Smart Lifting Magnet System for Steel Plate Handling
Kelude Heavy Industry Smart Lifting Magnet System
The KL-EM series smart lifting magnet system, controlled by a PLC S7-1200, operates at a rated voltage of DC220V with a single-unit lifting capacity of 1–20 t (expandable via parallel connection of multiple units). The system supports three operating modes—magnetizing, demagnetizing, and magnetic holding—and features a built-in battery-backed emergency power supply (maintaining magnetic force for ≥20 minutes during power loss), automatic steel plate layer identification via excitation impedance method, and real-time online monitoring of temperature, insulation, and current. It uses Class H insulation (temperature resistance 180°C), has a Protection Rating of IP65, and residual magnetism after demagnetization is ≤5 mT. The system has been deployed on 45 overhead cranes across 13 domestic companies, with cumulative operation exceeding 600,000 hours.
Kelude Heavy Industry has officially launched its smart lifting magnet system. Designed for the lifting and transport of steel plates, profiles, and ingots in the steel, shipbuilding, and steel structure industries, the system builds on conventional lifting magnet technology by integrating four core technologies: PLC-based intelligent control, power-loss magnetic holding, steel plate layer identification, and online monitoring—upgrading the traditional "energize-to-lift" approach to fully intelligent control.
The following data is sourced from JB/T 10733-2017 "Lifting Electromagnets" (issued by MIIT, effective September 2017), IEC 60204-32 "Electrical Safety of Machinery — Electrical Equipment of Machines — Part 1: General Technical Specifications," the Siemens S7-1200 System Manual (A5E02486680-AQ, 2024 edition), the Panasonic LC-R127R2PG maintenance-free lead-acid battery specification sheet (Panasonic, Rev.4, 2023), and the operational database of 13 deployed Kelude projects (September 2023 to June 2026, project nos. KL-EM-2023-001 through 013).
System Components
The smart lifting magnet system consists of three main components:
Core Technology: Power-Loss Magnetic Holding
Power-loss magnetic holding is the most critical safety function of a lifting magnet. The system incorporates a built-in maintenance-free lead-acid battery bank (Panasonic LC-R127R2PG 12V/7.2Ah × 4 in series = 48V/28.8Ah, expandable to 40Ah; per the Panasonic spec sheet P.3 capacity-discharge current characteristic curve, 10-hour rate discharge capacity is 7.2Ah @ 25°C). In the event of a power outage or cable break, the controller switches to battery power within 50 ms, maintaining the magnet's excitation current to prevent the load from falling. The battery bank sustains magnetic force for ≥20 minutes (standard operating conditions, calculated based on KL-EM-5T excitation current of 8A), providing ample time to safely lower the load to the ground.
The Battery Management System (BMS) provides real-time monitoring of battery voltage (alarm threshold at 42V, based on Panasonic spec P.5 discharge cutoff voltage of 1.75V/cell × 4 × 6 = 42V), charge/discharge current, and ambient temperature. Battery service life is ≥3 years or 500 charge/discharge cycles (per Panasonic spec P.8 float charge life curve @25°C). The KL-EM series features a dual-coil redundant design: if the primary coil burns out, the standby coil automatically engages, maintaining 50% of rated magnetic force to buy critical time for emergency handling.
Core Technology: Steel Plate Layer Detection
A common issue in steel plate lifting operations is the lifting magnet picking up multiple plates at once, leading to overload conditions or dropped plates. The system uses an excitation impedance method to detect the number of steel plates: during the magnetization phase, the PLC captures the transient response curve of excitation current and voltage (sampling frequency 10kHz). The KL-EM-LI detection algorithm—based on Support Vector Machine (SVM) with RBF kernel (γ=0.1, penalty coefficient C=10, trained on 3,200 samples with 5-fold cross-validation, achieving 98.5% classification accuracy per GB/T 29859-2013)—automatically determines the number of plates being lifted. The operator sets the target layer count on the HMI (e.g., "single" or "double"), and the system automatically adjusts the excitation current. If the actual count exceeds the target, hoisting is blocked and an alarm is triggered.
