The process by which a vacuum is obtained by a vacuum system is called vacuuming, also called pumping or venting. Drawn in unit time under the pressure of the gas volume called extraction rate, the pumping speed. Might as well be called the pump speed, unit is the L/S or a vacuum pump system in the exhaust after a long enough time can achieve the minimum air pressure is called ultimate vacuum.
Thin oil metal metallurgical requirements high vacuum conditions. So often the use of mechanical pump and diffusion pump configured to high vacuum unit of complete sets of equipment. Use mechanical pump and booster pump series vacuum to 10-6 pa. To further improve the vacuum degree, also can install widening adsorbent in the working system or cold trap, sucking pump no gas adsorption or condensation. Sometimes adding level of mechanical booster pump with series or parallel, to improve the ability of a range of vacuum suction.
In a high vacuum unit, the mechanical pump can reduce the pressure from one atmosphere, which is called the pre-stage pump. Diffusion pumps can only be pumped from lower air pressure to lower air pressure. Called secondary pumps. The pressure at which the secondary pump begins to work is called the prevacuum or prevacuum. Each the best pumping speed of vacuum pump is correspond to certain entrance pressure. Therefore, must be reasonable with good vacuum unit, to get the best benefit of vacuum. An unreasonable configuration will not only cause waste, has also led to the empty system vacuum can not meet the expected demand.
The reasonable configuration of the vacuum unit should solve the following main problems:
1) select the type of the main pump according to the requirements of the amount of gas produced by the vacuum equipment, the working pressure, the limit of its cavitation and the pumping time, etc.
2) calculate the pumping time and pressure of the vacuum equipment after the main pump is selected and equipped;
3) to understand the relationship between the tsuen parameter of vacuum pump and the passing capacity of the catheter, etc.