The service life of a rotary vane vacuum pump is determined by some key factors such as vapour in the vacuum pump, chemical attack and ageing of the moving parts. This article is to introduce what we shall do to avoid water vapour contamination.
Generally, the manufacturer specifies the vapour tolerance or vapour capacity of the pump in the operating manual. This figure indicates that when the gas ballast is open and the pump is at operating temperature. The vapour will not condense if the pressure is below the given value. The solution is to open the gas ballast, preheat the pump for 15 – 30 minutes to reach the optimum operating temperature of the oil, after which the gas ballast valve can discharge the vapour. If the water vapour is not displaced in time, the oil and water will mix and deteriorate (emulsify). The oil mist filter can be easily blocked and oil spraying will occur.
It is recommended to keep the gas ballast open and keep the pump running for about 15 minutes after the pump pressure is finished. The remaining vapour in the vacuum pump can be emptied to avoid pump corrosion and failure.
In some circumstances the rotary vane pumps have to be used in a vapory working condition. For example, in the glass factories the vacuum pumps are used to hold the glass for grinding and cleaning purpose. Water will be sucked into the pump with the air. In such case it is necessary to install an oil separator to remove the water.