Definition:
Non Stop Drilling (see comment)
Subject Area 1:
Drilling & Operations
Remarks:
It is a sub which is run between the drill pipe stands and it is like a kelly cock with a side entry. Before breaking each connection a hose will be attched to the side entry and the ball valve above the enry will be closed. Therefore it is possible to continue circulation and as a result no ECD change or cutting falling back can happen. usefull for MPD/UBD operations.