This document defines shaft misalignment and discusses its types, causes, effects, and characteristics. It describes two main types of misalignment: parallel (offset) misalignment, where shaft centerlines are parallel but not coincident, producing high 2X vibration and smaller 1X; and angular (gap) misalignment, where shafts meet at a point but are not parallel, producing strong 1X axial vibration with some 2X and 3X. The document outlines how misalignment can cause excessive vibration, noise, lost production, and increased maintenance costs if unchecked.

1. “MISALIGNMENT VIBRATION”
Definition, Types, Spectrum and Phases
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Doanta A. Edison G. M (15/385219/TK/43881)
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Diaz Brian P (15/385215/TK/43877)

2. Misalignment : Common (Combination)

3. Deffinition
Misalignment is a condition where the centerlines of coupled shafts do
not coincide. Misalignment is common due to poor alignment practices
or because of thermal growth, shifting foundations, pipe strain, etc.
Most misalignment cases are a combination of parallel and angular
misalignment. Diagnosis, as a general rule, is based upon dominant
vibration at twice the rotational rate (2X) with increased rotational rate
(1X) levels acting in the axial and in either the vertical or horizontal
directions.

4. Causes
Many causes exist for shaft misalignment. To ensure an alignment is successful, all of the possible causes of misalignment must
be addressed. The following are the most prevalent causes:
• Relative Movement – Thermal growth, or expansion, can cause one piece of equipment to move proportionately to another,
causing relative movement misalignment. Different materials expand at different rates when heated. Thermal growth must
be accounted for when equipment normally operates above ambient temperature.
• Strain – Strain induced by attached piping runs can force equipment out of alignment. Misalignment caused by strain can
reoccur after a successful alignment due to the continuous action of forces caused by strained equipment.
• Torsional Movement – The initial high torque caused during startup can force shafts out of alignment, causing torsional
movement misalignment.
• Settling – Over time, foundations or base-plates can settle to lower positions, causing settling misalignment. The equipment
can be realigned, but without addressing the cause of the misalignment, the problem can reoccur.
• Human Error – A mistake in an alignment procedure or not completing an alignment procedure can cause human error
misalignment.
• Misbored Couplings – Manufacturing defects, creating couplings that are misbored or otherwise distorted, can cause
misbored coupling misalignment. This form of misalignment is mostly found on new equipment; however, damaging a
coupling during an alignment will cause similar problems.

5. Effects
There are several effects that caused by misalignment. The effects of unchecked misaligned shafts include the following:
• Excessive Vibration – Misalignment is one of the leading causes of equipment vibration. In spite of self-aligning bearings
and flexible couplings, it is difficult to align two shafts and their bearings so that no forces exist that will cause vibration.
The significant characteristic of vibration due to misalignment is that it will be in both the radial and axial directions.
• Noise – Like vibration, noise can be detected simply by noticing a change in the equipment sounds during operation. All
running equipment produces a certain normal amount of noise. Only if an operator is familiar with normal equipment
noise will they be able to detect abnormal sounds.
• Lost Production – Misalignment can directly affect the lifetime of equipment. With a shortened service life, equipment
will require unplanned maintenance, thereby reducing the time available for production.
• Poor Quality of Products – Product quality can suffer directly from equipment misalignment. Misalignment can cause
both the manufacturing process to produce defects and directly damage product.
• Higher than Normal Repair Orders – Misalignment-induced failures will increase the amount of unplanned maintenance,
causing more repair orders to be generated.
• Increased Inventory of Spare Parts - As the amount of maintenance increases due to misalignment-induced failures,
more spare parts will need to be ordered. This results in increased spending and a larger spare parts inventory.
• Reduced Profits – As machines fail early and unexpectedly, more money must be spent for maintenance and spare parts.
Coupled with lower production, misalignments can rapidly reduce profitability.

6. Misalignment : Parallel (Offset)
Symptoms: 2X radial, small 1X radial (V & H)

7. Definition
If the misaligned shaft centerlines are parallel but not coincident, then
the misalignment is said to be parallel (or offset) misalignment. Parallel
misalignment produces both a shear force and bending moment on
the coupled end of each shaft.

8. Characteristics
With parallel misalignment, the 2X frequency is usually high in the
radial directions and the 1X frequency is typically smaller. There is also
a 180° phase difference between radial measurements on the coupled
shafts. The type of coupling may cause higher order frequencies to
occur, however there will be no raised noise floor like you would
observe for mechanical looseness. Note that with purely parallel
misalignment, the 1X and 2X frequencies will be low in the axial
direction

9. Spectrum
Due to the parallel (offset) misalignment, 2X can be quite high
compared to 1X vibration. The presence of 3X, 4X, 5X etc. will depend
on coupling type and degree of misalignment.
The peaks may be higher in vertical at one end of the component (e.g.
motor) but higher in horizontal at the other end of the same
component.

10. Phase
When comparing vertical and horizontal phase readings, they may be
in-phase or 180° out-of-phase. Vertical phase readings taken on
opposites sides of the coupling (e.g. motor drive end and pump drive
end) will be out-of-phase.

11. Misalignment : Angular (Gap)
Symptoms: 1X axial, small 2X axial, small 1X radial

12. Definition
If the misaligned shafts meet at a point but are not parallel, then the
misalignment is called angular or gap misalignment. Angular
misalignment produces a bending moment on each shaft, and this
generates a strong vibration at 1X and some vibration at 2X in the axial
direction at both bearings. There will also be fairly strong radial
(vertical and horizontal) 1X and 2X levels, however these components
will be in phase.

13. Characteristics
Axial vibration is usually stronger with angular misalignment; the 1X is
usually the strongest frequency, but the 2X and 3X frequencies may
also be present. In this scenario, the angular measurements on the
coupled shafts will be 180° out of phase. 1X and 2X frequencies will be
observed in the radial direction as well, but these will be in phase.

14. Spectrum
Due to the parallel (offset) misalignment, we see a high 1X peak in the
axial direction, and a small 2X and 3X peak depending upon the
"linearity” of the vibration. There may also be 1X and 2X in the radial
direction.

15. Phase
The components (e.g. motor and pump) will be out-of-phase axially
due to angular misalignment. Measure axially on the components on
either side of the coupling and remember to compensate for sensor
direction. The components are likely to be out-of-phase radially across
the coupling.

16. Reference
• http://www.mobiusinstitute.com/site2/item.asp?LinkID=8006&iVibe=
1&sTitle=Misalignment
• http://www.mobiusinstitute.com/site2/item.asp?LinkID=8005&iVibe=
1&sTitle=Misalignment
• http://www.xyobalancer.com/xyo-balancer-blog/vibration-caused-by-
misalignment
• https://www.techtransfer.com/blog/shaft-misalignment/