API drilling tools float shoe and float collar float neck.

API standard casing float collar and float shoe for cementing.

API 5CT casing float collar and float shoe.

After running the Collar to setting depth, the lower section is cemented in the conventional manner, except the cement is displaced with the flexible cementing plug furnished with the collar. This is bumped against the shut-off Baffle which is also included.

A float collar is installed near the bottom of the casing string. Cement plugs land on it during the primary cementing operation, thus retaining inside the casing a small portion of the cement slurry that may have become contaminated as the top plug scrapes the inside of the casing. It is similar to a float shoe; often both are used for redundancy. The internal check valves may be flapper type or spring-loaded balls.

The check-valve assembly fixed within the float collar prevents flow back of the cement slurry when pumping is stopped. Without a float collar or float shoe, the cement slurry placed in the annulus could U-tube, or reverse flow back into the casing. The greater density of cement slurries than the displacement mud inside the casing causes the U-tube effect.