Overhead foundry cranes for metallurgical

A foundry crane is one of the types of bridge cranes and is the main equipment in the steelmaking process. It is widely used in the metallurgical casting and casting industry. It is used for hoisting molten steel or molten iron in steel-making workshops and working in harsh environments with high temperatures and dust.

Types of foundry cranes:

As the capacity of the steelmaking furnace increases, the lifting capacity of the foundry crane is also increasing. According to the different requirements of users, foundry cranes include double-beam double-rail type, double-beam four-rail type, four-beam four-rail type and four-beam six-rail type. Double-girder double-rail type and double-beam four-rail type are used for small-tonnage foundry cranes, four-beam four-rail type are used for large-tonnage cranes, and four-beam six-rail type are used for extra-large tonnage cranes.

Parts of the foundry crane:

General foundry cranes are composed of the following parts: electric drag and electric control system, main trolley, cart operating mechanism, bridge frame, auxiliary trolley, gantry hook, etc. In addition, with the development of technology and the change in the steelmaking process, the types of cranes are also constantly changing.

Special requirements for foundry cranes:

In addition to meeting the general technical requirements of cranes, the main hoisting mechanism of foundry cranes should also meet the following special requirements:

• The main hoisting mechanism is driven by double motors. When one of them is suddenly damaged, the other one is required to undertake all the work in a short time, so as to lift the hoisted ladle to a safe place, or one motor can be used for half of the work. Lifting speed continues to work.
• Two sets of independent drive mechanisms: Each set of drive mechanisms must be equipped with two sets of brakes, if one of them fails, the other set should be able to undertake all the braking work.
• The lifting and lowering of the gantry hook group must be balanced and not inclined to prevent molten steel from overflowing.
• The steel wire rope system consists of four steel wire ropes, and each group of two steel wire ropes is equipped with a balance arm in the winding system to ensure that the steel wire ropes are evenly stressed. In addition, if one or two of the relative positions are broken during the work, the remaining steel wire ropes can support the load without causing the hook balance beam to tilt or fall.
• The hook swings freely in two directions. In the design, a hanging fork is added between the plate hook and the beam to avoid abnormal side load on the hook when the crane operating mechanism starts and breaks.
• The electronic control equipment is sealed against dust, heat insulation, and cooling.
  Set the electrical equipment in the main beam, add a thermal insulation layer to prevent radiated heat, and add a cooling fan in the electrical room to cool down to ensure the service life of the electrical components.
• The driving systems of the carts are placed in the two main beams, one set fails, and the other set can continue to work.

The development trend of foundry cranes:

With the development of the metallurgical industry, foundry cranes tend to develop in the direction of high-speed, large-scale, and intelligent. The hoisting speed of the main hoisting mechanism of the high-speed 450t and 500t foundry cranes has reached 12m/min and the auxiliary hoisting speed is 15m/min.

Large-scale, the largest foundry crane in the world has a lifting capacity of 550t, which is produced by the Liebherr Company. At present, the largest foundry crane in China has a lifting capacity of 450t.

The whole electrical control configuration is advanced, which has developed to the frequency conversion speed regulation of all mechanisms, advanced detection methods, automatic operation monitoring, automatic tracking, and intelligent detection, which provides convenience for maintenance and repair.

Power supply for foundry cranes

Small and medium-sized (below 200t) foundry cranes generally use a low-voltage power supply (380V) and generally do not use DC power supply.

Large foundry cranes, it is generally powered by high voltage. The crane is equipped with a transformer. The main hoisting motor is a 3000V high voltage motor, which is called a high voltage power supply and low voltage control.

Safety protection of foundry cranes:

• The power of the motor is relatively large, and the main hoisting mechanism is mostly driven by two motors. During normal operation, the two motors start and brake at the same time. If one motor fails during work, the other motor can continue to work for a short period of time, handle it urgently, and lift the load to a safe place. Generally, the power of a single motor is 0.6 to 0.65 times the total power of the hoisting mechanism. In instar drive, the power of one motor is 0.5 times the total power.
•  The two large gears in the reducer have meshed with each other through the two idle wheels. During operation, if one set of high-speed shafts of the hoisting device fails, the other set can still drive the reel on the faulty side, and the suspension will be suspended. The dangling ladle is safely lowered to a safe position.
• There are four separate wire ropes for the main hoisting. When one of them or two diagonally breaks, the remaining three or two can also protect the rated load.
• The safety factor of steel wire rope is generally above A7.
• Each group of drive motors is provided with two working brakes, and the braking torque of each brake is more than 1.1 times the total load of the main hoisting mechanism. Large foundry cranes generally use disc brakes to reduce the moment of inertia on the high-speed shaft of the main hoisting mechanism, reduce energy consumption during starting and braking, and facilitate maintenance and overhaul.
• A safety brake should be added to the hoisting mechanism of a large crane driven by a planetary reducer.
• Foundry cranes should be equipped with overload limiters or electronic scales for overload protection or weighing of the mechanism.
• Lifting limit switches, using two sets of lifting limit switches, one set of heavy hammer limit switches, one set of rotary limit switches, one set is installed next to the upper pulley block, and the other set is installed on the scroll shaft.
• Safety protection of the main hoisting motor:
  An Overspeed switch is installed on the motor shaft, when the hoisting speed exceeds 1.35 times the rated speed, the Overspeed protection hoisting motor stops rotating. There is overcurrent protection, overheating protection, phase loss protection, and so on.
• line protection, short circuit protection, grounding protection and zero protection, and voltage loss protection.
• The ingot crane should be equipped with a three-dimensional positioning device or an ingot aligner to make the ingot alignment accurate and improve production efficiency.
•  Large vehicles are equipped with infrared anti-collision devices and so on.

Conclusion

With the development of the steelmaking process, the use of foundry cranes is becoming more and more frequent. Since the lifting is molten metal, the work of the foundry crane is required to be safe and reliable, and even in the case of damage to some parts, it must be ensured that it does not occur. Overturning and falling accidents of tanks. In order to ensure that the steelmaking production can be carried out continuously, the foundry crane must be simple in structure and easy to maintain quickly. The foundry cranes produced by Weihua Group have advanced technology, high production efficiency, safety and reliability.