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Reasons and Solutions for Oil Pressure Problem of Generator Set

Aug. 10, 2018


When generating set is working, what reasons cause oil pressure gauge and what solution is there?

 

The principle of engine lubrication system produced by engine oil pump shows that the pressure of lubricating oil is mainly due to the resistance of oil flow in the pressure section of the system, and its pressure is related to the flow resistance of oil in the system. The oil pressure is high when the flow resistance of oil in the system is high, and the oil pressure is low when the oil flow resistance in the system.


Reasons and Solutions for Oil Pressure Problem of Generator Sets.jpg


 

In addition, the oil pressure display device is abnormal and the oil pressure value is not correct (that is to say, the oil pressure is too high), so that it is mistaken for the high oil pressure in the lubricating system.

 

 

Common causes of increased resistance to oil flow are as follow.

 

1 Excessive oil viscosity

 

The oil viscosity indicates the internal friction resistance of the oil flow. Oil viscosity is related to engine temperature. When engine temperature is low, engine oil viscosity is large; conversely, engine oil viscosity is small. When the oil viscosity is high, the fluidity is poor, but the seal is good, and the leakage is less. If the oil viscosity exceeds the specified value, the oil flow resistance in the lubrication system will increase and the pressure will increase. It can be seen that when the engine temperature is low or the oil itself viscosity is high (because of improper selection of engine oil grade, that is, engine oil brand number is not suitable for ambient temperature, such as summer oil with high viscosity in winter), the oil pressure will be high.

 

 

2. Too small clearance in pressure lubricating area or clogging of oil filter

 

The flow resistance of lubricating oil cycle loop is equal to the reciprocal sum of parallel branch oil flow resistance. The camshaft journal, connecting rod journal, crankshaft journal, rocker shaft and so on in the pressure lubricating position. If the gap between these lubricating parts is too small, the filter core of the fine filter is too dirty to block the oil circuit, and the pressure limiting valve adjusts the pressure too high, etc. Both will increase the flow resistance and pressure of the lubricating oil system.

 

3. Improper adjustment of pressure limiting valve

 

Pressure limiting valves limit oil pressure by balancing springs and ball valves (or cone valves) so that the oil pressure does not exceed the specified value of the technical documentation. When the oil pressure exceeds the specified value, the spring elastic force overcomes the spring to push the valve open to release pressure into the system. When the oil pressure is lower than the spring elastic force, the valve closes under the action of the spring, thus limiting the pressure to the prescribed range. Therefore, the oil pressure of the lubrication system depends on the spring elasticity. If the spring elasticity is too large, the oil pressure in the system will be too high.

 

Diagnosis and exclusion

 

 

1. In the case of a newly used or guaranteed engine, the oil pressure is obviously too high, indicating that the clearance between the journal and the bearing (tile) in the pressure lubrication position is too small, or the pressure limiting valve adjusts the pressure too high, The clearance between journal and bearing should be carefully checked. If the gap is too small, it should be adjusted or scratched to avoid burning out the matching pair because the gap is too small.

 

2. If the long-used diesel engine oil pressure is too high, indicating that the oil filter is blocked, should be cleaned.

 

3. If the engine oil pressure is too high at low temperature, the engine oil pressure is normal when the engine temperature rises, which indicates that the reason of the high oil pressure is the low temperature of the diesel engine.

 

4. If the oil pressure is significantly higher after oil replacement, the engine oil number is not properly selected. For example, the use of high viscosity in winter oil, that is, the oil pressure will be too high, should be reshuffled seasonally. The higher the number of engine oil (the larger the number), the lower the viscosity, whereas the greater the viscosity of oil. General ambient temperature can be first used with HC-14 oil. HC-11 and HC-8 engine oils with low freezing point can be used in cold northern areas.

 

 

Low oil pressure is one of the common faults of diesel generator set. The method of quick troubleshooting is helpful to solve the problem in time.

 

 

1. Check the oil pressure display device

 

Use replacement method to check, that is to replace the oil pressure gauge or sensor. If the oil pressure display is normal after replacement, the oil pressure display device has trouble. If the oil pressure indicator is normal, the oil pressure is reduced, and the fault is in the lubricating part, the following method should be used to judge.

 

Judging from the temperature of the oil

 

 

If the oil temperature is too low and the oil pressure is low, but when the temperature rises, the oil pressure is normal, it indicates that the oil is too thick and the oil channel is not smooth. For example, although the original impurity blockage of the oil filter is affected to some extent and the oil pressure is also reduced, it is still within the prescribed range. When the oil viscosity is too large, the oil collector will further block up. As a result, the oil pressure decreases again and falls below the specified value, the oil pressure of some diesel engines is too low; the sensor of the oil pressure display device of some diesel engines is set at the end of the lubricating oil line, and when it is difficult to pass through the filter, the oil pressure decreases. When below the specified value, the oil pressure is too low. And then. It is necessary to further investigate the causes of oil thickening (whether the oil number is suitable for the season, oil deterioration, etc.) and the obstruction of the oil channel (such as filter joints, filters, air-cooled radiators, etc.). After ascertaining, should be excluded.

 

If the oil pressure drops when the oil temperature is high, the oil viscosity is too small, or there is a large gap or leakage of friction parts. The reasons for the decrease in viscosity (such as improper selection of engine oil grades, poor quality of oil, poor temperature stability of viscosity, or the mixing of diesel and oil to dilute the oil) should be further identified and observed to see if there is a leak, Or the matching parts (such as crankshaft and bearing, connecting shaft diameter and bearing) which have been used for a long time and pressure lubricated have too big clearance, which should be found out and be dealt with accordingly.

 

2. Judging according to the service life of the equipment

 

If the oil pressure is too low and the failure occurs during the running period, most of the faults are suspected to be acrobatic clogging filters such as metal chips in the machine parts or moulding sand in casting, or if the pipes are bent and shrunken. Or improper assembly of oil leakage (such as too large bearing clearance, pipe joints or joint plane sealing) and so on. Should be easy first and then difficult to find out the reasons and to exclude.

 

 

 

3. Diagnosis by sudden and progressive reduction in oil pressure

 

If the oil pressure drops suddenly, indicate that the pipe or gasket ruptures, should identify and eliminate the leak.

 

If the oil pressure decreases gradually with the prolongation of service time, check whether the oil pressure is clogged, worn, oil deterioration, etc., find out the cause and remove it.

 

If the engine oil pressure decreases gradually in the normal service period, it shows that the oil pressure of the engine bottom is short, the oil path is clogged, the matching gap of the pressure lubrication part is increased, and the oil is deteriorated, which is caused by the decrease of the oil pressure at the same time. In general, a single cause may have an effect on oil pressure, but not too low. In diagnosis, oil storage and deterioration are checked first. If these two items do not meet the requirements, one of the reasons for the reduction of oil pressure is that the filter should be removed again to check the blockage of mechanical impurities. If there is obvious blockage, the fault will be found. You can also check the fit clearance between the crankshaft and the bearings of the associated parts. If wear increases, it is also one of the reasons for the reduction of oil pressure.

 

 

4. Check valve

 

Remove the pressure limiting valve after cleaning and reload and adjust (increase spring elasticity), if the oil pressure increases, it is the fault that the oil pressure is too low.

 

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