The soft connection of fans is mainly used in the ventilation pipes of civil and industrial buildings and the import and export of fans. 3 Fan soft connection classification According to the shape, fan soft connection can be divided into rectangular fan soft connection, round fan soft connection and round local soft connection. According to the material, fan soft connection can be divided into canvas fan soft connection, rubber fan soft connection, stainless steel fan soft connection, fabric fan soft connection can be divided into positive pressure fan soft connection, negative pressure fan soft connection, fan soft connection and other connection methods: flange connection, welding connection, hoop connection, etc. This kind of fan is generally installed indoors, mainly used for air flow and guidance, without high temperature, corrosion and aging restrictions. It is the earliest and most basic fan soft connection. Due to the requirements of fire protection, this kind of fan soft connection is gradually fading out of the market, because the fire protection effect of canvas can not meet the requirements, even if there is a three-proof cloth, it can not be used for 30 minutes at 280 degrees. Therefore, the silicon-titanium fireproof soft connection solves this problem and is also an important branch of fireproof soft connection. The rubber material of fan soft connection is used for high pressure, corrosion resistance and aging resistance, and it is used in outdoor places and places with moisture in the air. This kind of fan soft connection has good pressure resistance effect, and there is also a kind of fan soft connection with integrated rubber vulcanization which has super waterproof performance, making up for the defects of outdoor use of soft connection.