Center line butterfly valve according to the seat material into rubber lining center line butterfly valve and  fluorine plastic lining butterfly valve, rubber lining center line butterfly valve mainly for  cast iron valve body lining EPDM, NBR, VITON  rubber and so on rubber, mainly used for water, serous situation, often used in medium with fresh water, sea water, sewage etc.PTFE lined butterfly valve(Teflon lined butterfly valve) is mainly in WCB body lining PTFE, F46, and other plastics, mainly used in chemical anti-corrosion, often used in corrosive liquids such as nitric acid and sulfuric acid.