Rotary vane vacuum pump gas ball valve often discharge vapor or vapor and gas mixture, mainly water vapor, in vacuum applications. Normal rotary vane vacuum pump can not eliminate steam, steam into the rotary vane pump chamber will be compressed, gradually increased to saturated vapor pressure, the exhaust valve has not yet opened, excess steam began to condense into liquid, so the steam can not be exhausted.
The mixing of condensate and pump oil produces a suspension which causes the characteristics of the pump oil to deteriorate significantly. At the same time, the condensate with high saturated vapor pressure circulates to the inlet together with the pump oil, and evaporates again to the pumped space, which greatly deteriorates the limiting vacuum. Especially when steam condenses into water, it will cause chemical reactions in the pump.
Rotary vane vacuum pump
Firstly, water interacts with cast iron to form softened iron, ferric oxide continues to interact with water to form ferric hydroxide, ferric hydroxide interacts with organic acids in oil to form saponifies, and saponifies are also strong catalysts for accelerating oxidation reaction.
Because the pump oil continuously absorbs water during the compression process, the above effect occurs continuously. Finally, the pump oil becomes heavier and thicker, which makes the rotor difficult to rotate and the pump temperature rises. As a result, the seal, lubrication and cooling performance of the pump become worse, and the working life of the pump is greatly shortened.
If the steam is corrosive, the pump body will soon be seriously corroded. In order to avoid the influence of condensate on pump performance, the simplest and most effective way is to prevent vapor condensation in the pump by aeration, that is, a certain part of the compressed space connected with an adjustable aeration valve.
When the vacuum pump works, a certain amount of gas is mixed into the compression space through the valve, so that it can be mixed with steam. Before the vapor has condensed in the compression process, the pressure of the mixture has exceeded 0.1 MPa, so the exhaust valve can be pushed to discharge the pump, thus achieving the purpose of removing the vapor. The number of aerated stars depends on the amount of steam.
Though the gas valve can exclude steam, the limit vacuum of the pump will be reduced by an order of magnitude. Therefore, in actual use, when the steam is removed, the gas valve should be closed in time. The exhaust valve of vacuum electronic devices is generally not required to use gas valve.
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