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The tilting hydraulic cylinder is the core actuator of the hydraulic system, mainly used for controlling the angle positioning and reset of the ladle frame during ladle car movement and ladle tilting operations. It is a key component of the ladle slag removal system and the blast furnace body. This device drives the ladle tilting frame to a set angle and maintains stability through symmetrical hydraulic cylinders, working in conjunction with the slag remover to complete metallurgical operations. In the blast furnace, it undertakes the core actuator function of the furnace tilting structure. It employs coordinated control of hydraulic motors and hydraulic cylinders, integrates a safety locking circuit to prevent pipeline rupture and loss of control, adds a balancing circuit to address the negative load problem caused by the weight of molten steel, and also includes a fault handling circuit that utilizes an accumulator for emergency reset in case of power failure. The system design requirements meet the needs of industrial scenarios such as bidirectional synchronous movement and high-temperature operation. The dual-sided hydraulic cylinder arrangement structure is adaptable to the safety control requirements of tilting 100-ton ladles.
Hydraulic system
Introduction
The ladle car traveling and tilting hydraulic system is a specialized hydraulic system used during ladle slag removal operations to drive the ladle car and tilt the ladle tilting platform to a specific angle under the control of hydraulic cylinders. The ladle car travels using two hydraulic motors that drive the wheels to rotate, thus moving the ladle car. The ladle tilting platform is tilted to a certain angle by two symmetrical hydraulic cylinders (causing the ladle to tilt accordingly), and the cylinders are positioned at that angle. At this point, the slag remover performs the slag removal operation on the ladle. After slag removal, the hydraulic cylinders return the ladle platform to its tilted position. The ladle car traveling and tilting actions require significant force, and given the limited space, high hydraulic control power and small size, hydraulic control is feasible. The design uses hydraulic motors to drive the ladle car and hydraulic cylinders to control the lifting and tilting of the tilting platform. Since the hydraulic motors and cylinders operate on a ladle tilting platform that carries 140-300 tons of molten steel, the safety and reliability requirements for hydraulic control are extremely stringent. The hydraulic system design must consider ensuring the safe and reliable operation of the hydraulic circuit in the event of equipment failure or special circumstances (such as single-cylinder operation, sudden power outage, or pipeline rupture), thereby guaranteeing the safe conduct of ladle slag removal operations.
Basic Requirements:
The ladle car must move smoothly and synchronously in both directions; the ladle car must stop smoothly and must not lurch forward after stopping; it must provide handling conditions in case of failure; it must be able to withstand heavy loads; and it must overcome potential safety hazards caused by high temperatures.
Applications
(1) In the event of a hose rupture, the hydraulic cylinder carrying molten steel must not be allowed to drop uncontrollably or the hydraulic motor transmission to malfunction. A hose rupture or other pipeline problems can cause the hydraulic cylinder to drop uncontrollably (or the hydraulic motor transmission to malfunction), with potentially disastrous consequences. A safety locking circuit is designed and placed at the inlet and outlet of the hydraulic cylinder and hydraulic motor. If a pipeline problem occurs, the hydraulic cylinder and hydraulic motor can be immediately locked in their current positions, preventing accidents caused by loss of control.
(2) During slag removal operations, if a sudden power outage occurs, the ladle may be lifted and tilted, which is unsafe. The ladle must first be leveled and lowered to its seat position (the ladle cannot be lifted if it is not leveled). Then, the ladle should be lifted off the production line as quickly as possible and processed before the molten steel solidifies to avoid scrapping the molten steel and ladle. The fault handling circuit set up in the hydraulic system creates conditions for the safe removal of the ladle from the production line in the event of a fault. This circuit uses the hydraulic energy stored in the accumulator to control the hydraulic valve, so that the hydraulic cylinder tilts down to the ladle seat position by its own weight, facilitating the removal of the ladle from the production line.
(3)During the descent of the hydraulic cylinder, on the one hand, the pressure oil in the upper chamber of the hydraulic cylinder pushes the piston downward, and on the other hand, the weight of hundreds of tons of molten steel and the ladle itself also forms a thrust for the piston to move downward, thus forming a common negative load condition. Overcoming the negative load is essential to ensure the safe tilting of the ladle and achieve the goal of safe production. Adding a balancing circuit on the basis of the safety locking circuit is an effective way to solve the negative load problem. At the same time, we have increased the pressure adjustment range of the balancing circuit, adjusting the pressure to the optimal state while solving the negative load problem.
