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Check for and Correct Soft Foot Conditions

Proper Pump to Motor Alignment Techniques: Part 4 of 6

Proper Pump to Motor Alignment Techniques: Part 4 of 6

Check for and Correct Soft Foot Conditions

Checking for and subsequently correcting any existing soft foot conditions is a commonly skipped step that must not be overlooked when performing a proper pump to driver alignment.  A soft foot condition exists when, resting in an unrestrained condition (feet not bolted down), 1 or more of the pumps feet is not in contact with the baseplate surface.  Correction for this condition can be achieved by simply adding standard motor shims if the soft foot condition is parallel in nature, or by adding custom tapered shims if angularity exists between the pump foot and the baseplate surface.

To check for a soft foot condition, it is best to utilize a laser alignment system.  With the laser alignment tool setup, the system will direct the technician to loosen one pump foot at a time.  The machine will then calculate the amount of foot lift.  The technician will then be directed to re-tighten each foot before proceeding to the next.

The graphic above shows a classical soft foot problem, with a rock across feet B and C.  In this situation, the foot with the highest lift should be shimmed, followed immediately by rechecking the pump for soft foot using the laser alignment tool.  A simple way of viewing this condition is a restaurant chair with 1 leg that is slightly shorter than the other, with the common quick fix being to place some coasters underneath the shortest leg.

The correct permanent solution to this problem would be to re-machine the pumps feet parallel, at the same elevation during the next overhaul at a qualified repair facility.