Evacuate the  system using a vacuum pump. A vacuum pump cannot achieve a vacuum better than the Saturated Vapour Pressure of any moisture (water) or other contaminants that may be in the system or vacuum pump. This is because water or other contaminants that may have been drawn into the pump evaporates from the oil [...]

System must be evacuated to less than 1.0 Millibar absolute. After the system has been evacuated the vacuum pump should be isolated from the system. As a guide, with constant ambient conditions, the vacuum should not rise more than 0.13 Millibar in one hour. A greater rate of rise may indicate a leak or the [...]

A helium leak detector permits the localization of leaks and the quantitative determination of the leak rate, i.e. the gas flow through the leak. Such a leak detector is therefore a helium flow meter. In practice the leak detector performs this task by firstly evacuating the part which is to be tested, so that gas [...]