This document is intended to describe, discuss, and clarify the API Standard Paragraphs (SP) Section 6.8 which outlines the complete lateral and torsional rotor dynamics and rotor balancing acceptance program designed by API to ensure equipment mechanical reliability. Background material on the fundamentals of these subjects (including terminology) along with rotor modeling utilized in this analysis is presented for those unfamiliar with the subject.

The standard paragraphs are introduced with references to the appropriate background material to enhance the understanding. This information is intended to be a primary source of information for this complex subject and is offered as an introduction to the major aspects of rotating equipment vibrations that are addressed during a typical lateral dynamics analysis.