Created on:2021-07-22 14:10

Maintenance of steelmaking ladle_ Problems existing in hydraulic station of sliding nozzle

Maintenance of steelmaking ladle_ Problems existing in hydraulic station of sliding nozzle

(1) Hydraulic station of sliding nozzle in ladle

There are three steelmaking and continuous casting production lines in a company. In steelmaking workshop, reliable control of sliding nozzle is the guarantee of normal production. This puts forward very strict requirements for the hydraulic station to control the sliding nozzle of ladle: ① frequent action (30-500 times / furnace), reliable requirement and high sensitivity; ② There is a certain energy reserve, emergency sudden failure; ③ It is easy to operate and maintain; ④ Resistant to high temperature and dust.

There are various forms of hydraulic station, but from the actual use, it is not that the more complex the design, the higher the degree of automation, the better. In the production process, even if the occasional failure can not be solved, the sliding nozzle out of control, the consequences are unimaginable. It will pose a considerable threat to production, equipment and personal safety. Therefore, simple and reliable hydraulic station is the best choice to ensure continuous production.

(2) Problems existing in original hydraulic pressure station

The principle of the original ladle hydraulic station system is shown in Fig. J. From the actual use of steel-making hydraulic station, there are the following deficiencies: 1. Due to frequent action, bad working environment and design reasons, the failure rate is high; ② High maintenance requirements, in the production process, hydraulic workers to track for a long time.

Because the design requirements of the system do not adapt to the actual environment, there are many problems in the operation, such as the oil is easy to pollute and the temperature is difficult to control; Because of the frequent replacement of components, the skin bag is easy to be aged and damaged, and the energy storage effect is poor, so it is difficult to meet the emergency; The operation reliability is poor.

In addition, the tubing pressure relief is not sufficient, the quick coupling is difficult to load and unload, the sealing ring is easy to be washed away by the residual pressure, and the fuel consumption is high. Because some of the above faults can not be handled in a short time, the production is interrupted for a long time and the equipment is seriously damaged. The direct economic loss is hundreds of thousands of yuan every year, and the thermal shutdown is more than 100 hours.

(3) Cause analysis of the problem

Because the hydraulic station is difficult to meet the above requirements, it can not meet the needs of continuous casting production. Specific performance in the following aspects.

① It is difficult to control the oil temperature. There are two ways to control the oil temperature in this hydraulic design.

a. Magnetic assisted electric contact pressure gauge control. The starting and braking of the pump is controlled by the upper and lower contacts of the pressure gauge 5, so as to shorten the running time with load as much as possible, so as to control the oil temperature. Yx-150 pressure gauge is selected in the design, which requires that the inductance current is less than 45mA when the contact voltage is 380V. The inductance current of the contactor controlled by the actual contact is 60mA. Because the control stroke is long (about 40m), the action times are many, and the pressure drop is fast. In order to meet the control requirements, the difference setting range is small (about 40bar). The above factors lead to frequent starting and braking of the pump; Under the condition of over capacity, the contact times are more, and the phenomenon of arc welding appears; The pointer is easy to be damaged, the starting and braking are out of order, and the ideal control effect can not be achieved.

b. Unloading relief valve control (see Figure K for control valve principle). In actual operation, the control pressure range of the valve is greatly affected by the hardness of the cone valve core and the energy storage effect. Due to the influence of practical factors, the pressure drop of the system is fast, the pump runs many times with load, and the impact between the top rod and the poppet valve is frequent, which makes the poppet valve core of the valve easy to be hit bald and the pressure control range is reduced. In addition, the oil temperature of the system often exceeds the appropriate working temperature of the accumulator (10 ~ 70 ℃), the accumulator is charged and released frequently, and the skin bag is easy to be aged and damaged, which makes the nitrogen in the accumulator unable to be charged and the energy storage effect is poor. The accumulator not only can't keep constant pressure, but also can't deal with sudden failure.

The above factors make the pump run with load more times and longer time. Oil temperature is very easy to rise, often up to 100 ℃.

② Commutation reliability is poor. In practice, commutation failure often occurs. Because the hydraulic station adopts the outer cover type oil tank, there is no felt seal at the interface, and the oil is easy to be polluted. In addition, the oil temperature is too high and the viscosity is low, which makes the valve core often stuck and the reversing failure. In order to achieve the purpose of sensitive control, small impact, fast loading and unloading and removing the residual pressure in the pipe when connecting, two three position four-way electromagnetic directional valves with O-type and Y-type middle position function are used for series control. But the probability of commutation failure is doubled.

The system also uses a manual spring positioning two position four-way valve in series with the solenoid valve. Due to the frequent action and the influence of hydraulic shock and vibration, the spool of the valve is easy to be dislocated, which affects the reversing effect.

③ Because the oil is easy to be polluted, the filter screen of one-way filter is easy to be blocked, and the pressure in the pipe can not be fully discharged during unloading. It is difficult to load and unload the quick coupling. When unloading the coupling, the sealing ring inside is easy to be washed away by the residual pressure. The fuel consumption is increased, which needs 2 barrels / month.

④ The components are replaced frequently. Due to the high oil temperature, serious pollution and frequent action, the components are easily damaged. After 2 years of operation, 7 pumps, 11 electromagnetic directional valves, 10 unloading relief valves and 3 accumulators have been replaced.

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