|
Vacuum Ranges |
|
Class
Extreme High
Ultra High
High
Medium
Rough
|
mbars
<10-12
10-7 to 10-12
10-3 to 10-7
1 to 10-3
1 atm to 1
|
Atmospheric pressure, also known as air pressure, is
the force exerted on a surface by the weight of the air above it. It is measured
in units of force per unit area, such as Pascals (Pa) or pounds per square inch
(psi). At sea level, the average atmospheric pressure is about 1013 millibars (mb)
or 101.3 kilopascals (kPa), which is equivalent to 14.7 psi. The atmospheric pressure
decreases with increasing altitude, so it is less at the top of a mountain than
at sea level. The atmospheric pressure also varies with weather systems, and can
change rapidly with changes in temperature, humidity, and wind.*
The table below provides conversion factors between common units of force.
Standard units = pascal (Pa)
| 1 |
406.8 |
14.70 |
2116 |
75.99 |
1.013*106 |
1.013*105 |
1013 |
| 2.458*10-3 |
1 |
3.613*10-2 |
5.202 |
0.1868 |
2491 |
249.1 |
2.491 |
| 6.805*10-2 |
27.68 |
1 |
144 |
5.171 |
6.895*104 |
6.895*103 |
68.95 |
| 4.725*10-4 |
0.1922 |
6.944*10-3 |
1 |
3.591*10-2 |
478.8 |
47.88 |
0.4788 |
| 1.316*10-2 |
5.353 |
0.1934 |
27.85 |
1 |
1.333*104 |
1333 |
33.86 |
| 9.869*10-7 |
4.015*10-4 |
1.450*10-5 |
2.089*10-3 |
7.501*10-5 |
1 |
0.1 |
10-3 |
| 9.869*10-6 |
4.015*10-3 |
1.450*10-4 |
2.089*10-2 |
7.501*10-4 |
10 |
1 |
0.01 |
| 1.869*10-4 |
0.4015 |
1.450*10-2 |
2.089 |
7.501*10-2 |
1000 |
100 |
1 |
| in of water @ 4º C |
1 bar = 106 dyn/cm2 |
| cm of Hg @ 0º C |
1 atm = 29.92 in of Hg |
The standard atmosphere is a model of the Earth's atmosphere
that is used as a reference for measuring and reporting atmospheric pressure, density,
and temperature. It is defined by the International Civil Aviation Organization
(ICAO) and the International Standards Organization (ISO). The standard atmosphere
defines a pressure of 1013.25 hPa (hectopascals) at sea level, a temperature of
15 degrees Celsius (59 degrees Fahrenheit), and a relative humidity of 0%. As altitude
increases, the temperature, pressure and density of air decrease in a standard way
.It is also defined as a temperature gradient of -6.5°C per 1000m of altitude increase.
It's used in many fields, such as aeronautics, meteorology, and atmospheric science,
as a reference for the calculation of performance and safety of aircrafts, weather
forecasting and atmospheric pollution.*
Outgassing refers to the release of gases, usually
in the form of volatile compounds, from a material or substance. This can occur
due to a variety of reasons such as heating, pressure changes, or the presence of
a vacuum. Outgassing can be a problem in many different fields, such as materials
science, construction, packaging, and space travel. In space applications, outgassing
can cause problems such as instrument malfunctions or the adhesion of materials.
To prevent these issues, materials used in space-related applications are often
specially treated to reduce or eliminate the release of gases.*
* Outgassing properties of a few materials (after 1 hour):
Source:
Leybold
|
Aluminum
Iron
Brass
Copper
Gold
Mild Steel
Stainless Steel
|
3.0 X 10-7
2.7 X 10-7
1.5 x 10-6
2.3 x 10-8
1.1 x 10-7
6.2 x 10-7
1.9 x 10-7
|
|
|
|
Zinc
Titanium
Pyrex
Neoprene
PVC
PTFE
|
2.6 x 10-7
1.0 x 10-8
9.9 x 10-9
4.0 x 10-5
3.2 x 10-6
1.4 x 10-6
|
|
Outgassing is the phenomenon of embedded gasses escaping from materials, akin
to paint drying. Higher ambient temperature and/or lower ambient atmospheric pressure
usually increases the rate at which the gases escape. Testing of assemblies destined
for high altitude and/or space is performed in vacuum chambers which often include
control of temperature, acceleration and impact, and irradiation.
* Generated
by Chat GPT AI
|