Crane knowledge: Crane Basic Concepts and Terms

1. Crane lifting capacity

Crane rated lifting capacity: The maximum weight the crane is required to lift, including the weight of the loads, lifting devices or the loads dealing devices, such as, hooks, crane grab, electric magnetics, equalizing beam, etc.
Effective lifting capacity: The net maximum weight of the loads the crane is required to lift.

Note to crane lifting capacity:

• Hook crane. The maximum lifting capacity of hook crane usually refers to the maximum weight of loads under the hook.
• Electromagnetic crane. The maximum lifting capacity of electromagnetic crane usually refers to the maximum weight of loads and the weight of the electromagnetic together.
• Grab crane: The maximum lifting capacity of grab crane usually includes the maximum weight of loads and the weight of the grab.
•  Double trolley crane. It is important to confirm with the client about the total lifting capacity of the two trolleys and the each trolley.

2. Span

Cane span refers to the horizontal distance between crane rails on which the crane is supported and which the crane is to travel.

3. Lifting height

 Lifting or hook height: The vertical distance from crane hook to the floor, which is marked as H in the following crane picture. The crane lifting or hook height determines the height of crane runway from the floor and is subjected to the clear inside height of the building.       

 Note to crane lifting height:

In terms of the lifting height of semi-gantry crane, the vertical distance between the rails or the net height should be confirmed with the client.

Semi-gantry Crane

4. Crane service classification

Crane service classification is a vital element to choose a suitable crane for your applications. Crane service classification are mainly based on the average load intensity and loading cycles. Two cranes with same lifting capacity, span and size can be different in terms of service classification due to the different average load intensity and loading cycles, and the crane components may experience various short term and long term loading conditions.

According to different standards, there are different crane services classifications. The Crane Manufacturer Association of America (CMAA) classify bridge cranes into 6 classes based on average load intensities and number of cycles. While the International Organization for Standardization （ISO）, European Federation Standard (FEM) and Hoist Manufacturer Institute (HMI) classify all hoists based on a higher requirements including numbers of starts and maximum running time per hour. （More information please seen the Crane Knowledge: Crane Service Classes）

5. Speed

Lifting speed: The rate at which the loads within the rated lifting capacity travel vertically and stably in normally crane working condition.
Crane speed: The rate at which the loads within the rated lifting capacity travels horizontally or on runway.
Trolley speed: The rate at which the trolley travels on the horizontally rails with loads within the rated lifting capacity in the normal working condition of crane.
Note: It should be specified whether it is single speed, double speeds or frequency drive is required.

6. Wheel pressure

As for the EOT cranes and gantry cranes without cantilever, the wheel pressure refers to the pressure when the trolley travels to the limited position on one side with the loads within the crane rated lifting capacity.
Note: The crane wheel pressure is closely related with the bearing capacity of the steel structure of the building.