3Emergency Stop
Architecture: Independent hardwired emergency stop relay circuit with dual-channel redundancy directly controlling the main contactor coil power supply.
Response: Unaffected by wireless signal interruption or failure — pressing the Emergency Stop Button cuts the main power supply within ≤20ms.
Maintenance: It is recommended to test emergency stop reliability once per shift to ensure proper operation in an emergency.
4Control Mode Switching
Interlock: The Remote Control, Operator Cabin, and floor Push-Button Pendant are hardwired-interlocked via a three-position Key switch (Cabin / Remote / Off).
Safety: Only authorized personnel can switch modes; only one control method is active at any given time, preventing logic conflicts from simultaneous operation.
Installation: The selector switch is mounted on the Control Cabinet panel with an IP65 waterproof cover, suited for harsh Workshop environments.
Brand Recommendations: Premium — HBC (Germany) FSE series with frequency-hopping spread spectrum, dual-band 2.4GHz + 433MHz coverage; Telemotive (Sweden) MCS series for multi-unit coordinated operation and cross-zone roaming. Mid-range — NBB (Germany) 60 series; Autec (Italy) DLD series. Economy — Yuding (China) F21 series (over 60% domestic market share, excellent value) or Tianchebao TCB series. A recommended combination is an imported receiver paired with a domestic transmitter, with retrofit costs ranging from $900 to $2,200 per unit.
Installation Notes: Mount the receiver at the bottom of the Control Cabinet (away from heat-generating components), and route the antenna outside the cabinet at least 15cm from metal surfaces. Use 1.5mm² RVV copper flexible cable, with securely crimped terminals and numbered ferrules. Connect the emergency stop relay in series with the existing master emergency stop circuit to ensure it remains effective regardless of control mode. After wiring, perform a full-function test: verify all six motion directions — Hoisting/Lowering, Crane Bridge forward/reverse, and Trolley left/right — one by one. Emergency stop response must be ≤20ms, and remote commands must be correctly suppressed when limit switches are triggered.
Wireless Video Monitoring for Blind Spot Elimination
Adding a Remote Control alone does not solve line-of-sight blind spots — when the load is obscured by Workshop steel columns, equipment stacks, or walls, the operator still cannot position accurately. Installing a wireless video monitoring system is the most effective supplement, allowing the operator to see the load and its surroundings in real time from anywhere in the Workshop.
Camera Selection: Industrial-grade wireless cameras with the following key parameters — Resolution ≥1920×1080 (1080P full frame), frame rate ≥25fps (smooth motion without ghosting), infrared night vision range ≥20m (for dark or night operations), Protection Rating (IP) IP67 (Waterproof and Dustproof), operating temperature -20℃ to +60℃, and built-in digital wide dynamic range (DWDR) to handle drastic lighting changes in the Workshop. Recommended models: Hikvision DS-2DE series (360° panoramic) or Dahua SD series.
Installation Options: Option A — mounted at the center of the Main Girder near the Trolley Rail, covering a ±10m range directly below the load. Option B — mounted on the Trolley Frame, moving in Synchronization with the Trolley to always aim at the area directly below the Hook. A combined A+B dual-camera setup is recommended for 360° coverage with no blind spots. Video feeds from both cameras can be combined on a single display using picture-in-picture or split-screen modes.
Transmission & Display: Use a 2.4GHz/5.8GHz dual-band industrial wireless bridge (802.11ac protocol, e.g., TP-Link CPE710 or Ubiquiti NanoStation) with a transmission bandwidth of ≥300Mbps and video latency of ≤80ms to meet real-time operational requirements. In open environments, the transmission range reaches up to 500m; with obstructions in a Workshop, 150–300m. The PTZ head provides ±180° horizontal and ±90° tilt movement (360° panoramic dome optional), equipped with a 2.8–12mm motorized zoom lens capable of resolving ground markings up to 30m away. The display is a 10.1–15.6-inch high-brightness industrial touch screen (brightness ≥1000cd/m²); alternatively, the Remote Control can integrate a screen (Yuding F23 series 5.7-inch TFT color display) or wirelessly cast to a phone or tablet. Installation & Commissioning of the complete system takes approximately 1–2 days.
Encoder Positioning vs. Laser Positioning: A Comparison
Building on Remote Control and video monitoring, adding automatic Positioning functionality can significantly improve efficiency in repetitive lifting operations. The two mainstream approaches are Encoder-based Positioning and laser-based Positioning. The following comparison covers six dimensions: positioning principle, measurement Accuracy, measurement range, cost, Application Scenarios, and representative brands.
