Definition
Torsional Yield Strength — Torsional yield strength is the amount of applied torque at which a drill pipe body or connection begins to deform permanently, setting the safe limit on rotational torque that can be applied while drilling or making up connections.
Also known as: torsional yield strength, torsional yield, torque capacity
What torsional yield strength is
Torsional yield strength is the torque at which the steel of a drill pipe body or its connection starts to yield. It is derived from the material’s shear yield strength and the polar section modulus of the cross-section, so larger-OD, thicker-wall, higher-grade tubulars carry more torque before yielding.
Two separate torsional limits matter: the pipe body torsional yield and the connection torsional yield. In rotary drilling — especially long horizontal and extended-reach wells where surface torque is high — the string must be designed so that neither is exceeded.
Why it matters
- Drilling torque — surface torque plus reactive torque from the bit must stay below the string’s torsional yield.
- Make-up torque — recommended make-up is a percentage of the connection’s torsional yield.
- Double-shoulder connections — a second shoulder raises connection torsional capacity, often the limiting factor before the body.
Renting for high-torque wells
For high-torque directional work, connection torsional capacity often drives the pipe selection. We rent drill pipe and BHA components in standard and double-shoulder connections — contact us with your torque profile.