| 类别 | 100m 大允许压降(kg/cm²) | 流速(m/s) |
| (1)一般蒸汽 | ||
| 压力等级 | ||
| 0.0~3.5 kg/cm²G | 0.06 | 10.0~35.0 |
| 3.5~ 10.5 kg/cm²G | 0.12 | 10.0~35.0 |
| 10.5~21.0 kg/cm²G | 0.23 | 10.0~35.0 |
| >21.0 kg/cm²G | 0.35 | 10.0~35.0 |
| (2)过热蒸汽 | ||
| 口径(mm) | ||
| >200 | 0.35 | 40.0~60.0 |
| 100~200 | 0.35 | 30.0~50.0 |
| <100 | 0.35 | 30.0~40.0 |
| (3)饱和蒸汽 | ||
| 口径(mm) | ||
| >200 | 0.20 | 30.0~40.0 |
| 100~200 | 0.20 | 25.0~35.0 |
| <100 | 0.20 | 15.0~30.0 |
| (4)乏汽 | ||
| 从受压容器中排出 | 80.0 | |
| 从无压容器中排出 | 15.0~30.0 | |
| 从安全阀排出 | 200.0~400.0 |