Vacuum Evacuation Time

Overview

Engineering reference data for Vacuum Evacuation Time in miscellaneous.

Key Formulas

Unit Conversion

$y = x \cdot k$

Multiply by conversion factor.

Linear Interpolation

$y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}$

Estimate between two known points.

Percentage

$p = \frac{\text{part}}{\text{whole}} \times 100\%$

Part as fraction of whole.

Variables

Simplified Formula

For practical calculations, the evacuation time formula can be approximated as:

$t = \frac{V}{q} N$

where $N$ is the natural log constant based on the target vacuum level:

Practical Notes

• Leakage compensation: Leakage through seals and fittings effectively reduces the pump's capacity. To account for this, adjust the volume flow rate ($q$) downward by the estimated leakage rate.
• The formula assumes an ideal, leak-free system with constant pump performance throughout the evacuation range.
• Real-world evacuation times will typically be longer than calculated due to outgassing, leaks, and reduced pump efficiency at lower pressures.

Worked Examples

Given conditions:

• Enclosed volume: $V = 1 \text{ m}^3$
• Pump capacity: $q = 0.1 \text{ m}^3/\text{s}$
• Initial pressure: $p_0 = 1000 \text{ mbar}$ (atmospheric)

Key insight: Note that evacuating from 1000 to 100 mbar (removing 900 mbar) takes 23 s, while evacuating from 100 to 10 mbar (removing only 90 mbar) takes an additional 23 s. This logarithmic behavior means deeper vacuum levels require disproportionately more time.

References

• Original Source