Created on:2021-10-14 13:35

Locomotive equipment_ Failure of locomotive hydrostatic system

Locomotive equipment_ Failure of locomotive hydrostatic system

The cooling fan of a DF4B diesel locomotive adopts hydrostatic technology, which can meet the cooling requirements of locomotive diesel engine at different speeds. It controls the flow of working medium flowing into the hydrostatic motor through the throttling speed regulation principle of the temperature control valve in parallel with the static, so as to realize the stepless speed regulation of the cooling fan and ensure that the temperature of diesel engine oil and cooling water is within the required range, which not only reduces the power consumption of the cooling fan, but also improves the economy and service life of the diesel engine.

DF4B diesel locomotive adopts two high and low temperature cooling fans, each equipped with an independent hydrostatic system. The components in the system are exactly the same, which are composed of hydrostatic and hydrostatic motors, temperature control valves, safety valves, hydrostatic oil heat exchangers, hydrostatic oil tanks, high-pressure hoses and other pipe fittings.

Abnormal sound faults often occur in the operation of locomotives. Due to the large number of pipelines and components in the hydrostatic system and the complex system, it is difficult to judge and deal with, which not only increases the maintenance workload, but also prolongs the parking time of locomotive garage, affecting the normal operation order of locomotives. For example, df4b7064 locomotive predicts that there is abnormal sound in the hydrostatic system. After replacing the low-temperature hydrostatic oil tank, replacing the high-temperature temperature temperature control valve, and finally replacing the low-temperature hydrostatic pump, it took more than one month to enter the depot for inspection and treatment several times before the fault was eliminated.

(1) Causes, judgment and solutions of abnormal sound fault

Generally speaking, the working hydraulic cylinder of side louver, hydrostatic oil heat exchanger and high-pressure hose will not produce abnormal sound fault due to their simple structure. Failures often occur in hydrostatic pumps, hydrostatic motors, hydrostatic tanks and temperature control valves.

① Abnormal sound fault of hydrostatic pump and motor ZB732 hydrostatic pump and ZM732 hydrostatic motor adopted by DF4B locomotive are axial plunger type. Except that the shape of pump body and the structure of main shaft extension end are slightly different, their internal structures are completely consistent. The abnormal sound fault of hydrostatic pump and motor can be summarized in the following four aspects.

a. Because the hydrostatic system is not filled with hydraulic oil and there is air in the pipeline or components, strong noise is generated due to the evacuation, compression and expansion of the hydrostatic pump and motor, accompanied by severe pipeline vibration. The judgment of this situation is relatively simple. Just observe the oil level in the hydrostatic oil tank and whether there are a large number of milky white bubbles in the oil tank. If the oil level in the oil tank is low, replenish the oil; If there are a lot of bubbles in the tank, try to exhaust. When exhausting, the diesel engine must be kept at a high speed to rotate the cooling fan, so that the air in the oil pipe of the side louver working cylinder at a high position and the hydrostatic motor can be discharged through the exhaust hole of the oil tank.

b. Abnormal sound is generated due to excessive clearance between the plunger of the hydrostatic pump or motor and the hydraulic cylinder block. When the diesel engine speed drops from high to low, or when the cooling fan works at low speed, if you hear the sound of "rattle, rattle", it is caused. Because when the hydrostatic pump or motor spindle rotates, its connecting rod pushes the hydraulic cylinder block to rotate through the outer wall of the plunger. Because the axis of the hydraulic cylinder block and the main shaft is inclined at an angle of 25 °, each plunger connecting rod group also makes reciprocating motion while rotating, which produces oil absorption and drainage. If the matching clearance between the connecting rod plunger and the plunger hole of the hydraulic cylinder block is too large, it will affect the normal oil absorption and drainage of the plunger. When the speed of the diesel engine is high, due to the high noise at the hydrostatic transmission, the abnormal sound of the hydrostatic pump or motor will be covered up. When the speed of the diesel engine is low, this sound can be obviously heard. When the clearance between the plunger connecting rod group,, oil distribution plate and the hydraulic cylinder block is too large, the oil leakage will increase, which will reduce the volumetric efficiency of the hydrostatic pump and motor. Therefore, it can be judged by measuring its volumetric efficiency. The method is to disassemble the leaking oil pipe joint and collect the leaking oil through the measuring cup.

c. Abnormal sound due to bearing failure of hydrostatic pump or motor. If the hydrostatic pump or motor makes a "clack, Clack" sound when working, and the temperature is obviously high when touching the shell by hand, it is generally due to abrasion, cratering and peeling of the rolling element, working surface or ring mating surface of the inner and outer sleeve of the bearing, or flash, deformation and fracture of the bearing cage. This fault may lead to the jamming of hydrostatic pump or motor, which is very harmful. For example, df483479 locomotive once broke the bearing cage of hydrostatic motor and stuck the main shaft, resulting in the failure of cooling fan and machine failure.

