Engineering is iterative. The API 5C3 committee, composed of experts from major operators (Exxon, Shell, BP) and premium connection manufacturers, revises the formulas based on full-scale physical testing failures.

Recent iterations, including the Seventh and Eighth editions, have introduced more rigorous calculation methods to reflect modern drilling challenges, such as wells. API Specification 5CT, 10th Edition

The KT model calculates the collapse pressure ($p_c$) using an interaction formula that bridges elastic instability and plastic yielding. It treats the pipe as an imperfect cylinder rather than an ideal one, resulting in a formula that looks roughly like: