gravel slurry pump maintenance

3 Ways To Align a Centrifugal Pump

3 Ways To Align a Centrifugal Pump

A wastewater treatment operator called Crane Engineering with a problem. He was replacing bearings on the same centrifugal pump in his lift station again and again. When the operator's account manager visited in person, it was obvious something was wrong. Even before he saw the pump, he could hear the sound of grinding bearings from outside the lift station.

A quick check revealed misalignment of the pump and motor, causing excessive noise and premature bearing wear.

Up to 50% of damage to rotating machinery is directly related to misalignment. Machine vibration, bearing damage, premature seal wear, and coupling damage are all examples of issues pumps experience if improperly aligned at installation. Misaligned pumps can also draw up to 15% more energy than aligned pumps.

There are 3 common tools and methods used to align pumps. Here are the pros and cons of each:

Straight Edge

This method requires placing a straight edge on the pump and motor coupling, then making a visual check to see if the components are aligned.

• Pros
  • Quick and easy to perform
• Cons
  • Highly inaccurate. Today's high performance machinery and expectations for up time require more accurate measurement.

Reverse Dial Indicator

This method uses two indicators that check for radial run-out and angularity. The readings are then plugged into mathematical formulas to calculate shim requirements for proper alignment.

• Pros
  • Very accurate, far more accurate than the straight edge method.
• Cons
  • Time consuming, cumbersome
  • Requires a high level of technical skill
  • Reading errors

Laser Alignment

This method uses lasers to determine the relative shaft positions. The computer then makes recommendations for adjustments.

• Pros
  • The most accurate method available (to .0001)
  • Once familiar with it, operator can align pump/motor quickly
• Cons
  • Cost - by far the most expensive of methods available
  • At first, somewhat more complicated to set up

The wastewater operator chose to have this pump laser aligned by the Crane Engineering Service team and the noise from the bearings quickly subsided. Now, they ensure proper alignment of all their pumps before start-up.