The deformation of the cylinder block and cylinder head of a diesel generator during use is a common phenomenon, and the contact plane often undergoes warping deformation. Usually, deformation of the cylinder block can seriously affect the assembly quality of diesel generators, while deformation of the cylinder head can cause faults such as poor sealing, air leakage, water seepage, and oil leakage in the cylinder, and even damage the cylinder gasket with gas, resulting in a decrease in the power of diesel generators.

① During manufacturing, the aging treatment was not carried out or the aging removal was insufficient. Therefore, the internal stress of the parts is very high. During the operation of the generator set, it is subjected to high temperature, and the internal stress is redistributed to reach a new balance, resulting in deformation of the parts.

② The display agent method applies a layer of display agent on the platform, and places the inspected cylinder head or cylinder block on the platform for grinding. If the display agent is evenly distributed on a flat surface, it indicates that the surface is flat. Otherwise, it indicates that the plane is uneven.

③ When using the measurement method for inspection, stand the ruler on the side of the measured plane and use a thickness gauge to measure the gap between the ruler and the plane (multiple measurements are taken at different positions). When conditions permit, a flatness inspection instrument can be used for measurement.

The flatness error of the plane on the cylinder body shall not exceed 0.05mm within any 50 × 50 (mm2), and the six cylinder generator set shall not exceed 0.25mm on the entire plane; The four cylinder generator set shall not exceed 0.15mm on the entire plane. The flatness error of the lower plane of the cylinder head of a side mounted valve generator set shall not exceed 0.05mm within any 50 × 50 (mm2) range. The six cylinder generator set shall not exceed 0.35mm (cast iron cylinder head) or 0.25mm (aluminum alloy cylinder head) on the entire plane; The four cylinder generator set shall not exceed 0.25mm (cast iron cylinder head) or 0.15mm (aluminum alloy cylinder head) on the entire plane. If the flatness error between the upper plane of the cylinder block and the lower plane of the cylinder head exceeds the above range, it should be repaired.

① When using milling and grinding methods to repair the upper surface of the cylinder block, always use the centerline of the crankshaft bearing hole and cylinder hole as the machining positioning reference. Each upper plane of the machine body is allowed to be repaired up to 2 times, and the amount of each repair should be less than 0.25mm. The total amount of grinding should not exceed 0.50mm.

② After grinding the upper surface of the cylinder block, the height H of the cylinder block should be checked (i.e. the distance from the center of the crankshaft bearing hole to the upper surface of the cylinder block), and its value should be within the allowable range. Different generator sets have different values, so it is important to read the instruction manual when repairing them.

③ At the same time, after milling and grinding the plane of the cylinder block, in order to maintain the normal clearance between the piston and valve and the original compression ratio of the cylinder, thicker cylinder gaskets should be selected.

First, place a steel pad with a thickness of approximately 4 times the deformation of the cylinder head between the cylinder head and the flat plate. Press the pressure plate in the middle of the cylinder head, tighten the bolts, and make the plane in the middle of the cylinder head adhere to the flat surface. Use a small hammer to strike along the reinforcement of the cylinder head 2-3 times to reduce the internal stress generated during compression deformation. After staying for 5 minutes, move the pressure plate to 1/3 of the total length and strike it. Finally, move it to 1/3 of the other end for pressure calibration and striking. If the cylinder head is warped diagonally, the pressure plate should be diagonally pressed against the cylinder head. If there is excessive pressure calibration, the cylinder head can be placed next to the forge and heated for a moment to eliminate it.

After grinding the cylinder head, its thickness will become thinner, the combustion chamber volume will decrease, and the compression ratio will increase, resulting in detonation of the diesel generator. Therefore, when the thickness of the cylinder head is 2mm less than the standard thickness, a new cylinder head should be replaced, or an additional cylinder gasket should be added to continue using when the strength is not significantly affected.

The deformation of the cylinder head after grinding is prone to uneven combustion chamber volume, and the difference in volume change should generally not exceed 4% of the average value of each combustion chamber of the same diesel generator. For general diesel generators, the combustion chamber volume should not be less than 95% of the original specifications. Otherwise, there will be a tendency for detonation. Therefore, the cylinder head needs to be repaired.

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