Slip Crushing
When drill pipe, casing, or tubing are run in or pulled out of the hole, they are set on slips at rotary bushing for connecting or disconnecting pipes. When the pipe is sitting on slips, in addition to tensile load due to the buoyed weight of the string, the pipe also experiences radial load or hoop stress exerted by slip segments. The damage to the pipe that can be caused due to this additional stress by slip segments is called ‘Slip Crushing Effect.’ Calculations and analyzing tools help in determining the maximum load that can be placed on the slips without damaging the tubular subjected to a tensile load. Slip crushing is affected by the pipe diameter, slip angle, slip length, and the coefficient of friction between the slip and the master bushing.