d. Abnormal sound occurs due to excessive fit clearance between the spindle spline of hydrostatic pump and the spline sleeve of hydrostatic transmission. If the roar mixed with "squeaking and squeaking" is heard at the spline of the hydrostatic transmission and increases with the increase of the power consumption of the hydrostatic pump, it is generally due to the poor engagement and abnormal sound caused by the excessive side clearance between the spindle spline of the hydrostatic pump and the spline sleeve of the hydrostatic transmission. For example, df487062 locomotive has abnormal sound due to the wear of hydrostatic pump spindle. The wear trace at the spindle is obvious and there are many metal chips. However, sometimes it is difficult to distinguish this fault from the abnormal sound caused by the fault of hydrostatic oil tank, so we can only use the troubleshooting method.

② Abnormal sound fault of hydrostatic oil tank hydrostatic oil tank is mainly composed of box, oil gauge, magnetic filter, upper nozzle, lower nozzle, oil filler, oil plug and temperature sensor. The box body is divided into upper and lower cavities, and the upper cavity is equipped with a magnetic filter to filter the ferromagnetic solid impurities in the hydraulic oil; The lower chamber is an oil replenishment chamber with a nozzle device inside, which not only replenishes the oil leakage in the circuit, but also ensures the oil supply pressure at the oil suction port of the hydrostatic pump. There are mainly two kinds of abnormal sound faults of hydrostatic oil tank.

a. The lower nozzle mounting base of the oil tank is desoldered, resulting in the misalignment of the upper and lower nozzles of the oil tank. At this time, the high-speed hydraulic oil of the upper nozzle cannot be sprayed directly into the lower nozzle, resulting in the high-frequency vibration of the lower nozzle. In this way, the sound of "hiss, hiss" can be heard at the hydrostatic oil tank. If you touch the hydrostatic oil tank, you can feel the obvious vibration of the oil tank. For this fault, just open the oil tank inspection hole cover, check the nozzle mounting seat under the oil tank or knock the mounting seat with a wooden rod to see if it is loose. If dfb3452 locomotive predicts that there is abnormal sound at the hydrostatic oil tank, open the inspection hole cover and find that the mounting base has been desoldered at 2 places. However, it is very troublesome to drain the hydraulic oil every time, and the space at the hydrostatic oil tank is narrow, which affects the accurate inspection and judgment. Therefore, the process shall be revised in time. In view of the shortcomings of the current intermediate repair process, which is aimed at the hydrostatic oil tank without inspection hole cover, it is supplemented that the inspection hole cover must be opened during intermediate repair to check the status of upper and lower nozzles and support joints in the oil tank.

b. The fastening bolts of the magnet plate of the magnetic filter of the oil tank are loose, and the magnet plate produces high-frequency vibration and abnormal sound under the impact of hydrostatic oil. If this fault is not found and handled in time, the magnet plate will loosen, thus blocking the channels of the upper and lower oil chambers. Therefore, the measures of checking the magnetic core of hydrostatic oil tank during each auxiliary repair can be added to the scope of small and auxiliary repair.

③ Abnormal sound fault of temperature control valve temperature control valve is mainly composed of temperature sensing element, valve body, slide valve, valve cover and adjusting screw. Its function is to automatically control the speed change of cooling fan. If the hydrostatic cooling fan just starts to rotate, you can hear the crisp and continuous metal impact sound from the hydrostatic system, which is generally caused by the failure of the temperature control valve.

Because the DF4 locomotive adopts ZB732 hydrostatic pump, there is pulse in the hydraulic oil pumped out. If the matching clearance of the slide valve of the valve body is too large, the periodic impact of the hydraulic oil will cause the slide valve and the valve body to collide and send out a crisp impact sound. If the temperature control valve is disassembled and the slide valve and valve body are observed, the impact trace can be seen on it. This abnormal sound fault generally occurs when the speed of the diesel engine is about 700R / min and the cooling fan is in working state. To eliminate this fault, it is necessary to strictly control the fit clearance between the slide valve and the valve body, close the feed and control the internal quality of the slide valve and the valve body.

(2) Summary

After analyzing the above reasons and taking corresponding measures, the abnormal sound fault of the hydrostatic system of DF4B locomotive is basically eliminated, the operation quality of the locomotive is improved, and the parking time of the locomotive garage is reduced. However, due to the many components of the hydrostatic system and the complex layout of the piping system, it is necessary to make further exploration and research in the production practice to judge the abnormal sound fault of the hydrostatic system in time and accurately.

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