July 7, 2014
Using a Laser Shaft Alignment System to Check for Pipe Strain
By Michael Keohane
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.
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:
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:
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.
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.