Vibration monitoring

Troubleshoot Poor Machine Alignment

EP Editorial Staff | July 13, 2016

Industrial pump

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According to Tom Shelton of Richmond, VA-based VibrAlign Inc. (vibralign.com), there are a number of possible reasons that machinery-alignment results may not live up to expectations. Many, he says, can be eliminated in the pre-alignment phase.

To that end, Shelton and other VibrAlign experts and customers have compiled the following “evergreen” list of culprits that could cause the unintended movement affecting alignment outcomes. While these movement sources are different in many instances, they’re common in others.

As Shelton pointed out in a January 2016 blog post on the VibrAlign website, this list isn’t complete. “It’s intended,” he wrote, “to be used as a seed to help you find the source of pain in your alignment.”

To give credit where it’s due, he explains that the idea for the list originated with a student in a training class. He strongly recommends keeping a laminated copy of it with or near your site’s alignment tool(s).
— Jane Alexander, managing editor

Surrounding environment

  • Vibration caused by attached or nearby equipment
  • Interference in the laser beams, i.e., steam, condensation, rain, dust, anything that could reflect or refract a laser light.

Sensors

  • Loose brackets or other components
  • Dirty lenses
  • Inappropriate measuring mode for conditions
  • Incorrect machine dimensions input on set-up
  • Laser beam broken by coupling or structure
  • Gross misalignment causing beam to run off of sensor
  • Gross misalignment causing coupling influences of the rotational centerlines.

Shims

  • Dirt or debris between shims
  • Bent shims
  • Shims against threads on bolt
  • Actual shim thickness different than stamped thickness (Tip: Shims larger than 0.025 in. should mic’d.)
  • Multiple people shimming, putting different shim thicknesses under the feet
  • Wrong size shims (Tip: Always use the shims that give the most contact between the base and the machine foot.)

Machinery components

  • Excessive bearing or component wear (Tip: Do a lift check to determine bearing wear.)
  • Coupling bore off center or skewed
  • Cracked or broken machine case or frame
  • Soft foot
  • Coupling wear
  • Coupling-insert wear
  • Incorrect coupling gap
  • Shaft or hub contacting opposite component shaft
  • Coupling binding due to poor or incorrect rough alignment
  • Pipe and/or conduit strain
  • Motor “belly” contacting base.

Machine base

  • Broken or crumbling base
  • Dirt and debris under machine or machine feet
  • Rusted base, bolts, or feet
  • Top thread of bolt hole in a threaded base pulled up, creating a bump
  • Stripped hold-down bolts or studs
  • Cupped washers (Tip: Hardened machine-base washers or Grade 8 are recommended.)
  • Improper base installation, i.e., hollow or warped base.

Alignment processes

  • Mandatory pre-alignment steps not completed or improperly executed, i.e., inadequate rough alignment, soft foot not corrected or an improper or too aggressive tightening sequence
  • Poor backlash management
  • Lack of training. MT

For more information on the topic of equipment alignment, including what to do “when all else fails,” and/or to add to this list of possible culprits, see Shelton’s complete “Troubleshooting Tips” post at vibralign.com/blog/.

Tom Shelton, a technical trainer with VibrAlign, is a journeyman millwright/pipefitter who spent 16 years in the paper industry.

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