Vacuum system for pumping steam
In the process of vacuum impregnation, vacuum drying and vacuum freeze-drying, water vapor and other condensable vapors are the main gases pumped out by vacuum system. The working vacuum is mostly 10-10-1 Pa. Roots pump and oil seal mechanical pump are usually used to pump air abroad. For this reason, in recent years, foreign oil-seal mechanical pumps have the index of maximum inlet pressure of water vapor (usually 103~3*103Pa), but domestic oil-seal mechanical pumps generally do not have this index, and some mechanical pumps equipped with gas ballast valves have weak backstop effect, gas ballast effect is not significant, can not achieve the purpose of pumping a large amount of water vapor, resulting in water steaming. Vapor condenses in pump oil in large quantities. Oil and water mix to form a white emulsion, which reduces the sealing and lubrication performance of mechanical pumps. Emulsion will make the inner part of the pump rusty, rusty iron powder into the oil is reddish brown, and circulate with the pump oil in the pump, which has a negative impact on the service life and limit vacuum performance of the pump.
Several common vacuum systems for steam extraction are:
(1) Steam ejector pump pumping system. Steam ejector pump is suitable for vacuum system with large exhaust volume. The system needs to be equipped with working steam source.
(2) Oil booster pump + oil seal mechanical pump. This system is not suitable for gas-phase drying of transformer, especially in oil booster pump, bare electric furnace is used strictly, otherwise open fire will easily cause explosion accident.
(3) ZJ Roots Pump + ZJ Roots Pump + Double-stage Water Ring Vacuum Pump, the pumping system can obtain higher limit vacuum and larger exhaust volume. However, the investment cost of the system is relatively high, and the working fluid of the water ring pump can easily flow back into the vacuum container. Moreover, the pumping efficiency of the water ring pump is low, and the unit power consumption of the water ring pump is 50% higher than that of the slide valve pump. For example, various types of Roots water ring vacuum units.
(4) Slide valve pump + water ring pump or ZJ Roots pump + sliding valve pump + water ring pump, because the sliding valve pump in the system is equipped with a front pump (water ring pump), which reduces the compression ratio, so water vapor rarely condenses in the sliding valve pump, but there are still shortcomings of item 3.
(5) ZJ Roots Pump+Rotary Vacuum Pump, because of its high efficiency air ballast valve, reliable oil-water separator and reasonably designed lubrication system, enables the system to operate continuously at the inlet steam pressure of 3000Pa. This is an economical and reliable vacuum system for pumping steam used abroad in recent years. For example, various types of Roots rotary vane vacuum units.
Liquid Ring Vacuum Pump
Roots Vacuum Pump