Bridge foundry cranes for metallurgical plants

In modern foundry the majority of technological processes have a high degree of mechanization. Modern metallurgical plants use special-purpose materials handling equipment at many stages of their production cycles.

At metallurgical plants, as well as at metallurgical workshops of large machine-building plants, bridge metallurgical cranes are being actively used in carrying out of processing steps with liquid full-hot metals.

Bridge foundry cranes are operating at open-hearth shops, arc-furnace shops and oxygen-converter plants of steel mills. They are used in melted steel transporting to steel furnace, as well as for impurity metal elimination in special ladle furnace, liquid cast iron ladling into a furnace and for subsequent steel casting. Foundry cranes are also being used in a number of auxiliary operations, connected with ladle treatment and equipment repairing.

Being an essential part of a production process, modern high capacity metallurgical foundry cranes directly affect steel shop efficiency and total productivity of foundry process.

According to World steel association data, steel production volume in Russian federation has increased up to
6 000 000 ton in May 2021. Maximum was peaked at 6 804 000 ton.

The total growth of steel production affected in increasing of a new metallurgical cranes necessity. Many metallurgical plants are increasing their investments in technological infrastructure development and also in crane equipment for steel foundry production. As demand for foundry cranes is growing, leading domestic manufactures has been creating world standard level high-quality equipment.

Due to a considered and proper choice of foundry crane manufacturer, as well as to crane’s configuration and required number of technical parameters, both foundry shop productivity and manufacturing process continuity of steel mill are depending. Any minor malfunction of equipment could result in technological cycle slowdown and subsequently in melted steel solidifying in a ladle, which could lead to significant financial losses of metallurgical plant.

According to their production purpose, foundry metallurgical cranes are divided into three types:

·         Mixer foundry crane. Provides the pouring of molten iron from iron transporting cars to special mixer. Such a crane is operated in a mixer sector of an open-hearth shop. 

·         Charging foundry crane. Makes pouring molten iron to arc-furnace converter or to charging bay of arc-furnace. Charging foundry crane is operated in a furnace bay of open-hearth shop. 

·         Casting foundry crane. Provides casting liquid steel to casting molds or to continuous-casting machine. Such a crane is operated in casting bay of metallurgical plant open-hearth shop and also in steel and foundry shops of machine-building plant.

All these three types of cranes are actually identical by design. The difference is only in their technical features, such as lifting capacity of main and auxiliary lifting devices, crane’s width and lifting height, as well as in some tooling features. For instance, casting foundry crane has two lifting mechanisms on an auxiliary trolley unlike mixer foundry crane and charging foundry crane. Casting foundry cranes have the highest lifting capacity (up to 630 ton). Such a parameter is selected in accordance with furnace load size, filled ladle mass, traverse mass and other hang part mass.

Foundry bridge metallurgical crane consists of following main units:

·         Crane’s bridge combined with a travelling mechanism;

·         Main trolley combined with travelling mechanism and main lifting mechanism;

·         Traverse with cord tenders and plate hooks;

·         Auxiliary trolley combined with travelling mechanism and auxiliary lifting mechanism;

·         Hook block;

·         Crane rope set;

·         The Control cabin;

·         Electrical equipment cabin;

·         Safety devices;

·         Electrical equipment set.

In accordance with operating conditions and technological tasks foundry cranes can be manufactured in two-girder or four-girder performance. Main girders together with end beams form a single crane bridge. Unlike two-girder cranes, four-girder cranes are able carrying out ladle tilting in both sides.

The Bridge of four-girder foundry crane consists of two main girders with mounted rails of the main trolley on it and two auxiliary girders with mounted rails of the auxiliary trolley. Such a construction is capable to provide independent movements of main and auxiliary trolleys on different levels, expanding the technological potential of the crane.

The Bridge of foundry crane is equipped with pairs of wheels, bunched in balance groups. Some of pairs of wheels are driven. Crane travelling wheels moves crane by craneways.

The main lifting mechanism of the crane is intended for ladle with liquid metal transporting. The auxiliary lifting mechanism allows ladle tilting and treatment to be provided. The foundry crane, if necessary, could be equipped with two or three auxiliary lifting mechanisms, allowing carrying out repairing or cleaning works.

Traverse with two hooks, intended for hanging and holding a ladle is a lifting device of the main trolley of foundry crane. For its frame protection against extreme temperature impact, while handling a liquid metal, traverse has a reflecting iron sheet fixed below.

The trolley of auxiliary lifting mechanism is equipped with a special hook assembly, which is used for ladle tilting, as well as for some auxiliary repairing works. An empty ladle weight defines the required lifting capacity of auxiliary lifting mechanism.

On foundry crane’s main hoist at its high lifting capacity and wide range of speed regulation AC electric motors are used. In certain cases the usage of asynchronous DC electric motors is more efficient. While having much less weight, they are 2.5 times cheaper.

In crane’s main hoist drive arrangement two basic solutions could be realized: traditional – an open gear system or new generation solution – a differential speed reduction device applying.

The most important parameters, considered while designing foundry metallurgical cranes are reliability and operating safety. For example, main lifting system for cranes of this type is constructed in the following way: any motor has a capacity, sufficient for lifting a filled ladle by oneself; only two of eight main trolley wheels are travelling, the others are reserved; in case of main trolley failure the crane has another similar trolley.

For an emergency stop of main hoist mechanism in case of emergency (over speed lowering, service brake malfunction, rope drum-motors drive connection failure) hydraulic backup brakes, installed on each rope drum are provided in the main hoist design. Safety stop is carried out by disk backup brakes application on a brake shoe flange of main hoist rope drums.

Service galleries along the main girders, as well as stairways and staircases, providing an easy and secure access to mechanical and electrical units are designed on the crane. All crane’s units design must provide an assembly replacement of out of order equipment, without large metal structures being dismantled.

Considering peculiar operating aspects, many of foundry metallurgical cranes are intended for operating at harsh temperature conditions, up to 80°C, and also are capable to stand short time extremal high temperature actions. In those cases, electrical system of the crane is often located inside its girder, made of special heat-resistant steel. For crane’s power supply and signal cables safety, they are sheltered in a special sleeve, the Pirojacket, which is capable to stand up to 260°C temperature for a long time.

From the control cabin, installed below the bridge gallery, all crane mechanisms control is carrying out. The Control cabin is thermally insulated. It is air conditioned and if necessary, is equipped with heaters. Specialized refrigerants, such as Freon R23B or R142B are used to maintain a comfortable microclimate in the control cabin.

Foundry metallurgical cranes are intended to operate in harsh and extremely harsh working modes A6-A8.

TEHNOROS Production Association is specialized in design, manufacture and “turnkey” construction supply of complicated hoisting equipment for metallurgy. For decades we have been providing a lot of successful solutions in foundry cranes creation for metallurgical plants. The company is deservedly considered as one of the leaders on Russian metallurgy cranes market.