What Are Tower Cranes? Understanding Their Structure, Functionality, and Selection Tips

At construction sites where high-rise buildings rise from the ground and factories gradually take shape, there is always a "steel giant arm" standing tall, precisely lifting heavy materials such as rebar, concrete, and steel structures. This is the tower crane. As a core heavy-duty equipment in construction, tower cranes, with their exceptional lifting height, flexible operating radius, and stable load-bearing capacity, have become indispensable "workhorses" for high-rise buildings and large factory constructions. However, most people only see its massive silhouette and are not familiar with what tower cranes are. Now, let's take a deeper look at them.

What Is a Tower Crane?

A tower crane is a full-rotation crane with a vertical tower body. Due to its unique structural design, it can efficiently move heavy loads in three-dimensional space:

Structural Components

The tower crane mainly consists of the following components:

Metal Structure: Tower body, jib, and base.

Working Mechanism: Lifting, jib movement, rotation, and walking mechanisms.

Electrical System: Motors, controllers, distribution cabinets, connection wires, signal devices, and lighting equipment.

Operating Principle

The crane lifts or lifts and moves heavy objects using a lifting hook or other grabbing devices. The lifting mechanism picks up the load from its origin point, and the rotating or jib movement mechanism moves the material horizontally. The walking mechanism allows the load to move within the crane's reach.

Features

Tower cranes have significant advantages in engineering. With their long jibs, high radius utilization, and large lifting heights, they are capable of vertical and horizontal transport simultaneously. Moreover, modern tower cranes are highly standardized, offering smooth and reliable operations.

However, they are also large, heavy, require significant time for transport and relocation, and need professional operators.

How Do Tower Cranes Work?

The working essence of a tower crane is to precisely move heavy objects from a "starting point" to a "destination" using its metal structure for support, coordinated mechanisms, and electrical system control. The entire process can be broken down into three core phases: structural support, mechanism linkage, and load control, which, combined with typical operational processes, enable efficient transport.

Structural Support

The crane’s operation relies on a sturdy metal structure that acts as the “skeleton,” ensuring that no tilting or collapse occurs under load. The key structural components include:

Tower Body: The vertical core support, determining the crane’s maximum lifting height. It includes ladders and cable channels and provides the installation base for the rotating mechanism.

Jib: The horizontal force-bearing component, one end connected to the tower body and the other end with counterweights. This is the key part for achieving “horizontal transport distance.” Depending on the design, it can be either a "luffing jib" or a "top running crane."

Base & Anchorage: Mobile tower cranes move using their base, while fixed tower cranes are anchored to a concrete foundation. If the height exceeds certain limits, they require an “attachment frame” to connect with the building structure to prevent tower swaying.

Counterweight Arm: Positioned symmetrically opposite to the jib, the counterweight arm balances the lifting load, ensuring the crane's overall stability.

Four Core Mechanisms

Lifting Mechanism: Driven by a motor, the winch rotates, winding the steel wire to raise the hook. Reversing the winch releases the wire to lower the hook. The pulley system magnifies the lifting capacity, while the overload and height limiters provide continuous safety.

Jib Movement Mechanism: For luffing cranes, the jib angle is adjusted via a winch that moves the steel rope, changing the jib's angle. The luffing limit device prevents over-extension.

Rotation Mechanism: The slewing ring drives the rotating part, turning the load from one direction to another. The rotation is slow and smooth, and the rotation limit prevents excessive twisting of cables.

Walking Mechanism: Only mobile tower cranes have this mechanism. They can move in a straight line, turn, or rotate in place. This makes repositioning for tasks easy. Fixed tower cranes do not have this mechanism and must be disassembled and reinstalled for relocation.

Electrical System

Control Side: The operator’s cabin is equipped with a control handle, a dashboard, and an emergency stop button.

Execution Side: The electrical system adjusts motor speeds via contactors and inverters, and sensors continuously monitor load, position, and other data. If the values exceed the limits, the system triggers a protective shutdown.

Types of Tower Cranes

Tower cranes are classified in various ways based on structural features, mobility, operational modes, and other key attributes. Different types have significant differences in their applicable scenarios and performance. Below is a systematic classification, elaborated with structural principles and engineering applications:

1. By Mobility

Fixed Tower Crane: After installation, the position remains fixed without walking ability. Requires a concrete foundation and attachment frame. It offers high lifting heights, strong stability, and large lifting capacities, suitable for high-rise buildings and large factory installations in fixed areas. However, installation and disassembly are complex and require assistance from mobile cranes, and the operating area cannot be changed.

