The concept of extracting vacuum of MHV-1&MHV-2 for Automatic Siphon Machine:

Are there many differences between 1atm and 7kpa? It looks a lot differences from the data. The extracting vacuum we called refers to the differences between pressure in container and atmospheric pressure. More differences between data stand for more cleaning of air extracted inside the parts; more oil or water will be penetrated into it.

General mechanical pump can extract vacuum to 1atm, actually about 1Torr (0.13kpa)-10Torr (1.3kpa). If we calculate according to 1 atmospheric pressure equaling to 100kpa, the difference is 98.7-99.87kpa comparing to atmospheric pressure. But MPIF42 requires reducing the container pressure lower than 7Kpa, if the container pressure is 3Kpa, the difference is 97Kpa comparing to the atmospheric pressure. Thus the ratio is 98.7/97=1.017 or 99.87/97=1.030, just 2-3% difference. Actually the extracted air difference should be smaller; the oil leakage quantity is almost the same. Furthermore according to MPIF42, when the container pressure is lower than 7kpa, it can be 1kpa, so they have no difference. It is impossible if the machine is required to reach 1atm (0kpa). Diffusion pump just can achieve to 0.000013kpa or -0.9999999atm.