Dump Truck directional valve technical conditions (a)
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This standard outlines the general requirements, performance criteria, testing conditions, equipment, methods, type and factory tests, inspection procedures, markings, packaging, transportation, and storage for reversing valves used in dump truck lifting systems. It applies specifically to hydraulic directional valves—manual, pneumatic, or hydraulic—that use hydraulic oil as the working medium.
The standard references several key documents, including QC/T 460 for dump truck hydraulic cylinder technical conditions, QC/T 484 for automotive paint coatings, GB/T 3766 for general hydraulic system requirements, and GB/T 2828 for batch sampling procedures.
General requirements include compliance with this standard, proper assembly according to approved drawings, quality inspection of all components before assembly, appropriate selection of nominal pressure based on QC/T 460, protection of valve ports against rust and dust, painting of exposed surfaces as per QC/T 484 TQ6 Table 1, lubrication of seals and dust-proof parts, clean casting surfaces free from defects, and pre-assembly cleaning. Manual valves must also meet GB/T 3766 requirements.
Performance requirements specify that the valve should operate smoothly under rated pressure and flow without abnormal noises, ensure accurate direction changes, limit pressure loss to no more than 0.3 MPa, restrict internal leakage to 0.6% of rated flow, withstand pressure without rupture or leakage, and maintain performance after durability testing.
Testing conditions require an oil temperature of 50°C with allowable variations depending on the measurement level (A, B, or C). The oil viscosity must be between 17 × 10â»â¶ and 43 × 10â»â¶ m²/s at 50°C, and filtration must be at least 25 μm. Test equipment and instruments must meet specified accuracy levels, with type tests requiring at least B-level precision and factory tests at least C-level. Measurement tolerances vary by grade, and test reports must indicate the test level used.
Test device setup includes placing pressure measuring points at least 10d away from disturbances and 5d from the test valve, where d is the pipe diameter. This ensures accurate and reliable test results. Additional considerations such as environmental control, calibration of instruments, and documentation of test procedures are essential for maintaining consistency and compliance.