The latest active version of this standard is . This edition technically revised and replaced the previous 2006 version. Key updates in the 2019 edition include:
The ISO 23251 standard provides guidelines for the design, manufacture, testing, and documentation of industrial process surveillance instruments, including those used for monitoring and control of process variables such as temperature, pressure, flow, and level. iso 23251 pdf
New requirements for choke valve failures and addressing acoustic fatigue . The latest active version of this standard is
Why? Because changing a contract to cite a newer PDF requires re-engineering studies and legal re-approval. Consequently, the 2006 PDF remains the "law of the land" for billions of dollars of existing refineries and offshore platforms. iso 23251 pdf