What Is The Slip Crushing EffectSlips exert hoop compression on the Drill Pipe which can deform the pipe if conditions are unfavorable.
A unit tensile stress St from hanging weight will result in a hoop stress Sh that is a function of many factors such as slip length, coefficient of friction between slips and bowl, pipe diameter and others.
The slip crushing constant is defined for a given set of conditions as the ratio Sh/St. Slip crushing constants for a variety of conditions are listed in below table.
A coefficient of friction of 0.08 between slips and bowl is normally used. If the pipe is not stuck, the maximum tension carried by the slips is the working load, Pw, which is the buoyed weight of the Drill Pipe and Bottom Hole Assembly BHA.
In order to prevent any deformation of the pipe, the working load Pw times the crushing constant should be less than 0.8Y, or