Butterfly valves are a type of rotary valve that use a rotating disk to control flow through a pipe. The disk is generally operable through 90 degrees and provides a linear flow characteristic. For throttling control applications, one type of butterfly valve is now the industry standard: high performance butterfly valves (HPBVs) or double offset valves. Their advantages include a straight-through flow path, very high capacity, and ability to pass solids and viscous media