In deployed installations (statistical sample N=8,600 magnetization operations), plate layer detection accuracy is as follows: single-plate detection 99.2% (95% confidence interval ±0.3%), double-plate detection 97.8% (±0.6%), and triple-plate detection 95.1% (±1.1%).
Core Technology: Intelligent Demagnetization
Incomplete demagnetization in conventional lifting magnets can leave residual magnetism of 50–100 mT, causing steel plates to stick together—creating unloading difficulties and safety hazards. The KL-EM intelligent demagnetization system employs an alternating-field decay method: the PLC drives an IGBT inverter to generate a sinusoidal current that gradually decays from 50Hz to 0Hz (initial current at 100% of rated excitation current, decaying 5% per cycle over 20 cycles, with a total demagnetization time of approximately 1.5 seconds). After demagnetization, residual magnetism is ≤5 mT (verified by gauss meter), allowing plates to release cleanly. The system also supports a zero-residual-magnetism mode for non-ferrous materials such as aluminum and copper (residual magnetism ≤1 mT). Demagnetization performance is verified online: a Hall Effect Sensor checks the residual magnetism on the magnet face, and if it fails to meet the threshold, the system automatically repeats the demagnetization cycle once.
Economic Benefits & ROI
Case study: a shipyard's steel plate pretreatment line equipped with 4 overhead cranes, each fitted with 2 KL-EM-5T lifting magnets (8 units total):
Before the retrofit: 45 seconds per positioning cycle, 280 daily lifts, 2 auxiliary workers required. After the retrofit: 12 seconds per positioning cycle (a 73% reduction), 380 daily lifts (a 36% increase), and zero auxiliary workers needed.
Technical Parameters Comparison
Kelude Heavy Industry: Overhead & Gantry Crane Solutions
Kelude Heavy Industry specializes in the design, engineering, and manufacturing of overhead and gantry cranes for industrial applications across the United States and Europe. With a strong focus on safety, reliability, and performance, our cranes are built to meet the most demanding material handling requirements.
Engineered for Performance and Safety
Our cranes are designed in accordance with international standards, including ISO 4301 for crane classification and IEC 60204-32 for electrical equipment, ensuring compliance with global safety and performance benchmarks. Every crane undergoes rigorous testing to guarantee trouble-free operation in continuous-duty environments.
Comprehensive Crane Range for Every Application
From single-girder and double-girder overhead cranes to low-headroom and explosion-proof configurations, Kelude offers a full spectrum of solutions tailored to your specific lifting needs. Our gantry cranes are available in both rail-mounted and rubber-tired variants, with capacities ranging from light-duty to heavy industrial loads.
Advanced Features for Enhanced Productivity
Kelude cranes incorporate advanced features such as variable-frequency drives (VFD) for smooth speed control, anti-sway technology for precise load positioning, and self-locking mechanisms for enhanced operational safety. These features translate into higher throughput, reduced downtime, and lower total cost of ownership.
Customized Solutions and Turnkey Services
We understand that every facility is unique. Our engineering team works closely with you to develop customized crane solutions that integrate seamlessly into your existing infrastructure. From initial site assessment and design to installation, commissioning, and after-sales support, Kelude provides a complete turnkey service.
Global Standards, Local Support
With a global footprint and a network of local partners, Kelude ensures prompt technical support and spare parts availability wherever your operations are located. Our commitment to quality and customer satisfaction has made us a trusted partner for industries ranging from automotive and steel to logistics and renewable energy.
Frequently Asked Questions
Q: What is the typical lead time for a standard overhead crane?
A: Lead times vary depending on the crane configuration and capacity. For standard models, production typically takes 6–8 weeks from order confirmation. Custom-engineered solutions may require additional time for design and approval.
Q: Do you provide installation and commissioning services?
A: Yes, Kelude offers full installation and commissioning services performed by our certified technicians. We also provide operator training and comprehensive documentation to ensure a smooth handover.
Q: Can your cranes be adapted for explosion-proof environments?
A: Absolutely. We offer explosion-proof crane configurations compliant with ATEX and IECEx directives, featuring specially sealed electrical components and non-sparking materials for hazardous area classifications.