The equipment’s operating sequence is as follows: the residual electrode aligning device aligns the residual electrode stacks; the chain conveyor transports the aligned residual electrodes to the head; and the residual electrode loading device pushes the stacks into the converter. The specific operation and characteristics of each component are described below:
(I) Aligning Device
1. A forklift transports the stacked residual electrodes from the electrolysis workshop to the tail of the residual electrode feeder and places them on the residual electrode support. Pressing a length adjustment button activates the length adjustment hydraulic cylinders on both sides, causing the baffles to drop to their limit positions. At this time, the forklift operator pushes the stack back and forth 3-4 times using the push plate in the spring-type buffer on the forklift, aligning the stacks along their length.
2. Pressing the width adjustment button activates the width adjustment hydraulic cylinders on both sides, using the alignment push plate to push the stacks back and forth, aligning them along their width. The number of times the hydraulic cylinder pushes back and forth is determined by a pre-set number in the equipment’s counter. If the required number of repetitions has been reached, the width repetition automatically stops. If the repetition does not meet requirements, to control the dimensions of the residual electrode stack and ensure smooth head insertion, the repetition device is equipped with photoelectric tube detection devices in the width and height directions. If the repetitioned residual electrode is too wide or too high, the buzzer will sound an alarm through the photoelectric tube. In this case, auxiliary handling and re-repetition are required.
3.When everything is normal, press the length adjustment confirmation button. At this time, the length adjustment hydraulic cylinder begins its return motion, while the forming hydraulic cylinder falls along the guide frame and applies pressure to the residual electrode stack with the help of the forming pressure plate until the given pressure time has elapsed, at which point the forming hydraulic cylinder returns. The rollers and pressure plate are connected together for guidance. When the hydraulic cylinder returns to its limit position, after a given time, the chain conveyor automatically completes one stack of residual electrodes (i.e., 6 chain plate pitches, totaling 1.8 meters). Then, it begins the alignment operation for the next stack of residual electrodes. This process is repeated until all the residual electrodes required for converter blowing are loaded onto the conveyor. The purpose of alignment is primarily to ensure that the stack of residual electrodes can smoothly enter the chutes of the head unit. The purpose of shaping is to increase the mutual resistance between the residual electrodes, preventing them from scattering and sliding during transportation. If it is confirmed that the conveyed cold material will not scatter, the shaping and pressurizing process can be omitted.
(II) Chain Plate Conveyor:
The chain plate conveyor operates intermittently. First, the aligned residual electrodes are intermittently transported stack by stack to the head of the conveyor at equal intervals, and loaded onto the chain plate residual electrode brackets according to the set number of stacks for temporary storage. During loading, the conveyor stops operating when the first stack reaches the set position at the head of the conveyor, triggered by the photoelectric tube at that head. When it is necessary to add them to the converter, the conveyor again intermittently transports the temporarily stored residual electrodes stack by stack to the head of the conveyor, where they are added to the converter stack by stack by the residual electrode loading device. A photoelectric tube is installed where the conveyor transitions from the inclined section to the horizontal section to detect whether the residual electrode stacks are scattered during transport. If the scattering exceeds a specified value, the equipment stops operating, and operation can only resume after manual handling.
(III) Residual Electrode Loading Device:
Because all operations of this device are program-controlled, the loading and alignment of residual electrodes cannot be performed simultaneously (the capacity of the hydraulic system is also designed accordingly). Every action from the start to the end of the loading operation is automatically performed through the control of time relays, limit switches, various hydraulic components, photoelectric tubes, etc. The main operating instructions are as follows:
1. First, position the converter tuyeres horizontally, ensuring the furnace opening faces the direction of the residual electrode material discharge.
2. Start the hydraulic press unit, allowing each hydraulic cylinder to complete its loading preparation (check the operation of each hydraulic cylinder individually and return it to the designated position).
