Alignment of Rotating Machines

What's the ALIGNMENT?

Alignment is a method used to check the Co linearity of the true center lines of the driver and driven shaft.

Basically, we want the motor shaft axis and our rotating equipment driven shaft axis to be co-linear and co-axial. 

Why is it so Important?

The alignment process certainly takes a lot of effort and in a large rotary machine, it is time takings and difficult task to complete.
So it’s better to know the importance and why it’s essential.

1. Energy consumption

a. Eliminates reaction forces and therefore reduces energy consumption.
b. Significant power savings can be made through accurate alignment.
Reaction forces at the shaft ends occurs due to imbalance of axis, waste energy, and decrease the overall efficiency of the machine.

2. Mechanical seal life

a. Protects the asset and increases the product quality as vibration is reduced to a very low level.
b. The larger the offset misalignment, the greater the reduction of mechanical seal life.
Excessive vibration is among the top most reason for damaging the mechanical seal of rotary equipment. Mechanical seal is the most critical component and nobody wants it to get damaged therefore Alignment need to right.

 3. Bearing life

a. Proper alignment Eliminates reaction forces and thus reduces the load on the bearing.
b. Temperature of operation is lowered thereby improving the lubrication property.
c. Increases maintenance savings through reduced parts consumption and storage costs.
d. The rate of repairs was seen to decline as shaft alignment tolerance was made

4. Shaft Breakage

a. Misalignment leads to fatigue loading on the shaft.
b. In case of improper alignment there is various instances where shaft/coupling
failures have taken place.

Factors that lead to bad alignment

To get the best result of alignment you must be aware of the factors that can cause the alignment process unsuccessful.
The following are the factors 

a. Foundation and grout condition
b. Machine soft foot
c. Piping stresses and supports
d. Shaft and coupling radial and face run outs
e. Measuring Bracket Sag

Alignment techniques
1. Straight edge method - This method is suitable for small diameter shaft alignment. This method employs a straight edge which is placed on the shaft coupling and visual inspection is done to check any misalignment between the couplings. Not much accurate, good for light machines only.
2. Face and Rim

a. Two dial method - In this method, we use dial gauge to measure the misallignment between the coupling. 2 dial gauges are employed and fix at a stationary machine as shown in the diagram. The movable machine coupling is rotated and reading on dial guages are noted at 4 locations(0, 90, 180,360)

b. Three dial method -  This method is similar to the 2 dial method with an addition of one dial gauge at bottom to increase the accuracy. This method is primarly used for Large Machines.
3. Reverse dial indicator (or)graphical method. - In this method, 2 dal gauges are used in opposite direction and reading are noted, and a graph is made to analyse the misalignment. 
4. Laser alignment - Laser alignment uses beams of light to check the alignment and as per the condition mislaignment reading will be show digitally as in the below image.

Visit the 2nd part of the alignment topic to know about hot alignment and how the Calculations done in each method to achieve the perfect alignment.

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