Factors and Diagnosis of Excessive Engine Oil Pressure in Diesel Generators

Do you know why the pressure of diesel engine oil is too high? Today, Dingbo Power takes everyone to understand the reason. The principle of pressure generation in the diesel generator lubrication system by the oil pump indicates that the oil in the lubrication system can generate pressure mainly due to the flow resistance of the oil in the pressure section of the system. The pressure is related to the flow resistance of the engine oil in the system. When the flow resistance of the engine oil in the system is high, the engine oil pressure is high, and when the flow resistance of the oil in the system is small, the engine oil pressure is low. From this, it can be seen that the high engine oil pressure in the lubrication system is inevitably caused by the excessive flow resistance of the engine oil in the system.

In addition, the oil pressure display device is malfunctioning and displays an abnormal oil pressure value (i.e., the oil pressure is displayed as too high), leading to the mistaken belief that the lubrication system oil pressure is too high.

Common causes of increased oil flow resistance in diesel generators include:

(1) Excessive oil viscosity

The viscosity of the engine oil indicates the internal friction resistance when the engine oil flows. The viscosity of engine oil is related to the engine temperature. When the temperature of a diesel generator is low, the viscosity of engine oil is high. On the contrary, when the engine temperature is high, the oil viscosity is low. When the viscosity of engine oil is high, its flowability is poor but its sealing performance is good, resulting in less leakage. If the viscosity of the oil exceeds the specified value, the flow resistance of the oil in the lubrication system will increase, and the pressure will also increase. From this, it can be seen that when the temperature of the diesel generator is low or the viscosity of the oil itself is high (due to improper selection of the oil grade, i.e. the oil grade is not suitable for the ambient temperature, such as selecting oil with high viscosity in summer in winter), the oil pressure will be high.

(2) The clearance between the pressure lubrication parts is too small or the oil fine filter is blocked.

From the lubricating oil circuit, it can be seen that the flow resistance of the lubricating system oil circulation circuit is equal to the sum of the reciprocal of the flow resistance of the parallel branch oil. The camshaft journal, connecting rod journal, crankshaft journal, rocker arm shaft, etc. in the pressure lubrication area. If the clearance between these lubrication areas is too small, the filter element of the fine filter is too dirty, causing the oil circuit to be blocked, and the pressure limit valve is adjusted too high, all of these will increase the flow resistance of the lubrication system oil circuit and increase the pressure.

(3) Improper adjustment of pressure limiting valve.

According to the composition and working principle of the diesel generator pressure limiting valve, the pressure limiting valve limits the oil pressure by relying on a balance spring and a ball valve (or cone valve), and ensures that the oil pressure does not exceed the specified value in the technical documents. When the oil pressure exceeds the specified value, it overcomes the spring force and pushes the valve open to release pressure into the system. When the oil pressure is lower than the spring force, the valve closes under the action of the spring, thereby limiting the pressure within the specified range. From this perspective, the oil pressure of the lubrication system depends on the size of the spring force. If the adjusted spring force is too large, it will cause the oil pressure in the system to be too high.

Diagnosis and troubleshooting

(1) If it is a newly put into use construction machinery or a warranty diesel generator, and the engine oil pressure is significantly too high, it indicates that the clearance between the journal and bearing (tile) in the pressure lubrication area is too small, or the pressure limit valve adjustment pressure is too high. The clearance between the journal and bearing in the pressure lubrication area should be carefully checked. If the gap is too small, it should be adjusted to avoid burning due to the small gap.

(2) If the engine oil pressure of a diesel generator that has been in use for a long time is too high, it indicates that the fine oil filter is blocked and should be cleaned.

(3) If the engine oil pressure of the diesel generator is too high when it is at low temperature, and the engine oil pressure is normal when the engine temperature rises, it indicates that the reason for the high engine oil pressure is due to the low temperature of the diesel engine.

(4) If the oil pressure is significantly too high after changing the oil, it indicates that the oil grade is not selected properly. For example, selecting oil with higher viscosity in winter can cause excessive oil pressure, and it is recommended to switch to a seasonally suitable oil.

If you are interested in diesel generator sets, please feel free to contact us via email dingbo@dieselgeneratortech.com .