# How To Measure The Internal Combustion Engine Cylinder Of Diesel Generator Set

Feb. 17, 2023

The purpose of measuring the internal combustion engine cylinder of diesel generator set is to measure the out-of-roundness and conicity (also known as roundness and cylindricity) of the cylinder, find out the wear degree of the cylinder, and determine whether it can continue to be used. If repair is required, determine the repair scope and repair level.

The cylinder gauge is usually used to measure the cylinder. The measurement steps are as follows.

1、 Determine the original size of the cylinder.

The method is to consult the data records or use the cylinder gauge combined with the outside micrometer measurement to determine. If the original dimension can only be obtained by measuring, it is necessary to measure the upper edge of the cylinder (that is, the upper end of the first piston ring when the piston is at the top dead center) or the lowest part of the cylinder liner to correctly obtain the original cylinder diameter, because these two parts usually do not wear and can represent the original diameter of the cylinder to a certain extent.

2、 Measure the out-of-roundness of the cylinder

In order to ensure the accuracy of measurement, three parts are generally measured.

The first part: the upper part of the cylinder, that is, the position with the largest wear of the cylinder. When the piston is at the top dead center, the corresponding lower part of the first piston ring (about 5-10mm) is about 20mm from the top edge. The second part: in the middle of the cylinder, that is, when the piston is at the top dead center, near the first oil ring, about 40~60mm from the top edge. The third part: the lower part of the cylinder, that is, when the piston is at the bottom dead center, near the second oil ring, about 20~40mm from the bottom edge of the cylinder.

The measurement method is as follows: in the above three positions, measure the cylinder diameter values of the front and rear (perpendicular to the direction of the crankshaft centerline) and the left and right (parallel to the direction of the crankshaft centerline) respectively. The difference between the measured dimensions in the two directions is the out-of-roundness of the cylinder. However, after measurement, the maximum of the three values shall be taken as the basis for the out-of-roundness of the cylinder.

Wear amount of cylinder=maximum diameter - standard size (original size of cylinder).

3、 Measure the taper of the cylinder.

Measure the cylinder diameter values at the front, rear, left and right of the above three parts respectively. The difference between the maximum and minimum values at the upper and lower parts is the taper of the cylinder. As the cylinder is the core component of internal combustion engine, its wear, out-of-roundness and taper are the main basis for determining the repair category of internal combustion engine. When its wear, out-of-roundness and taper exceed a certain range, it will have a serious impact on the working performance of the internal combustion engine.

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