Definition(s)
Underwater Safety Valve (USV)
Automatic valve assembly installed at an underwater wellhead location which closes on loss of power supply. NOTE Where used in this International Standard, the term is understood to include a USV valve and USV actuator.
Source: API SPEC 6A, Specification for Wellhead and Christmas Tree Equipment, Twentieth Edition, October 2010 (Addendum November 2012). Global Standards