ISO 22923:2017 Crane Load Indicator Standard Explained
ISO 22923:2017, "Cranes — Load Indicators," is the international standard governing load indicating devices (Lifting Capacity and moment indicators) on cranes. The standard defines the classification, performance requirements, test methods, and calibration rules for load indicators — applicable to load indicating and overload protection devices on all crane types.
Load Indicator Types and Functions
Kelude manufactures in strict compliance with international standards. ISO 22923:2017 classifies crane load indicators into three categories. The Load Indicator displays the current suspended load in real time (in tons or kilograms), allowing the operator to monitor the actual Lifting Capacity and prevent overload. Minimum requirements: accuracy of ±5% and a Response time of ≤1 second. The Load Limiter automatically cuts off the hoisting-up motion (allowing lowering only) when the Lifting Capacity exceeds the set value. The trigger threshold is 110% of the Rated Lifting Capacity, with an accuracy of ±5% and a Response time of ≤0.5 seconds. The Load moment limiter (LML) calculates the load moment in real time (moment = load × Working radius) and compares it against the Rated load moment at the current radius. An early warning (yellow alert) is issued when the moment reaches 90% of the rated value; an alarm with automatic shutdown of dangerous-direction motions (red alert) is triggered at 105%. Moment measurement accuracy is ±5%. All load indicators must consist of the following components: sensors (Load cell, angle sensor, length sensor, etc.), a data processing unit (microprocessor), a display unit (LED/LCD display screen), and alarm outputs (Audible & Visual Alarm plus relay outputs for cutting the control circuit). The standard specifically requires a self-check function: the indicator must run an automatic self-check at every power-on (verifying that all indications and alarm functions are operational). If the self-check fails, crane operation must not be permitted.
Sensor Requirements
The standard specifies the following sensor requirements. Lifting Capacity sensors may be either force sensors (installed at the fixed end of the hoisting rope) or Pressure Sensors (installed at the hydraulic cylinder inlet of the hydraulic hoisting system). Sensor accuracy must be ≥0.5% FS (full-scale accuracy), with long-term Stability (annual drift ≤0.2% FS). Overload capacity: sensors must withstand 2 times the rated load without damage (safety margin). Environmental adaptability: operating temperature from -20°C to +70°C, with a Protection Rating (IP) of at least IP65 (dustproof and Water Jet Proof). Angle sensors (for Boom angle measurement) must provide accuracy of ≥±0.2° and Resolution of ≤0.1°, applicable to luffing and Tower Crane Boom angle measurement. Length sensors (for Telescopic boom length measurement) must provide accuracy of ≥±0.5%, applicable to Telescopic boom length measurement on Mobile Cranes. Wind Speed Sensors must provide accuracy of ≥±0.5 m/s, applicable to all outdoor cranes. Signal transmission from sensors to the data processing unit must use Shielded Cable (to prevent electromagnetic interference) or wireless transmission with encryption and verification between the sensor and receiver (to prevent signal loss or interference). The standard further requires sensors to have Fault Diagnosis capability: when a sensor fails or a signal is abnormal, the load indicator must detect the fault, display a Fault code, and simultaneously cut off dangerous-direction motions — safety first: operation must not continue under fault conditions.
Calibration and Verification
The standard sets out the following calibration and verification requirements for load indicators. Factory calibration: every load indicator must be calibrated unit by unit using Standard Weight or a load cell before delivery, with calibration records delivered with the equipment (including calibration date, calibration body, and calibration data). The calibration report must state the deviation between measured values and characteristic values at each calibration point; all deviations must be within ±2%. On-site calibration: after installation on the crane, the load indicator must be calibrated on site by actual loading with Standard Weight of known weight (or via hydraulic load cell) at each major Working radius, comparing and adjusting the sensor output against the actual load. At least 3 load points (50%, 75%, and 100% of rated load) and 3 radius points (Minimum radius, intermediate radius, and Maximum radius) must be used. Every crane must undergo on-site calibration before delivery and after each installation (for Tower Cranes, after each re-installation at a new site) to confirm that the load indicator's measurement accuracy is within ±5%. Periodic calibration: load indicators must undergo accuracy verification every 12 months (by loading with Standard Weight or a comparison dynamometer at major radii); verification records must be archived for at least 6 years. After major Maintenance or Retrofit of the crane (e.g., Boom replacement or changes to the Rated Lifting Capacity), the load indicator must be recalibrated. Load indicators that fail calibration must not remain in service — they must be repaired or replaced and then recalibrated.
