The gases present in the air such as oxygen and carbon dioxide can dissolve with air and cause corrosion. Using a Vacuum pump can remove these gases and lower the dissolved gas level in the system preventing corrosion.
Once air is removed from a system and a vacuum is created, steam requires a very low pressure to flow across the system.
Since the pressure of the system decreases, the boiling point of water also decreases. This results in a reduction of the fuel consumption. Vacuum pumps can also be used for lifting the condensate to the receiver. This is necessary to prevent water hammering.
Vacuum pumps are specified in the amount of air they can move at a given vacuum. They can produce vacuums of the range of 5, 10 and 15 inches of Hg.