Failure Analysis Of Wd615 (E2-3a) Piston In A Typical Case
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Failure Analysis Of Wd615 (E2-3a) Piston In A Typical Case

On August 19, 2008, our company accepted a Shanghai dealer to sell the piston (model: wd615e2-4a) of Binzhou Bohai piston Co., Ltd. the engine burned oil shortly after replacing the piston. Because the customer did not provide all the damaged parts, we can only organize relevant technicians to analyze the cause of the accident according to the piston ring provided by the customer and the damaged piston:

Accident Phenomenon Of WD615 Piston:

Piston

The top of the six pistons are distributed with more hard carbon deposits in the outer circle near the exhaust valve, and the top is accompanied by reddish brown impurities as a whole.

Some piston skirts are seriously worn on the side pressure surface.

There is a serious hard carbon deposit on the outer circle of the piston head above the first piston ring.

In addition, there are no color spots in the inner cavity of the piston that are caused by overheating and cause the oil to gel.

Piston ring:

second compression ring

First gas ring:

Oil ring:

Accident Phenomenon:

Piston

Piston ring:

a. First gas ring:

b. Second gas ring:

Oil ring:

The movement of the piston ring in the cylinder is extremely complex and has not yet been fully understood. It is generally considered that there are the following movements:

1. Follow the reciprocating motion of the piston.

2. Due to the taper and out of roundness of the cylinder wall and the back pressure of the gas acting on the inner surface of the ring, the piston ring makes an alternating movement of opening and contraction.

3. The ring rotates in the ring groove.

4. Due to the ring groove clearance, the piston ring has axial vibration under the action of gas pressure, inertial force and friction.

5. Due to piston side pressure and cylinder deformation, the ring also vibrates radially.

6. Due to the swing of the piston, the ring also has torsional vibration.

7. Under oil buoyancy, the ring may also produce the so-called “flutter” in the ring groove.

 

The piston ring actually floats freely in the ring groove. It only shows the above movement tendency under various specific use conditions.

3、 Accident overview:

From the above analysis, the piston of the engine did not appear relatively early damage, but the three piston rings showed different degrees of melting wear, corrosion wear and abrasive wear; The early oil channeling of the engine is not due to piston failure, but due to abnormal early wear of the piston ring caused by failure in repair, use and maintenance.

This accident is not a piston quality problem. The company has corresponding explanations for the causes of piston ring damage!

For the corresponding test report, please contact the manufacturer or relevant technical appraisal organization directly.

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