alignment.ppt

Alignment

Alignment

 Alignment, primarily for rotating machinery is the

 Alignment, primarily for rotating machinery is the

activity to check that centerlines of two rotating

activity to check that centerlines of two rotating

shafts ( of Driver & Driven machine ) are in line i.e.

shafts ( of Driver & Driven machine ) are in line i.e.

collinear with each other at operating conditions

Driver  Driver 

Rotating Machinery

Driver  Driver 

Rotating Machinery

Driver 

Driver  DrivenDriven

Rotating Machinery

Driver 

Driver  Connector Connector  DrivenDriven

Rotating Machinery

Motor  _Pump Coupling

Rotating Machinery

Shaft Alignment Fundamentals, Techniques

& Execution Methods

 Introduction to shaft alignment  Understanding alignment

 Objectives of accurate alignment  Effect of misalignment

 Types of misalignment

 Misalignment tolerance guide  Pre alignment checks

  Alignment techniques

 Symptoms of misalignment  Do’s & Don’ts of alignment  Conclusion

Introduction to Shaft Alignment

 Shaft misalignment is the deviation of relative

shaft position from a collinear axis of rotation measured at the points of power transmission when equipment is running at normal operating condition.

Introduction to Shaft Alignment

 Prime interest of alignment is to set the

centerline of rotation of shaft for two or more pieces of rotating machinery collinear. However, in practice alignment check is performed on the coupling & it is assumed that coupling hub bore & shaft are concentric with each other. So it’s necessary to ensure that coupling hub bores & shaft centerlines are concentric to each other.

Objectives of Accurate Alignment

 Reduce excessive axial and radial forces on the

bearings to insure longer bearing life

 Minimize the amount of shaft bending

 Minimize the amount of wear in the coupling

components

 Reduce mechanical seal failure

 Maintain proper internal rotor clearances

 Eliminate the possibility of shaft failure from cyclic

fatigue

 Lower vibration levels in machine casings,

Pre Alignment Checks

 Shaft run-out  Soft foot

 Distance Between Shaft Ends  Rough Alignment

 Piping strain

Pre Alignment Checks – Soft Foot

Pre Alignment Checks – Soft Foot

 Set the machine in place, but do NOT tighten the

hold-down nuts

  Attempt to pass a thin feeler gage – check for gap  Tighten all hold-down nuts on the machine to be

aligned

 Secure a dial indicator holder on one foot  Set the dial indicator to zero (0)

 Completely loosen the hold-down nut(s) on that

foot only. Watch the dial indicator for foot movement during the loosening

 If the foot rises from the base when the hold-down

Machine To Be Moved

The machine which is easy to move & can be moved in least time with minimum effort is

preferred for movement i.e.

 For Pump & Motor train, motor shall be preferred

for movement

 For pump & turbine train, turbine shall be

preferred for movement

 For compressor, G.box & Turbine train, first

fixing the G.box & carrying out adjustment on turbine& compressor shall be preferred

 Alignment Techniques

 Straight edge & feeler gauge

 Shaft alignment using dial indicators :

- Face-Rim method

~ Two indicator method ~ Three indicator method - Reverse indicator method

Straight Edge & Feeler Gauge Method

 Advantages :

 Simplest & cheapest of all methods.  Does not require too many tools.

 Does not require specialized skills

Disadvantages:

 Least accurate of all methods.

Symptoms of Misalignment

 Premature bearing or Mech. seal failures  Excessive radial and axial vibration

 High casing temperatures at or near the

bearings

 Excessive amount of oil leakage at the bearing

seals

 Loose foundation bolts

 Loose or broken coupling bolts

 Unusually high number of coupling failures

 The shafts are breaking (or cracking) at or close

Do’s

  Always use calibrated dial gauges

  Adjust the plunger of the dial gauges so that they are

pressed half ways

 Ensure that uniform conventions i.e. top, bottom, north

& south is followed throughout the procedure

 Measure all the readings facing the same direction

 Follow uniform practice for dial readings-division or mm  Before rotating the machine, ensure that bearings are

lubricated

  Always use pre-cut SS shims

 Ensure the correctness of readings by taking at least

two set of readings

 Check the surfaces where measurements are to be

Don’ts

 Do not hammer the machine feet directly for side

movement. Use side jackscrews for movement

 Do not use poorly fabricated or rough alignment

brackets. Use properly machined & sturdy brackets

 Never use magnetic dial stand for alignment

 Don’t use trial & error method for corrective

movements

 Don’t grind shank of the holding down bolts if 

restricting the movement, enlarge the holes

  Avoid using too many shims

 While measuring the readings if you have passed

the 90 Deg. mark never rotate back, complete the whole revolution