Mobile Tower Crane: Comes with walking mechanisms, allowing for easy relocation and installation without the need for a fixed foundation. It is flexible, convenient for outdoor projects, and small-to-medium-sized buildings. However, it has a lower lifting height and weaker stability compared to the fixed type and is not suited for operation in high winds. Subtypes include tire-mounted, crawler-mounted, and rail-mounted.

2. By Rotation Mode

Top-Slewing Tower Crane: The rotation mechanism is installed at the top of the tower. The tower body is fixed while the crane rotates 360°. The tower height can be increased by adding standard sections. It has a large lifting capacity, a wide range of applications, and is suitable for high-rise buildings and large factories.

Bottom-Slewing Tower Crane: The rotation mechanism is installed at the base of the tower. The entire crane rotates around the base, and the tower is typically monolithic, unable to be extended in height. It is compact, has a lower height, and is easy to assemble and disassemble. It is suitable for low-rise buildings, indoor factory installations, and small construction sites.

3. By Jib Movement

Trolley-Slewing Tower Crane: The jib is a rigid structure with a movable trolley that adjusts the working radius by moving along the jib track. It is quick, flexible, and evenly distributes the weight across the jib. This type is the mainstream choice for high-rise residential, office buildings, and other projects requiring frequent adjustments to the working radius.

Luffing Jib Tower Crane: The jib consists of a hinged truss arm, and the working radius is adjusted by changing the jib's angle via a winch. The jib is foldable, making transportation easier, and it offers high lifting capacity and the ability to operate at extended ranges. It is suitable for heavy equipment installation and port unloading tasks.

4. By Lifting Capacity

Lightweight: Rated lifting capacity ≤5 tons, torque ≤80 kNm. Suitable for low-rise buildings, small renovations, and material handling.

Medium-Sized: Rated lifting capacity 5-20 tons, torque 80-250 kNm. Suitable for multi-story buildings and medium-sized factory construction.

Heavy Duty: Rated lifting capacity 20-100 tons, torque 250-1000 kNm. Suitable for high-rise buildings and large factory steel structure installations.

Super Heavy Duty: Rated lifting capacity ≥100 tons, torque ≥1000 kNm. Suitable for ultra-high-rise buildings and large engineering equipment installations.

5. Special Types

Internal Climbing: Installed within the building core, it climbs as the building rises, saving external space. Suitable for narrow sites and super-high-rise buildings.

Flat-Top Tower Crane: The jib and counter-jib are level with the tower, without a tower head, which makes assembly and disassembly easy and enhances safety at high altitudes. Ideal for multiple cranes working together.

Fast Assembly: Modular design with detachable parts for easy transportation and quick installation. Suitable for temporary projects, emergency rescue, and short-term use on small construction sites.

How Much Weight Can Tower Cranes Lift?

The lifting capacity of a tower crane is not a fixed value; it depends on the model, working radius, tower height, jib type, and other factors. The core principle follows the torque balance formula: Lifting Capacity × Working Radius = Rated Torque. Torque is a fixed value by design, and safety limits must be strictly adhered to during operation to avoid accidents.

Key Factors Affecting Lifting Capacity

Working Radius: The most direct influencing factor. The lifting capacity is highest when the hook is closest to the tower and decreases significantly as the hook moves farther away.

Model Specifications: Basic performance sets the upper limit. Lightweight cranes ≤5 tons, medium cranes 5-20 tons, heavy-duty cranes 20-100 tons, and super-heavy-duty cranes ≥100 tons.

Jib Type: Trolley-slewing cranes have a consistent lifting capacity throughout the jib's movement, suitable for handling general materials. Luffing jib cranes can lift more with a greater angle, ideal for heavy-duty and long-distance tasks.

Tower Height & Attachment: The higher the tower, the weaker the stability. For towers over 30 meters, the addition of an attachment frame can reduce the lifting capacity by 10-20%. Mobile tower cranes generally have lower lifting capacity than the same-sized fixed cranes.

Operational Safety Limits

Hardware Protection: Torque limiters provide real-time monitoring. If the actual torque exceeds 90% of the rated capacity, an alarm will sound, and the power will be cut off if it exceeds 105%, preventing overload.

Operational Guidelines: The operator’s cabin will display a "Rated Lifting Capacity Chart," and the operator must follow the guidelines without relying on experience.

Environmental Restrictions: Operations must stop if wind speeds exceed 6 levels. When the temperature is below -20°C, the steel strength decreases, potentially reducing the lifting capacity by 20%.

How to Pick the Right Tower Crane for Your Project?

Choosing the right tower crane should focus on project requirements, site conditions, safety regulations, and the balance between efficiency and cost. Incorrect crane selection can lead to problems. The process can be broken down into four core steps: define your needs, evaluate site conditions, select crane type, and conduct a comprehensive assessment.