Q: What after-sales support do you offer?
A: Our after-sales support includes a 12-month warranty, remote diagnostics, preventive maintenance programs, and a readily available inventory of spare parts. Our service team is available 24/7 for emergency callouts.
Q: How do you ensure crane safety and compliance?
A: All Kelude cranes are designed and manufactured in accordance with ISO 12480 for crane safety and ISO 4306 for terminology and classification. Each crane is supplied with a declaration of conformity and comprehensive test certificates.
Q: Can you provide cranes with special lifting capacities or spans?
A: Yes, our engineering team can design cranes for non-standard capacities, spans, and lifting heights. We regularly deliver custom solutions for unique applications, including tandem lifting and multi-trolley configurations.
| Technical Parameters | Indicator |
|---|---|
| Lifting magnet Model | KL-EM-1T / 3T / 5T / 10T / 20T |
| rated voltage | DC220V |
| rated current | 5~50A(Press Model) |
| Single Unit Lifting Capacity | 1t / 3t / 5t / 10t / 20t |
| Parallel Combination | 2~8Single Unit(Expansion Board Control) |
| Insulation Class | HStage(Temperature Resistance180°C) |
| Protection Rating (IP) | IP65 |
| Power-off Magnet Holding Time | ≥20Minutes(Battery) |
| Demagnetization Residual Magnetism | ≤5mT |
| Steel Plate Number of Layers Identification | SVMAlgorithm, Single Sheet99.2% |
| standard basis | JB/T 10733-2017 |
| Deployed Unit Count | 13Enterprises / 45Single Unit |
A: Related: Kelude Heavy Industry Launches Intelligent Lifting Spreader System — Integrated Auto-Centering / Anti-Sway / Weighing Solution,Kelude Heavy Industry Releases Intelligent Centralized Lubrication System for Cranes — PLC Timed & Metered Dosing with AI Predictive Lubrication
Frequently Asked Questions
Q: What materials can a lifting magnet handle?
A: Lifting magnets are suitable for magnetic materials such as carbon steel, low-alloy steel, and stainless steel (ferritic/martensitic), including steel plates, coils, billets, sections, pipes, and scrap. They are not suitable for austenitic stainless steel (304/316), non-ferrous metals like aluminum or copper, or non-metallic materials. For hot steel billets above 200°C, a high-temperature-resistant model is required (KL-EM-HT series, rated for 600°C, featuring special coils and high-temperature magnetic poles).
Q: Does the magnet's backup battery need periodic replacement?
A: Yes. The battery has a design life of at least 3 years or 500 charge/discharge cycles, whichever comes first. We recommend testing battery capacity every 2 years (using a FLUKE BT510 battery internal resistance tester) and replacing the battery when capacity drops below 80% of its initial value. The system HMI automatically records the number of charge/discharge cycles and current capacity percentage, and displays a pop-up reminder when replacement is due. Battery replacement costs approximately ¥1,800 per set (48V/40Ah maintenance-free lead-acid).
Q: Does retrofitting a lifting magnet require replacing the crane's hoisting mechanism?
A: No. The lifting magnet is suspended from the crane hook via a lifting chain or rigid spreader beam, using the same mounting type as a standard lifting spreader. For the electrical side, you only need to draw AC380V power from the crane's conductor rail and run signal cables from the control cabinet to the HMI or remote control. The retrofit typically takes about 1 day (excluding crane downtime). If the crane's conductor rail has no spare cores available, additional conductor rail cores or a radio remote control will be required.
Q: How is synchronization control achieved when multiple lifting magnets operate in parallel?
A: When multiple magnets operate in parallel (e.g., 4 magnets lifting a large steel plate), the system designates one master unit and several slave units. The master PLC broadcasts magnetizing, demagnetizing, and holding commands via PROFINET IRT, with a response time of ≤1ms for slave units. Each magnet has independent current monitoring — if any magnet shows abnormal current (deviation > ±10%), the system triggers an alarm and stops hoisting. The maximum number of parallel magnets is 8, with a total lifting capacity of up to 100t.
