Plug valves are available in four different patterns. The pattern indicates basic information about the valve.
Short Pattern Plug Valves have compact face to face dimensions (like a Gate Valve) and port areas of 40% to 60% of a Full Bore plug valve. This provides an economical valve for services where some reduction of flow rates can be tolerated. The Short Pattern is only in classes 150 and 300.
Regular Pattern Plug Valves have longer face to face dimensions and port area of 50-70%. This configuration provides minimal loss of flow while economising on the overall valve dimensions from using rectangular port.
Venturi Pattern Plug Valves also have a longer face to face but with a small port opening of 40-50%. These are typically used on services where flow rate is not critical. The long lead into and out of the port minimises pressure drop when the valve is fully opened.
Full Bore Plug Valves have long face to face dimensions and a round port that is not smaller than minimum diameter specified in Annex A of ASME B16.34 or/and API 6D. This configuration provides unrestricted flow and allows the passage of pigs through the valve. It is also recommended for highly abrasive conditions as it minimises pressure drop and erosion in the valve.
The plug valve is used primarily for on - off service and some throttling services. It controls flow by means of a cylindrical or tapered plug with a hole in the centre that lines up with the flow path of the valve to permit flow. A quarter turn in either direction blocks the flow path.