Specified Minimum Yield Strength (SMYS)

The various grades of API line pipe have minimum yield strength specifications. That is, the yield strength of the steel must meet or exceed these minimums to receive that level or category of specification. For example an X70 grade must have minimum yield strength of 70,000 psi (or 70 ksi). Since yield strength is defined as a strength at which a certain amount of permanent deformation occurs, exceeding the SMYS will result in permanent deformation to the pipe.