1. Introduction
Figure Q assembly diagram of spindle and oil seal end cover
1. Cover; 2- Oil seal; 3- Spindle; 4- Oil seal end cap
On the DF4 locomotive, a static hydraulic motor is used to drive the cooling fan and cool the cooling water system to maintain normal oil and water temperatures, thereby ensuring the normal operation of the diesel engine. In practical application, hydraulic motor oil seal leakage often occurs, which not only wastes oil and pollutes the environment, but also may cause abnormal operation of the cooling fan when the oil leakage is severe, resulting in machine damage and temporary maintenance, seriously affecting the transportation safety of railways.
The main shaft of the static hydraulic motor adopts a skeleton oil seal axial sealing structure, and the oil seal model is SG65 × 90 × 12. Its assembly with the main shaft and oil seal end cover is shown in Figure Q.
2. Fault situation analysis
A survey was conducted on 51 DF4 locomotives in a certain locomotive depot. The main task of the locomotives is passenger and freight traction. Due to the large slope fluctuations and multiple tunnels on the line, the working time of the static hydraulic motor at full speed is long, resulting in many faults of oil leakage in the static hydraulic motor oil seal. There have been a total of 22 incidents of hydraulic motor oil seal leakage in the past two years. The main fault locations are as follows:; 12 pieces of spindle wear; 9 oil seals cracked; Other items. The biggest hazard among them is oil seal cracking, as there is a high possibility of machine failure due to the large amount of oil leakage caused by this malfunction; Next is spindle wear.
3. Analysis of Fault Causes
(1) Improper assembly resulted in damage to the oil seal.
In order to ensure good sealing between the oil seal and the oil seal cover, the installation interference fit between the oil seal and the oil seal cover is 0.1-0.2mm. Therefore, a large force is required during the installation of the oil seal into the oil seal cover. In actual assembly, due to the lack of suitable specialized press fit tools, workers often use the wooden handle of a screwdriver or other objects to strike the oil seal, or simply use sharp objects to press the oil seal into the oil end cover. This may cause deformation of the iron skeleton of the oil seal, slight cracks in the oil seal rubber, and other problems after assembly. After installation and use, it may cause oil seal leakage or even oil seal rupture failure.
(2) The spindle of the static hydraulic motor is worn.
The working oil pressure Z of the static hydraulic motor is as high as 14MPa or above. In order to ensure good oil seal function, the inner diameter of the oil seal is about 3mm smaller than the outer diameter of the main shaft, and it is tightly clamped on the main shaft with a spring clamp. There is a certain friction force when the main shaft rotates during operation. In addition, for the cooling fan installed on the hydraulic motor spindle, there is no dynamic balance test device in each locomotive depot. When the fan works at full speed, it causes a certain deflection force on the hydraulic motor spindle, thereby increasing the frictional force mentioned above. Therefore, after long-term use, the spindle generally has a circumferential groove at the sealing belt, which affects the sealing effect of the oil seal. When the groove reaches a certain depth, it may cause oil leakage from the oil seal.
4. Countermeasures
(1) Use thickened oil seal end caps. For the fault of oil seal leakage caused by spindle wear, the traditional treatment method is generally to lift the leaking static hydraulic motor off the vehicle, repair the spindle of the static hydraulic motor with coating or chrome plating, restore the original size, and then put it back into use. This method has many inconveniences in practical situations on site. Firstly, the static hydraulic motor on the vehicle only leaks oil from the oil seal. If the static hydraulic motor is lifted down and completely disassembled, it will inevitably result in a waste of manpower and material resources; Secondly, chrome plating repair for the wear of the main spindle neck circumference of the hydrostatic motor requires a large amount of work and is costly.
We have made a thickened oil seal end cap through observation and analysis. By replacing it with the original oil seal end cap, we can adjust the position of the skeleton oil seal on the main shaft of the static hydraulic motor, move the installation position of the oil seal upward, avoid the wear area of the main shaft of the static hydraulic motor, and make the main shaft reused. The thickened oil seal end cap is shown in Figure R. Simply increase the dimensions of A and B in the oil seal end cap with drawing number DLT220-00-O1-1 by 3mm each.
Figure R thickened oil seal end cap
(2) Use specialized press fit tools for oil seals. For the fault of oil seal rupture, a special tool can be made, as shown in Figure S. When assembling the oil seal, increase the bearing area when the oil seal is pressed down to prevent damage to the oil seal rubber and internal skeleton.
Figure S Oil Seal Pressure Tool
By taking the above measures, the oil leakage of the static hydraulic motor oil seal in the locomotive depot has been significantly reduced, and the machine damage and temporary repairs caused by it have been effectively controlled, and the maintenance cost of locomotives has been reduced, ensuring the safety of train operation.
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2025-04-11