Crane Limit Switch Types & Selection Guide
Key Point Crane limit switches are safety protection devices that automatically cut off the power supply when a mechanism travels to its extreme position. ①They fall into five categories: hoisting limit switches (weight-type/worm-type), travel limit switches (crane bridge/trolley), overload limiters, door limit switches, and phase-loss limit switches; ②The hoisting limit switch trigger point is set ≤200mm from the hook's upper limit position, with an actuation tolerance of ≤20mm; ③Travel limit switches are mounted at both ends of the crane rail and, once triggered, cut off the travel power while retaining braking capability; ④Kelude Heavy Industry cranes come standard with five-fold limit protection, offering QCX-series overload limiters and LX-series travel switch accessories.
Limit Switch Types and Selection Parameters
Limit switches serve as the first line of defense in a crane's electrical safety protection system. Hoisting limit switches prevent the hook from striking the upper stop, travel limit switches keep the crane bridge and trolley from running off the rails, overload limiters guard against lifting beyond rated capacity, door limit switches keep maintenance personnel from entering hazardous areas, and phase-loss limit switches forcibly cut the main power supply when a contactor welds shut. The crane safety protection system engineering design requires that the trigger point and cut-off time of limit switches comply with ISO 4301 and GB/T 28264 Safety Monitoring and Management System standards. Kelude Heavy Industry commissions the actuation position of every limit switch unit by unit before delivery.
| Type | Common Model | Actuation Mode | contact Capacity | Protection Rating (IP) | reference price(Unit) |
|---|---|---|---|---|---|
| Weight Typehoisting limit switch | LX36-80 | Weight Drop Machinery Trigger | AC-15 380V/3A | IP54 | 40~80 |
| Worm Gear Typehoisting limit switch | BLKT-D | worm gear/Rotation Cam | AC-15 380V/5A | IP55 | 80~180 |
| Travel Limit Switch(Crane Bridge) | LX19-111 | Lever Roller/Impact Trigger | AC-15 380V/3A | IP54 | 30~60 |
| Travel Limit Switch(Trolley) | LX33-10 | Trip Bar Type/Impact Trigger | AC-15 380V/2A | IP54 | 30~50 |
| Overload Limiter | QCX-H2Z | Sensor+Instrument/Electronic Type | Relay Output220V/5A | IP54 | 600~2000 |
| Door Limit switch | LXW5-11 | Micro Switch/Door Open Trigger | AC-15 380V/1A | IP54 | 20~50 |
| power-off limit switch | QHX-20 | mechanical lock Latch/Contactor Sticking Protection | AC-15 380V/10A | IP44 | 80~200 |
Limit Switch Installation and Commissioning Requirements
| limit switch Type | installation position | Trigger Distance | Actuation Tolerance | reset method |
|---|---|---|---|---|
| Hoisting / Lifting Upper Limit | Drum Above/Wire Rope Side | ≤200mm | ≤20mm | manual reset |
| Crane Bridge Travel Limit Switch | Crane Rail Both Ends/End Carriage Side | Distance Buffer stop≥1.5m | ≤50mm | Auto Reset |
| trolley travel limit | Main Girder Both Ends | Distance Buffer stop≥0.5m | ≤30mm | Auto Reset |
| Overload Limiter | Hook block/Drum Bearing Housing | ≥110%rated load | ≤±5% | Auto Reset |
Limit Switch Selection Precautions
Limit Switch Wiring and Commissioning Parameters
Limit switch wiring must comply with GB/T 28264-2017: the hoisting limit switch is wired in series with the hoisting contactor coil circuit (normally closed contact). When triggered, it cuts power to the hoisting-up circuit but leaves the lowering circuit energized, allowing the hook to be lowered to a safe position. Travel limit switches are wired in series with the crane bridge and trolley travel contactor coil circuits; when triggered, they cut travel power while keeping the brake supply live.
Commissioning standards: When the hoisting limit switch is triggered, the clearance between the hook at its upper limit and the underside of the trolley frame must be ≥200 mm (per ISO 4301), with an actuation error of ≤±20 mm. After a travel limit switch is triggered, the crane's coasting distance must not exceed 80% of the buffer stroke, and the trigger point must be at least 1.5 m from the end of the crane rail (bridge travel) or 0.5 m (trolley travel). Overload limiter calibration: zero the unit at no-load, then apply the rated load to set full scale, with the 110% early-warning and 130% cut-off thresholds configured. Power-cut limit switch test: manually open the main contactor contacts, apply power, and verify that the power-cut limit switch forces a complete shutdown of the main power supply.
Limit Switch Electrical Selection Parameters
Kelude Heavy Industry: Overhead & Gantry Crane Solutions
Kelude Heavy Industry specializes in the design, engineering, and manufacturing of heavy-duty overhead cranes, gantry cranes, and electric hoists. With a strong focus on safety, performance, and longevity, our material handling equipment is built to meet the rigorous demands of industrial environments across the globe. From standard configurations to fully customized systems, we deliver reliable lifting solutions that optimize workflow and ensure operational continuity.
Engineered for Performance and Reliability
Our cranes are constructed with high-strength steel and feature advanced control systems for precise load handling and smooth operation. We integrate proven components from leading global manufacturers to ensure every unit delivers consistent performance under the most challenging conditions. Whether it's a single-girder design for lighter duty cycles or a double-girder configuration for heavy lifting, our equipment is engineered to maximize uptime and minimize maintenance requirements.
