Articulated Boom Crane Load Moment Indicator (LMI)

Articulated Boom Crane Load Moment Indicator also known as crane LMI or crane Safe Load Indicator (SLI) is a safety protection device applied to boom type lifting machinery, it can prevent the crane due to overload and operation errors caused by accidents, so that the safe use of the crane to achieve standardization and scientific. Its essence is a safety accessory to provide overload protection, often used in lifting equipment, lifting torque once exceeded the limit can automatically break, stop action to protect the equipment.
The Load Moment Indicator uses the moment balance principle to calculate the actual lifting load. According to the principle of moment balance, the equivalent mass of the boom at the head position is calculated when the boom is not loaded. Because the equivalent mass of the boom is different at different lengths and angles, an infinite number of values need to be calibrated.
Because of the existence of boom, the algorithm of Load Moment Indicator is different from that of truck crane, so a specific no-load calibration algorithm should be proposed to equate the dead weight of boom and boom in the boom head. According to the structure and force characteristics of the crane with folding arm, the mathematical model of the working device is established, and the no-load calibration is realized by calibrating the weight and center of gravity of the lifting arm.

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SZ-AB100P Articulated Boom Crane LMI

Product Overview

The SeeZol SZ-AB100P Articulated Boom Crane Load Moment Indicator (LMI) is an intelligent safety monitoring instrument that integrates measurement, control and micro-computer technology. It reflects boom angle, boom length, lifting weight and overload status on the cab display in real time, keeping the folding-boom crane within its safe operating envelope. Compared with the SZ-AB100, the SZ-AB100P features optimized software—revised angle calibration and weight-input methods—for higher data accuracy and stability. When the crane approaches or exceeds the allowable limit, the system triggers audible/visual alarms and sends relay outputs to cut dangerous motions (e.g. hoisting).

Applicable Models

● Articulated boom trucks / Truck-mounted folding boom cranes
● Lifting equipment featuring a folding boom that requires monitoring of the dual angles (main boom and folding boom) and boom length

Key Features

● Real-time display of current load / maximum allowable load at current position (dual-value display)
● Real-time load percentage bar graph (yellow by default; turns red when thresholds are exceeded)
● 2D vehicle attitude display showing height, working radius, boom/articulated arm angles, and boom length
● Audible and visual alarms + three-color indicator light + relay control output (cuts off hazardous movements when thresholds are exceeded)
● Alarm data logging (trigger/clear times, severity level, source, and values); data exportable via USB drive
● Day/night display mode switching
● System language in Chinese and English (other languages ​​customizable)
● Independently configurable percentage thresholds for pre-alarms and alarms

System Parameters

Parameter

Specification

Operating Voltage 

DC 12–36V
Operating Temperature

−30℃ ~ +80℃

Relative Humidity

<95% (25℃)
Operating Mode

Continuous

Power Consumption

<10W
Control Output Capacity

10A AC220V / 10A AC36V

System Error

≤ ±5%
Alarm Error

≤ ±5%

Main Components

  • Indicator
  • Weight Sensor
  • Angle Sensor
  • Length Sensor
  • Three-Colour Light

Application Case

A forestry operator deployed SeeZol articulated-boom LMIs on truck-mounted cranes, preventing overload during log handling where boom geometry changes constantly.

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