21 Jan

Vacuum Chamber

There are many situations which require the application of a vacuum in the laboratory such as degassing and drying.  A chamber which can support 29 inches of Mercury (29 inHg) or 736 millimeters of Mercury (mmHg) or more vacuum is referred to as a vacuum chamber.

Vacuum desiccators are designed to keep samples dry during storage and transport.  Desiccators can be glass or plastic and are designed to maintain vacuum levels of 26 to 29 inHg.

Vacuum units of measure can be very confusing.  The convention is to refer the the vacuum as if it were pressure but it is the opposite.  For example 26 to 29 inHg could just as well be 4 to 1 inHg as 30 inHg is 0 atm (atmosphere).  Here is a helpful chart for converting vacuum units:

%
Vacuum
Torr
(mm Mercury)
Micron psia,
(lb/in2)
abs
Inches
Mercury
Absolute
Inches
Mercury
Gauge
kPa
abs
0.0 760.0 760,000 14.7 29.92 0.00 101.4
1.3 750.0 750,000 14.5 29.5 0.42 99.9
1.9 735.6 735,600 14.2 28.9 1.02 97.7
7.9 700.0 700,000 13.5 27.6 2.32 93.5
21.0 600.0 600,000 11.6 23.6 6.32 79.9
34.0 500.0 500,000 9.7 19.7 10.22 66.7
47.0 400.0 400,000 7.7 15.7 14.22 53.2
50.0 380.0 380,000 7.3 15.0 14.92 50.8
61.0 300.0 300,000 5.8 11.8 18.12 40
74.0 200.0 200,000 3.9 7.85 22.07 26.6
87.0 100.0 100,000 1.93 3.94 25.98 13.3
88.0 90.0 90,000 1.74 3.54 26.38 12
89.5 80.0 80,000 1.55 3.15 26.77 10.7
90.8 70.0 70,000 1.35 2.76 27.16 9.3
92.1 60.0 60,000 1.16 2.36 27.56 8
93.0 51.7 51,700 1.00 2.03 27.89 6.9
93.5 50.0 50,000 0.97 1.97 27.95 6.7
94.8 40.0 40,000 0.77 1.57 28.35 5.3
96.1 30.0 30,000 0.58 1.18 28.74 4
96.6 25.4 25,400 0.49 1.00 28.92 3.4
97.4 20.0 20,000 0.39 0.785 29.14 2.7
98.7 10.0 10,000 0.193 0.394 29.53 1.3
99.0 7.6 7,600 0.147 0.299 29.62 1.0
99.9 1.0 1,000 0.01934 0.03937 29.88 0.13
99.9 0.75 750 0.0145 0.0295 29.89 0.1
99.99 0.10 100 0.00193 0.00394 29.916 0.013
99.999 0.01 10 0.000193 0.000394 29.9196 0.0013
100 0.00 0 0 0 29.92 0
  • 1 psi (lb/in2) = 6,894.8 Pa (N/m2) = 6.895×10-3 N/mm2 = 6.895×10-2 bar
  • From The Engineering Toolbox; www.EngineeringToolBox.com.

Robin Prymula