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Pump Talk: Shaft Alignment for Base Mounted Flexible Coupled Pumps

Alignment gauge

Pumps are serious business in the world of commercial building. Engineers spend hours reviewing usage requirements so that the correct pumps are specified, purchased and installed for building and system needs.

However, you may hear months or years later that the building owner is experiencing problems with that same pump you painstakingly selected.

Here’s a little nugget of engineering truth: you can select the absolute perfect pump for an application, but if the pump isn’t installed and aligned correctly, that pump will never run properly and will almost certainly fail before it should.

Base-mounted flexible coupled pumps MUST be aligned properly before running. (Side note: If you never want to worry about pump alignment, you can always choose a vertical inline pump!)

If you want to avoid costly and inconvenient downtime and repairs, review this checklist of things to share with the installing contractor and the building owner to ensure that base-mounted flexible couple pumps are installed and aligned correctly.

  • A straight-edge alignment should be done to the pump and motor shafts before tightening the pump base to the housekeeping pad.

  • The pump base should be leveled on the housekeeping pad before tightening the bolts and grouting.

  • Before final alignment, the pump flange bolts should be removed to demonstrate no pipe weight is transmitted to the pump housing, and then reattached.

  • Final alignment should be performed after the system and the pump/motor have reached normal operating temperature.

  • Use a laser alignment tool for the most accurate alignment results.

  • A printed report from the laser alignment tool should be presented to the owner and reflect alignments have been completed within the following tolerances:

    • Parallel: 0.002”

    • Vertical: 0.002”

    • Angular: 0.0017 / 1” - this one is the most critical

This is an example of a laser alignment printout. You can see the Before and After numbers. In the After boxes, the numbers from top to bottom mean:

  • Side Angular: 0.0002 / 1”

  • Vertical: 0.0022”

  • Overhead Angular: 0.000 / 1”

  • Parallel: 0.0001”

Example of a laser alignment printout

The numbers to the right are recommended adjustment numbers to get to 0.0”, but those greatly depend on the accuracy of the instrument placement.

With proper installation, alignment and maintenance, the pumps you select today should be humming along for many years into the future.

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