Created on:2021-07-26 09:29

Failure analysis of hydraulic support of coal mine equipment_ Cause analysis and working principle of column damage

Failure analysis of hydraulic support of coal mine equipment_ Cause analysis and working principle of column damage

The column is the main bearing component of the hydraulic support, and its performance plays an extremely important role in the roof maintenance and safety production of the underground working face. Therefore, it is of great significance to find out the damage causes of the column and reduce the damage to the lowest point. The column structure of hydraulic support has three types: single telescopic type, double telescopic type and single telescopic belt mechanical extension type. Taking the double telescopic column as the research object, according to various damage forms, find out the damage reasons and put forward preventive measures.

(1) Cause analysis of column damage

According to the statistics of support overhaul for many years, the damage form and proportion of column in each support overhaul are shown in the table below.

 

Damage form of column

Form of damage

所占比例

 

损坏形式

所占比例

外缸、中缸局部胀缸,上、下腔串液

3%

 

导向套与缸体连接处的密封面损坏

1.5%

中缸、活柱弯曲

4%

 

外缸、中缸内壁锈蚀、磨损

5%

外缸、中缸内壁轴向划伤

3%

 

电镀面碰伤、划伤、镀层脱落

20%

导向套与缸体连接螺纹损坏

1.5%

 

 

 

 

Double telescopic column is composed of outer cylinder, middle cylinder, movable column, bottom valve, guide sleeve, piston and other parts. Its structure is shown in Figure n, and its technical parameters are shown in the table below.

N.jpg

Technical parameters of double telescopic column

立柱

类型

外缸/cm

中缸/cm

活柱/cm

工作

阻力

/kN

外缸

内压

/MPA

中缸

内压

/MPa

总长

/cm

外径×内径×长度

外径×内径×长度

直径×长度

ZFS5100

ZZ560K

ZZP5200

φ24.5×φ20×φ125

φ27.3×φ23×128

φ27.3×φ23×124

φ19×φ16×90

φ22×φ18×93

φ22×φ18×91

φ14×110

φ16×123

φ16×128

1200

1372

1300

38.2

33

31.3

60

54

50.9

335

335.1

321.6

 

 

(2) How it works

① When the control handle is pulled to the lifting position, the high pressure liquid from the control valve enters the piston chamber of the first stage cylinder (outer cylinder) through the pipe joint, so that the second stage cylinder (middle cylinder) extends out first. Once the piston of the second stage cylinder touches the guide sleeve, the liquid in the piston of the second stage cylinder rises. Open the bottom valve (one-way valve) to make the pressure liquid enter the piston chamber of the second stage cylinder, and the movable column extends. At this time, the initial support force is the area of the second stage cylinder multiplied by the oil supply pressure [see Figure o (a)].

② After the column bearing top beam contacts with the top plate, the top plate pressure is transferred from the top beam to the movable column. Because the pressure liquid is closed by the bottom valve, the movable column cannot retract, so the pressure is transferred to the bottom of the secondary cylinder. At this time, the pressure of the piston chamber of the first stage cylinder increases with the pressure of the top plate until it exceeds the working resistance of the column (i.e. the rated working pressure of the safety valve), the safety valve begins to unload, and the second stage cylinder shrinks. When the pressure drops below 90% of the rated working pressure of the safety valve, the safety valve closes and the column begins to bear the load. Before the secondary cylinder is fully retracted, the pressure transmission and the action of the safety valve are repeated. When the secondary cylinder is lowered to the final position, the valve stem of the bottom valve contacts the bottom of the cylinder, the bottom valve opens, and the pressure fluid in the piston cavity of the secondary cylinder enters the piston cavity of the primary cylinder (which can not be reached in the actual use process). This part of pressure fluid raises the secondary cylinder for a certain distance, and the bottom valve closes after leaving the bottom of the cylinder. If the roof pressure exceeds the working resistance of the column, the safety valve will act again, the secondary cylinder will drop to the final position, and the bottom valve will open again. This repeated action ensures that the bearing capacity of the column is within its working resistance range [see Figure o (b)].

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