Created on：2021-07-17 10:30

# Boiler hydraulic fault diagnosis and maintenance_ Measures to solve the vibration of coal mill

Boiler hydraulic fault diagnosis and maintenance_ Measures to solve the vibration of coal mill

In order to solve the problem of vibration of coal mill and fracture of loading rod, the best variable loading force of coal mill under the condition of safe and stable operation can be determined by adjusting the variable loading force.

The calculation method in variable load operation is as follows.

P1 -- upper cylinder pressure of hydraulic cylinder, MPa;

P2 -- lower cylinder pressure (back pressure) of hydraulic cylinder, MPa.

The regulation function curve P1 is as follows

p1=X × seven point five × 0.05＋A

Where X -- coal consumption coefficient, which can be set by operators according to operation load;

A -- pressure constant, the set value is 7MPa.

The adjustment function curve P2 is as follows

p2＝(100-Y × 7.5) × zero point zero four three × 0.4+B

Where y is the coal quality coefficient, which can be set by operators according to the coal quality report;

B -- back pressure constant, the set value is 1.5MPa.

The vibration of coal mill is caused by high loading pressure during low load operation. The loading pressure can be changed by changing the coal quality coefficient in the back pressure curve and increasing the back pressure constant of the hydraulic system. In the process of the experiment, three coal mills are selected as the test objects. Each coal mill samples the pulverized coal under different loads, tests the pulverized coal fineness, and optimizes the rotating speed of the rotary separator to determine the best back pressure value of the hydraulic system. When the back pressure constant B is increased to 2.5MPa, the mill runs stably, and the corresponding reduction of loading pressure is as follows:

F=p´2 × S × 3＝1.0 × zero point one one two × three point one four × three × 103 =111.72 (kN)

Where p ′ 2 is the back pressure value (2.5-1.5 = 1.0MPa), s is the area of the lower chamber of the hydraulic cylinder, and constant 3 indicates that each mill has three loads, that is, when the back pressure increases by 1.0MPa, each mill reduces the loading pressure by 111.72kn.

The specific tests are shown in the table below.

Test value of coal mill test

 project 磨煤机编号 10磨 30磨 40磨 磨煤机出力/kgf·s-1 9.1 7.55 9.25 磨煤机电流/A 54 50 51 加载油压/MPa 10.28 9.8 10.3 背压/MPa 3.56 3.1 3.2 分离器转速/r·min-1 60 81 60 一次风量/kg·s-1 22.27 21.5 22.5 煤粉细度(R90)/% 28 30 32 试验结果 合格 合格 合格

The curve of the coal mill after back pressure adjustment is shown in Figure M.

The high loading pressure causes vibration when the coal mill operates at low load, and the back pressure of the coal mill has a great influence. The loading pressure can be changed by changing the coal quality coefficient and increasing the back pressure constant of the hydraulic system. The specific method is to sample the pulverized coal of each coal mill under different loads, test the fineness of pulverized coal, change the rotating speed of rotary separator, and determine the best back pressure value.

After the adjustment of the loading pressure system of the coal mill, the vibration is greatly reduced to a safe value, and the loading rod is no longer frequently broken, which ensures the stable operation of the boiler.

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