What is the purpose of API Standard 598?

API Standard 598 specifically focuses on the inspection and testing of valves in various applications. Its purpose is to establish criteria and procedures to ensure that valves are functionally sound and meet specified requirements during manufacturing, installation, and testing processes. This includes guidelines for checking the tightness and performance of the valve under specified conditions, thereby ensuring reliability in operation and compliance with safety standards.

While the other options refer to different aspects of industry standards – such as welding inspections, pressure vessel integrity, and pipeline quality control – they do not pertain to the specific focus of API Standard 598, which is dedicated to valves. This clear delineation of purpose makes the selection of B the correct answer, as it directly relates to the standard's defined scope.