Figure 4. The Varco Top Drive sits below the traveling block and rotates the drill string. The WKM valve (V) is used to close off the drill pipe in the event of a kick, but the wireline has to be removed before the valve is closed. The wiper (W) cleans salt water off the wireline. The wireline ram (R) seals the core line and allows the driller to increase pressure for high-pressure (>400 psi) circulation while the coring line is in the hole or to shoot the APC.