Created on:2022-02-15 13:27

Cause analysis and measures of oil seal failure of ZM732 hydrostatic motor

Cause analysis and measures of oil seal failure of ZM732 hydrostatic motor

1. Introduction

ZM732 hydrostatic motor is used on DF4B and DF4D locomotives. In the actual working process of ZM732 hydrostatic motor, the main shaft frame oil seal is easy to fail. The hydrostatic oil leaks from the oil seal and is sucked and blown away by the high-speed rotating fan, which is attached to the cooling section, fan blade and top louver in the form of fog, The oil dirt formed after catching dust reduces the heat transfer efficiency of the cooling section, increases the resistance of air flowing through the cooling section, fan blades and top louver blades, and reduces the cooling capacity of the whole cooling system. With the increase of oil leakage at the oil seal, the lack of oil in the hydrostatic system leads to the failure of the hydrostatic motor to drive the fan to rotate, and the oil and water temperature of the locomotive cooling system exceed the normal range, which is easy to lead to diesel engine piston cylinder pulling, oil pressure drop, oil pressure relay action, locomotive unloading, and machine failure and temporary repair, which seriously interfere with the normal transportation order of the railway, It also causes certain economic losses to the locomotive depot.

2. Oil seal failure

Due to tight time and tasks, DF4B and DF4D locomotives are running at full load. Generally, ZM732 hydrostatic motor of locomotives runs at full speed for a long time, and the oil seal of main shaft frame fails frequently. In less than one year, the main shaft frame oil seal of DF4B and DF4D locomotives used has failed at least once. The oil seal assembly drawing is shown in Figure U. Failure mainly takes the following forms.

(1) The outer circumference of the framework oil seal is out of round and leaks oil. The framework oil seal is wrapped with a steel framework. During the manufacturing and installation process, the steel framework is deformed, the outer circumferential surface of the framework oil seal and the inner circumferential surface of the end cover framework oil seal installation hole are not sealed, and the hydrostatic oil leaks from the lower bottom surface of the gland through the gap between them.

(2) Eccentric wear and abnormal wear of the main lip of the framework oil seal. The main lip of the framework oil seal plays the main sealing role. After long-term application, one side of the main lip is seriously worn compared with the other side, resulting in eccentric wear. Seriously, the main lip rubber on one side is completely worn, the main lip spring is in direct contact with the main shaft, the spring is broken, and the main shaft of the hydrostatic motor grinds out a groove along the circumference. The abnormal wear of the main lip and the main shaft also leads to the failure of the main lip seal.

(3) Wrong selection of rubber type of framework oil seal leads to oil leakage. According to the diameter of the spindle oil seal of ZM732 hydrostatic motor and the maximum linear speed or maximum speed, the skeleton oil seal made of acrylate rubber (ACM) shall be selected. When purchasing materials, the working environment at the spindle of the hydrostatic motor was ignored and the skeleton oil seal made of other kinds of rubber was selected, resulting in abnormal wear, poor oil resistance, cracking of the rubber body and leakage of hydraulic oil along the crack.

(4) The wrong model of skeleton oil seal is used, resulting in seal failure. According to the requirements of ZM732 hydrostatic motor drawing, the model sg65 shall be used × ninety × The oil seal is a double lip high-speed oil seal with inner skeleton. The auxiliary lip plays the role of preventing dust and rain from invading into the oil seal along the main shaft. Sometimes the maintenance personnel will mistakenly receive the model SD65 × ninety × The oil seal of L2 is a single lip low-speed oil seal without auxiliary lip. Dust and rain are easy to invade the main lip of the oil seal, thus accelerating the wear of the main lip. In addition, the applicable speed of the latter is low. When the fan rotates at high speed, the sealing effect of the main lip fails.

3. Cause analysis

The skeleton oil seal is the only seal at the shaft extension of the main shaft of ZM732 hydrostatic motor. It is easy to lose its sealing effect due to the harsh application environment, assembly, procurement, selection and material selection. Therefore, to analyze the causes of the failure of the skeleton oil seal, it is necessary to analyze it from three aspects: the objective conditions of the application of the skeleton oil seal in the locomotive cooling system, its own manufacturing requirements and the selection and assembly of the skeleton oil seal according to the working environment and assembly process of the skeleton oil seal.

