Valve assembly with a plug permanently mounted across the conduit so that, when rotated 90°, it effects a closure. EXAMPLES Plugs may be straight, tapered, ball, etc.
Source: API RP 17A Addendum 1, Design and Operation of Subsea Production Systems—General Requirements and Recommendations, December 2010. Global Standards
Wedge shaped, reduced part valve with 90- degree rotation; causes high-pressure drop.
Source: IADC UBO / MPD Glossary, December 2011. Global Standards