Cause Analysis of Common faults

一、Common fault type

As the moving part of engine cavity, piston ring has a variety of fault causes and complexity. Associated with adverse symptoms associated with the piston ring, the common ones are:

*high engine oil consumption, commonly known as "burning oil or running oil"

*Engine 'gas channeling

* Piston ring fracture

*early wear of piston rings

*piston ring is biased towards wear

* Piston ring matching

* engine noise

二、Common fault analysis

2.1 High oil consumption

1. Cause of piston ring

1）Piston ring leakage

2 ) The design surface pressure of the ring is too small

3）A ring with an outer cone, which causes an inverse cone in production.

4）The thermal stability of the ring is poor, and the elastic force disappears greatly.

5）The size of the ring does not meet the requirements, resulting in improper matching tolerance

2, cylinder hole (sleeve)

1) The inner diameter of the cylinder liner is too large to match the piston ring

2）Cylinder liner circle loss

3）Cylinder block perpendicularity difference

4) The roughness of the inner circle of the cylinder liner does not meet the requirements

5) cylinder liner inner mesh lines do not meet the requirements

6)Cylinder liner material does not meet the requirements

3, valve, oil seal reasons

1）The valve tappet is too long and the valve is not closed strictly

2) The valve gap is too large, and the valve closing is not proper.

3）Valve tube clearance is large

( 4 ) Valve oil seal aging , failure

(5) The valve material does not meet the requirements, and the wear is too large

4. Piston cause

1)The ring groove is uneven

2) Piston ring groove size does not meet the requirements, side gap, back gap is inappropriate

3）Piston with poor thermal stability, deformation and cracking

4) Piston skirt profile line does not meet the requirements

5. Assembly reasons

1) Improper selection of Piston Ring size

2）Outer cones or twisted rings in reverse direction

3）When the ring is installed, the opening of the ring is not staggered

(4) No replacement of the abandoned piston and old cylinder liner

6. Other reasons

(1) The oil gauge is incorrect and the oil level in the oil pan is too high

2) Crankcase ventilation valve hole is blocked, the pressure is too high, the oil is pressed into the combustion chamber

3)The clearance of the bearing is too large and too much oil is thrown into the cylinder wall into the combustion chamber

4) The return hole in the cylinder head is blocked and the oil cannot be returned to the crankcase and consumed

5)Engine temperature is too high and too low

6)Oil leakage

(7)Poor oxidation resistance of oil

8）Engine with supercharger

9) With piston cooling, cooling nozzles not clogged with positive or cooling pipes

10）Cooling system failure

11）Oil system failure

2.2 Engine 'gas channeling

1. Cause of piston ring

①Piston ring leakage

2) Small elastic force of piston ring

3) Large elastic loss rate of piston ring

4) The piston ring is uneven and warp does not meet the requirements

5）Vibration of piston ring

(6) The clearance between the two rings is too small, so that the pressure imbalance between the first and second rings leads to the suspension of the first ring.

2. Piston cause

1)Cracking or burning of piston top

2) Uneven grooves of piston rings

3)Piston outer diameter is small, and the clearance between piston and cylinder liner is too low.

4) The first ring groove of the piston is too large, resulting in a large amount of gas channeling.

3 . Cause of cylinder sleeve

1)The inner diameter of cylinder liner is too large and the ring can not be sealed;

2) The cylinder liner is deformed and the ring can't fit well.

Cylinder liner exceeds standard

4. Other reasons

1) The compression ratio is too large, resulting in the gas channeling down.

2) The pressure of crankcase is too high, resulting in the upward channeling of exhaust gas.

3）Rupture of cylinder gasket

4）Cylinder liner, piston block cylinder, the sealing surface of the failure to escape

5）Cylinder liner, piston ring excessive wear, sealing gas capacity to drop sharply.

6）Gas explosion, combustion chamber pressure.

7）Engine with supercharger, improper or undesirable

2.3 Main causes of Piston Ring fracture

1. Cause of piston ring

1)Piston ring material does not meet the requirements, poor mechanical properties

2) The surface treatment layer of the ring is too thick and the poor fatigue resistance is decreased.

3)The size of the ring does not meet the requirements

4)Damage during installation or transit

2. Piston cause

1)When the ring groove is worn out, the ring is in the shape of a horn, which makes the piston ring break when it is working.

