According to the definition in the Special Equipment Directory, lifting machinery refers to electromechanical equipment used for vertical lifting or vertical lifting combined with horizontal movement of heavy objects. This category includes lifting machines with a rated lifting capacity of 0.5 tons or more, as well as handling bridges with a rated lifting capacity of 3 tons or more (or a rated lifting moment of 40 ton-meters or more, or a productivity of 300 tons per hour or more), provided that their lifting height exceeds 2 meters. Additionally, mechanical parking equipment with two or more levels is also classified as lifting machinery.
It is important to note that lifting machinery used at construction sites for building and municipal engineering is not classified as special equipment.
Classification
Lifting machinery can be classified according to different criteria. For example, based on function, it can be divided into hoisting machinery, load-bearing machinery, and lifting machinery. Additionally, based on its application, it can be categorized into lifting machinery used at construction sites, in ports and docks, and for railways and bridges. Each type of lifting machinery has distinct features and application scenarios.
According to the classification in the Special Equipment Directory, lifting machinery is divided into 9 categories with a total of 28 varieties. These include overhead cranes, gantry cranes, handling bridges, tower cranes, mobile cranes, portal cranes, elevators, and mechanical parking equipment. Each type of lifting machinery serves specific purposes and application scenarios.
Overview of Common Lifting Machinery
In the Special Equipment Directory, lifting machinery is a broad category that encompasses various types of equipment. These machines not only play a crucial role in industrial applications but are also widely used in many other sectors. The following sections introduce some of the most common types of lifting machinery and their characteristics.
Among lifting machinery used in industrial zones, overhead cranes are the most prevalent, followed by gantry cranes. In construction projects, tower cranes and crawler cranes frequently appear. The following sections provide a detailed examination of these types of lifting machinery.
Overhead Cranes
Overhead cranes, often referred to as “bridge cranes” or “traveling cranes,” have a bridge structure that moves along elevated tracks at both ends. Overhead cranes are generally classified into single-girder and double-girder types, both of which are widely used in industrial applications. These cranes hold a crucial position in industrial settings.
Gantry Cranes
Gantry cranes, commonly known as “portal cranes” or “gantry hoists,” feature a bridge structure supported directly on ground-level tracks or foundations through legs on both sides. This design ensures the crane’s stability and safety across various working environments.
Tower Cranes
Tower cranes, often called “tower hoists,” are specialized lifting devices. Their key characteristic is a boom fixed at the top of a vertical tower, with a lifting mechanism suspended at the boom’s end or moving along the boom on a trolley. This design enables full rotation of the boom, allowing for versatile lifting operations.
Crawler Cranes
As a type of mobile crane, crawler cranes are distinguished by their tracked travel mechanism, which provides excellent lifting capacity and climbing ability. These cranes can maneuver effectively even in confined spaces and maintain exceptional stability. However, their large size, slow travel speed, potential road surface damage, and relatively high maintenance costs are factors that must be considered in practical applications.
Lifting Machinery Parameters
1. Rated Lifting Capacity
The rated lifting capacity refers to the maximum net weight that a crane can safely lift under normal working conditions for a specific type and load position.
2. Span
For bridge-type cranes, the span (denoted as “S”) represents the horizontal distance between the centerlines of the supporting structures, measured in meters.
3. Operating Speeds
- Lifting (Lowering) Speed: The vertical movement speed of the crane’s rated load under stable conditions, measured in meters per minute.
- Crane (Main Trolley) Travel Speed: The speed at which the crane moves along a horizontal surface or track while carrying the rated load.
- Trolley Travel Speed: The speed at which the trolley moves along the horizontal track while carrying the rated load.
Safety Protection Measures for Lifting Machinery
As crucial engineering equipment, lifting machinery must adhere to strict safety regulations. To ensure stable and secure operations, a series of safety protection devices are installed. These devices play a vital role in preventing accidents and ensuring the safety of personnel and equipment.
Overhead cranes and gantry cranes are typically equipped with the following safety devices:
1. Lifting Height Limiter
This device is designed to automatically cut off the lifting power source when the load reaches or approaches the maximum permitted height, ensuring safe operation. Additionally, a sufficient clearance is maintained above the extreme position to accommodate braking distances.
2. Travel Limiters
To prevent cranes or trolleys (excluding suspended electric hoist trolleys) from exceeding their designated travel limits, travel limiters must be installed in each operating direction. These devices automatically cut off the power source in the forward direction when the limit is reached.
3. Load Limiter
For power-driven cranes with a lifting capacity exceeding 1 ton or those with a risk of tipping over, a load limiter must be installed. This device monitors and restricts lifting loads to ensure safe operation.
4. Anti-Wind, Anti-Slip, and Anti-Tipping Devices
Outdoor track-mounted cranes must be equipped with these devices to meet wind resistance and stability requirements during both operational and non-operational states. Such devices include brakes, wheel brakes, and rail clamps. Their braking and release mechanisms should be interlocked with the running system and capable of remote operation from the control room.
