Definition(s)
Lower Kelly Valve
A full-opening valve installed immediately below the kelly, with outside diameter equal to the drill pipe tool joint outside diameter. NOTE 1: This valve can be closed under pressure to remove the kelly and can be stripped into the hole if a closed IBOP valve is installed above it. NOTE 2: Some lower kelly valve models are not designed to withstand external pressure encountered in stripping operations.
Source: API STD 53, Blowout Prevention Equipment Systems for Drilling Wells, Upstream Segment, Fourth Edition, November 2012. Global Standards
Lower Kelly Valve
An essentially full-opening valve installed immediately below the kelly, with outside diameter equal to the tool joint outside diameter. Valve can be closed to remove the kelly under pressure and can be stripped in the hole for snubbing operations.
Source: API RP 7G, Recommended Practice for Drill Stem Design and Operating Limits, Upstream Segment, Sixteenth Edition, August 1998 (Addendum 2: September 2009). Global Standards
Lower Kelly Valve (Kelly Cock)
Essentially full-opening valve installed immediately below the kelly, with outside diameter equal to the tool joint outside diameter. NOTE The valve can be closed to remove the kelly under pressure and can be stripped in the hole for snubbing operations.
Source: API RP 7G-2, Recommended Practice for Inspection and Classification of Used Drill Stem Elements, First Edition, August 2009. Global Standards