Customized Solutions for Diverse Industrial Applications
We understand that every facility has unique material handling needs. That's why we offer a comprehensive range of customization options, including span, lifting height, trolley speed, and control systems. Our engineering team works closely with clients to develop solutions that seamlessly integrate into existing workflows, enhancing efficiency and safety. From automotive assembly lines to steel processing plants, our cranes are deployed across a wide spectrum of industries, providing dependable service day in and day out.
Rigorous Quality Assurance and Global Compliance
Quality is at the core of our manufacturing process. Each crane undergoes rigorous testing and inspection at every stage of production, from raw material verification to final load testing. Our equipment is designed and manufactured in accordance with international standards, including ISO 4301 for crane classification and IEC 60204-32 for electrical equipment, ensuring compliance with the stringent safety and performance requirements of the North American and European markets.
Comprehensive After-Sales Support and Service
Our commitment to our customers extends well beyond the initial sale. We provide complete after-sales support, including installation supervision, operator training, preventive maintenance programs, and readily available spare parts. Our global service network ensures prompt response times and expert assistance, minimizing downtime and extending the lifespan of your equipment. With Kelude, you have a dedicated partner committed to the long-term productivity of your operations.
Contact Kelude for Your Lifting Needs
Ready to enhance your material handling capabilities? Contact our team of experts today to discuss your specific requirements and discover how Kelude heavy-duty cranes can deliver measurable value to your business. We look forward to engineering a solution that meets your exact needs and exceeds your expectations.
| limit switch Type | rated voltage(V) | rated current(A) | mechanical life(10,000 Cycles) | Protection Rating (IP) | Applicable Environment |
|---|---|---|---|---|---|
| LX36-80(Weight Type) | AC 380 | 3 | 30 | IP65 | Indoor/Outdoor |
| LX19-111(Travel Limit Switch) | AC 380 / DC 220 | 5 | 50 | IP64 | Indoor |
| QCX-2E(Overload Limiter) | AC 220 / DC 24 | 2 | — | IP54 | Indoor/Outdoor |
| power-off limit switch | AC 380 | 10 | 10 | IP54 | Indoor |
Kelude Heavy Industry's QCX series overload limiters feature digital tube or LCD displays with real-time display of lifting capacity percentage, and parameters are saved in memory upon power-off. The sensors use column-type or S-type tension/compression force sensors with comprehensive accuracy of ±0.5% F.S.
Limit Switch Routine Inspection & Replacement
Routine Inspection: Manually trigger the limit switch before each shift to confirm proper operation; check contact oxidation and terminal looseness monthly; measure normally closed contact resistance with a multimeter quarterly (≤0.1Ω).
Scheduled Replacement: Hoisting limit switches should be replaced every 2 years or after 200,000 actuation cycles; travel limit switches every 3 years or 500,000 cycles; overload limiter sensors require calibration every 5 years, with immediate instrument replacement upon failure; power-off limit switches are replaced together with the control cabinet overhaul (every 5 years). Immediate replacement is required under the following conditions: welded or fused contacts, cracked housing, stuck counterweight, or corroded terminal blocks.
Common Fault Troubleshooting for Limit Switches
Fault 1: Mechanism does not stop after limit trigger — Check whether contacts are welded (using multimeter resistance mode), verify wiring is correct, and rule out welded main contactor contacts.
Fault 2: Limit triggers prematurely — Check the trip dog position and angle; for counterweight-type switches, verify the counterweight is not obstructed by foreign objects; for travel limit switches, inspect the crane rail for obstacles.
Fault 3: Overload limiter false alarms — Inspect the sensor cable for damage, check the connector for water ingress, and verify instrument parameters have not drifted. Recalibration resolves most false alarm issues.
Fault 4: Power-off limit switch fails to reset — Use a flat-head screwdriver to manually reset the latch mechanism and confirm the return spring has not failed. Kelude Heavy Industry offers limit switch spare part kits and on-site commissioning services, with nationwide response within 48 hours.
FAQ
Q: What causes hoisting limit switch failure?
A: ① The counterweight is caught on the wire rope and fails to descend; ② limit switch contacts are oxidized or burned; ③ terminal connections are loose or broken; ④ the worm gear mechanism is seized. Kelude Heavy Industry recommends manually testing the limit action monthly and replacing the switch immediately upon failure.
Q: How is the overload limiter calibrated?
A: QCX series overload limiter calibration procedure: input the sensor signal to the instrument, perform no-load zero adjustment, then load calibration (using standard test weights or hydraulic testing), set the alarm point (110% of rated load) and the cut-off point (130% of rated load). Kelude Heavy Industry offers on-site calibration services.
Q: Can the travel limit switch be adjusted?
A: Yes. The LX19 series travel limit switches allow the trigger point to be changed by adjusting the trip dog angle and position. Kelude Heavy Industry recommends leaving buffer distance during installation (crane bridge ≥1.5m, trolley ≥0.5m) to ensure sufficient braking distance after the limit is triggered.
Q: What is the difference between a power-off limit switch and a standard limit switch?
A: The power-off limit switch is a safety redundancy protective device. When the main contactor cannot interrupt power due to welded contacts, the power-off limit switch directly cuts the main power supply inlet (main circuit) through a mechanical lock, serving as the final physical protection. Standard limit switches only control the secondary circuit (contactor coil). Kelude Heavy Industry cranes are equipped with power-off limit switches as standard.
The above serves as a complete technical guide for crane limit switch selection and installation & commissioning. Kelude Heavy Industry cranes come standard with five levels of limit protection (hoisting limit switch + travel limit switch + overload limiter + door limit switch + power-off limit switch), and offer QCX series overload limiters along with LX series switch accessories. For limit system configuration, please contact the Kelude Heavy Industry technical team.
