Introduction to Crane Warning Systems

The crane warning system is a comprehensive safety protection system that integrates sensing, calculation, control, and early warning functions. Its primary purpose is to alert operators and on-site personnel through various means, such as sound, light, and electrical signals, before accidents occur. Additionally, it can automatically implement intervention measures to prevent hazardous operations and ensure the safety of lives and property.

Part 1: Core Functions of the Crane Warning System

The functions of the alarm system can be categorized into the following levels based on their warning logic and intervention intensity:

1. Warning Function

Provide operators with advance warnings when approaching hazardous working conditions, allowing them ample time to adjust their operations.

Typical scenario: When the load reaches 90% of the rated lifting capacity (or a preset value), the system triggers a pre-alarm, usually indicated by a slow buzzing sound and a yellow flashing light to signal "approaching limit, please operate with caution.

2. Over-Limit Alarm Function

When the crane's parameters reach or exceed the rated limits, a strong warning is issued, requiring the operator to immediately stop the hazardous action.

Typical scenario: When the load exceeds 100% of the rated lifting capacity, the amplitude surpasses the maximum limit, and the lifting height reaches its limit, the system will trigger an emergency alarm. This alarm usually consists of a rapid buzzing sound and a red flashing light, accompanied by the warning: "Exceeded limit, stop immediately.

3. Automatic Protection Function

Function: This is the most essential security feature. If the operator does not respond promptly during or after the alarm, the system will automatically halt any dangerous operations.

In a typical scenario, when the system is overloaded, it will automatically cut off the hydraulic oil circuit or power to the hook lifting, arm extension, and amplification functions. However, it will still allow operation in safe directions—such as hook lowering, arm retraction, and amplitude reduction—to enable the resolution of hazardous situations.

4. Status Monitoring and Display Function

Real-time display of key job parameters, enabling operators to clearly understand the current status.

Display information such as real-time load, rated load, load percentage, working range, boom length, boom angle, wind speed, and more.

5. Data Recording and Traceability Functions

Automatically record all operational logs and alarm events, including time, load, amplitude, and operational actions. This is essential for conducting accident analysis, assigning responsibility, and improving future operations.

6. Self-Diagnostic Function

Function: The system can monitor the operational status of its sensors, circuits, and other components in real time. If a fault occurs—such as sensor damage or circuit breakage—it will immediately issue a fault alarm to the operator to prevent safety function failures caused by system malfunctions.

Part 2: Specific Alarm Products and Their Characteristics

The crane warning system is not a single product but consists of a series of independent or integrated devices. The following are the main types of products:

1. Load Moment Indicator（Click to view detailed information）

This is the most advanced and comprehensive alarm system, integrating the majority of the functions mentioned above.

Features:Core calculation: By collecting pressure (load) and length/angle (amplitude) signals, the working torque is calculated in real time and compared with the rated lifting table stored in the system.

Multi-parameter monitoring: Simultaneously monitor multiple hazardous working conditions, such as overload, excessive amplitude, and extreme height.

Graded alarm and control system: equipped with comprehensive warning features, over-limit alarms, and automatic cut-off functions.

Multi-Condition Support: It supports switching and calculations across multiple working conditions, including the main arm, auxiliary arm, fixed auxiliary arm, and super lift.

Product Form:An independent system consists of a main controller, display screen, angle sensor, pressure sensor, length sensor, and other components.

Features comprehensive functionality, high precision, and strong reliability. It is legally required equipment for mobile cranes, such as truck cranes and crawler cranes.

2.Load Indicator（Load Limiter)（Click to view detailed information）

It can be considered a  or  of the torque limiter, primarily focusing on load weight.

Features:Focus on preventing overload rather than on changes in amplitude.

Weight is typically estimated indirectly by measuring the hydraulic pressure of the lifting mechanism or the tension in the steel wire rope.

It also includes warning, alarm, and automatic cut-off functions.

Product Form:Commonly used for gantry cranes, tower cranes, and other cranes with fixed or limited range of motion.

Characteristics: The structure is relatively simple and cost-effective; however, its functionality is limited, making it unable to handle the risk of torque variations caused by changes in amplitude.

3. Travel Limiter

Used to limit the travel range of each operating mechanism.

Features:Height limiter: prevents the hook from toppling over (hitting the lifting mechanism) or from being lowered too far (causing the rope to tangle).

Amplitude limiter: prevents the boom from pitching beyond its maximum or minimum angle.

Rotation limiter: restricts the rotation angle to prevent cable twisting in cable-powered cranes.

Product Form:Mechanical limit switches include devices such as heavy hammer limit switches (for height limits) and cam limit switches (for amplitude or rotation limits). These switches are characterized by their simple structure, reliability, and low cost; however, their accuracy and ease of adjustment are somewhat limited.

Electronic/magnetic induction types include devices such as absolute value encoders (used for measuring angle and position) and magnetic proximity switches. These devices are characterized by high precision, non-contact operation, long lifespan, and easy integration with electronic control systems.

4. Wind-Resistant and Anti-Climbing Device

Features:Anemometer: Provides real-time monitoring of wind speed, issues an alarm when the wind speed exceeds the safety threshold, and prompts the operator to stop work, rotate the boom to the downwind direction, or lower it to a safe angle.

Rail clamp: Used for track-mounted cranes (such as gantry cranes and tower cranes) to secure the track after parking or during windy conditions, preventing the crane from moving (crawling) due to strong winds and avoiding derailment.

Anchoring device: Physically secure the crane base to the ground foundation.

Characteristics: This product is essential for ensuring the wind safety of large outdoor cranes, particularly in complex wind environments such as coastal areas and canyons.

5. Anti-Collision System

Features:Used in scenarios where multiple cranes operate simultaneously or when cranes are close to surrounding buildings.

Real-time monitoring of the distance between the crane and surrounding obstacles or other cranes using technologies such as laser ranging, radar, or GPS.

When the distance becomes too close, an alarm will sound to alert the operator, and the system may automatically slow down or stop movement in the dangerous direction.

Characteristics: This system features high technical content and plays a crucial role in enhancing the safety of tower operations and dense yard activities.

6. Video Surveillance System

Features:By installing waterproof, shock-absorbing cameras in blind spots—such as behind the hook, on both sides of the crane legs, and near the drum—video footage can be displayed in the cab.

Significantly expands the operator's field of vision, compensates for the limitations of visual observation, and helps prevent collisions or compression accidents caused by blind spots.

Characteristics: Although it is not classified as a direct alarm device, it serves as an active safety auxiliary device that can effectively prevent accidents and is often integrated with other alarm systems.

Modern advanced cranes typically utilize integrated, platform-based safety management systems that consolidate multiple subsystems into a central controller and display screen. This integration enables unified monitoring, alarm management, and data processing, offering operators the most comprehensive and reliable safety assurance. When selecting a system, a comprehensive configuration should be determined based on the crane's type, operating conditions, regulatory requirements, and budget.