Pump Mechanical Rebuild: Do it Right for a Longer Life

An electrical mistake is known quickly--sparks fly, or the lights flicker. However, mechanical mistakes on machinery aren't always apparent post-repair or after a rebuild. What if you miss a critical step in alignment, disregard bearing fits, or leave the shaft unbalanced in your pump? The machine may run but not for long. Ten years of running time will decrease to two years. This blog post will line up essential points to consider for a pump rebuild or repair. 

• Take a set of alignment measurements before pulling components apart. Misalignment will cause friction with bearings and seal faces.  Inspect the pump base and feet for signs of soft foot. Also, verify the pump base is clean and making good contact at each foot location. No more than three shims under each foot. The pump base should be rigid and solidly mounted. A good alignment starts with a good base.

• Investigate for signs of piping strain. Pipe strain is often an issue and can cause misalignment and stress on a pump casing.  A simple check can avoid piping misalignment and its stress on critical pump components.

• Then, with all pieces removed, check for shaft straightness. Even a slightly bowed shaft reduces a sea and bearing life from years to months.

• Dynamically balance all the rotating components of the pump when it is disassembled.  Often overlooked by pump rebuilders, it's cost-effective and avoids downtime caused by excessive vibration, which may not be able to be corrected once the pump is assembled.

• It's essential to install anti-friction bearings properly to ensure the bearing stays round and does not get cocked or damaged during installation. The bearing has an interference fit on the rotating component, typically the shaft of the pump. To fit a bearing properly, use a bearing heater suited to this purpose. Make sure the bearing doesn't get too hot, or you'll trim off some years of its life span. Keep the bearing squared to the shaft shoulder. Any irregularity will cause internal misalignment.  Don't ever hammer a bearing onto a shaft as this will cause brinelling of the races, permanently damaging the bearing.

• When assembling the pump, always be sure to check the impeller clearance. Impeller suction to wear ring clearance is crucial for performance.

• To save on energy and ensure your pump is working at its capacity, verify the pressures and flows and, if necessary, trim the impeller's diameter so as not to cause overload and/ or cavitation. 

Here's an example of a machinery service repair AME has performed:

An industrial company called AME to perform a rebuild on one of their pumps. First, we replaced the pump's seal, radial, and thrust bearings. Then, we reassembled, repainted, and reinstalled the pump. Finally, we reconnected all flanges and restored the gaskets on the input and output flanges of the pump.

We found that the pump motor required new hold-down fasteners, so we replaced them. After reinstalling all components, we aligned the motor to the pump using PRUFTECHNIK's Rotalign Touch Laser. We made adjustments following the data provided by the alignment system.

We ended the job by performing a vibration analysis to establish a baseline using PRUFTECHNIK's VIBXPERT II. Our data showed that we were well within accordance with ANSI/HI and API standards for pumps, in addition to the ISO 10816-3 Standards of machinery vibration.

Rebuilding requires skill and focus on detail. Performing the restoration in-house may cost you time and money in the long run. We suggest you work with a reputable mechanical contractor who has years of experience under their belt. AME has over 200 years of combined experience in machinery service and repair. We even operate two full machine shops in Fort Lauderdale Florida for all of your machinery repair needs.