Categories: Shaft Alignment,Machinery Maintenance,Other Topics

Rolled Steel Frame Electric Motors

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By on August 9, 2017

In the precision shaft alignment business, we encounter all types of electric motors.  One type we come across are “Rolled Steel Frame” (RSF) motors.  These motors have a frame housing and feet that are made from mild, rolled steel.  They range from very small up to about 25hp.  They are common in many industries; however, they require some special consideration when aligning.

RSF motors have a housing and feet that are stamped from mild steel and are not exceptionally ridged.  Most of them don’t have 4 separate feet but instead have a plate welded onto the housing with 4 holes stamped or drilled in it.  These can be the most difficult to align. RSF Motors are more prone to soft foot issues than cast iron frame motors due to their mild steel feet.  The process of finding and correcting soft foot becomes even more important and must be done carefully.


Another step that must be performed carefully when aligning RSF motors is the process of torqueing down the hold down bolts during the correction phase of a precision shaft alignment.  A “cross torque” pattern must be established and followed with at least 3 passes around the pattern before final torque is reached. Some RSF motors may require more passes.  This will minimize flexing of the mild steel feet and creating soft foot when none may have existed.  It is recommended that one person follow this tightening sequence, this will ensure that the same torque is applied to each hold down bolt/foot.

Throughout VibrAlign’s Shaft Alignment Best Practices training course, we explain the causes of these alignment issues and practice the best ways to correct soft foot and other common issues that can occur during rotating machinery installation and alignment.

About the Author

James Pekarek joined VibrAlign in 2013. He has 18 years of experience in machine installation, electrical systems, maintenance and service management.

James began his career in the automation industry installing and maintaining various types of machinery and performing technical training to customers in the semiconductor industry. He spent 3 years with Cummins Industrial Power Generation as Service Manager. James also spent 3 1/2 years as lead Electrical Instructor at a vocational college serving the Wind Industry. While there, he gained his NFPA 70E certification as well as NEC 1910. James is also a certified Electrical Safety Instructor.

During his technical instruction career, James was introduced to VibrAlign and many of the products. He was impressed by the company philosophy and values and decided to pursue a career as a technical instructor with us.

James and his family live in Vancouver, Washington. He enjoys the outdoors, family time and building cars.

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