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The Foundation of Good Shaft Alignment

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By on July 15, 2012

There are several things that must come into play to achieve a quick and accurate shaft alignment. One of those things is starting with a good foundation. By foundation, I mean everything between the bottom of the machine and the floor.

So, let’s start at the bottom and work our way up.

Inertia Block or Base – The inertia block, or base, serves two purposes:

  1. Give a solid, flat mounting surface for the machine. The machine may be bolted directly to the base, but often the entire machine skid is mounted to the base.
  2. Facilitate sufficient mass to support the machinery and its secondary components, such as piping and ductwork. The mass also serves to minimize unwanted vibration.

Skid or Frame – The skid should be solidly bolted to the base. Shims are sometimes used to level the base. Shims should be located under the bolts to provide maximum stiffness to the frame. Bolts should be sufficiently tightened and should be rechecked periodically since concrete bases can shrink creating gaps under the frame.

Isolator Springs – In many instances, isolator springs are used between the frame and base, especially when the machine is located “off grade” or on an upper floor or roof. The isolator springs serve to isolate any machine vibration from reaching the base, and becoming a nuisance vibration or noise issue. Isolator springs are normally sized according to the mass of the machine they are supporting, and should be adjusted to have the proper spring compression to minimize this nuisance vibration.

Motor Risers and Adaptors – These are often used to raise the motor to a height sufficient to allow the motor to be aligned to the driven machine. Make sure the adaptor is attached solidly to the frame.

When performing a shaft alignment, especially on newly-installed machinery, all of these components should be check prior to performing the alignment.

  • Confirm that all bolting is tight.
  • Check for cracked welds.
  • Check for proper isolator spring compression. If you do not know the proper compressed height, step on the machine to see how “springy” the isolators are. If they move easily, check with your supervisor or engineering department to confirm that they are adjusted correctly.

Taking a few minutes to inspect the things that support the machine will help confirm that the machine can be quickly and accurately aligned.

About the Author

Stan Riddle joined VibrAlign in 2008. He has 30 years experience in aligning industrial machinery. Stan received his AAS Degree in Machinist Technology from Surry Community College in Dobson, NC, and also holds a diploma in Industrial Systems Technology from Forsyth Technical Community College in Winston-Salem, NC, where he was also an instructor in the program.

Stan began his maintenance career working as a machinist and millwright for companies such as Weyerhaeuser, R.J. Reynolds, and Tyco Electronics. He also has over 25 years experience in Predictive Technologies, such as vibration analysis, thermography, oil analysis, and ultrasonic inspection. He is a certified Level III Vibration Analyst with the Vibration Institute, and is a Past Chairman and Board Member of the Piedmont Chapter.

Stan and his wife live in Yadkinville, NC.

One response to “The Foundation of Good Shaft Alignment”

  1. These points are really essential in this work. I want to say thanks for this helpful post. Do you have more ideas like this one?

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