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Inspection of common damage to piston vulnerable parts of diesel generator sets

July 22, 2022
The piston is the main moving part of diesel generator crank connecting rod mechanism, including the top, leak-proof part, pin seat part and skirt part, and the cylinder head, cylinder block to form the combustion chamber, the piston work under high temperature gas, piston pin huge mechanical stress and thermal stress, high-speed movement is also subject to the cylinder wall friction. Therefore, the piston is a fragile part of the diesel generator, common damage includes: wear of the piston ring groove, wear of the piston skirt, wear of the piston pin seat hole and damage to the top of the piston.
The most worn part of the piston is the piston ring groove, where the lower plane of the first ring groove is often the most worn. After the ring groove wear, the groove section becomes trapezoidal, the side gap becomes larger, so that the cylinder airtightness becomes poor, and also aggravate the pumping effect, causing "oil" and "gas".
n Piston skirt wear is much smaller than the ring groove, but the skirt and cylinder clearance is too large, will occur poor guidance, resulting in knocking cylinder and lubricant consumption increases.
If the piston pin hole shows early and serious wear, it is mostly due to excessive clearance between piston pin and pin hole or too rough surface. Since the piston pin hole is mainly subjected to the force in the up and down direction, it causes the piston pin hole to wear into an oval shape, and the wear in the up and down direction of the pin hole is the largest. Excessive wear of the piston pin hole will cause a loose fit and a rattling sound, and in severe cases, cracks will appear.
n The damage to the top of the piston is due to deflagration or premature combustion and other abnormal combustion caused by the local burnout and piercing.
For diesel generator piston damage and overhaul analysis, the key practices to prevent piston damage are.
1. strengthen the correct use and maintenance of the fuel supply system, lubrication system and cooling system of the diesel engine.
ü Reasonable adjustment of injection pressure, injection advance angle, to ensure that the injectors work well. Avoid slamming the throttle, long-term overload work, so that the diesel generator always maintain a good technical condition.
ü Correct selection and replacement of lubricating oil to prevent the entry of pollutants, timely cleaning and maintenance of the filter.
ü improve the cleanliness of the intake air, reduce the load of the diesel engine, and avoid overheating, carbon accumulation and deflagration of the diesel engine.
2. in the process of diesel engine maintenance, strictly follow the technical process requirements for assembly and ensure the quality of parts.
By increasing the knowledge of the piston, understand clearly its structural characteristics and role, deepen the understanding of the characteristics of the common damage to the piston, learn how to judge whether the piston can continue to use and do a good job of prevention of piston damage, the user can greatly reduce the occurrence of unit failure.