You're referring to the ASME PTC 19.2 standard!
ASME PTC 19.2-2019, "Steam Turbines"
This code provides procedures for conducting performance tests on steam turbines, including measurement of steam flow, power output, and efficiency. It covers various types of steam turbines, including impulse, reaction, and combined impulse-reaction turbines. asme ptc 192
Here's an overview of the standard: