What API Standards Govern Rotor Dynamics Analysis?

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Hello and welcome to this December edition of the Intro to Rotor Dynamics Blog; and if you’re re-reading this, welcome back! Here are the other entries in this series if you want to retrace our steps thus far:

Series Preface

What is Rotor Dynamics? And Where is it Found?

Why is Rotor Dynamics so Important?

So now that we’ve covered the basic definition of rotor dynamics and established the consequences of inaccurate/incomplete analyses, let’s look at what standards govern rotor dynamics.

In general, there are several different codes and standards that rotor dynamics engineers look to in order to make machines compliant. The standard they look at for compliance depends on the location of the company, as well as the kind of machine, what industry the company/machines are present in, and what the machine’s application is.  With so many different applications, there are many different places to consult in order to make a compliant machine.

So, what are the governing bodies on rotor dynamics and vibration analyses as well as the balancing of rotating machines? Well, there are several

  • – First, you have the American Petroleum Institute, commonly known as API.
  • – Next, there’s the International Organization for Standardization, known as ISO.
  • – There’s also ANSI, the American National Standards Institute.
  • – Lastly, each company may have internal rules and standards, with their own calculations and tests that are more stringent than the requirements put forth by the other governing bodies.


So where would you find the rules relating to rotor dynamics in the API’s and the ISO’s long lists of standards and regulations? I’m glad you asked.

Governing Bodies for Rotordynamics

API Standards

In the API standards, you can find the following documents for rotor dynamics:

  • – API 684: Outlines the complete set of standards for lateral and torsional rotordynamics and as well as rotor balance designed by the API to ensure machine reliability.
  • – API 610: Governs the design standards for centrifugal pump.
  • – API 611 & 612: Govern the two different kinds of steam turbines (which are general purpose and special purpose) as they are distinguished by the API; for a more in depth look at the differences, I found this site quite helpful: http://www.mechanicalengineeringsite.com/difference-between-api-611-and-api-612/
  • – API 541: Covers the requirements for induction motors, specifically form-wound squirrel cage induction motors that are 375kW (500HP) and larger.


By now it should be clear that the API covers a wide range of rotating machinery and has many publications covering the acceptance criteria for their vibration, bearing performance inspection methods, and balancing specifications. The API is constantly updating their standards to keep up with the new challenges as engineering technology and science continue to advance. If you don’t have any established reference for your rotor dynamics analyses, the API standards and website should be your first stop; but keep in mind that the standards should not be strictly applied without good engineering judgment and experience with operating rotating machines.


In the ISO standards, you can find the rotor dynamics regulations and standards in the following articles:

  • – ISO1940
  • – ISO 14839/20824
  • – ISO 10436 which is equivalent to API 611
  • – ISO 10437 which is equivalent to API 612, conveniently enough!


­While what I have listed here is certainly not an exhaustive list, you can find more details on the standards governing rotor dynamics analyses online; the section on rotor balancing by ISO is located here: https://www.iso.org/standard/54074.html

Coming up in next month’s rotation…

Next month we’ll be diving into 2020 with an article covering the basic definitions and the fundamental concepts of vibrations in rotating equipment. Until then, keep an eye on your rotating equipment and turbomachinery, and have a happy holiday season!

Have questions about the blog, or perhaps want to explore opportunities to learn about the fundamentals of rotor dynamics? Email us at info@softinway.com or visit our classroom schedule at http://www.softinway.com/en/education/classroom-training/rotordynamics-bearings-design/ 

Interested in using AxSTREAM or our AxSTREAM RotorDynamics package for your project? Shoot us a message at sales@softinway.com

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