(1) The manufacturing quality of the framework oil seal itself does not meet the requirements. The manufacturing of framework oil seal should meet the requirements of national standards, but due to the different levels of manufacturers, some finished products have quality problems. For example, the outer circumferential surface and upper surface of the finished skeleton oil seal are not smooth and have model indentation; The diameter of the outer circle is less than 90mm.

(2) The objective conditions for the application of skeleton oil seal in locomotive cooling system are bad.

1) The external environment of skeleton oil seal is dusty, and there is hydraulic oil with temperature not exceeding 100 ℃; In rainy and snowy weather and when cleaning the locomotive roof, water is easy to invade the frame oil seal.

2) Operating parameters and conditions of skeleton oil seal: there is pressure difference P ≤ 0.03mpa in return oil; High spindle speed, maximum speed n = 1500r / min; The diameter of the main shaft at the seal is D1 = 65mm.

(3) Selection and assembly of framework oil seal

1) According to the internal environment of the skeleton oil seal, it is required to seal the return oil with pressure not higher than 0.03mpa and temperature lower than 100 ℃ at the clearance fit; For the external environment, it is required to block the dust, water and corrosive cleaning fluid in the cooling section. The oil seal that cannot play the role of these two aspects at the same time will inevitably cause abnormal wear and failure.

2) When assembling the framework oil seal and the end cap, the framework oil seal is pressed into the end cap seat hole with uneven force, and the steel framework in the oil seal will be deformed due to unilateral knocking and rough assembly; If the radial interference does not meet the requirements, the skeleton oil seal rotates in the end cover seat hole, the cylindrical surface along the axial direction is not sealed, and the hydrostatic oil will leak out from the cylindrical surface, resulting in the failure of the skeleton oil seal.

3) According to the application parameters and references of ZM732 hydrostatic motor spindle skeleton oil seal, the skeleton oil seal made of acrylate rubber (ACM) should be selected. The skeleton oil seal made of other kinds of rubber can not meet the wear-resistant requirements under the rotation speed of the main shaft, which will cause rapid wear and make the oil seal invalid.

The analysis shows that the main reasons for the failure of the skeleton oil seal are poor working conditions, poor manufacturing quality, wrong oil seal model (including the type of rubber) and failure to assemble in strict accordance with the process.

4. Measures

In order to prevent the failure of framework oil seal, the following corresponding solutions are formulated.

(1) Make a special press fitting tool for rubber skeleton oil seal, increase the stress area of the end face of rubber skeleton oil seal when pressing into the end cover seat hole, and press it evenly to prevent skeleton deformation.

(2) Prevent the use of low-speed oil seal instead of high-speed oil sealing vehicle, and use sg65 in strict accordance with the requirements × ninety × 12 rubber frame oil seal; The appearance quality of the oil seal shall be good and the size shall meet the requirements. After the oil seal is pressed in place, it shall be sealed with the axial cylindrical surface of the end cover seat hole to prevent hydrostatic oil from leaking from the cylindrical surface and ensure the normal use of the skeleton oil seal.

(3) In order to adapt to the working environment of the spindle of ZM732 hydrostatic motor, seal the return oil with the pressure not higher than 0.03mpa and the temperature lower than 100 ℃, and block the dust, water and corrosive cleaning fluid in the cooling single section, the double lip rubber inner bone frame oil seal with main and auxiliary lips shall be selected according to the drawing, and the single lip rubber inner bone frame oil seal with only main lip shall not be selected.

(4) In view of the harsh service environment of rubber skeleton oil seal, one rubber skeleton oil seal sg65 of the same specification can be added as shown in Figure v × ninety × 12。 The added rubber skeleton oil seal prevents the invasion of external dust and other pollutants and protects the auxiliary lip of the original skeleton oil seal; Under the condition of oil leakage, the main seal lip plays a role in the failure of the hydraulic seal. The added rubber frame oil seal mounting seat can be made according to figure W.

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By taking the above measures, the failure of the rubber skeleton oil seal of the spindle of ZM732 hydrostatic motor has been effectively controlled, and there has been no machine damage and temporary repair caused by the failure of the oil seal for half a year, which eliminates the out of range repair of the fan caused by the failure of the oil seal, saves a lot of manpower and material resources, reduces the maintenance cost of the locomotive and ensures the operation safety of the locomotive.

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