(2) The piston is deformed or cracked by heating so that the ring is deformed and broken under pressure

3) The groove of piston ring is uneven, the ring is stuck and loses elasticity, and is broken by impact.

4) The lower chamfer of the piston ring groove is too small, and a large number of burrs will be produced after operation, which will cause the ring to be stuck and broken.

3 . Cause of cylinder sleeve

1)Cylinder liner with small inner diameter, piston ring opening head stuck and broken

2)The inner diameter of cylinder liner is large, the end gap of ring is large, and the flutter of ring is aggravated and broken.

3)The cylinder liner is wavy and the ring is broken by irregular force.

4)Cylinder liner exceeds the standard, aggravates the working load of the ring.

4. Other reasons

1)Failure due to excessive installation or working stress

(2) The wear of the ring has exceeded its use limit, and the mechanical strength has decreased and the ring has been broken after continuing use.

3) Piston ring and system produce resonance and break

4) steps that do not eliminate the up-and-down point of the old cylinder liner

5)Engine overload operation

6)The engine is detonating and detonating

2.4 Main cause of early wear of piston ring

1. Cause of piston ring

1) The material structure of piston ring does not meet the technical requirements, and the organization is loose.

2) Piston ring has low hardness and does not meet the requirements

3)The thermal stability of piston ring is poor and the metallographic structure changes greatly.

4)Piston ring surface pressure seriously exceeded the standard

2. Cylinder liner cause

Inner diameter of cylinder liner is not up to requirements, is too large or too small

(2) the internal roughness of the cylinder liner does not meet the requirements, and the oil film is not easy to form.

(3) cylinder liner perpendicularity, roundness does not meet the requirements, cylinder liner installation deformation

4）Cylinder liner material gold phase, hardness does not meet the requirements.

3, piston cause

1) The diameter of piston is small, and the oil film is destroyed by gas scouring cylinder wall.

2) The diameter of piston is larger than that of piston, and the friction surface is damaged by the abrasion of cylinder wall.

3) Piston material expansion is too large, abrasion cylinder wall damage friction surface

4,Other accessories

1)Air filtration, poor oil quality, a large amount of dust into the cylinder block, excessive oil impurities

2) Improper selection of friction pairs

5, oil quality

1 ) Poor oil quality

(2) The poor quality of fuel oil and the formation of abrasives or corrosive substances resulting from combustion products that cause abrasive or corrosive wear

6. Repair

1) When repairing, the cleanliness is not enough and there are impurities such as sand or iron in the cylinder block.

2) Improper selection of piston ring or piston dimensions

3) When assembling the moving parts, the torque of the bolts does not meet the requirements.

7. Aspects of use

1）Engine temperature is abnormal, too high, too low will aggravate the wear and tear of the parts.

2）Engine idle speed or high speed movement time is too long, overload operation

3）Engine failure to run and maintain as required.

8, other aspects

1）The wear of piston ring groove is horn shape.

2) Insufficient combustion and serious wear of carbon deposited on the piston groove in the cylinder block

3) Roughness of piston grooves does not meet the requirements (side wear)

4)Engine temperature is too low and too much corrosive substance is formed in the cylinder.

2.5The main cause of bias Wear of Piston Ring

1. Piston cause

1) The center line of the pin hole is not perpendicular to the center line of the piston, and the piston moves towards the cylinder, which causes the piston ring to be worn out.

2) The ring groove plane is not perpendicular to the center line of the piston, and the piston ring is subjected to deflection force.

3) The weight of the piston connecting rod group varies too much by cylinder, and the imbalance of the piston operation causes the piston ring to be worn out.

2, connecting rod cause

1) Bending and deforming of connecting rod, piston moving towards cylinder, causing piston ring to be worn out

2) If the center line of the connecting rod is not parallel, the piston moving towards the cylinder will cause the piston ring to be worn out.

3) If the gap between the big end of the connecting rod and the crankshaft is too large, the piston will move on the cylinder, which will cause the piston ring to be worn out.

3, cylinder liner cause

1)Cylinder liner is worn out of circle due to installation and thermal stress deformation

2) The positioning step of the cylinder liner is not perpendicular to the central line of the cylinder liner, and the piston moves in a split cylinder.

4. Other reasons

1）The center line of the crankshaft is not perpendicular to the center line of the cylinder liner, and the piston is used for the eccentric movement.

