What are the reasons for the large exhaust gas pressure in the crankcase of the diesel generator set?

The poor or non-circulating exhaust gas in the crankcase of the diesel generator set is an important factor that causes carbon deposition in the combustion chamber of the diesel engine, sludge deposition in the crankcase, paint film adhesion on the surface of the parts, as well as the sticky rings of the piston rings, oil channeling and corrosion and wear.

 

Excessive pressure of the lower exhaust gas (crankcase exhaust gas) of the diesel engine of the diesel generator set is one of the common faults of diesel engines. There are many reasons for the excessive pressure of diesel engine crankcase exhaust gas, mainly as follows:

 

(1) The piston ring or cylinder liner is severely worn. If the piston ring or cylinder liner is seriously worn, the seal between the piston and the cylinder liner is not tight, and a large amount of compressed gas will enter the crankcase through the tiny gap between the ring and the cylinder liner during the compression and expansion of the diesel engine, resulting in Crankcase exhaust pressure increases.

 

Accompanying phenomena: serious exhaust under the respirator, insufficient diesel engine power, and blue smoke may also be emitted.

 

(2) Piston ring counterpart. Although the piston rings are not worn, if the openings of the rings are all aligned, a large amount of high-pressure gas will enter the crankcase during the compression and expansion process, resulting in an increase in the exhaust gas pressure of the crankcase.

 

Accompanying phenomenon: The exhaust gas under the diesel engine is serious, the oil consumption increases, and the exhaust gas may emit blue smoke.

 

(3) The piston ring is stuck or broken. The adhesion, fracture or loss of elasticity of the piston ring will cause the cylinder to be loosely sealed, and the combustion gas will flow down into the crankcase, which will greatly increase the exhaust gas pressure in the crankcase.

 

Accompanying phenomena: high crankcase exhaust gas pressure, blue smoke from diesel engine, insufficient power, abnormal noise in the cylinder, etc.

 

(4) The top of the piston is ablated or the cylinder is pulled. Serious ablation of the top of the piston or pulling the cylinder will cause the cylinder to lose its seal, and it is natural that the exhaust gas pressure in the crankcase will increase.

 

Accompanying phenomenon: abnormal noise of diesel engine, black smoke from exhaust, insufficient power or diesel engine cannot rotate.

 

(5) Failure of crankcase breather

 

1. The respirator membrane or (respirator) piston is damaged. Damage to the respirator membrane or (respirator) piston will cause the crankcase to lose balance with the atmosphere, resulting in an increase in the exhaust gas discharge from the crankcase under the action of the internal and external pressure difference.

 

Accompanying phenomena: increased oil consumption, serious blue smoke from exhaust, but basically no effect on power.

 

2. Blockage of the tiny ventilation holes that balance the respirator with the atmosphere. The blockage of the tiny ventilation holes in the balance between the respirator and the atmosphere will make it impossible to maintain the balance between the interior of the crankcase and the atmosphere. Also, under the action of the internal and external pressure difference, the exhaust gas discharge of the crankcase will increase.

 

Accompanying phenomena: increased oil consumption, serious blue smoke from exhaust, but basically no effect on power.

 

(6) The amount of oil refueling is too much. Too much oil refueling will cause the crankcase exhaust gas pressure to increase. This is because the space in the crankcase is limited and the oil is added too much, and the high-speed moving parts such as the crank connecting rod will seriously hit the oil and make it splash, forming oil mist. Causes crankcase exhaust pressure to increase.

 

Accompanying phenomenon: crankcase exhaust gas pressure is high, oil level is too high.

 

(7) There is serious blow-by in the air compressor. If the piston ring of the air compressor is seriously worn, it will cause the compressed gas of the air compressor to enter the crankcase together with the oil, resulting in an increase in the exhaust gas pressure of the crankcase. When there is no problem in checking the piston ring, cylinder liner, breather, etc. of the diesel engine, but the exhaust gas pressure in the crankcase is still large, the air compressor needs to be checked accordingly.

 

Accompanying phenomena: crankcase exhaust gas pressure increases, oil consumption increases, equipment air system pressure builds very slowly, and there is oil. At this time, the quality of the air compressor should be checked, the air system of the equipment should be cleared, and the components such as the air compressor (piston ring, etc.) or the air safety valve should be replaced as appropriate.

 

(8) The main difference between the piston ring or cylinder liner factor and other factors leading to the large exhaust gas pressure in the crankcase.

 

1. The piston ring or cylinder liner is worn, and it is the combustion gas that enters the crankcase. Therefore, the crankcase exhaust gas has a strong smell of combustion gas, while other factors do not have this smell.

 

2. The blow-by gas caused by the piston ring or cylinder liner is easy to make the oil turn black in a short time, and other factors make the oil turn black at a normal time.

 

3. The blow-by gas caused by the piston ring or cylinder liner will lead to insufficient power of the diesel engine, black smoke, abnormal noise in the cylinder, etc., while the blow-by gas caused by other factors does not have these phenomena.

 

(9) The hazard of high crankcase exhaust gas pressure. 1. Increase the oil consumption; 2. The diesel engine emits blue smoke seriously; 3. It is easy to cause carbon deposits on the top of the piston or the piston ring groove, resulting in the failure of the cylinder; Directly introduced into the intake pipe of the diesel engine), which can easily lead to ablation failure of the top of the piston.