Abstract: The oil pump is the core component of the lubrication system of diesel generators, and the causes of diesel generator failures are mostly due to abnormal wear and tear of the oil pump. The oil circulation lubrication provided by the oil pump ensures the normal operation of the diesel generator. If the oil pump experiences abnormal wear or damage, it will directly lead to the burning of the diesel generator tiles or even damage, with very serious consequences. So, the normal operation of the oil pump can effectively ensure the normal operation of the diesel generator. This article mainly analyzes the abnormal wear phenomenon of the oil pump of the diesel generator, and proposes specific maintenance methods based on the problems that occur to ensure the continuous and stable operation of the diesel generator.
1、 Working principle of oil pump
The main function of the diesel generator oil pump is to force clean oil with a certain pressure and suitable temperature to circulate back and forth inside the diesel generator, thereby lubricating and cooling various moving parts of the diesel generator. When the diesel generator is in operation, the crankshaft drives the oil pump drive shaft to rotate, and the main shaft drives the drive gear or inner rotor to rotate. As the oil pump drive shaft rotates, the volume chamber of the oil pump inlet gradually increases and generates a vacuum. The oil is sucked into the oil inlet under the pressure difference. During the continuous rotation of the oil pump drive shaft, the gear or rotor volume chamber of the oil pump is filled with oil, The volume chamber begins to decrease and the pressure increases. Under the pressure compression, the oil is discharged, and the oil achieves reciprocating circulation flow.
The main function of the oil pump is to ensure that the lubricating oil can continuously circulate and flow in the lubrication system. Under the circulation of lubricating oil, not only can the frictional resistance of moving parts be reduced, but also the heat generated by each moving part during operation can be effectively carried away. Secondly, the oil pump can also play a cleaning role while completing the oil circulation lubrication. The oil circulation can take away various powders generated by high-speed rotating friction of the parts. Finally, a layer of oil film is formed on the surface of the parts to protect them, so the oil pump is the core component of the lubrication system of the diesel generator. The oil pump is mainly divided into flat installation, horizontal installation, and plug-in installation according to its internal structure and installation method. Its main components mainly include the outer rotor, inner rotor (gear type is active and driven gear), driving shaft, transmission gear, pump body, pump cover, and pressure limiting valve. The oil pump is an important guarantee for the normal operation of diesel generators.
2、 Analysis of oil pump faults
Only by conducting in-depth analysis of the faults in the diesel generator oil pump can we quickly and targetedly find solutions to the problem of oil pump faults. Effectively avoid the occurrence of abnormal wear and tear of the diesel generator oil pump during use, and improve the operational reliability of the diesel generator. The following text will analyze the causes of oil pump failures.
1. Oil seal detachment
In the customer feedback of the malfunction, oil seal detachment occurred during the actual use of the oil pump, and the installation position of the oil seal. For diesel generator oil pumps, the extraction force of oil seals is mainly affected by factors such as the size of the interference fit between the oil seal and the oil seal hole, the cylindricity of the oil seal hole, and the assembly accuracy of the oil seal. These factors are all concentrated in the extraction force of the oil seal.
(1) Selection of oil seal fit interference
The interference tolerance between the oil seal and the oil seal hole must be selected reasonably. Excessive fit interference can cause the skeleton oil seal to collapse or produce cutting phenomenon during assembly, making the oil seal unable to function properly. A too small fit fit will cause the oil seal to loosen when subjected to internal working pressure of the oil pump. The appropriate amount of interference can refer to mature design experience and necessary experimental verification. The selection of this tolerance is not fixed and is closely related to the material and operating conditions of the oil pump body.
(2) The cylindricity of the oil seal hole
The cylindricity of the oil seal hole has a significant impact on the interference fit of the oil seal. If the oil seal hole is elliptical, there may be a phenomenon where the local fitting surface of the oil seal and the oil seal hole do not fully fit. Uneven clamping force may cause the oil seal to loosen during later use.
(3) Assembly of oil seals
Oil seal detachment and failure caused by assembly issues have also occurred. The failure of pressing is mainly due to the design of the oil seal hole guide structure and pressing method issues. Due to the larger interference between the oil seal and other parts, it is required that the oil pump body oil seal hole has a small angle and a long guiding angle. In addition, the upper and lower press fixtures must be centered to ensure the correct press fit of the oil seal.
2. Excessive crankcase pressure
Excessive internal pressure in the crankcase is also one of the reasons for the failure of the oil pump. During high-speed operation, diesel generators will inevitably generate a certain amount of heat. During operation, gas will enter the crankcase through the piston, which not only pollutes the engine oil but also mixes with the steam in the crankcase, causing an increase in gas in the crankcase. If this situation is not dealt with in a timely manner, it will affect the normal operation of the oil pump, such as oil seal detachment, and more seriously, it can lead to crankcase explosion. At the same time, during the bench and vehicle retest experiments after repairing the faulty diesel generator, the changes in the crankcase pressure of the diesel generator were re monitored, and through repeated experiments, the final conclusion was drawn: if the crankcase remained in a negative pressure state, the fault of oil seal detachment would not occur.
