How to Calculate Shims for Pump Couplings

When installing a pump it's important that the pump and the driver are properly aligned. Ideally, you want them to be working on the same axis, which will minimize the amount of vibration and excessive motion. Sometimes, though you need to make very small adjustments to raise or lower the pump or the driver and that is where shims come in. With a simple formula and a few measurements, you can figure just how many shims needs to be added or subtracted to align the pump and driver.

Measuring tape
Pump alignment indicators

Instructions

- 1
  Mount pump indicators on the unit. The indicators should be mounted on the movable unit, with the dial plunger touching the unmoving part of the unit. Take a reading. These indicators will give you the face, or angular, and rim readings you need to complete the formulae for figuring out the necessary shims.
- 2
  Measure the diameter at the indicator point of the pump. Measure the length from the indicator point to the first motor support and then from the indicator point to the second motor support. Write down the face indicator reading and the rim indicator reading. These are all the numbers you'll need to figure out the shims required.
- 3
  Figure out the shims under the first motor support using this formula: L1/D X F + 1/2R. Written out it means: Divide the distance between the indicator point and the first motor support, multiply the result by the face reading and add half the value of the rim indicator reading.
- 4
  Figure out the shims under the second motor mount using this formula: L2/D X F + 1/2R. Divide the distance between the indicator point and the second motor mount, multiply it by the reading value and add half the value of the rim indicator reading.

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