SS H A F TH A F T

AA L I G N M E N TL I G N M E N T

Contents

Basic terms What is shaft alignment Why is shaft alignment so important Types of alignment Alignment methods Alignment Tolerances chart Causes of misalignment

Basic terms in shaft alignment

Co-linearity Rotational centers Misalignment Stationary and Movable Machines Horizontal and vertical misalignment

What is shaft alignment?

Shaft alignment is the positioning of the rotational centers of two shafts such that they are co-linear when the machines are under normal operation.

Why is shaft alignment so important?

When shafts are misalign, forces are generated in the coupling. Energy will be lost and increased loads will be placed on any mechanical components which provide for rotation, seals, bearing housing, etc

snap

Types of misalignment

Shaft alignment begin by defining two types of misalignment:

1.Offset misalignment

2.Angular misalignment

Alignment methods There are a wide variety of methods for

measuring alignment, the most common ones are:

1.Mechanical method 2.Dial indicator method

a) Rim-Face methodb) Reverse Rim method

3.Laser method

Alignment Tolerances chart

RPM Excellent Acceptable Excellent Acceptable

3600 0.3 0.5 1 21800 0.5 0.7 2 41200 0.7 1 3 6900 1 1.5 4 8

Angular misalinment Mils/inch 0.001/1

Offset misalignment Mils 0.001

Causes of misalignment

Increased vibration Increased energy loss Increased load on bearings, seals and

other mechanical components Reduced production capacity Reduced product quality

Vibration

Misalignment causes vibrations. Vibrations are measured horizontally, vertically and axially and there are some rules of thumb in the analysis of the vibrations.

Horizontal vibrations indicate imbalance (H).Vertical vibrations indicate a weak or loose foundation (V).

Axial vibrations indicate misalignment (A)

Vibration

Alignment methods

Straight Edge

Reverse Rim

Rim-Face

Laser

Co-linearity

Two shafts are said to be co-linear when their respective rotational centers form a single line.

Rotational centers

All shafts, whether they are straight or bent, rotate on an axis called the rotational center. The rotational center forms a straight line.

Misalignment

Shafts are misaligned when their rotational centerlines are not co-linear, when the machines are operating.

Stationary and Movable Machines

When aligning any two machines, one is designated as stationary and one as movable.

Horizontal and vertical misalignmentHorizontal Misalignment

Misalignment conditions viewed from the top and corrected by sliding the front and back of the machine from side to side are termed horizontal misalignment.

Vertical Misalignment

Misalignment conditions viewed from the side (elevation) and corrected by making shim changes at the front and back of the machine are termed vertical misalignment.

Horizontal Misalignment

Vertical Misalignment

1.Offset misalignment

In shaft alignment, offset misalignment pertains to the deviation of one shaft centerline from another shaft centerline at a given point (or plane) along the length.

2.Angular misalignment

Angular misalignment is most easily defined as the slope relationship between two rotational centers.

1.Mechanical Method

Straight edge/feeler gauge method:

Offset misalignment is measured using a straight edge and set of feeler gauges.

Angular misalignment is measured by using feeler gauges, taper gauges.

snap

Straight edges

Offset

Angular

2. Dial Indicator Methods

Rim-Face Method:

This was the standard method of alignment. When using a rim-face method, one measurement is taken on the rim of the coupling to determine shaft offset. Another measurement is taken on the face of the coupling to determine shaft angularity.

Rim-Face Method:

Why is shaft alignment so important?

Forces generates on coupling

Damaged seal

TT H A N K H A N K

YY O U O U

GHULAM MOHIUDDIN