Manual for Refrigeration Servicing Technicians - UNEP - Division of ...
Manual for Refrigeration Servicing Technicians - UNEP - Division of ...
Manual for Refrigeration Servicing Technicians - UNEP - Division of ...
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4<br />
<strong>Servicing</strong> Practices<br />
Pressure units <strong>for</strong> vacuum<br />
A variety <strong>of</strong> different units <strong>of</strong> measurement<br />
are employed <strong>for</strong> quantifying pressures,<br />
which can easily lead to confusion. The<br />
below Table 4.1 provides a conversion<br />
<strong>of</strong> certain units <strong>of</strong> pressure <strong>for</strong> standard<br />
atmospheric pressure, 1 bar, and the<br />
recommended highest level <strong>of</strong> vacuum<br />
(ideally, evacuation pressure should be<br />
below this). Note also that the pressures are<br />
indicated in absolute pressure, not gauge<br />
pressure.<br />
SI units<br />
Standard<br />
atmosphere<br />
1 bar (absolute)<br />
Preferred vacuum<br />
level (absolute)<br />
bar 1.01325 bar 1 bar 0.001 bar<br />
kilo Pascal 101.3 kPa 100 kPa 0.10 kPa<br />
micron 1013250 microns 1,000,000 microns 1000 microns<br />
millibar 1013.25 mbar 1000 mbar 1 mbar<br />
Pascal (Pa)<br />
Non-SI units:<br />
101325 Pa 100,000 Pa 100 Pa<br />
inch <strong>of</strong> mercury 30.5 in Hg 29.5 in Hg 0.030 in Hg<br />
mm <strong>of</strong> mercury 760 mm Hg 750 mm Hg 0.75 mm Hg<br />
Torr 760 Torr 750 Torr 0.75 Torr<br />
pounds (<strong>for</strong>ce)<br />
per square inch<br />
15.0 psi 14.5 psi 0.015 psi<br />
95
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