Created on:2021-10-19 10:25

Locomotive equipment_ Fault analysis of locomotive hydrostatic system

Locomotive equipment_ Fault analysis of locomotive hydrostatic system

According to statistics, from January 2003 to the end of September 2005, there were 11 hydrostatic system faults and 123 temporary repair faults in a section, which seriously disturbed the normal order of safe transportation.

Failure cause analysis

① The strong vibration of hydrostatic system pipeline is the direct cause of pipeline fracture. According to the analysis of the following table, it is found that the locomotive causing the pipeline crack of the hydrostatic system has a remarkable common feature that the hydrostatic pipeline has strong high-frequency vibration, the amplitude in the middle of the pipeline is the largest, and it is numb to touch the pipeline by hand. It is easy to produce fatigue crack at the root of pipeline joint, and then pipeline crack and leakage fault occurs. As the pressure of the hydrostatic system is as high as 17Mpa, under the action of such high pressure, the crack expands rapidly, a large amount of oil leaks out, and the hydrostatic pump and motor can not work normally, resulting in the failure of the cooling fan, the rapid rise of the temperature of diesel oil and water without cooling, resulting in the unloading or natural shutdown of the diesel engine, and the locomotive can not continue to run, resulting in engine failure. After investigation and analysis, the causes of pipeline vibration of hydrostatic system mainly include the following aspects.

Vibration detection limit value of hydrostatic system

Pipeline and connector

名称

编号

最大值/g

有效值/g

峭度/(ds/dt)

 

管路、接头

名称

编号

最大值/g

有效值/g

峭度/(ds/dt)

低温液压缸出油管接头

D1

50

15

4

 

高温液压缸出油管接头

G1

20

6

3

低温泵体

D2

45

14

3

 

高温泵体

G2

45

11

3.8

低温温控阀进油管接头上

D3

32

12

2.6

 

高温温控阀进油管接头上

G3

30

10

2.0

低温温控阀进油管管身

D4

70

25

2.5

 

高温温控阀进油管管身

G4

60

30

2.3

低温温控阀进油管接头下

D5

30

8

3.3

 

高温温控阀进油管接头下

G5

30

9

3

低温温控阀出油管接头上

D6

40

15

10

 

高温温控阀出油管接头上

G6

35

12

4.5

低温温控阀出油管中部

D7

45

12

4

 

高温温控阀出油管中部

G7

40

11

3.5

低温温控阀出油管接头下

D8

40

12

5

 

高温温控阀出油管接头下

G8

35

10

4.0

低温安全阀进油管接头上

D9

35

10

3.5

 

高温安全阀进油管接头上

G9

18

5

3

低温安全阀进油管接头下

D10

30

15

6.5

 

高温安全阀进油管接头下

G10

18

5

3

低温安全阀出油管接头上

D11

30

15

6.5

 

高温安全阀出油管接头上

G11

20

6

4

低温安全阀出油管接头下

D12

30

15

6.5

 

高温安全阀出油管接头下

G12

20

6

4

 

a. Low cleanliness is the main cause of pipeline vibration in hydrostatic system. Through the disassembly and inspection of the locomotive with hydrostatic system pipeline crack and leakage fault, it is found that the engine oil of the locomotive with hydrostatic pipeline crack is dirty and has more impurities. Especially, when checking the bottom of hydrostatic oil tank, it is found that there are a large number of impurities or copper powder precipitated, which is also the reason for the failure of the locomotive under medium repair in the factory after running 10000 ~ 20000 kilometers or even thousands of kilometers. As the hydrostatic system is a closed system, impurities will not be brought in from the outside of the system during normal operation. There are two reasons for the existence of impurities in the system: on the one hand, during the assembly process, due to poor protection of fittings and pipeline joints and nozzles, impurities are brought in or foreign matters are dropped; On the other hand, the static pump and pump are poorly assembled or the running in test is not carefully carried out after assembly, resulting in wear after loading, resulting in copper powder, iron powder and other impurities.

b. The open welding of the nozzle fixing seat of the hydrostatic oil tank and the over limit coaxiality of the upper and lower nozzles are an important reason for the vibration of the hydrostatic pipeline. When the hydrostatic system works, the hydrostatic oil with a certain pressure enters the upper oil chamber through the return pipe. After being filtered by the magnetic filter, it is sprayed from the upper nozzle into the lower nozzle at high pressure. After being diffused by the lower nozzle, it enters the oil suction pipe of the hydrostatic pump, so that the free oil suction of the hydrostatic pump becomes pressure oil supply. When the coaxiality of the upper and lower nozzles exceeds the limit (greater than 0.1mm), or the gap between the upper and lower nozzles is too large and too small [required to be (4.6 ± 0.2) mm], it is easy to cause the oil suction of the hydrostatic pump to form a "hole" phenomenon and make the oil pressure fluctuate. When the fixed seat or lower nozzle seat is desoldered, the coaxiality and gap distance between the lower nozzle and the upper nozzle will cause corresponding changes, resulting in unstable oil supply to the hydrostatic pump, resulting in high and low oil pressure of the high-pressure pipeline of the hydrostatic system, resulting in oil pressure fluctuation and impact, resulting in high-frequency vibration of the pipeline.

The poor assembly of the hydrostatic pump and motor and the over limit matching clearance are another main cause of the hydrostatic pipeline vibration. If there are differences in the matching clearance of each plunger of the hydrostatic pump, high-pressure fluctuating oil pressure will be formed during rotation, resulting in pulsating impact and pipeline vibration.

d. Poor function of temperature control valve and hydrostatic safety valve is also a cause of pipeline vibration. As the temperature control valve continuously adjusts the opening size of its plunger slide valve due to the change of oil and water temperature, the oil pressure fluctuates. On the other hand, the slide valve of the safety valve acts with the pressure impact, which also fluctuates the pipeline pressure of the hydrostatic system, resulting in pipeline vibration.

② Another reason for pipeline crack is that the pipeline joint has other force during assembly. Due to the existence of other forces, stress concentration often occurs at the root of the joint, and fatigue crack occurs under the alternating load of high-pressure hydrostatic oil.

③ Hard injury and serious deformation of the pipeline are also one of the reasons for pipeline cracking. It is easy to form stress concentration and fatigue crack at the hard damage and deformation of the pipeline.

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