Internal Blow-out Preventers
There are a variety of tools used to prevent formation fluids rising up inside the drillpipe. Among these are float valves, safety valves, check valves and the kelly cock. A float valve installed in the drillstring will prevent upward flow, but allow normal circulation to continue. It is more often used to reduce backflow during connections. One disadvantage of using a float valve is that drill pipe pressure cannot be read at surface. A manual safety valve should be kept on the rig floor at all times. It should be a full opening ball-type valve so there is no restriction to flow. this valve is installed onto the top of the drillstring if a kick occurs during a trip.
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