Display and Alarm Requirements
The standard specifies the following display and alarm requirements. Display content: the load indicator's display screen must show the following parameters in real time: actual Lifting Capacity (t or kg), current Working radius (m), current load moment (kN·m), and percentage of Rated load moment (%). Optional display parameters include Boom angle (°), jib length (m), wind speed (m/s), and number of working cycles. Display brightness must be adjustable and remain clearly readable under bright light (50,000 lux) and in low-light conditions. Alarm modes are divided into two levels. Early warning (yellow): when the moment reaches 90% of the rated value, a yellow LED flashes with an intermittent buzzer (500 ms on / 500 ms off) to alert the operator. Alarm (red): when the moment reaches 105% of the rated value or the Lifting Capacity reaches 110% of the Rated Lifting Capacity, a red LED flashes with a continuous buzzer, and dangerous-direction motions — hoisting up, increasing radius, and extending the boom — are automatically cut off. Only safe-direction motions (lowering, decreasing radius, retracting the boom) remain available. Alarm reset: the alarm state can only be manually reset after the load returns to the safe range (moment < 90% of rated value), at which point dangerous-direction motions are restored. The standard also requires load indicators to have data logging capability, recording the time and load parameters of each alarm event. Data must be retained for at least 3 months for safety traceability and incident analysis.
| Loadindicating device | function | accuracy requirements | calibration interval |
|---|---|---|---|
| Load moment limiter (LML) | real-time Torque%display | ±5% | monthly |
| load indicator | Lifting Capacity%display | ±3% | monthly |
| Radius indicator | Working radiusreal-time display | ±2% | weekly |
| operating conditionsselector | operating conditions Parametersetting | accuracy | each timeoperating conditionsswitching |
| calibration item | requirements | calibration interval | method |
|---|---|---|---|
| display Accuracy | ≤±5% | annually | Test Weight Calibration |
| functional test | Audible and Visual Alarm | monthly | Lifting Testing |
| Sensor | guardsnormal | weekly | visual inspection |
| connecting cable | free from damage | monthly | visual inspection |
FAQ
Q: What accuracy requirements does ISO 22923 set for load indicators?
A: The standard requires a comprehensive accuracy of ≤±5% for load indicators. This accuracy covers the combined error of the sensor, signal processing circuit, and display instrument. Calibration should be performed annually using standard weights, with point-by-point verification and a calibration curve recorded.
Q: What is the difference between a load limiter and a load indicator?
A: A load indicator displays the real-time load value for the operator's reference. A load limiter automatically cuts off the power source to stop hazardous movements when the load reaches a preset value. The two are often used together — the indicator shows the current value, while the limiter triggers an automatic shutdown at 110% overload. The standard requires that both be verified separately.
Q: How should load indicators be routinely checked?
A: Perform a functional test monthly — lift standard weights of known mass and verify that the displayed value falls within the allowable error range. Test points include no-load, 50% rated load, and 100% rated load conditions. If deviation exceeds acceptable limits, stop operation immediately and notify qualified maintenance personnel for adjustment.
Q: What sensor types and protection ratings apply to load indicators?
A: Common sensors include strain-gauge force sensors (mounted on the drum support or hook block sheave) and pressure sensors (for hydraulic cranes). Sensors must have a protection rating of at least IP54, or IP65 in high-temperature, dusty environments. Sensors should be cleaned and inspected on a regular basis.
