An oil failure alarm appeared on the dashboard of a working excavator. Check the oil level and viscosity through the oil dipstick and remove the oil filter to check that the filter is in a normal state. What should I do if there is no suitable detection tool? Inspection? What factors will cause the abnormal oil pressure of the excavator engine in the work project? In response to these problems, the excavator maintenance master made a detailed analysis.
The lubrication system of the diesel engine is mainly composed of the oil pan, the oil pump, the oil filter, the radiator, the main oil passage, the oil passage, the low oil pressure alarm sensor, the high oil temperature alarm sensor, the pressure limiting valve and the bypass Valve composition. There are several reasons for the low oil pressure:
1. The amount of engine oil is insufficient
If the amount of oil is insufficient, the amount of oil in the oil pump will be reduced or the pump will not be lubricated due to the air, so the pressure of the oil will drop. Therefore, the oil level in the oil pan should be checked before working every day to ensure that the oil level is normal. If the oil level is insufficient, the same type of engine oil produced by the same manufacturer should be added.
2. The oil pump does not rotate
If the flat key of the drive gear of the oil pump and the drive shaft are damaged or fall off; the filter is damaged and the oil pump sucks in foreign objects, and the gear is stuck, it will stop the oil pump and the oil pressure will drop to zero. At this time, the damaged flat key or filter should be replaced.
3. Oil pump wear
The clearance between the pump shaft and bushing of the oil pump, the clearance between the gear end face and the pump cover, the flank clearance or the radial clearance are too large due to wear, which will lead to a reduction in the amount of pump oil and a decrease in oil pressure. At this time, the worn parts should be replaced, and the inner surface of the pump cover should be ground to restore the clearance between the end face of the gear and the standard range.
4. The engine temperature is too high
Excessive scaling of the engine cooling system of the excavator, poor heat dissipation, long-term overloading operation or too late fuel supply time of the fuel injection pump will overheat the engine, accelerate the aging, deterioration, and thinning of the engine oil, and leak from each cooperation gap. The pressure is reduced. The scale should be removed, the fuel supply time should be adjusted, and the engine should be operated within the rated load.
4. The clearance between the main bearing and the connecting rod bearing increases
After long-term use of the excavator engine, the gap between the main crankshaft and the connecting rod bearing gradually increases, the leakage increases, and the oil pressure decreases. For every increase of 0.01mm in the fit gap, the pressure drops by 0.01MPa. At this time, the crankshaft can be repaired, and new connecting rod bearings and main bearings can be selected to restore the fit clearance.
5. The bypass valve is damaged
In order to maintain the normal oil pressure of the main oil passage, a bypass valve is provided. If the pressure-regulating spring is softened or improperly adjusted, the matching surface of the valve seat and the steel ball is worn or stuck and is not closed tightly, the oil return amount increases, the main The pressure in the oil passage will drop. At this time, the bypass valve should be removed for inspection, and finally the pressure should be adjusted to the normal range.
6, oil radiator oil leakage
External leakage will pollute the surface of the engine and the pressure will drop; internal leakage will cause the oil to enter the water tank, the cooling effect of the cooling system will become worse, the excavator engine will overheat, the oil will become thinner and the pressure will drop. Remove the radiator, repair or replace it, and restore its function. (Engine protector)
7. Pressure sensor failure or oil passage blockage
If the pressure sensor fails or the oil passage from the main oil passage to the pressure sensor is blocked and the oil flow is not smooth, the oil pressure will drop. The following checks can be made: the engine runs at idle speed, loosen the tubing connector, and observe the oil flow
8. The set pressure of the pressure limiting valve is too low
In the lubrication system, the oil pumped by the oil pump must ensure an appropriate pressure before reaching the lubricating parts of the engine. If the set pressure of the pressure limiting valve is too low, the pressure regulating spring becomes soft or the sealing surface leaks, it will cause the set pressure to be too low. At this time, the pressure limiting valve should be adjusted to restore the pressure to normal.
9. The oil grade is not suitable
Different excavator engines need to add different brands of oil, the same model of engine should also use different brands of oil in different seasons. If the selected engine oil is unsuitable or of inferior quality, the engine will increase leakage due to too low viscosity and reduce the pressure. The engine oil should be selected correctly and reasonably to adapt to different models or seasons.
10. The oil filter is clogged
When the oil filter is blocked and cannot circulate, the bypass valve provided on its base is opened, and the oil directly enters the main oil passage without filtering. If the opening pressure of the bypass valve is set too high, when the oil filter is blocked, it cannot be opened in time, the pressure of the oil pump will rise, the internal leakage will increase, the amount of oil supplied to the main oil passage will decrease, and the oil The pressure will drop. The cleanliness of the oil filter should be ensured; the opening pressure of the bypass valve should be adjusted correctly, and the damaged components or mating surfaces should be replaced or repaired in time to restore their normal working performance.
11. Clogged filter
(engine protector) Under normal circumstances, the oil pressure should be higher at the large throttle than at the small throttle, but sometimes abnormal conditions may occur. If the oil is too dirty or too viscous, it will easily block the filter. When the engine's small throttle is running at low speed, because the oil pump's oil absorption is not large, the main oil passage can still establish a certain pressure, so the oil pressure is normal; but when the throttle is increased at high speed, the oil pump's oil absorption will be due to the filter The resistance is too large and obviously reduced, so the indication of the oil pressure gauge drops because the main oil passage is insufficient. The suction filter should be cleaned or the oil should be changed.
Through the above analysis, we took the oil pressure gauge and oil quality analyzer to the construction site, and used the oil quality analyzer to check the quality of the oil, and found that the viscosity and pollution degree of the oil met the requirements. Connect the oil pressure gauge and measure the oil pressure at low speed and high speed respectively. It is found that the oil pressure is lower than 0.15MPa. Under normal circumstances, the oil pressure is 0.15MPa at low speed and 0.6MPa at high speed, so that you can know that the oil pressure is low. Normal pressure cannot be reached. We checked the bypass valve on the oil filter seat according to the principles of simplicity to complexity, from the outside, and inside. After disassembly, we found that the sealing surface between the steel ball and the seat of the valve was not tight, resulting in oil leakage and reduced pressure. By grinding the sealing surface, the sealing performance is restored, the pressure is adjusted to the standard value, and the oil pressure alarm light goes out, indicating that the machinery is back to normal and the fault is removed.
By eliminating this fault, it means that the mechanical failure is not terrible. As long as you understand the working principle of the system and analyze it carefully, you will be able to eliminate the fault.
