Dump Truck directional valve technical conditions (a)
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This standard outlines the general requirements, performance specifications, testing conditions, equipment, methods, type and factory tests, inspection procedures, labeling, packaging, transportation, and storage for reversing valves used in dump truck systems. It applies specifically to hydraulic directional valves—manual, pneumatic, and hydraulic—that use hydraulic oil as the working medium in dump truck lifting systems.
Reference standards include QC/T 460 "Dump Truck - Hydraulic Cylinder Technical Conditions," QC/T 484 "Automotive Paint Coating," GB/T 3766 "General Technical Conditions for Hydraulic Systems," and GB/T 2828 "Sampling Procedures and Sampling Tables for Batch Inspection."
The general requirements specify that reversing valves must comply with this standard and be manufactured according to approved drawings and technical documents. All components must pass quality inspections before assembly. The nominal pressure of the valve should follow QC/T 460 guidelines. Inlet and outlet ports must be protected against rust and dust, while other surfaces should be painted according to QC/T 484 TQ6 Table 1. Seals and dust-proof components should be coated with a thin layer of oil or grease to prevent damage. Casting surfaces must be smooth, free from sand sticking, cracks, or burrs. The valve must be cleaned before assembly, and manually operated valves must meet GB/T 3766 requirements.
Performance requirements include flexible operation under rated pressure and flow, no abnormal noise, and accurate direction switching. Pressure loss across each channel must not exceed 0.3 MPa at rated flow. Internal leakage should not exceed 0.6% of the rated flow per minute. The valve must withstand pressure without rupture or oil leakage. Durability tests must meet the criteria set for pressure loss and internal leakage.
Testing conditions require an oil temperature of 50°C, with allowable variations depending on the measurement level (A: ±1.0°C, B: ±2.0°C, C: ±5.0°C). Oil viscosity must be between 17 × 10â»â¶ and 43 × 10â»â¶ m²/s at 50°C. Filtration precision should be at least 25μm. Test equipment and instruments must meet accuracy levels based on the test category, with type tests requiring at least B-level accuracy and factory tests at C-level. Instrument tolerances are specified, and test reports must indicate the test level used.
Test device setup requires pressure measuring points placed at least 10d from disturbances (such as valves or elbows) and 5d upstream from the test valve, where d is the pipe diameter. This ensures accurate and reliable test results.