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| Comparison Parameter | EncoderPositioningSolution | LaserPositioningSolution |
|---|
| PositioningPrinciple | Incremental encoder mounted on the drive wheel shaft end, mechanically connected via a flexible coupling, with PLC high-speed counter pulse acquisition for axis coordinate calculation | Industrial laser distance sensor emits a laser beam to measure distance to a reflective surface, outputting RS485 or 4~20mA signal to the PLC |
| MeasurementAccuracy | ±5mm(10mWithin travel range),Subject to wheel slippage and wear, accuracy gradually degradesGraduallyLowering | ±1~2mm(SICK DT50as±2mm,Banner Q4Xas±1mm),Non-contact measurementnutrunner |
| Measuring range | Theoretically unlimited(Increases with pulse accumulation),Cumulative error over long distances requires periodic zero resetCalibration | 0.5~30m (Standard type), Response time ≤20ms, No cumulative error |
| Per-axis cost | 1500~3000RMB/Axis,High cost-effectiveness | 4000~8000RMB/Axis,ApproximatelyEncoder2~3times |
| Application Scenarios | AccuracyGeneral-purpose applications,e.g.SteelYard,Warehouse,GeneralMaterial Handling | Precision Assemblyand high-precision applications such as mold changingAccuracyGeneral-purpose applications,e.g., precision machiningWorkshop,MoldWarehouse,automated production line |
| Representative brands | OmronE6B2-C,Pepperl+FuchsPVM58Series | SICK DT50Series,Banner Q4XSeries |
One-Key Positioning & Anti-Sway System
One-Key Positioning (GOTO Function): Pre-set up to 99 work station coordinates (crane bridge X-coordinate + trolley Y-coordinate) via the touch screen or remote control keypad. During operation, simply select the target station number and the system automatically drives both the crane bridge and trolley to the target position simultaneously. Repeat positioning accuracy is ±10 mm (±5 mm with laser-based solution), reducing repeat positioning time by 50%–70%. Retrofit case study: In a steel mill, plate handling cycle time dropped from 2 min 30 s to 55 s—a 63% efficiency gain, allowing approximately 40 additional steel plates to be moved per shift.
Anti-Sway Function: The PLC runs a ZV Shaper input-shaping algorithm that superimposes reverse vibration-cancellation signals onto the hoisting, bridge, and trolley drive commands. Measured results: before activation, residual sway was ±300 mm with a settling time of ~30 s; after activation, residual sway is ≤±50 mm with settling time reduced to 8 s. The effect is especially pronounced on medium-to-large cranes (capacity >16 t) and high-speed travel (bridge speed >30 m/min). Installation and commissioning of the complete positioning + anti-sway system takes approximately 1–2 days.
Electrical System Upgrade — Old Cabinet to New
Legacy electrical cabinets in service for 10–20 years typically suffer from oxidized contactor contacts causing increased contact resistance, unreliable relay operation, cracked cable insulation posing leakage hazards, and corroded enclosures with degraded protection ratings (originally IP30 or lower). An electrical upgrade is a critical part of any comprehensive crane retrofit.
Main Circuit: Outdated CJ-series contactors are replaced with Schneider TeSys or Siemens 3RT series units, offering electrical life ≥1,000,000 operations and mechanical life ≥15,000,000 operations. Main circuit cables are sized per ISO 4301 Crane Design Standard (copper conductor at 1.5 A/mm²), rated at no less than 1.25× the motor's rated current. Cables are oil-resistant, temperature-rated RVV shielded type (working range −20 °C to +85 °C).
Control Circuit: Kelude recommends upgrading the relay cabinet to a PLC (Mitsubishi FX3U series with 16 inputs/16 outputs or Siemens S7-200 SMART CPU SR20), reducing control voltage from AC 220 V to safe DC 24 V. The PLC program includes safety interlock logic (limit switches + overload + emergency stop in series for safe shutdown), control mode switching logic (cab / remote / off with interlock), fault self-diagnostics (contactor feedback detection, encoder disconnection, VFD faults), and audible and visual alarm outputs.
Variable Frequency Drive (Optional): Add an ABB ACS580 or Inovance MD520 series drive (open-loop vector control, 150% overload capacity for 60 s) for stepless speed control of hoisting, bridge, and trolley motions. Hoisting speed improves from the original two-speed (5/0.8 m/min) to infinitely variable 0–8 m/min; bridge travel from 15 m/min to 0–30 m/min stepless, with noticeably smoother operation. A braking resistor is fitted (mandatory for the hoisting mechanism) to ensure stable braking during full-load lowering.
Cabinet Enclosure: Replaced with an IP54 stainless steel sealed cabinet featuring a thermostatically controlled cooling fan (ON at 35 °C / OFF at 30 °C), a moisture-proof heater (auto-start at humidity >80% to prevent condensation), and LED lighting (door-activated). A 7-inch industrial touch screen (HMI) on the cabinet door displays real-time operating status of each mechanism, load weight in tons, bridge/trolley positioning coordinates, VFD frequency, and fault codes. Post-retrofit design life is ≥10 years, with a fault rate reduction of approximately 80%, insulation resistance ≥2 MΩ, and cabinet internal temperature maintained between −10 °C and +45 °C.
