Definition
Slip Crushing — Slip crushing is the radial deformation or collapse of a pipe body caused by the gripping load of the rotary slips when a heavy string is suspended in them, a limiting concern when running very heavy strings such as deep casing on a landing string.
Also known as: slip crushing, slip crush, slip-crushing
What slip crushing is
Slip crushing occurs when the wedging action of the rotary slips squeezes the pipe body hard enough to deform or collapse it. As the slips take the hanging weight of the string, the axial load is converted into a radial (hoop) load on the pipe through the taper of the slip bowl. If the hanging weight is very high or the slip contact is short, the resulting hoop stress can exceed the pipe’s strength and crush it.
The ratio of hoop stress to tensile stress depends on the slip length, the pipe OD and the friction in the bowl — captured by the classic slip-crushing (Reinhold-Spiri) relationship used in design.
Managing slip crushing
- Slip length — longer slips spread the load and lower the crushing stress.
- Pipe grade and wall — higher-strength, heavier-wall pipe resists crushing.
- Landing strings — deep casing runs are the classic slip-crushing case and need rated pipe and slips.
Renting crush-rated equipment
Heavy casing and deep strings demand matched slips and high-capacity pipe to avoid crushing. We rent drill pipe suited to landing service and handling tools including rated slips — contact us with your hanging weight.