ASTM D7278-11

The analyzer sample system lag time estimated by this guide can be used in conjunction with the analyzer output to aid in optimizing control of blender facilities or process units.

The lag time can be used in the tuning of control programs to set the proper optimization frequency.

The application of this guide is not for the design of a sample system but to estimate the performance of existing sample systems. The principles listed in this guide are there to help understand design concepts and allow the application of this guide for its intended scope. Additional detailed information can be found in the references provided in the section entitled Additional Reading Material.

1.1 This guide covers the application of routine calculations to estimate sample system lag time, in seconds, for gas, liquid, and mixed phase systems.

1.2 This guide considers the sources of lag time from the process sample tap, tap conditioning, sample transport, pre-analysis conditioning and analysis.

1.3 Lag times are estimated based on a prediction of flow characteristics, turbulent, nonturbulent, or laminar, and the corresponding purge requirements.

1.4 Mixed phase systems prevent reliable representative sampling so system lag times should not be used to predict sample representation of the stream.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.