01/08/2025
The following is a text-based inspection guide for bridge cranes, based on Chinese national standards (GB/T 14406-2017) and industry safety practices, specifically designed for quick on-site inspections.
During inspection, prioritize the following five items. If any one of them fails to meet standards, immediately reject the product; do not compromise.
1. Main beam deformation: The acceptable standard is that the deflection of the main beam does not exceed 1/1000 of the span. If measured using the string method (tighten a fine string at both ends and measure the gap between the lowest point of the span and the string), if the deflection exceeds 20mm, it indicates structural damage, and the product must be rejected.
2. Wire rope damage: The acceptable standard is that the number of broken wires does not exceed 10% of the total number of wires, and the diameter wear of the wire rope is ≤7%. If broken wires are densely visible to the naked eye or the diameter measured with a caliper is less than 93% of the new rope's diameter, the product must be rejected immediately.
3. Loose critical bolts: High-strength bolts connecting the main beam to the end beams must be securely fastened. When randomly inspecting with a torque wrench, if any three or more bolts can be rotated more than 1/4 turn (or are noticeably loose when hand-tightened), there is a risk of fracture, and the product must be rejected.
4. Cable insulation failure: The qualified standard is interphase insulation resistance ≥ 1.0 MΩ. When measuring the power supply end with a multimeter, if the reading is < 0.5 MΩ or exposed copper wires or damaged insulation are found, there is a risk of leakage or short circuit, and the product must be rejected immediately.
5. Limit switch failure: During no-load testing, manually trigger the upward/downward limit switch; the equipment must shut off power within 0.5 seconds. If the hook collides with the top or there is a delay in the emergency stop, indicating safety device failure, the product must be rejected.
10-minute rapid inspection process
Step 1: 5-minute safety scan
Walk around the equipment, focusing on the main beam welds: use a smartphone flashlight to shine diagonally on the surface. If new cracks or rust water seepage are detected, this indicates structural damage.
Gently tap the crane track. If a dull sound (not a crisp sound) is heard, this indicates track bending or deformation. Simultaneously, check if all safety warning signs are present; missing signs constitute a violation.
Verify that the equipment nameplate parameters match the contract specifications, with a focus on critical data such as rated load capacity and span.
Step 2: 3-Minute Core Testing (Basic Tools Required)
Wire Rope Inspection: Visually count broken wires along a 1-meter length. If broken wires are clustered or the diameter measured with a caliper is below the critical value (new rope diameter × 0.93), mark immediately.
Cable test: Set the multimeter to the resistance range and measure the insulation resistance between phases. If the reading is 5 cm indicates a rope guide failure); pressing the emergency stop button must cause the equipment to power off within 0.5 seconds.
Note: If any abnormalities (unusual noises, smoke, or jamming) are detected, stop the machine immediately and do not continue testing.
Critical actions within 24 hours after inspection
Take photos for evidence: Take high-resolution photos of the defective areas, which must include a scale reference (e.g., a tape measure placed next to the broken wire rope), and take a panoramic photo of the equipment (including the nameplate and the license plate of the transport vehicle).
Written report: Issue a formal notice to the supplier (handwritten or printed).
Freeze the equipment: Apply red warning tape to the problematic area, clearly mark “Do Not Operate,” and document the equipment's status in writing to prevent the supplier from shifting responsibility.
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