Shaft Alignment

Type of misalignment Shaft alignment is the process to align two or more shafts with each other to within a tolerated margin.

Parallel or Lateral misalignment

Shaft in Alignment

Combined Angular and

Lateral misalignment Angular misalignment

Types

•Parallel or Lateral misalignment•Angular misalignment•Combined Angular and Lateral misalignment

Disadvantages of Misaligned shafts

• Forces are generated• Vibration, noise, bearing damage, shaft damage,

coupling damage and Looseness.• Shaft to fracture and break.

Shaft Aligning Techniques

• Conventional method

• Dial Test Indicator (DTI)

• LASER Equipment

• By using computer

Preliminary alignment procedure Clean the machine base, bolts. Remove rust burrs etc. Check coupling & shaft run-out Check bearing clearance (especially for old machines) Check strain of pipes, cables & conduits Rough alignment Check DBSE Check soft foot Check dial gauges before taking readings Check indicator sag Verify accuracy of readings Use correct bolt tightening procedure Don’t lift the machine more than necessary Put the stem of dial gauge perpendicular to the surface Use jack bolts Use stainless steel shims

Run-out check

Max. allowable run-out;

0 – 1800 rpm = 125 µm (5 mils)1800 – 3600 rpm = 75 µm (3 mils)3600 + rpm = 50 µm (2 mils)

(unless otherwise not given by vendor)

Rough alignment

Within 0,5 mm (20 mils)

Angled soft foot

Parallel soft foot

Soft Foot

Soft Foot correction

Shell DEP and API 686;

min shim height 3 mm at beginning of alignment

Hold Down bolts tightening

Soft Foot checking

Shell DEP max 0.03 mm (API 686 max 0.05 mm (2 mils))

What is Sag?

Shell DEP ≤ 0.02 mm/ meter

Sag check

Perpendicular to the coupling surface.

Fixing of Dial gauges

Rim and Face Method

VERTICAL; V TIR = 180ᴼ - SAG - 0ᴼ, Face FVₒ = TIR, Rim RVₒ = TIR/2, VO = RVₒ - (VA x C x (C1/C)), VA = FVₒ/ C2Shim MNf = VA x (B + C) - RVₒ, Shim MFf = VA x (A + B + C) - RVₒ

HORIZONTAL;H TIR = 90ᴼ - 270ᴼ, Face FHₒ = TIR, Rim RHₒ = TIR/2, HO = RHₒ - (HA x C x (C1/C)), HA = FHₒ/ C2Move MNf = HA x (B + C) - RHₒ, Move MFf = HA x (A + B + C) - RHₒ

Alignment TolerancesShell DEP

Parallel =

All speeds and coupling spacer lengths ≤ 250 mm; 0.05 mm

All speeds and coupling spacer lengths > 250 mm; 0.02 mm per 100 mm of spacer length

Angular =

0.05 mm (based on a diameter of 150 mm)

Piping AlignmentShell DEP

Off-set = 0.3 mm/ of 100 mm flange diameter and max 1.5 mm

Angularity =

For flange dia. < 300 mm; max 0.2 mm

For flange dia. 300 to 600 mm; max 0.3 mm

For flange dia. > 600 mm; max 0.5 mm

Gap = Gasket spacing and ± 1.5 mm