jqp alignment mach technique

Prepared By

TALAT MEHMOOD

Types of Alignment

In case of shafts, there are two types of alignment.

• Radial Alignment Radial alignment means to check the relative position of

rotating members in the vertical and horizontal planes. In other words, it must be checked that the axis of rotation of the members are in line / desired line.

Radial alignment can be further classified as

• Radial Vertical alignment

• Radial Horizontal alignment

Types of Alignment (Cont.)

• Axial Alignment Axial alignment means to check the relative position

between the axis perpendicular to the axis of rotation of the two members to be coupled. In other words, it must be checked that the said axis are parallel or have the required divergence.

Axial alignment can also be classified as

• Axial Vertical alignment

• Axial Horizontal alignment

Alignment States

• Cold Alignment Alignment which is carried out when the machine is at cold state.

• Hot AlignmentAlignment which is carried out when the machine is at hot state.

• In Situ AlignmentAlignment which is carried out when the machine is in operation.

Pre Alignment Checks

Before undertaking an alignment job, it is prudent

to check for other deficiencies which would largely

nullify the benefits or prevent the attainment and

retention of good alignment. Below is the List of

factors to be considered before checking the

alignment:

Pre Alignment Checks (Contd.)

• Foundation Adequate size and good condition. A rule of thumb calls for concrete weight equal to three times machine weight for rotating machines and five times for reciprocating machines.

• Grout Suitable material, good condition, with no voids remaining beneath baseplate. Tapping with a small hammer can detect hollow spots, which can then be filled by epoxy injection or other means.

Pre Alignment Checks (Contd.)• Baseplate

Designed for adequate rigidity. Machine mounting pads should be flat, parallel and clean. Shims should be made from corrosion and crush-resistant material. If commercial pre-cut shims are used, check for actual versus marked thickness to avoid a soft foot condition. Machine hold-down bolts should be of adequate size, with clearance to permit alignment corrective movement. Pad height should have at least 2 in. jacking clearance beneath center at each end of machine element to be adjusted for alignment. If jackscrews are required, they are to be mounted with legs sufficiently rigid to avoid deflection. Water or oil cooled or heated pedestals are usually unnecessary, but can in some cases be used for onstream alignment thermal compensation.

Pre Alignment Checks (Contd.)• Piping

Check the associated piping is well fitted and supported, and sufficiently flexible, so that no more than 0.003 in. vertical and horizontal (measured separately – not total) movement occurs at the flexible coupling when the last pipe flanges are tightened.

• Coupling Installation Some authorities recommend installation on typical pumps and drivers with an interference fit, up to .0005 in. per in. of shaft diameter. This can give problems in subsequent removal or axial adjustment. If an interference fit is to be used, we prefer a light one-say 0.0003 in. to 0.0005 in. overall, regardless of diameter. Coupling cleanliness, and for some types, lubrication, are important and should be considered.

Line Diagram

• Position of the shaft, when the machine is in cold state, can be represented graphically. This is called line diagram of the machine.

• It is a very useful tool for visualizing the actual position of the shaft, when carrying out the alignment.

Alignment Methods (Shafts)• There are three methods of aligning the centerline of two

shafts:

Aligning the shafts using feeler gauge & knife edge.

Aligning the shafts with reverse method. It is also sometimes

referred as graphical method.

Aligning the shafts using with dial indicators.

Alignment Methods (Cont.)

• Alignment with dial indicators. For using dial indicators, it is necessary to prepare a suitable outfit, which can hold three dial indicators simultaneously. One dial indicators (R), with the axis in the radial direction, will measure the radial misalignment of the shafts. The two dial indicators (A1 and A2), with the axis in the axial direction, will measure the axial misalignment of the shafts.


Note :For having accurate readings, ensure dial indicator rod remains perpendicular to the face while taking readings.


• Alignment with dial indicators

Alignment data can be measuredBy rotating one of the shafts, allowing the dial indicator slide on

the flange of the other shaft which remains fixed.

By rotating both the shafts at the same time.

If possible, proceed in the later manner because in this case the

collected alignment data will be independent of the machining

and shape of the coupling flanges.


• Dial IndicatorDial Indicator works with the index of mm scale. Before rotating

the shaft and collecting the misalignment data, ensure that all the three dial indicators are set to zero. Also make sure that traveling margin is available in these indicators.

When recording the data, the plus sign shall be given when the rod of the dial indicator goes back into its seat or move inward. Minus sign shall be given when the rod comes out.

When the dial indicator main pointer rotates by 3600, the dial indicator small pointer will show 1mm displacement of the rod


• Radial AlignmentPlace the dial indicator on the rim of the coupling hub

and secure it with the help of suitable outfit. Measure the data during a rotation of 3600. The algebraic

sum of the values read on the horizontal plane (900 & 2700) will be equal to the values read on the vertical plane (00 and 1800).

When noting down the alignment values, always specify the hub (Driver or Driven) on which the dial indicator moves.


Radial vertical misalignment = x

2

Radial Alignment (Vertical Plane)Dial Indicator readings:

-y -y = -x

- y

- x

- y

0

Place shims of thickness x/2 mm under all the feet of machine BAction required :

AB

A

B

Side View


Radial Vertical Misalignment = x

2

Radial Alignment (Vertical Plane)

(-y -y = +x)

Dial Indicator readings:

- y

+x

- y

0

Remove shims of thickness x/2 mm from all the feet of machine BAction required :

BAB A

Side View


Radial Alignment (Horizontal Plane)

x

2Radial Horizontal Misalignment =

Dial Indicator readings:

(x -x = 0)

+x

0

-x

0 BA

B

A

Plan View

Move the motor (A) upward by distance x/2. During movement, ensure that axial alignment may not get disturbed.

