Pumps & Systems - September 2007

Revisiting Pump-to-Motor Alignment

With regards to “Revisiting Pump to Motor Alignment”

(Pumping Prescriptions, July 2007), during my 22 years at my previous employer, I had the pleasure to work with one of the finest reliability engineers,

“Big Al” Newburn, who had an unstoppable drive for precision work and reliability. In the late 1980s we implemented 0.001-in TIR for reverse dial indicator alignment as part of a 48-month MTBF pump life program.

A note: Our millwrights could do an accurate precision alignment with reverse dial indicators as fast as or faster than the laser alignment vendors. We verified all repair quality, including the alignment, with vibration readings using 0.15-ips peak-c (calculated) for our standard.

We achieved 48+ months and with proper training, our millwrights could complete a precision alignment correctly and in minimal time. I do not recall the exact time, although we scheduled 4 hours for a cartridge seal replacement and alignment of an ANSI pump. In the process of implementing this MTBF pump life program, we eliminated unbalance and misalignment as causes for pump vibration. So to your readers, precision alignment does pay and does not take extra time.

An added benefit: because our millwrights did precision alignment on ANSI pumps when they did alignment on our compressors, they were fully comfortable doing precision alignment on these major compressors. The other components of the 48-month MTBF pump:

• Precision alignment 0.001-in TIR, including soft foot check.

• Synthetic oil in a closed bearing housing noted in the following. (An added benefit of synthetic oil and closed bearing housing: no PM oil change. Oil changes were done based on condition, not time)

• Labyrinth seals on pump housings.

• ISO g 1.0 motor rotor and pump rotor balance (shaft and impeller); yes, we could get repeatability after removing the impeller during installation.

• Closed loop oilers with an evolution to bulls-eye sight glasses.

• Vacuum pressure diaphragm compensator on the bearing housing to minimize “breathing.”

• 0.15-ips peak-c overall vibration repair quality.

• Pump assembly on clean paper.

• Verification of bearing diameters and housing/shaft fits to assure final fits are intolerance.

• Millwrights who treated bearings and mechanical seals as precision assemblies.

• Bearing heater with degaussing.

• Cartridge mount seals with RCA on all failed seals and seal flush systems.

• RCAs on failed bearings – done for several years to document failure modes and match with vibration signatures.

• Magnetic seals on the motor inboard bearing.

• Motor bearings with a single shield toward the grease injection port.

• Motor (new and repaired) test stand quality control checks 0.07-ips peak-c overall, 1x max 0.05-ips peak-c, non synchronous peaks max 0.02-ips peak-c.

• No more than 5 final shims; a spacer block shim was used for preliminary move.

• SS shims.

• Motor feet flat and in the same plane and no bolt bound feet.

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