What is the anti-collision system in a tower crane?

The construction of high-rise buildings and large infrastructure projects often involves the use of multiple tower cranes working in close proximity. With the complexity of these operations, the risk of crane collisions increases. This is where anti-collision systems¹ come into play. These safety technologies are designed to prevent accidents, protect workers, and keep operations running smoothly. In this article, we’ll explore the anti-collision system in tower cranes, how it works, and its essential role in ensuring safe construction site operations.

Anti-collision systems in tower cranes are designed to prevent accidents by automatically managing crane movements, ensuring safety and efficiency on crowded construction sites.

Let’s dive deeper into how these systems function and why they are a critical safety feature on modern construction sites.

What is the purpose of the collision avoidance system?

The purpose of a collision avoidance system in a tower crane is simple: to prevent accidents. With multiple cranes operating in the same area, the risk of a crane colliding with another crane, a building, or other objects is high. These accidents can cause significant damage to equipment, delay projects, and most importantly, lead to injuries or fatalities.

Key Functions of a Collision Avoidance System

1. Prevent Crane-to-Crane Collisions
   One of the primary purposes of the system is to ensure that multiple cranes working in close proximity do not collide. The system coordinates the movements of several cranes and adjusts their operation to maintain a safe distance from one another.

2. Protect Workers and Equipment
   Beyond preventing crane-to-crane collisions, anti-collision systems help ensure that no part of the crane, especially the boom or load, comes into contact with workers or nearby structures. This is particularly critical when the cranes are positioned close to the edge of buildings or working over pedestrian areas.

3. Maximize Site Efficiency
   These systems improve site productivity by allowing cranes to operate in close proximity without interfering with one another. This is especially useful in dense urban construction projects where space is limited.

How Does Anti-Collision System Work?

The anti-collision system works through a combination of sensors, GPS, radar, and software that continuously monitor and control the crane’s movements. Here’s a step-by-step explanation of how it functions:

1. Sensors and GPS Technology

The system uses sensors to track the position of the crane’s parts, including the jib, hook, and load. GPS units on each crane allow the system to map the location of each crane in real-time. This data is then used to track crane positions on the construction site.

2. Radar and Proximity Detection

Radar sensors are often used to detect the presence of other cranes or objects in the crane’s operational area. If another crane or object is detected within a certain range, the system can trigger a warning or automatically adjust the crane’s movement to avoid collision.

3. Automatic Movement Control

When the anti-collision system detects that two cranes are on a collision course, it can automatically slow down or stop the crane's movement to prevent the collision. The system can also adjust the speed of the crane, limit its movement, or modify the range of its operations to ensure a safe distance is maintained.

4. Visual and Audible Warnings

In addition to automatic control, operators receive visual and audible warnings when the system detects a potential collision. This allows operators to take corrective action manually if needed, in case the automated system fails or doesn’t fully mitigate the risk.

Benefits of Anti-Collision Systems

What is the purpose of the anti-two-block device in a crane?

An anti-two-block device is an essential safety feature in a crane designed to prevent the hook block from coming into contact with the crane’s boom tip, a situation known as "two-blocking." Two-blocking occurs when the hook block is raised too high and the hoist line becomes fully reeled in, causing the hook block to hit the boom. This can lead to serious damage to the crane, and in some cases, catastrophic failure.

Key Purpose of the Anti-Two-Block Device

1. Prevent Crane Damage
   The primary purpose of the anti-two-block device is to prevent damage to the crane’s boom, hoist line, and hook block. The device ensures that the crane’s components do not come into direct contact with each other, which could cause costly repairs and downtime.

2. Protect Workers
   Preventing two-blocking also enhances worker safety. A sudden block impact can cause the load to drop unexpectedly, putting workers on the ground or other equipment at risk.

3. Automatic Shutdown or Warning
   When the anti-two-block device detects the hook block is too close to the boom tip, it either activates an automatic shutdown mechanism or issues a warning to the operator. This allows the operator to stop lifting immediately and avoid damage or injury.

What are the safety devices in a tower crane?

Tower cranes are equipped with several safety devices that work together to ensure safe operation on construction sites. These devices help prevent accidents, protect workers, and ensure that cranes function at optimal performance levels.

Common Safety Devices in Tower Cranes

1. Load Moment Indicator (LMI)
   The Load Moment Indicator is a device that helps the crane operator monitor the load weight and the crane’s capacity. It provides real-time data about the load, ensuring the crane doesn’t exceed its maximum lifting capacity, which could lead to tipping or structural failure.

2. Anti-Collision System
   As discussed, anti-collision systems are critical for ensuring multiple cranes operating on a site don’t collide. This system uses radar, GPS, and proximity sensors to prevent accidents by controlling crane movements.

3. Overload Protection Device
   This device prevents the crane from lifting loads that exceed its rated capacity. If the crane detects an overload, it will stop the lifting operation and issue a warning to the operator.

4. Wind Speed Indicator
   Cranes are vulnerable to strong winds, and a wind speed indicator helps crane operators assess if wind conditions are safe for operation. If the wind speed exceeds a certain limit, the crane will automatically stop lifting and secure its load until the conditions improve.

5. Limit Switches
   Limit switches are installed to prevent the crane’s parts from moving beyond certain safety limits. These switches can automatically stop crane movement if it approaches the maximum permissible reach, preventing the risk of mechanical failure or collision.

6. Emergency Stop Button
   The emergency stop button is a last-resort safety feature. If a hazardous situation arises, the operator can press the button to immediately stop all crane movements and prevent accidents.

Conclusion

Anti-collision systems in tower cranes are a crucial part of ensuring safety on construction sites. They help prevent crane-to-crane collisions, protect workers, and improve operational efficiency. Together with other safety devices such as anti-two-block mechanisms, overload protection, and wind speed indicators, these technologies work to minimize risk and ensure cranes operate safely within their designated limits. The integration of these systems not only protects equipment but also saves lives, making modern construction sites much safer for everyone involved.