Introduction
Truck-mounted cranes, as special equipment integrating transportation and lifting functions, are widely used in engineering construction, logistics transportation, emergency rescue and other scenarios. Their quality and reliability are directly related to operational safety and transportation efficiency. Based on GB/T 3811-2022 “Crane Design Code” and JB/T 13074-2021 “Truck-mounted Cranes” and other specialized standards, this article interprets the process from raw material entry to process control, final assembly and commissioning, and finished product delivery.
1. Quality inspection of raw materials and core purchased components
1.1 When the raw materials for truck-mounted cranes enter the factory, the material certificate and third-party test report should be checked to verify whether the mechanical properties such as yield strength and tensile strength meet the design requirements. At the same time, tensile and impact tests should be carried out by batch sampling to ensure the toughness and fatigue resistance of the materials under low temperature and vibration conditions.
2.2 Quality inspection of core outsourced components focuses on “compatibility” and “reliability.” As the power core of the truck-mounted crane, the hydraulic system, including components such as hydraulic pumps, multi-way valves, and cylinders, requires verification of manufacturer qualifications and product certifications. Sampling tests are conducted on sealing performance, pressure resistance (1.5 times the rated working pressure), and response sensitivity to ensure no leakage or jamming under bumpy road conditions. Crane hooks and chassis-compatible components (such as brackets and connecting bolts) must be verified for their matching accuracy with the original chassis. The torque coefficient and anti-loosening performance of high-strength bolts require specialized testing to avoid the risk of loosening during operation.
2. Quality inspection of structural manufacturing and component processing
Material preparation process: The entire manufacturing process of the truck-mounted crane, from material preparation, welding, forming to component processing , is monitored. High-precision laser cutting technology is used in the material preparation stage to control the dimensional deviations, bevel angles, and edge roughness of the cut parts. For complex structural components such as the boom and main beam, the material preparation accuracy is ensured to meet assembly requirements. In the forming stage, the bending and rolling processes require strict control of the radius of curvature and springback. The boom’s telescopic guide surface requires precision machining to ensure smooth operation of the telescopic mechanism.
Welding process: Welding quality is the core guarantee for structural load-bearing capacity, and a triple control system of “process qualification + certified operation + non-destructive testing” is implemented. The appearance of the weld must be free of defects such as porosity, slag inclusion, and incomplete penetration, and the undercut depth must be ≤0.5mm. Important load-bearing welds (such as boom butt welds and lifting point welds) must be 100% ultrasonically tested (UT), and special parts are supplemented with magnetic particle testing (MT) to ensure that there are no defects exceeding the standard inside the weld.
3. Quality inspection of final assembly and hydraulic and electrical systems
The core of quality inspection during the final assembly stage is “coordination” and “safety.” Before mechanical assembly , all component surfaces must be cleaned to remove burrs, oil, and impurities. The connection between structural components and the chassis must be precisely positioned using locating pins. High-strength bolts must be tightened evenly to the designed torque (error ≤ ±5%), and a torque re-tightening verification must be performed after tightening to ensure no loosening during driving and operation. The assembly of the telescopic boom requires testing the extension stroke and synchronization, ensuring there are no jamming or abnormal noises.
After assembly, the hydraulic system requires specialized commissioning and testing. First, the system must be flushed to ensure the hydraulic oil cleanliness meets NAS Class 8 standards. Then, a no-load cycle test is conducted to assess the flexibility and coordination of each action. The load test should be performed at 1.1 times the rated load to check the hydraulic system’s pressure stability and flow regulation accuracy, ensuring no leakage or pressure loss under rated load. The braking system requires verification of the coordination between the parking brake and service brake, with a braking response time ≤0.5s and braking torque meeting 1.25 times the rated load requirement to prevent the vehicle from slipping during operation or travel.
Electrical system quality inspection covers “control accuracy” and “safety protection.” The control system’s operating handles and remote controls must be tested for button sensitivity and signal transmission stability, ensuring no signal interference or delay within a 100m range. Safety interlocking functions such as limit switches and emergency stop devices must be 100% tested. The errors of lifting capacity limiters and torque limiters must be controlled within ± 10 %, and when the rated load reaches 110%, the lifting and luffing power source must be automatically cut off and an alarm signal issued. Electrical wiring must avoid high-temperature and vibration areas, using flame-retardant wires and waterproof connectors, with an insulation resistance value ≥1MΩ and a grounding resistance ≤4Ω, ensuring no short circuit or leakage risk under harsh working conditions.
4. Final Verification: Overall vehicle performance and factory quality inspection
The finished product inspection of truck-mounted cranes needs to simulate actual working conditions and conduct a comprehensive assessment encompassing “static testing + dynamic testing + vehicle compatibility verification.” Static testing includes measuring parameters such as the overall vehicle dimensions to ensure compliance with road transport regulations and work site requirements; operating parameters such as lifting height, luffing angle, and slewing radius must be consistent with the design documents, with an error ≤ ±2%. Dynamic testing is divided into no-load and heavy-load tests. Under no-load conditions, each mechanism runs continuously for 60 minutes to test operational stability, noise levels, and braking reliability; the loading test applies 100 % of the rated load and performs combined lifting, luffing, slewing, and telescopic movements to verify the mechanism’s coordination and structural load-bearing capacity, while simultaneously measuring the deformation of the main beam and boom to ensure no residual deformation after unloading.
Conclusion
Before leaving the factory, a comprehensive re-inspection is required, including functional verification of all safety devices, appearance quality inspection (paint smoothness, absence of dents and scratches), and review of the completeness of technical documents (including quality inspection report, product certificate, instruction manual, and maintenance manual). After all inspection items pass, a product nameplate and safety warning signs are affixed to a prominent position on the crane, clearly indicating key information such as rated lifting capacity, working radius, and design service life. At the same time, operation training and quality inspection data are provided to users to ensure that users use the crane in accordance with regulations.
