At present,there are two main storage principles for sulfur hexafluoride recovery and purification in the world:

　　***using freezing liquefied method principle,is in the process of sulfur hexafluoride gas recovery,under certain SF6 gas pressure,the use of refrigeration units make SF6 gas temperature is reduced to the pressure of saturated steam temperature,SF6 gas to liquid to liquid,and stored in a liquid form,advantage is fast recovery speed,liquid;

　　The second is to use the principle of high-pressure liquefaction,sulfur hexafluoride recovery and purification process,at the ambient temperature at that time,the use of a compressor to increase the SF6 gas pressure to the temperature of saturated steam pressure,SF6 gas began to convert into liquid,and in the form of liquid storage.Advantage is simple,the disadvantage is that the system work pressure,high recovery efficiency is low,when the temperature of the SF6 gas,SF6 gas after compressor compression temperature can reach 80℃above)more than the critical temperature of 45.55℃,cannot make its liquefaction,the high temperature and high pressure of the SF6 gas stayed after a period of time(when the temperature dropped to below the critical temperature would be converted into liquid.

　　In addition,in sulfur hexafluoride recovery and purification system with oil or without oil system,as to which is better,there is a certain controversy.

　　The Oil system can theoretically do SF6 gas to 100%no contact with oil,known as oil-free,such as the membrane compressor used in China.This kind of sulfur hexafluoride recovery and purification device has large volume,low recovery efficiency and heavy maintenance workload.

　　By***case came second with no oil system,sulfur hexafluoride recycling purification plant master-the SF6 gas compressor for grease lubrication of piston compressor,such as direct contact with SF6 piston ring with self-lubricating materials,is just the crankshaft of the crank case,crank pin,piston pin piston parts of the rotating components using grease lubrication(no lubricating oil in the crankcase),It is called oil-less,or precisely less Oil.After long-term use,a trace of oil vapor can be mixed into SF6 in theory,but in practice,this trace oil vapor has little effect on Sf6.This kind of compressor has high manufacturing process requirements,and most of them are imported compressors.The advantage is small size,light weight,the disadvantage is that the price is high,because there is no oil,service life and oil compressor compared with a big discount.