace the contaminated engine oil, clean the oil passage, oil nozzle and intake passage, and install high-quality three filters.

(6) Replace high-quality fuel injectors, fuel pump plungers and fuel outlet valves in a timely manner.

(7) After starting the engine, the load must be gradually increased from small to large for several hours of running-in.

(8) Before allowing the engine to operate normally after the running-in procedure, replace the oil filter element again, and loosen the plug of the oil pan drain hole to remove the metal debris in the running-in oil, or replace it with new oil.

In conclusion, the cylinder liner assembly is the most crucial component in an engine. When selecting it, it is essential to prioritize quality and purchase products with reasonable prices. The IZUMI cylinder liner assembly from the original equipment manufacturer is your best choice with both reasonable price and quality. There are many counterfeit IZUMI cylinder liner assemblies on the market. Please choose genuine IZUMI products. Because if you use counterfeit IZUMI products, apart from having a short service life, frequent replacement will cause related damage to the cylinder liner installation holes of the engine block, and even lead to irreparable consequences. When replacing the cylinder liner assembly, it is necessary to have a technician with genuine experience in the maintenance of imported construction machinery engines take the lead in identifying the cause of the damage to the replaced cylinder liner assembly. Special attention should be paid to checking the technical condition of the engine block and the positional accuracy of the cylinder liner holes. Other factors that may cause damage to the cylinder liner assembly should be eliminated, and the cylinder liner assembly should be replaced carefully. For the supplied semi-finished thin-walled cylinder liners, installation and honing of the inner holes must be carried out strictly in accordance with the process specifications to ensure the quality and concentricity of the inner surface of the cylinder liner. After replacing the cylinder liner assembly, the contaminated engine oil should be replaced. The impurities in the oil passage, oil injector and oil pan should be cleaned. High-quality air filters, diesel filters and oil filters should be replaced. The cooling system should be inspected and adjusted. High-quality fuel injectors with high processing accuracy and good thermal stability should be replaced to ensure the quality of fuel atomization. Be sure to control the overheating of diesel engines! After the engine is reassembled, let the diesel engine undergo several hours of running-in with loads gradually increasing from small to large. By ensuring the quality of the cylinder liner assembly from the purchasing stage to the maintenance, assembly, use and maintenance stage, the engine can work healthily and long, and achieve the best performance.