Step 1: Define Core Requirements

Maximum Load: Calculate the heaviest component plus the weight of lifting accessories. For example, if a slab weighs 6 tons and the lifting gear is 0.5 tons, the total load will be 6.5 tons. It’s important to differentiate between standard load and peak load.

Working Radius: Calculate the maximum (distance from the crane’s center to the farthest point of operation) and minimum radius. The required torque can be determined by the formula: Minimum Rated Torque = Maximum Load × Maximum Radius × 1.2 (safety margin).

Lifting Height: Calculate as Building Height + Safety Margin (5-10 meters) + Distance from Hook to Jib (3-5 meters). For ultra-high-rise buildings, consider a crane with a modular tower structure.

Work Efficiency: For high-frequency lifts, choose a trolley-slewing type crane. For low-frequency heavy loads, choose a luffing jib crane.

Step 2: Evaluate Site Conditions

Space Size: For narrow sites, choose fixed or internal climbing cranes. For open and dispersed sites, mobile cranes are ideal. For elongated sites, a rail-mounted crane is suitable.

Ground Load Capacity: For hardened surfaces, choose fixed cranes with embedded foundations. For soft ground, select crawler cranes. For temporary sites, choose fast-assembly cranes.

Surrounding Environment: If there are obstacles, choose a high-lift or small-radius crane. For multiple cranes working together, a flat-top crane is suitable. In residential areas, opt for a low-noise, frequency-controlled crane.

Step 3: Select Tower Crane Type

Based on the defined needs and site conditions, narrow down the crane types, then match the specifications and additional configurations.

Step 4: Comprehensive Assessment of Costs and Risks

Cost: For short-term projects, renting is more cost-effective. For long-term projects, purchasing might be more economical. Be sure to factor in additional costs such as foundations, transportation, and installation.

Risk: Before installation, ensure that large equipment can enter the site. During operation, ensure a safe distance from power lines. Plan crane placement before dismantling.

Suppliers: Prioritize selecting top manufacturers with outstanding quality and deep industry expertise. For example, SANY, established in 1989, operates globally with a comprehensive product portfolio covering concrete machinery, excavation equipment, lifting machinery, tower cranes, and other engineering equipment. With its technological strength and strong market reputation, SANY maintains a leading position in the global industry. In the field of tower cranes, SANY has demonstrated significant advantages, offering a wide range of models that cater to various specifications and application scenarios. Its performance parameters meet international high standards, precisely fulfilling the diverse needs of construction projects while providing enhanced safety assurance.

Conclusion

What are tower cranes? In fact, tower cranes are not simple “lifting tools” but rather complex equipment that integrates structural mechanics, mechanical control, and engineering needs. In real-world projects, whether it's clarifying lifting requirements, evaluating site conditions, or selecting machine models and controlling costs, it’s essential to assess the performance characteristics of tower cranes in conjunction with the project's actual circumstances. In the future, with advancements in construction technology, tower cranes will continue to evolve in directions such as intelligent operation and lightweight designs, further adapting to more complex construction demands.

FAQs

How Do Tower Crane Operators Go to the Toilet?

Tower crane operators primarily rely on "preventive measures and emergency handling" for toilet needs:

Before Work: Operators aim to empty their bladder an hour before their shift and avoid drinking too many liquids. They use scheduled ground breaks (1-2 times during their shift) to address any needs.

If Unable to Descend: Male operators use a sealed urinal, while female operators use a special urine collector with a sealed bag. In extreme cases, adult diapers may be used, and these must be disposed of after use, with the used diapers being brought down from the cabin.

Strict Rules on Descending: It is prohibited to leave the tower crane without proper authorization. In urgent situations, operators should contact the ground team via radio to stop the crane’s operation and maintain cleanliness in the cabin to ensure operational safety.

How Much Does a Tower Crane Cost?

The price of a tower crane varies significantly based on the model, brand, and specifications. SANY has many products to choose from and is highly trusted for its technical strength and market reputation.

*Disclaimer: Considering that prices vary significantly across different brands and regions, please contact local dealers for price inquiries.

What Keeps Tower Cranes from Falling Over?

The prevention of tower crane tipping is not dependent on a single measure but rather a complete system: "Solid foundation → Counterweight balance → Anchor fixation → Monitoring and safety regulations." Any failure in one of these components can lead to safety hazards.

How Do They Get Tower Cranes Down?

Disassembling a tower crane requires a professional team, compliant equipment, and a detailed plan to avoid damaging the equipment or causing a safety incident. In practice, the disassembly process is adjusted based on the specific crane model, installation height, and the site environment, ensuring each step meets industry standards.