Categories: Shaft Alignment,Machinery Maintenance

Using a Laser Shaft Alignment System to Check for Pipe Strain

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By on July 7, 2014

Pipe strain is a relatively common problem seen in pump installations. It is a cause of premature bearing and seal failure. Here is a link to an excellent article from Pumps and Systems magazine that discusses the detrimental effects of pump strain.

http://www.pump-zone.com/topics/seals/how-do-plant-pipe-strain-problems-affect-my-pumping-systems

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You can easily measure the effects of pipe strain using dial indicators or your laser system. Simply measure the misalignment with everything tight and then re-measure after loosening the pipe flange. Here is an example:

1 – Measure misalignment with everything tight:

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In this case the machine is well within alignment tolerances for an 1800 RPM machine

2 – Loosen the pipe flange and re-measure the misalignment:

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In this particular example the vertical misalignment did not change very much but the horizontal changed quite a bit indicating that pipe stain is an issue in the horizontal direction.

3 – If you want and have the capability you can use a foot-lock function to see the effects on the pump itself. Alternatively, you could have also set up with the pump as the moveable element and look at it that way.

 

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Unlike OL2R (off-line to running) measurements made to check for thermal growth, you would not typically try and compensate for pipe strain during the alignment but it is very important to correct it up front for maximum machine life.

About the Author

Mike Keohane has been involved in machinery reliability since 1985. He started as a field service engineer for IRD Mechanalysis. Prior to that he was a wireline logger for Schlumberger Well Services. He joined VibrAlign in 1992 and supports clients in Georgia, South Carolina, Alabama and the Florida Panhandle. In addition to precision alignment, he has field experience in vibration analysis, field and shop balancing, oil analysis and ultrasonics. Mike holds a BSME from Michigan State University. Mike and his wife and two children currently live in Peachtree City, GA.

3 responses to “Using a Laser Shaft Alignment System to Check for Pipe Strain”

  1. Noah says:

    Hey Mike , would you tell me location of dial for pipe strain on , its not a leaser alignment ,thanks.

  2. Mike Keohane says:

    Noah,

    You can mount a dial on the shaft and go across the coupling. You should consider mounting dials in both the horizontal and vertical directions. Zero the dial and then loosen the pipe flange to check for movement.

  3. Kane says:

    Where to out dti for pipe strain when joining pipe work to a pump. Axially on pipe flange. Or input flange. Or under output flange.

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