The Importance of Motor Shaft Alignment

Proper motor shaft alignment increases the operating life span of rotating machinery. To achieve this goal, components that are the most likely to fail must be made to operate within their acceptable design limits.

The Advanced Manufacturing Office of the U.S. Department of Energy has released a white paper with information and tips regarding misalignment and tips for alignment. (Access it here.) The following information comes from the paper.

While misalignment has no measurable effect on motor efficiency, correct shaft alignment ensures the smooth, efficient transmission of power from the motor to the driven equipment. Incorrect alignment occurs when the centerlines of the motor and the driven equipment shafts are not in line with each other. Misalignment produces excessive vibration, noise, coupling- and bearing-temperature increases, and premature failure of bearings, couplings or shafts.

There are three types of motor misalignment:

Angular misalignment occurs when the motor is set at an angle to the driven equipment. If the centerlines of the motor and the driven equipment shafts were to be extended, they would cross each other, rather than superimpose or run along a common centerline. The “gap” (gap difference between coupling faces) or difference in slope of the motor shaft when compared with the slope of the stationary machine shaft can occur in the horizontal direction, vertical direction or both. Angular misalignment, in particular, can cause severe damage to the driven equipment and the motor.

Parallel misalignment occurs when the two shaft centerlines are parallel, but not in the same line. There are two planes of parallel misalignment as shafts may be offset horizontally (displaced to the left or right), vertically (positioned at different elevations) or both.

Combination misalignment occurs when the motor shaft suffers from both angular misalignment and parallel misalignment simultaneously. This is the most common misalignment situation encountered in the field.


Larger motors are usually directly coupled to their loads with rigid or flexible couplings. Rigid couplings do not compensate for motor-to-driven-equipment misalignment, while flexible couplings tolerate small amounts of misalignment. Flexible couplings also can reduce vibration transmitted from one piece of equipment to another, and some can insulate the driven-equipment shaft against stray electrical currents. Even flexible couplings have alignment requirements, defined in the instruction sheet for the coupling.

It is a mistake to rely on coupling flexibility for excessive misalignment. This is because flexing of the coupling and of the shaft will exert forces on the motor and driven-equipment bearings. These forces may result in premature bearing, seal or coupling failure, shaft breaking or cracking, and excessive radial and axial vibrations. Secondary effects include loosening of foundation bolts, and loose or broken coupling bolts. Operating life is shortened when shafts are misaligned.

In practice, proper alignment is difficult to achieve without using alignment equipment such as dial indicators or laser alignment tools. The proper shaft-alignment procedure is to secure the driven equipment first because moving a pump, for example, would stress the connected piping. Next, install the coupling to the driven equipment. The motor should then be moved into proper alignment and joined to the coupling.

After the equipment has operated long enough to become temperature-stabilized, shut it down and immediately recheck alignment. Alternatively, monitor the relative positional changes of the machines with a laser system equipped to do so. Due to thermal growth, machines aligned in the “cold” preoperating condition are almost always out of alignment when operating temperatures are attained. Many equipment manufacturers publish thermal offset values so the alignment technician can correct for thermal growth during the initial alignment process.

Suggested actions

  • Check newly installed equipment for alignment changes due to foundation settling after 3 to 6 months of operation.
  • Check shaft alignment of all production-critical equipment annually.
  • Monitor for vibrations and for increasing vibration trends as an indication of misalignment. Misalignment might be caused by foundation settling, insufficient bolt tightening or output shaft faults.
  • Apply predictive maintenance techniques, including vibration tests and frequency spectrum analysis, to distinguish between bearing wear, shaft misalignment or electrically caused vibrations.


  • Featured Product: Liquiphant From Endress + Hauser

    Vibronic instruments are widely used in the process industries. Available from multiple manufacturers, millions of these devices have been installed worldwide over the past few decades. While the basic technology of vibronic instruments hasn’t changed much over the years, today’s instruments now employ technological innovations to bring them into the digital age. Find out how […]

  • SPONSORED: Ultrasonic Bearing Friction, Cavitation, and Leak Detection Sensors – UltraTrak 850s...

    Significant damage to critical assets that lead to unplanned downtime is one of the most expensive hurdles your facility encounters. While there is never a convenient time for this to happen, there are better ways to be prepared and minimize the impact. The UltraTrak 850S family of sensors are versatile modern sensors and transmitters – […]

  • SPONSORED: Connect your pressure measurement to the future

    The Cerabar and Deltabar pressure transmitters offer safety, reliability and IIoT connectivity for your plant. Cerabar and Deltabar can be configured and verified quickly and easily with the SmartBlue app via the Bluetooth® interface. Thanks to Heartbeat Technology, verification is completed in 15 seconds – without interrupting the process. The pressure gauges signal any anomalies […]

  • Featured Product: OnTrack SmartLube

    One of the biggest reoccurring challenges that plants must face is how to extend and optimize their bearing lubrication processes on their more expensive assets. Since 60%-80% of premature bearing failures are due to lubrication-related missteps such as under lubricating, over lubricating, or using the wrong type of grease, it is important to utilize the […]

  • Clamp-On Flowmeter

    Prosonic Flow W 400 brings the company’s Proline series to clamp-on ultrasonic flowmeters. The W 400 clamp-on and I 400 insertion units provide comprehensive process monitoring with reported long-term cost efficiency and extensive diagnostics. These sensors pair with the Proline 400 transmitter to provide a complete flow metering solution. The flowmeter uses a nonintrusive method […]

  • Cables, connectors

    Murrelektronik data cables are high-flex shielded Ethernet Cat5e cables offering various connector styles, including D-coded M12 to M12, M12 to RJ45, RJ45 to RJ45, and M12 to pigtail. The cables are flame-retardant and chemical resistant with a TPE (thermoplastic elastomer) jacket for typical industrial applications. A selection of RJ45 IDC field wireable connectors and adapters […]

  • Turbine flow meter

    TRP Pelton-wheel high-temperature turbine flow meter monitors and controls the cooling and process efficiency of high- and ultra-high-temperature oil used in heating and cooling circuits. Four flow ranges are available across all meter sizes from 0.5 to 1 in. The meters are said to tolerate operating pressure to 290 psi. AW-Lake Oak Creek, WI

Sign up for insights, trends, & developments in
  • Machinery Solutions
  • Maintenance & Reliability Solutions
  • Energy Efficiency
Return to top