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Baotou Beiben heavy truck accessories share with you that the piston ring (the metal ring embedded in the piston groove) is broken, which is one of the common damage forms of the piston ring. Generally, the first and second way piston rings are easy to break, and the broken parts are mostly near the lap joint. The piston ring can be broken into several sections, or it may be crushed or even missing. The broken piston ring will aggravate the wear of the cylinder. The broken ring of a two-stroke diesel engine may be blown into the exhaust pipe or scavenging box, or even into the turbocharger turbine end to damage the turbine blades, causing serious accidents.

In addition to material defects and low processing quality, the common causes of piston ring fracture are mainly due to poor maintenance management and poor assembly quality in use. In peacetime, the following nine situations are the most common:

1、 The lap gap is too small. When the lap gap is less than the assembly gap, the heating temperature of the piston ring increases during operation, which will cause the metal at the lap to expand, resulting in bending at the top of both ends of the lap and breaking near the lap.

2、 Carbon deposition in the ring groove, poor combustion, and overheating of the cylinder wall will lead to oxidation or burning of the lubricating oil, which will cause serious carbon deposition in the cylinder. When the carbon deposit is serious, the ring movement is blocked, the ring and cylinder wall have a strong effect, the scraped lubricating oil and metal chips are mixed, and local hard carbon deposits are formed on the lower end face of the ring groove under the effect of the leaked gas. There is local hard carbon deposit under the piston ring, which is subject to periodic gas pressure, resulting in bending fatigue fracture of the piston ring.

3、 Cylinder liner grinding table, a grinding table appears on the upper part of the cylinder liner after the cylinder liner is worn due to the long-term relative movement between the piston assembly and the cylinder liner. When the piston goes up to the top dead center, the first piston ring is broken due to impact on the grinding table.

4、 The ring groove is excessively worn, and the lower end face of the ring groove is inclined (trumpet shaped) after excessive wear. When the piston is near TDC, the gas pressure makes the ring close to the lower end face of the inclined ring groove, resulting in distortion of the piston ring, excessive wear of the piston ring groove and fatigue fracture.

5、 The piston ring hangs on the air port, and two-stroke diesel engines often get damaged when the piston ring hangs on the scavenging and exhaust ports, causing the ring to break. Since the opening of the piston ring has the largest tension and large thermal deformation, while the ribs between the air ports on the cylinder sleeve are easy to deform when heated. When the piston moves, the ring meets the air port. At this time, as long as the opening of the ring slightly catches the air port, the ring will break.

6、 The piston ring is subject to radial expansion and contraction fatigue. When the elasticity of the piston ring is insufficient or the cylinder liner is excessively worn, the piston ring and the cylinder wall cannot cling closely, that is, the piston ring cannot maintain sufficient air tightness, so that the high pressure gas leakage will press the ring into the ring groove. When the piston goes down, the gas pressure in the cylinder decreases, and the piston ring pops out of the ring groove. The piston ring expands and contracts continuously in a radial direction, causing fatigue fracture.

7、 Excessive wear of the piston ring causes the ring to break because its strength cannot meet the requirements. At present, the piston ring is made of brittle materials such as gray cast iron, alloy cast iron, nodular cast iron, etc. In addition, pores, cracks or component segregation may occur in the internal structure during the casting process, resulting in local strength reduction or stress concentration at the cracks, which may cause impact fracture or fatigue fracture during the work.

8、 When the cylinder liner is severely worn, the shoulder is caused by stepped wear at the upper and lower dead points, or the big end of the connecting rod is greatly worn, or the original dead point position is changed after the big and small end bearings of the connecting rod are repaired, the ring will break due to impact under the action of inertial force.

9、 Cooperation between lubricating oil and fuel oil: From the perspective of fuel oil properties, some fuels contain high sulfur, so there is more SO2 and SO3 produced when the fuel is burned. However, SO2 and SO3 are gaseous at high temperatures, and their direct interaction with metals will cause gas corrosion. It also makes the carbon deposit and colloid deposit hardened, and increases the wear of cylinder liner and piston ring. If the engine does not use the cylinder oil matched with the fuel or uses engine oil to replace the cylinder oil during operation, the ability of the lubricating oil to neutralize the acid generated by combustion will be reduced, and the accessories of Baotou Beiben heavy truck will cause more serious corrosion of acidic substances to the piston and piston ring, resulting in frequent rupture of the piston ring.

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