What is overhead crane (bridge crane)?

Overhead crane is an important tool and equipment to realize mechanization and automation of production process in modern industrial production and lifting and transportation. It is widely used in workshops, warehouses, and other material handling occasions in machinery manufacturing, metallurgy, petroleum, petrochemical, ports, railways, civil aviation, electric power, food, paper, building materials, electronics, and other industries.

overhead crane

Classification of bridge cranes:

At present, there are mainly two types of bridge cranes, such as hook bridge cranes and hoist double girder bridge cranes. The difference between these two types of cranes lies in the form of the hoisting mechanism. The hoisting mechanism of the hook bridge crane, such as the reel, brake, motor, running mechanism, and motor brake, are installed separately, and then assembled into a trolley, with a larger overall volume. The hoist double-girder bridge crane directly uses the hoist as the hoisting mechanism, without a reel, and generally speaking, the volume is relatively small.

The hook bridge crane can carry a strong working level and can be used in more complex and harsh working conditions. At present, cranes above 32t basically use hook bridge cranes. However, the hook bridge crane has a complex structure, long manufacturing cycle, heavy self-weight, large wheel pressure, and high workshop cost. Therefore, in recent years, hook bridge cranes below 100t have gradually replaced products, that is, large-tonnage hoist double-girder cranes. Like Demag has produced a 100t hoist double girder overhead crane, Konecranes‘ 80t crane also uses a hoist as a hoisting mechanism.

overhead crane

Advantages of overhead cranes:

Overhead cranes, especially those under 100t, have been implemented with an electric hoist as the hoisting mechanism. The hoist is driven by a variable frequency motor to achieve a two-speed operation, and the working level of the whole machine can reach the A5 level. Imported brand cranes have advanced design concepts, superior material performance, compact dimensions, low building headroom, light dead weight, low wheel pressure, and low energy consumption. These features can reduce the height, plant cost, and operating cost to a certain extent.

How to choose an overhead crane?

Bridge cranes are widely used and have many models. It is more important to choose the appropriate model of bridge crane according to different uses. Generally speaking, for general-purpose bridge cranes, the model can be determined according to the lifting materials. The hook bridge crane (QD) can be used for lifting and transporting general goods; the electromagnetic bridge crane (QC) can be used for lifting and transporting ferromagnetic materials.

The grab bridge crane (QZ) can be used to lift bulk materials; there are dual-purpose cranes and three-purpose cranes for lifting two kinds of materials; the hook bridge crane (QE) with double trolleys can be used for lifting longer goods.

Single-girder overhead cranes can be selected for those with a small lifting weight, and double-girder overhead cranes can be selected for those with large lifting weights.

bridge crane

Maintenance of overhead cranes

Daily maintenance

Ensure the cleanliness of the equipment, electrical appliances, and other parts of the double-girder bridge crane; check the connection of the bolts of each piece of equipment, and strengthen the loose parts in time; ensure the lubrication level of each part, especially the lubrication of metal components; check the motor, gearbox and other components. Temperature and operating conditions, to ensure that the motor does not exceed 80% of the rated problem during operation, etc. 

Maintenance of the lifting mechanism

Do a good job in cleaning the hooks and wire ropes of the QD double-girder bridge crane, add lubricants in time, and frequently inspect and maintain. In strict accordance with the safety regulations of crane equipment, check whether the equipment meets the safety technical requirements and test whether the performance is normal. Regularly check the cracks of the pulley to ensure that it meets the requirements of the lifting equipment. If the situation is serious, it should be repaired or replaced in time. If the screws and bolts are loose, test the degree of wear and replace them in time to ensure the normal operation of the lifting structure.

Maintenance and maintenance of transmission and running gear

Focus on whether the electric motor of the crane enters water and oil, and daily prevention and treatment; ensure that the observation hole and junction box of the electric motor is tightly covered, and it is required that the operation is not lower than 85% of the rated voltage. The lubrication of the equipment ensures the quality and life of the various components of the crane, so the lubrication work is very important, and the methods of distributed lubrication and oil pool lubrication can be used in each structural part. Note that the wear of the wheel rim of the crane should not exceed 50% of the original thickness. During the daily inspection and maintenance, serious wear and tear should be replaced in time.