GB/T 40344.1-2021 in English

Analysis of the core content of the standard

Key technology implementation points

1. Test hood design specifications

The standard clearly stipulates that the nominal diameter of the test hood DN must be consistent with the pump inlet, and a 45° conical adapter must be used for pumps with DN<100mm. The test hood should include:

• Pressure measurement interface (at height D/2)
• Temperature monitoring point
• Optional baking device (150-300℃)

2. Volume flow rate measurement comparison

Measurement uncertainty control

According to the requirements of Appendix B, each method must meet the following requirements:

• Pressure measurement ≤ 3%
• Flow measurement ≤ 2.5%
• Aperture diameter ≤ 0.5%
• Final combined uncertainty ≤ 10%

Special note: When l ≈ 2d, the aperture conductance needs to be corrected by 3%

Standard implementation recommendations

1. When measuring basic pressure, baking for 3h@120℃ is required for pressures above 10^-4Pa, and 48h@300℃ is required for ultra-high vacuum
2. Compression ratio measurement should use test gas with a purity of ≥ 99.999%
3. The measurement cycle Δt₁ of the vacuum method needs to be > 8s to eliminate the influence of valve delay
4. All measuring equipment must provide ISO/IEC17025 calibration certificates