ISA-TR75.25.02:2024

ISA-TR75.25.02-2024, Control Valve Response Measurement from Step Inputs, offers a comprehensive reference on the response characteristics of throttling control valves to step input signals, addressing both static and dynamic behaviors. It explains how factors such as valve design, actuator type, accessories and process conditions impact performance metrics like dead band, resolution, dead time, overshoot and step response time.


This technical report defines four regions of valve response based on input signal size and discusses appropriate testing environments and methods for measuring valve behavior under various conditions, including bench tests, laboratory flow simulations and in-process operation. It also addresses maintenance and design considerations that affect valve performance, such as stem seal materials, mechanical tolerances, positioner effects and sizing issues. Additionally, it explores the effect of valve response on overall process control loop dynamics, emphasizing the importance of aligning valve characteristics with process requirements to manage control loop gain, avoid oversizing and maintain stability. Detailed annexes provide insights into nonlinearities, sources of lost motion and stiction, as well as practical examples of specifications and test procedures tailored to different control objectives.