3. Abnormal increase in oil pressure
The oil seal mainly plays a sealing role during the operation of the oil pump, and its sealing performance is crucial. If the oil pressure in the rotor chamber of the oil pump increases abnormally, it may cause the oil seal to fail and cause the oil seal to flush out, resulting in oil leakage during the operation of the diesel generator. Serious safety hazards may even arise. In order to ensure that the oil pressure does not increase abnormally, the oil pump usually sets a pressure limiting valve (also known as a safety valve) on the oil outlet chamber of the oil pump. The pressure limiting valve is mainly composed of a valve core, spring, and valve cover. When the oil pump is working, if the internal pressure suddenly rises abnormally beyond the normal value, under the action of the oil pressure, the valve core will push the spring to act, quickly releasing excess pressure. After the pressure reaches the normal range, the lower limit pressure valve will quickly close under the action of the spring force. The released oil returns to the oil pump inlet chamber or diesel generator oil pan to ensure that the oil pump and diesel generator always operate within a safe pressure range. Experiments have shown that abnormally high oil pressure not only causes oil seal failure, but also intensifies the wear of the inner and outer rotors (or master slave gears) during the operation of the oil pump, while increasing the working noise. The wear of the inner and outer rotors (or master slave gears) directly causes a decrease in the oil pump flow rate, affecting the lubrication of diesel generators.
3、 Maintenance methods
1. Repair method for abnormal increase in oil pressure
If there is an abnormal increase in pressure during the operation of the oil pump, the main reasons include excessive oil viscosity, stuck pressure limiting valve of the oil pump, and blockage of the lubricating oil circuit of the diesel generator.
(1) Reasons for excessive oil viscosity
Mainly due to the user’s failure to select the specified grade of lubricating oil as required, or the fact that the diesel engine has just been ignited and is in the hot engine stage. Because the higher the viscosity of lubricating oil, the poorer its fluidity, making it impossible to circulate quickly in the lubricating oil circuit, and various moving parts of diesel generators cannot receive sufficient lubrication and cooling. To avoid the problem of excessive oil viscosity, users must strictly choose lubricating oil with appropriate viscosity according to the usage environment. At the same time, when the diesel engine is just started, users should be reminded to give the diesel generator enough time to heat up and heat up. When the diesel generator reaches the appropriate temperature (usually 85 ℃~95 ℃), the lubricating oil temperature will also rise to the most suitable temperature. At this temperature, Lubricating oil has good fluidity and can flow freely in the circulating oil circuit. At the same time, it has a certain viscosity, sufficient oil adhesion, and can also form a layer of oil film on the moving parts to protect the friction surface of the moving parts, ensuring reliable lubrication of the diesel generator.
(2) The cause of the oil pump pressure limiting valve sticking
Mainly due to stuck oil pump valve core, poor surface roughness of pressure limiting valve hole, unstable spring, etc. To avoid jamming of the oil pump valve core, it is necessary to select reasonable fitting tolerances and surface roughness in the design of the oil pump valve core and valve core hole, and choose appropriate machining methods during the machining of the valve core hole to ensure the machining accuracy of the valve core hole. The ultimate guarantee is that the valve core can move freely within the oil pump valve core hole. The instability and excessive disturbance of the pressure limiting valve spring are also another main reason for the sticking of the oil pump pressure limiting valve. If the spring is unstable, it will cause abnormal bending of the spring during operation and touch the valve core hole wall. This requires that the spring be designed based on the initial opening pressure and cut-off pressure of the pressure limiting valve, and suitable wire diameter, spring stiffness, compression length, and heat treatment should be selected. During the production process, the spring of the pressure limiting valve undergoes a full elasticity inspection to ensure the stable and reliable operation of the pressure limiting valve through these measures.
2. Repair methods for excessive pressure in the crankcase
Related experiments have shown that if the crankcase force is in a negative pressure state, it will not cause the oil seal to fall off. So it is necessary to ensure that the pressure in the crankcase during the operation of the diesel generator is not too high, which will also prolong the service life of the equipment and reduce the wear of components. If the pressure exceeds the safe range during operation, crankcase ventilation can be implemented. Firstly, check the ventilation status of the crankcase to reduce obstacles and ensure natural ventilation. This can reduce pressure while also reducing energy consumption. However, if abnormal high pressure occurs, mandatory ventilation must be carried out to reduce crankcase pressure. Secondly, during the operation of diesel generator equipment, sufficient oil needs to be provided to ensure the smooth operation of the diesel generator and effectively extend its service life.
Summary:
The oil pump is a device used for forced lubrication in diesel generators. It extracts engine oil, pressurizes it, and sends it into the lubrication system to ensure that the diesel engine is in good lubrication condition. The performance of the oil pump directly affects the lifespan and performance of the diesel generator set, so it is a very important spare part. The above content is about the fault phenomena, causes, and maintenance methods of the oil pump, especially the maintenance methods mentioned above, which are proposed based on the specific causes of abnormal wear of the diesel generator oil pump. They have a certain degree of pertinence and practicality, and can effectively improve the abnormal wear of the diesel generator oil pump.
Post time: Mar-05-2024