1. Advantages: a. Simple structure, easy produce and maintenance b. The stroke is small, open and close within short time. c. Good sealing, small friction between sealing surfaces, long using period. 2. Disadvantages: a. Large fluid resistance, required large force when opening and closing. b. Doesn't apply the fluid which with particles, big viscosity, easy coking. c. Poor regulation performance. According to the type of stem location, could classified as FNPT or NPT type. According to the flow direction, could classified straight-through type, DC type, and angle type. According to the sealing form, could classified packing seal type or bellows sealed type. Source: Valvehardware
Source:
http://www.valvehardware.com/news/20100711.html
