How to Overhaul the Wear of Marine Cylinder Liners

Cylinder liners are vulnerable spare parts.

The inner surface of the upper part of the cylinder liner is an integral part of the combustion chamber, which is directly affected by the high temperature, high pressure and corrosion of the gas. The relative movement with the piston assembly makes it withstand side thrust and strong friction. The outer surface of the cylinder liner and the inner wall of the cylinder form a cooling effect. Water cavity, subject to cavitation and electrochemical corrosion.

The inner hole of the new cylinder liner has certain dimensional accuracy, geometric shape accuracy and roughness grade. The machining errors of general geometric shapes, such as roundness error and cylindricity error, should be within 0.0125~0.045mm, and the roughness should be within Ra0.4~Ra l.6um. After the cylinder liner is installed on the cylinder block, the geometric shape error increases, and the roundness error and cylindricity error should be controlled within 0.05mm. When the diesel engine is running, the reciprocating motion of the piston moving parts in the cylinder liner causes uneven wear on the inner surface of the cylinder liner, the wall thickness is reduced, and the roundness error and cylindricity error are greatly increased. Usually, when the wear amount of the cylinder liner exceeds (0.4%~0.8%) D (D is the cylinder diameter), the combustion chamber loses its sealing performance. Therefore, excessive wear of the cylinder liner will deteriorate its working performance, reduce the power of the diesel engine and cause damage to other parts.

The wear of the cylinder liner should be detected according to the requirements of the manual and the operation of the diesel engine, and the wear of the cylinder liner should be mastered and controlled to prevent excessive wear.

1. Wear measurement of inner surface of cylinder liner
At present, the wear conditions of the inner surface of the cylinder liner are all using general measuring tools, such as inner diameter micrometers, inner diameter dial indicators or random special inner diameter dial indicators. By measuring the cylinder diameter and calculating the roundness error, cylindricity error or inner diameter increment, the wear rate and comparing with the instructions or relevant standards, the judgment of whether it can continue to be used is finally made.
When measuring, the data of each measurement point should be recorded accurately, and the roundness of each cross section should be calculated according to this data and the maximum roundness should be calculated; Bore diameter increment; compared with the last measurement, the interval between the two measurements is determined so that the wear rate of the cylinder liner during this period of time can be calculated.
Compare the calculated maximum roundness, maximum cylindricity, or maximum inside diameter increment to instructions or standards to determine wear levels and repair options.

2. Maintenance of cylinder liner wear
When the cylinder liner is worn out, all indicators do not exceed the requirements of the instructions or standards, except that there are slight scratches or scratches on the inner surface of the cylinder liner, large grinding table and excessive wear, which can be repaired by maintenance personnel. The general method used is the boring repair method, that is, large pull marks, scratches and grinding tables are generated on the inner surface of the cylinder liner, or the roundness and cylindricity of the cylinder liner exceed the standard, but the inner diameter increment still meets the standard, use Machining (ie, boring) methods eliminate surface damage and geometric errors but the internal diameter increment after boring should still be within the standard.

For example, when the increase of the inner diameter of the cylinder liner exceeds the standard, the boring is carried out on the premise of ensuring the wall thickness and strength of the cylinder liner to eliminate the geometric error of the inner surface of the cylinder liner and the damage such as pull marks, scratches and grinding tables. The rear bore is equipped with a new piston assembly to restore the fit clearance between the cylinder liner and the piston.

After the cylinder liner is repaired, the running-in operation must be carried out before the normal operation of the installed machine, according to the requirements of the manual or depending on the repair condition.
The replacement time of the original and supporting factories of the medium-speed machine is generally 20,000 hours, the replacement time of high-quality professional products is 12,000-1,600 hours, and the counterfeit products are only 6,000 hours. When choosing cylinder liner products, we should pay more attention to quality in addition to comparing prices.

Technical Articles

Cylinder Liner, Overhaul the Wear of Marine Cylinder Liners

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