Optical Alignment, Thermal Growth & Machinery Movement - Presented For The Vibration Institute - February 17 2007

Q: What types of (mis)alignment are discussed for two machine shafts?

The document describes parallel misalignment as rim offset between two shaft centerlines, angular misalignment as coupling face deviation from parallel, and their combined misalignment condition.

Q: How are alignment accuracy requirements evaluated?

Alignment tolerance charts tie shaft speed, coupling span, and misalignment in horizontal and vertical directions to assess whether realignment is required.

Q: What problems does optical alignment help address in achieving hot (operating) alignment?

It explains that cold shaft alignment targets can be invalidated by thermal growth and static deflection during operation, and OA is used to improve hot alignment accuracy.

Oct 12, 2026

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Optical Alignment, Thermal Growth & Machinery Movement presents how high-precision optical measurement improves hot shaft alignment when conventional cold alignment is insufficient. The material defines parallel, angular, and combined shaft misalignment, then explains alignment factors and tolerance criteria linking rotational speed, coupling span, and allowable deviation in horizontal and vertical directions. It compares cold alignment targets against thermal growth and static deflection, showing how OA enables accurate measurement and optimization of machinery alignment.

LanguageEnglish

CategoryPresentations

FormatPDF

Pages22

Reading Time8 min

AccessFree to download

Introduction

Basic Shaft Alignment

Alignment Factors

Alignment Criteria

Alignment Accuracy

What is Optical Alignment?

Why Optics?

Optical Alignment Equipment

By Stanley R. Bognatz, P.E. Optical Alignment, Thermal Growth & Machinery Movement 75 Laurel Street, Carbondale, PA 18407 Ph. (570) 282-4947 email: [srb@mbesi.com](srb@mbesi.com) Optical Alignment, Thermal Growth, & Machinery Movement Presented For: The Vibration Institute, February 17th, 2007 By: Stanley R. Bognatz, P.E. President Introduction Our customers often seek help achieving precision alignment of their critical machinery when standard alignment techniques do not provide satisfactory operation. While helping them achieve the simple goal of good hot alignment, we ve identified many mechanical issues using Optical Alignment ( OA ) that were not intuitive to those involved, and were not previously solved using vibration analysis or other techniques. We would like to share some OA background with you, and how we apply OA to optimize shaft alignment and eliminate machinery problems. © 2007 M&B Engineered Solutions, Inc. Optical Alignment, Thermal Growth & Machinery Movement 2007 M&B Engineered Solutions, Inc. 1 By Stanley R. Bognatz, P.E. Optical Alignment, Thermal Growth & Machinery Movement 75 Laurel Street, Carbondale, PA 18407 Ph. (570) 282-4947 email: [srb@mbesi.com](srb@mbesi.com) Basic Shaft Alignment How do we define the (mis)alignment of two machine shafts? Parallel misalignment: coupling rim offset between two shaft centerlines Angular misalignment: coupling face deviation from parallel Combined Misalignment Angular (Face) Misalignment Parallel (Offset) Misalignment Combined the usual field condition . © 2007 M&B Engineered Solutions, Inc. Optical Alignment, Thermal Growth & Machinery Movement Alignment Factors How accurate do we need to be? What factors might you consider? | More Critical: | Less Critical: | | --- | --- | | High speed (=> 1,800 rpm) | Low speed (< 1,800 rpm) | | Rigid couplings | Geared Couplings | | Disc-pack couplings (for offset) | Flexible Couplings | | Short coupling spans | Long coupling spans | | | | What criteria do you have? © 2007 M&B Engineered Solutions, Inc. Optical Alignment, Thermal Growth & Machinery Movement 2007 M&B Engineered Solutions, Inc. 2 By Stanley R. Bognatz, P.E. Optical Alignment, Thermal Growth & Machinery Movement 75 Laurel Street, Carbondale, PA 18407 Ph. (570) 282-4947 email: [srb@mbesi.com](srb@mbesi.com) Alignment Criteria The Alignment Tolerance Chart ties speed, coupling span, and misalignment in the horizontal & vertical directions together to assess alignment accuracy. Shaft deviation is calculated for each side of the coupling (h & v) and plotted as a function of speed to determine if alignment is required. We can see that at 3,600 rpm, deviation much beyond 1 mil/inch should be realigned. 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 SHAFT DEVIATION ( MILS/ INCH) © 2007 M&B Engineered Solutions, Inc. Optical Alignment, Thermal Growth & Machinery Movement Alignment Accuracy So, once again: How accurate does our alignment need to be? To muddy the water just a bit more: What is the point in setting a cold shaft alignment within 0.002" if adjacent bearing housings move 10 ~~ ~~ 20 mils (or more!) in different directions due to cold alignment, with the shafts collinear, it is a sure bet thermal growth and static deflection? If we set a perfect that thermal growth and static deflection will ruin our alignment when the machine is operating. This is where Optical Alignment will provide significant improvement in our operating (hot) alignment accuracy. © 2007 M&B Engineered Solutions, Inc. Optical Alignment, Thermal Growth & Machinery Movement 2007 M&B Engineered Solutions, Inc. 3 By Stanley R. Bognatz, P.E. Optical Alignment, Thermal Growth & Machinery Movement 75 Laurel Street, Carbondale, PA 18407 Ph. (570) 282-4947 email: [srb@mbesi.com](srb@mbesi.com) What is Optical Alignment? OA -The use of high-precision optical instrum

FAQs

What types of (mis)alignment are discussed for two machine shafts?

The document describes parallel misalignment as rim offset between two shaft centerlines, angular misalignment as coupling face deviation from parallel, and their combined misalignment condition.

How are alignment accuracy requirements evaluated?

Alignment tolerance charts tie shaft speed, coupling span, and misalignment in horizontal and vertical directions to assess whether realignment is required.

What problems does optical alignment help address in achieving hot (operating) alignment?

It explains that cold shaft alignment targets can be invalidated by thermal growth and static deflection during operation, and OA is used to improve hot alignment accuracy.

Oct 12, 2026

Upload by Melati