During the operation of the hydraulic system of the vertical mill, various failures will occur, such as the failure of the grinding roller to rise or the inability to load and pressurize, the rupture and damage of the nitrogen bag of the gas storage tank, and the unstable vibration of the hydraulic system. This article shares 9 fault phenomena and corresponding solutions for the hydraulic system of vertical mills.

1. The nitrogen bladder of the gas storage tank of the accumulator is damaged, there is a “pop” sound, and the pipeline produces shock vibration. Use a special pressure gauge to detect and diagnose whether the pressure of the nitrogen bag in the gas storage tank is reduced or seriously zero. If the pressure is reduced or zero, it means that the nitrogen bag is leaking and damaged. The main reasons are: poor quality of the nitrogen bag, damage to the inlet and outlet valves of the gas storage tank, and impurities in the hydraulic oil, which lead to the damage of the nitrogen bag and the pressure fluctuations, resulting in vibration shock and “banging” noise. Solution: Replace the high-quality nitrogen bladder made by professional manufacturers or replace the damaged inlet and outlet valves of the gas storage tank and improve the structure of the bacteria-type valve to improve the strength of the valve stem, clean the impurities in the hydraulic pipeline and use an oil filter with a filtration accuracy of not more than 5μm. , add hydraulic oil to reach NAS7 grade.

Common faults and treatment of vertical mill hydraulic system

2. Oil leakage from hydraulic pipeline flange. The main reasons are: the aging and damage of the seals or the improper installation, the burrs or the unevenness of the two flanges and the loose bolts of the dislocated flanges, the stressful flanges of the pipelines are not concentric, resulting in oil leakage from the flanges. Solution: replace the aging seal regularly (check once every 12 months); when installing the seal, it should be straightened and completely placed in the groove to prevent the seal from being damaged by extrusion force and failure; adjust the two flanges of the pipeline to be concentric and Parallel and evenly tighten the connecting bolts and fix the pipes firmly to prevent oil leakage.

3. When the oil pump and filter are working normally, the grinding roller is rising normally, and the grinding roller does not drop or the lifting roller does not move when the roller is lowered. The main reason is that the hydraulic oil does not enter the rod cavity of the cylinder, resulting in the inability to pressurize and reduce the grinding roller. The main reason why the lifting rollers do not move is that the hydraulic oil does not enter the rodless cavity and the rod cavity of the cylinder, resulting in the inability to load and lift the rollers. Solution: After analysis and inspection, the three-position four-way solenoid valve is stuck due to wear or oil, and the spool can only work on one side, the other side cannot work, or both sides cannot work normally. The worn three-position four-way solenoid valve should be replaced with a new one; if the oil is dirty, it will be stuck. Disassemble and clean the three-position four-way solenoid valve, and filter the hydraulic oil. The oil cylinder works normally, and the lifting and lowering rollers are normal.

4. Two of the four grinding rollers can be lifted to the limited position, and the other two grinding mill rollers can be lifted slowly, and the rollers cannot be lifted in place within the set time (120s). The main reason: According to the status that there are already two grinding rollers that can be raised, there is no problem with the diagnosis of the hydraulic system, and there is no other mechanical problem. The main reason is that the oil in the other two grinding roller cylinders can also have a compression space, and there is excess gas in the cylinders when the rollers rise slowly. Solution: After the rodless cavity of the cylinder is safely depressurized, use a wrench to loosen the exhaust plug of the cylinder, release the pressure in time to discharge the gas in the cylinder, turn on the oil pump again, and the four grinding rollers are raised at the same time normally.

Common faults and treatment of vertical mill hydraulic system

5. The grinding roller cannot rise. The central control operation activates the roll-up command until the end of the program, and the on-site grinding roll does not rise. According to the operating experience, combined with the principle of the hydraulic control system, the comprehensive diagnosis is that the oil does not enter the rodless cavity of the cylinder or leaks in the pipeline and hydraulic components. main reason:

① The system filter is blocked;

②The oil pump is damaged and no oil enters the rodless cavity cylinder;

③ No rod cavity pipeline leakage;

④ The stop valve on the rodless cavity pipeline is not closed;

⑤ The solenoid valve is still energized or the spool is not in place after the power is turned off;

⑥The hydraulic control check valve is stuck.

Solution:

①Clean the clogged filter;

②Replace the damaged oil pump;

③ Handling flange seals of rodless cavity pipelines;

④Close the shut-off valve connected to the pipeline of the rodless cavity to be tight and leak-free;

⑤ Deal with the power failure of the solenoid valve or clean the solenoid valve spool;

⑥Clean the hydraulic control check valve controlled by the solenoid valve and filter the hydraulic oil. After the above implementation methods are adopted, the hydraulic system works normally, and the grinding rollers are raised normally.

6. The loading pressure of the grinding roller cannot rise, cannot be pressurized, and the grinding roller cannot go down.

main reason:

①The oil circuit stop valve is not closed;

②There is leakage in the rod cavity pipeline;

③ The solenoid valve is still working with electricity or the spool is not in place after the power is cut off;

④The hydraulic control check valve controlled by the solenoid valve is stuck;

⑤ The overflow valve is blocked and the leakage is blocked.

Solution:

①Close the corresponding oil circuit stop valve;

② Deal with the leakage of the rod cavity pipeline;

③ Power off the solenoid valve or clean the valve core;

④Clean the hydraulic control check valve controlled by the solenoid valve;

⑤ Clean the blocked overflow valve. After the above implementation methods are adopted, the hydraulic system works normally, and the pressure drop roller of the grinding roller works normally.

7. The hydraulic oil pump and the hydraulic system of the oil cylinder work normally. After a certain grinding roller is pressurized, the up and down range of the oil cylinder piston is small, and the piston rod expands and contracts small or basically does not move.

main reason:

① Inspection found that the tie rod joint bearing connected with the cylinder piston rod was broken and damaged;

②The lifting lug tie rod has old defect cracks from the thread position.

Solution:

①Remove the joint bearing of the broken tie rod and replace it with a new one, and the grinding roller is loaded and works normally;

②Replace the new lifting lug rod assembly.

8. During the normal production and operation of the mill, the hydraulic system of the oil cylinder works normally, and the oil cylinder shakes up and down as a whole during flash loading. The main reason: the joint bearing of the lifting lug of the oil cylinder base is broken and damaged, and the oil cylinder is not firmly fixed and moves up and down. Solution: Remove the broken joint bearing and replace it with a new joint bearing. After loading, the oil cylinder does not move up and down, and it is fixed and works normally.

9. The hydraulic plunger pump produces noise.

main reason:

① Air is mixed into the oil (formed air bubbles);

②The loosening of the fastening bolts of the axial piston pump or motor produces external vibration;

③ The oil level in the fuel tank is too low;

④The oil temperature is too low and the viscosity resistance is large.

Solution:

①Check the leak point of the system pipeline and exhaust it;

②Tighten loose anchor bolts;

③Add the oil level to the position marked on the scale;

④ Check that the temperature control system, heating system and cooling system are in good condition and work normally to ensure that the oil temperature is automatically controlled. Most of the failures of the hydraulic system of vertical mills are caused by secondary pollution caused by improper maintenance and maintenance, which causes the hydraulic oil to be dirty and the hydraulic valve to be blocked. Doing a good job in daily maintenance, regular maintenance, and timely discovery of hidden troubles can effectively improve production efficiency.


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