ISO/PAS 12835:2013 is intended for assessment of casing connections for those field applications in which the design of the casing-connection system is strain-based, and in which primary axial loading is on the casing-connection system driven by constrained thermal expansion, and in which that primary loading exceeds the casing-connection system's yield envelope. Consequently, ISO/PAS 12835:2013 should be considered as a protocol that is complementary to ISO 13679, which applies to classic elastic-design applications.

ISO/PAS 12835:2013 describes the structure of the Thermal Well Casing Connection Evaluation Protocol (TWCCEP) and provides guidelines for its use by new or repeat TWCCEP users, whose familiarity with the TWCCEP provisions might vary. Clause 6 describes fundamental assumptions adopted in the TWCCEP.