ISO 10245-5:2008 Limiters & Indicators for Cranes
ISO 10245-5:2008 "Cranes — Limiters and indicators — Part 5: Bridge and gantry cranes" is the dedicated safety device standard for bridge and gantry cranes. It specifies the technical requirements, test methods, and calibration intervals for safety devices including load limiters, load moment limiters, height limit switches, and travel limit switches.
Load Limiter Technical Requirements
Load limiters on bridge and gantry cranes are mounted at the wire rope dead end or on the drum support, determining the suspended load mass by measuring wire rope tension or drum torque. Sensor types include pin-type load cells with ±1% accuracy and a measuring range of 120% of rated load, tension/compression load cells with ±1% accuracy welded to the wire rope dead-end plate, and electronic load measuring devices that indirectly calculate the lifting capacity by monitoring motor current or drum torque with ±3% accuracy. The load limiter trip point is set at 105% of rated load — when the suspended load exceeds 105%, hoisting is automatically stopped while lowering remains permitted. The limiter must be configured independently of the load moment limiter to serve as a backup protection device. The current suspended load is displayed in real time with ±5% accuracy and a refresh cycle of ≤0.5s.
Limit Switches and Safety Requirements
The height limit switch prevents the hook from over-traveling into the boom. An early warning is issued 0.5m before the hook reaches its highest permitted position (first-stage limit with audible and visual alarm), and hoisting is automatically stopped 0.3m before the top position (second-stage limit) by cutting power to the hoisting motor while allowing lowering. The device uses weight-type or spiral-type travel switches with double-break contacts configured as one normally-open and one normally-closed pair to prevent contact welding. Trolley and crane bridge travel limit switches are arranged at both ends of the crane rail: a deceleration limit switch triggers ≤2m before the end stop to reduce speed to creep, and a stopping limit switch triggers ≤1m before the end stop to cut power to the corresponding direction motor. Mechanical buffers and buffer stops are fitted at both rail ends. The limit function is manually triggered and checked each shift, with quarterly inspections of contact wear and terminal block oxidation. Protection rating ≥IP65.
| safety device | Function | Setpoint | Accuracy |
|---|---|---|---|
| Lifting Capacity Limiter / Load Limiter | Overload protection | 105%Stop Hoisting / Lifting | ±1%~±3% |
| Load moment limiter (LML) | Torque Protection | 90%early warning/100%Stop | ±5% |
| Height Limit Switch | Anti-two-block | 0.5m/0.3m | —— |
| Travel Limit Switch | Anti-runaway | Pre-limit1m | —— |
| Buffer | Shock absorption | At limit | —— |
Maintenance and Calibration Intervals
Routine maintenance and calibration of safety devices are essential to ensuring reliability. At the start of each shift, verify the LML self-test function — the power-on buzzer and display self-check should operate normally, and the sensor connecting cable must be free of damage with no loose plugs. Monthly, use Standard Weights to verify the Load Limiter at 50% and 100% of capacity; the deviation between displayed and actual values must not exceed ±3%. Every six months, perform a full-range calibration of the load moment limiter using a force sensor or test weights, with five loading points at 20%/50%/75%/100%/110% of the measuring range. Test each point three times and use the average value; the combined error must be ≤±5%. Limit switches are manually triggered and tested each month. Calibration records must be kept in archival storage for at least 3 years, with the calibration label affixed to the display housing. All safety devices on Kelude bridge and gantry cranes are fully calibrated before delivery.
| maintenance item | Cycle | Method | acceptance criteria |
|---|---|---|---|
| LMLSelf-check | Per shift | Power-on Buzzer | Normal |
| Sensor Connection | Per shift | Visual | No damage/Looseness |
| Lifting Capacity Limiter / Load Limiter | Monthly | 50%/100%Load application | ±3% |
| Load moment limiter (LML) | Semi-annually | 20%/50%/75%/100%/110% | ±5% |
| Limit Switch | Monthly | Manual Trigger | Sensitivity/Alarm |
Frequently Asked Questions
Q: What is the difference between a lifting capacity limiter and a load moment limiter?
A: The lifting capacity limiter stops hoisting at 105% of rated load. The load moment limiter stops both hoisting and derricking at 100% of rated load moment. The lifting capacity limiter operates independently of the load moment limiter as a backup protection.
Q: What are the height limit switch settings?
A: The first stage triggers an early warning at 0.5m, and the second stage initiates an automatic stop at 0.3m. The weight-type or spiral-type travel switches feature double-break contacts. A functional check is required every shift, with contact inspection performed quarterly.
Q: What is the protection rating of the sensors?
A: Sensors are rated at IP67 or higher (no water ingress after submersion at 1m for 30 minutes). Displays are rated at IP54 minimum for indoor use and IP65 for outdoor applications. The connecting cable is shielded and protected by a metal hose.
Q: What is the recommended calibration interval?
A: The lifting capacity limiter requires a two-point calibration (50%/100%) every month. The load moment limiter needs a five-point calibration (20%/50%/75%/100%/110%) every six months. Limit switches undergo a functional check monthly. Calibration records must be retained for at least 3 years.
