We need to buy vacuum pump with these specification:
Capacity: 3-6 TON/horizontal
1Ton/vertical
Air-blast fan:+ air flow: 60m3/min
Vacuum pressure: -442mmHg
Vacuum pressure range: 0~760mmHg
Vacuum switch: 100A
Rear air-flow silencer: d = 250
Auto overload valve: 100A
Motor: 100HP x4P
Cyclone:  Opposing dust: 85%
Dust-collecting equipment: + filter section: 48m