3. Connect the conveyor power supply. Position the conveyor to the “interlocking” operation position, advancing it one residual electrode stack pitch to transport the residual electrodes to the head limit position (i.e., the position where the push plate can begin to push). The conveyor will then stop via the electromagnetic clutch brake. If the residual electrodes are not properly dispersed at this point, an alarm will sound via the photoelectric tube, and the loading operation will automatically stop.
4. If everything is normal, after a given time since the conveyor stopped, the lifting hydraulic cylinder will begin to operate. The piston rod will descend, and simultaneously, the lifting platform hinged to the piston rod, as well as the push hydraulic cylinder mounted on the lifting platform, will also descend to the horizontal limit position shown in the diagram. A photoelectric tube for position determination is installed on the lower platform of the lifting hydraulic cylinder. Only when the descent position meets the requirements can the next process be automatically initiated. When the piston rod of the lifting hydraulic cylinder begins to descend, the tilting hydraulic cylinder simultaneously performs a reset operation (positioning the tilting chute in a horizontal position to receive the residual electrode stack).
5. After a given time following the tilting hydraulic cylinder reaching its specified limit position, the pushing hydraulic cylinder begins to operate. Using a residual electrode pushing plate fixed to the piston rod, it pushes the residual electrode stack delivered by the conveyor into the tilting chute, which has been reset to a horizontal position. After the residual electrode has been pushed in for a specified time, the pushing hydraulic cylinder resets.
6. After a given time following the reset of the pushing hydraulic cylinder, the lifting hydraulic cylinder resets. Simultaneously, the tilting chute containing the residual electrode stack tilts 90 degrees from its horizontal position, aligning it with the loading hydraulic cylinder, the guide chute, and the water-cooling chute on the same axis. The gate opens via an interlocking device when the lifting hydraulic cylinder resets (i.e., the piston rod rises).
7. After a given time for loading the residual electrodes, the loading gate closes, and the loading hydraulic cylinder resets to the specified position, completing one cycle. The gate is opened and closed using a 0.5-ton electric hoist. If the gate is jammed and cannot be opened, an alarm will sound according to the overcurrent protection; if it is blocked and cannot be closed, an alarm will also sound if the limit position is not reached within a given time. Each chute is constructed of welded steel plates, and its clearance dimensions are adapted to the residual electrode stack, thus preventing the residual electrodes from tilting within each chute. The chute 21 extending into the side fume hood of the converter is made of water jacket type, and its cooling water is supplied by a high-level water tank located in the workshop; an alarm will sound if the water supply is interrupted.
8. When the loading hydraulic cylinder pushes in the residual electrodes, the chain conveyor, through interlocking and the electromagnetic clutch brake, engages the continuously running motor, causing the chain to rotate and transport the residual electrode stack towards the head (at this time, the lifting hydraulic cylinder has reset, freeing up space for the residual electrodes to advance). Operation stops only when the loading hydraulic cylinder returns to its limit position. At this point, the conveyor has advanced exactly one residual electrode stack pitch.
9.The above operation is automatically repeated until all the residual electrodes loaded on the conveyor are added. If the residual electrode stack on the conveyor needs to be added to the converter in two stages (e.g., loading in the first and second copper-making stages of the converter operation), then the conveyor should leave one or two pitches between the corresponding stacks before loading to facilitate control. Furthermore, all the residual electrodes on the conveyor must be loaded before the next alignment and loading operation can begin. When the anode feeding equipment itself malfunctions, pressing the emergency stop button, or in the event of a converter accident causing a tilt, will stop all train-mounted or loading operations through interlocking.
(IV) Hydraulic System
The actions of each hydraulic cylinder in the aforementioned residual electrode alignment and loading devices are accomplished through various hydraulic components. The reversal of each hydraulic cylinder’s action is controlled by electromagnetic proportional valves. Furthermore, these electromagnetic proportional valves can achieve stepless speed regulation of the hydraulic flow to change the cylinder speed to meet production requirements. The lifting and forming hydraulic cylinders are positioned via a hydraulically controlled auxiliary check valve (hydraulic system diagram omitted). In summary, this equipment has a well-considered structure and a high level of mechanization and automation. If it can be widely applied in suitable locations, it will bring significant economic and environmental benefits.
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