2) Using inferior fuel oil, the combustion produces blasting vibration, piston pin and piston being impacted and deformed, which results in the piston moving towards the cylinder.

2.6 The main cause of engine noise

1. Cause of piston ring

1)The piston rings elastic force are small

(2 )The piston ring is broken

(3 ) Impingement of ring and ring groove after excessive wear

4)Piston ring and cylinder liner pull cylinder.

2, The cause of the piston

1)Piston head, skirt diameters and cylinder liner clearance are not suitable to knock on the cylinder, pull the cylinder

2) Piston skirt collides with crankshaft weight distribution block

3)The piston head ruptured and made a noise

(4) The bending deformation of the connecting rod and the offset of the piston running into the cylinder

5)Piston pin and connecting rod bushing too tight.

3, cylinder liner cause

1) The inner diameter of the cylinder liner is too large

2)The two-stroke engine cylinder has a small or no chamfering Angle on the valve hole.

4. Other reasons

1) Twisted deformation of connecting rod

2)Large valve clearance; valve collision with piston; valve spring fracture; valve seat loosening

3)Large crankshaft clearance

4)Engine detonation, detonational ignition; engine deflagration

5)Rocker arm

6) oversize clearance between camshaft and bearing

7)Gear clearance of timing drive is too large or damaged

8)Fan fastening screw loosening or blade breaking

9)Belt slip

2．7The main cause of Piston Ring matching

1. Cylinder bore (sleeve) cause

1) Because of the ellipse passing through the cylinder hole, the rotary movement of the piston ring is not smooth or even stagnated, and the other piston rings of different rings have the corresponding phenomenon in the large part of the lost circle.

2) The deformation of the cylinder hole (sleeve) is too large.

2, The cause of piston connecting rod group

1)Because of the connecting rod bending, piston design requirements such as gravity departures piston connecting rod set on one side of the shock pressure relative to the other side, when the piston ring parts turning to larger pressure of the side, were also shock resistance, poor piston ring rotation or cannot continue to roll, lead to different ring a counterpart in the same place and cannot continue to stagger

3, The reason of mechanical lag

(1) Because piston ring groove burrs, foreign matter and other reasons, the piston ring is sluggish or stuck, resulting in counterpart.

4, assembly reason

1) Piston ring opening is not staggered during assembly.

2.8 Main reasons for engine cylinder pulling

1. Cause of engine cooling system

1)Engine cooling system is short of water, cooling water can not circulate heat dissipation, resulting in the engine temperature is too high

2) The thermostat is out of order and the water circulation is not good.

3)Fan belt too loose or fan cracked, resulting in insufficient air volume and high water temperature

4) Poor water quality, excessive scale deposited in the cylinder water jacket, resulting in poor heat dissipation effect of the cylinder sleeve

2. Cause of engine lubrication system

1) The engine oil is insufficient, the oil pressure drops, resulting in the lack of lubrication or lubrication.

2 ) Oil deterioration , oxidation of oxides and acids under high temperature oxidation , lower lubrication

3)Oil viscosity is too low, high temperature friction surface is not easy to form a thick enough oil film, resulting in poor lubrication

4)Oil temperature is too high, resulting in lower oil viscosity, coking, resulting in piston ring stuck, body wear

3, engine fuel supply system

1) The injection pump is not working well, the fuel supply time is too early and too late, which causes the engine to overheat.

2) excessive fuel supply, resulting in incomplete combustion, serious coke deposition in the combustion chamber and wear of the accelerator parts

3)The injector pressure is too small, the fuel atomization is poor, the fuel injection time is long, resulting in insufficient combustion.

4) The fuel injector is atomized, not completely burnt, forming too much carbon, and the engine performance is reduced.

5) Incorrect fuel injection angle, inadequate mixing of fuel and air, abnormal combustion and excessive engine temperature

4, other reasons

1) The cylinder gap between the piston and the cylinder sleeve is unreasonable, the piston deflects and collides with the cylinder wall.

2) Cylinder liner deformation or cylinder pad damage resulting in cylinder pulling

3) Improper maintenance or failure of the "three filters" of the engine, resulting in the entry of foreign bodies into the cylinder, resulting in the piston pulling cylinder

4) Improper selection of friction payment: for example, chromium-plated cylinder liner used chromium-plated piston ring

5)Long term heavy load, overload operation or long term low load operation

6)Crankshaft connecting rod deformed, piston pin spring off, piston pin running out, etc.