Vacuum pumps are Ac Vacuum Pump china component of one of the final processes in the repair process. After you’ve diagnosed and repaired any leaks or other issues in the machine it’s time to recharge. 
Before recharging you want to make sure the machine is free of any undesirable gasses, air, or water. If they were to stay in the system, it would turn the oil it operates on into sludge and keep behind damaging impurities.
The draw on vacuum pressure pump is usually divided into its “CFM,” or Cubic Feet each and every minute. To estimate what your CFM requirements, consider the tonnage of the systems you work on. Take the square root of that quantity and you’ll obtain the approximate CFM you must have to work with that system. Typical home systems need 4-5 CFM, while commercial and rooftop systems generally require as much as 6-8 CFM.