Action required :


• Axial AlignmentPlace the two dial indicators at 1800 by the vertical axis. The necessity to use two dial indicators is due to the fact

that axial displacement of the two shafts to be coupled may occur during the rotation of the two flanges.

By the use of two dial indicators the possible displacements along the axis are annulled, where the face displacements of the two hubs to be coupled remain unattended.


Axial Alignment (Vertical Plane)

Measure the data during a complete rotation of 3600.

The value of axial misalignment on the vertical plan will be the algebraic half difference of the reading (consider with their signs) made on the dial indicators A1 and A2 after a rotation of 1800 i.e.

A1a = 0

d

c

b

A2e

h

g = 0

f

c - e

2•Axial vertical Misalignment =

Alignment Methods (Cont.)Axial Alignment (Vertical Plane)

A2+e

h

g = 0

f

A1a = 0

d

-c

b

Dial Indicators readings:

Case 01

Side view

A1= 0A2 = +e

A1= -cA2 = 0

A1

A2

c - e

2Axial vertical misalignment =

Whenever misalignment result has minus sign, the flanges are open downwards.

Alignment Methods (Cont.)Axial Alignment (Vertical Plane)

Case 02

A1= 0A2 = 0

A1= 0A2 = 0

A1

A2

Side View

A1a = 0

d

c = 0

b

A2e = 0

h

g = 0

f


c - e


Whenever misalignment result is ‘0’, there is no axial misalignment in vertical plane.


Axial Alignment (Vertical Plane)

A1a = 0

d

+c

b

A2-e

h

g = 0

f

Dial Indicators readings: Case 03

Side view

A1= 0A2 = -e

A1= +cA2 = 0

A1

A2

c - e


Whenever misalignment result has plus sign, the flanges are open upwards.

Alignment Methods (Cont.)Axial Alignment (Horizontal Plane)• Measure the data during a complete rotation of 3600.

The value of axial misalignment on the horizontal plan will be the algebraic half difference of the reading (considered with their signs) made on the dial indicators A1 and A2 after a rotation of 900 and 2700 c.e.

Axial Horizontal Misalignment =

A1a = 0

d

c

b

A2e

h

g = 0

f

(b – d) – (h - f)

2


Axial Alignment (Horizontal Plane)

A1a = 0

+d

c

-b

A2e

+h

g = 0

-f


Axial horizontal misalignment =(b - d) - (h - f)

2

Whenever misalignment result has minus sign, the flanges are open to the left.

Case 01

Right

Left

A1

A2

Plan view

A1 = + dA2 = + h

A1 = - bA2 = - f

Alignment Methods (Cont.)Axial Alignment (Horizontal Plane)

A1a = 0

-d

c

+b

A2e

-h

g = 0

+f


Axial horizontal misalignment =(b – d) – (h - f)

2

Case 02

A1= - dA2 = -h

A1= +bA2 = + f

A1

A2

Left

Right

Plan viewWhenever misalignment result has plus sign, the flanges are open to the right.

Alignment Methods (Cont.)Axial Alignment (Horizontal Plane)

A1a = 0

d

c

b

A2e

h

g = 0

f

Dial Indicators readings: Case 03

Plan view

A1 = dA2 = h

A1 = bA2 = f

A1

A2

Left

Right

Axial horizontal misalignment =(b – d) – (h - f)

2= 0

Misalignment result is ‘o’, the flanges are axially aligned in horizontal plane.


• Alignment Correction ProcedureAfter taking the complete alignment data, draw the line

diagram. This helps in visualizing the actual physical condition of the machine. It thus helps in deciding the actions to be taken in order to get the desired alignment readings.

Always correct the axial alignment in the vertical plane first. One performs the correction by changing the height of the shims placed underneath the feet of the machine.


• Alignment Correction ProcedureAfter correcting the axial alignment in the vertical plane, correct the

radial alignment in the vertical plane. Raise or Lower the machine by adding or removing the shims from all the feet of the machine. By doing such, axial alignment of the machine in both the planes would not change.

Best method to carry out the above action is to tight the bolts of both the feet of one side first and than add / remove the shims from the feet of another side. Repeat the same process for removing / adding the shims from the feet of first side.


• Alignment Correction ProcedureAfter correcting the axial and radial alignment in the

vertical plane, correct the axial alignment in the horizontal plane.

As per alignment readings, make any foot of the machine a “pivot”. This can be done by tightening the bolt of that particular machine foot. After that, move the machine in a horizontal plane about the pivot to get the desired alignment readings.

In the last, correct the radial alignment in the horizontal plane.

Important Tips• If the machine has more than four feet, then it is better to

carry out the alignment of the machine by reverse / graphical method.

• Always carry out the alignment job in the early day time. This will help in precluding the error which can occur due to sunlight.

• Shims should be kink free. Also try to keep the no. of shim as less as possible.

• Before alignment, always ensure that there is no “soft footing” in the machine. If it exists, remove it prior to align.

Important Tips• Do not expect symmetrical thermal growth in unsymmetrical

machines.• Before decoupling the machine, take alignment reading, if

time permits. It serves as a reference reading, as some time it becomes difficult to get the desired readings.

• Associated piping / supports have a tendency to induce stresses in the machine during operation if they are not properly designed. If machine gets misaligned during operation, review the same

Effects of Misalignment Misalignment can cause the following problems on the running machine.

• Vibration occurs due to misalignment in the machine and associated / linked equipment’s.

• Excessive wear and temperature rise in the bearings. • It causes coupling failure.• Abnormal noise arises because of misalignment• Over loading of prime movers• Decreases the efficiency of the machine

Reciprocating Machine Train Alignment

jqp alignment mach technique

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