Safety Device Installation — Limit, Overload & Anti-Collision
The following protective devices are installed in accordance with GB 6067.1-2010 Safety Rules for Lifting Appliances and TSG Q7016-2016 Rules for Periodic Inspection of Lifting Appliances:
Lifting Height Limit Switch: Rotary limit switch (LX26 series counterweight type or DXZ series cam type). The first-stage limit is triggered 200 mm before the highest working position, cutting power to the hoisting-up contactor. A second-stage redundant limit, set 50 mm before the extreme position, operates on an independent power-disconnect circuit for dual protection. Protection rating ≥IP65, contact rating ≥5 A / 250 VAC. Test monthly and recalibrate after wire rope replacement.
Travel Limit Switch: Omron D4MC series roller-type limit switches are installed at both ends of the bridge and trolley rails, with an actuation accuracy of ±2 mm and contact life ≥1,000,000 operations. Combined with polyurethane buffers (compression stroke ≥200 mm, energy absorption ≥5 kJ) and welded rail end stops (≥20 mm thick), triple protection ensures the crane cannot run off its rails. Limit signals are wired to both the PLC and an independent safety relay circuit.
Overload Limiter: Changzhou Changxin CA series or Yichang Weite WTC series electronic overload limiter, with sensors mounted at the fixed end of the hoisting wire rope or beneath the pulley block spreader beam. Sensor accuracy is ±0.5% F.S., with a system comprehensive accuracy of ±2%. At 90% of rated load, a pre-warning is triggered—indicator light flashing with intermittent buzzer alarm; at 105%, the hoisting-up circuit is immediately cut off (lowering direction only remains active). After installation, on-site calibration is performed using standard test weights (or a calibrated hook scale) and signed off for record.
Anti-Collision Device: Infrared photoelectric sensors (Banner QS18 series, detection range 0.5–10 m adjustable, response ≤2 ms) or laser radar (SICK TiM series, 270° scanning angle) are installed on the crane end carriages and trolley sides. When approaching the safety distance, the crane automatically decelerates to creep speed (≤5 m/min); continued approach triggers automatic locking and stop. Anti-collision signals are transmitted via a 433 MHz wireless module, eliminating the need for cabling. Real-time crane positions and spacing can be displayed on the control room monitor.
Anemometer & Alarm: A three-cup anemometer (accuracy ±0.5 m/s, starting wind speed ≤0.5 m/s) is mandatory for outdoor cranes. At Beaufort Force 6 (10.8–13.8 m/s), a yellow warning with audible and visual alarm is activated; at Force 7 (13.9–17.1 m/s), all crane motions are automatically locked out. LED audible and visual alarms (sound pressure ≥105 dB @ 1 m, red/blue rotating beacon) are mounted at both ends of the main girder, flashing and buzzing automatically during operation to alert personnel nearby.
Retrofit Acceptance & Inspection Procedure
Acceptance Basis: ISO 4301, GB 6067.1-2010, TSG Q7016-2016, JB/T 10559-2019, JB/T 12987-2016.
The retrofit acceptance process is carried out in seven progressive stages, from documentation review to compliance filing:
1
Documentation Review
Verify the retrofit plan and design drawings, electrical schematic and wiring diagrams, component certificates of conformity and 3C certification, PLC program backup, Factory Acceptance Test Report (FAT), installation and commissioning records, and safety device calibration certificates.
2
Visual & Dimensional Inspection
Check the overall structural integrity of the crane, weld quality on the main girder and end carriages, fastening of all connections, installation of safety devices and travel limit switches, and verify that all dimensions meet the design drawings and relevant standards.
3
No-Load Functional Test
Operate each mechanism without load to verify correct direction of motion, smooth start/stop, limit switch actuation at the proper positions, emergency stop functionality, and proper operation of the PLC control logic, HMI display, and audible/visual alarms.
4
Static Load Test
Apply a static test load of 125% of the rated load, hoist it to a height of 100–200 mm and hold for 10 minutes. Verify no permanent deformation, cracks, or abnormal sounds in the main girder, end carriages, and hoisting mechanism. Measure the main girder deflection and confirm it meets the standard requirement (typically ≤1/800 of the span).
5
Dynamic Load Test
With a test load of 110% of rated load, perform repeated hoisting, lowering, bridge travel, and trolley travel cycles. Verify smooth acceleration and deceleration, effective braking, proper operation of the overload limiter (alarm at 90%, cutoff at 105%), and stable performance of the anti-sway system.
6
Safety Device Verification
Individually test each safety device: lifting height limit switch, travel limit switches, overload limiter, emergency stop, anti-collision system, anemometer (if applicable), and audible/visual alarms. Confirm each device triggers at the correct set point and performs the required safety action.
7
Acceptance & Compliance Filing
Compile the complete acceptance report including all test records, calibration certificates, and as-built drawings. Submit the report to the local special equipment supervision authority for filing and obtain the updated crane registration certificate. The retrofit is officially complete only after this filing is approved.
Visual Inspection
The electrical cabinet must be securely mounted (perpendicularity ≤ 2 mm/m), with wiring per specification (terminal torque ≥ 0.8 N·m). Cables must be routed along cable trays with protection (bend radius ≥ 6× cable outer diameter), wire markers clearly legible, and grounding reliable (resistance ≤ 4 Ω).
