Packed ValvesOne of the oldest design valves. Primarily used for corrosive and liquified gases. The sealing is a metal to metal seat. Tied Diaphragm ValvesThis optimizes the design for corrosive gas service, eliminates particle shedding moving parts and minimizes the surface area of the wetted cavity. The valve incorporates a "soft seat" which can be Kel-F or PVDF.