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How To Check The Piston Clearance Of Diesel Generator Set

Feb. 28, 2023

How to check the piston side clearance, back clearance and opening clearance of diesel generator set?


1、 Check the side clearance.

Side clearance (also called side clearance) refers to the clearance between the piston ring and the groove plane (between the upper and lower planes in the groove). If the side clearance is too large, it will affect the sealing effect of the piston. If the side clearance is too small, it will make the piston ring stuck in the groove.


The measurement of side clearance is to place the piston ring in its respective ring groove and roll around the ring groove for a circle. It should be able to roll freely without looseness and astringency. Use a feeler gauge to measure according to the specified clearance size.


If the side clearance of piston ring is too small, the following methods can be used.


① Place the piston ring on a very fine (No. 00) abrasive cloth for grinding. During grinding, the abrasive cloth should be placed on the flat plate and slightly coated with oil to make the ring close to the abrasive cloth, and carefully and evenly rotate.


② Coat the flat glass with abrasive (emery) and oil, and grind the piston ring flat and fine. If the side gap is too large and the piston ring will not be used, the thickened piston ring shall be used. But the more common method is to replace the piston.


diesel generator set

2、 Backgap inspection.

Back clearance (also called slot clearance) refers to the clearance between the back of the piston ring and the piston ring groove after the piston and piston ring are installed in the cylinder. For the convenience of measurement, it is usually expressed by the difference between the groove depth and the ring thickness (it can be measured with a vernier caliper with a depth gauge). Generally, the piston ring should be 0.2~0.35mm lower than the ring bank to avoid jamming in the cylinder. If the back clearance is too small, the piston ring can be deep.



3、 Check the opening clearance.

Opening clearance (also called end clearance) refers to the clearance between the two ends of the piston ring opening after the piston ring is installed in the cylinder. The size of the opening gap is related to the diameter of the cylinder. The first ring is the largest, and then decreases in turn. If the opening clearance is too large, the cylinder seal is not good. If the opening clearance is too small, the piston ring will be stuck in the cylinder after thermal expansion.


To check the opening clearance of the piston ring, first place the piston ring in the cylinder to be matched, use the piston head to push the piston ring to the non-worn part of the cylinder (or any part of the new cylinder), make the piston ring parallel to the plane of the cylinder block, and then measure the clearance between the two ends of its opening with a feeler gauge.


If its opening clearance exceeds the specified value, it cannot be used, and the piston ring must be replaced. If the opening gap is too small, you can file one end of the ring mouth with a fine file to adjust it. Attention shall be paid when filing: the end face of the ring mouth shall be flat, and chamfer shall be left after filing to prevent the sharp edge of the outer ring mouth from damaging the cylinder, and inspection shall be conducted while filing to prevent excessive opening clearance.


Founded in 1974, Jiangsu Starlight Electricity Equipments Co.,Ltd. is a wholly-owned subsidiary of Jiangsu Starlight Power Group. It is one of the earliest manufacturers of generator sets in China. Starlight Power has 64 sales and service departments, which provide users with long-term technical advice, free debugging, free maintenance, and free training services. Looking forward to your inquiry, for more details, please contact us with sales@dieselgeneratortech.com.

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