Definition:

Pipe strain is caused by misalignment between the equipment suction and discharge flanges to the corresponding pipe flange connections. Parallel and angular misalignment of piping flanges at the equipment nozzle results in component failures that lead to poor equipment reliability, costly repairs, and increased downtime.

How to Measure:

The effect of pipe strain on equipment can be estimated by measuring laser shaft alignment for full assembled equipment. After that, disassemble suction/discharge line and re-measure the alignment and compare the results. According to API 686, the maximum shaft movement in either the vertical or horizontal directions after the flange is tightened/loosened shall be 0.05mm or less. If the shaft movement is more than 0.05mm, the piping flange shall be loosened from the equipment and to be corrected. Flange face separation shall be within the gasket spacing plus or minus 1.5mm. Unfortunately, the case in attached video is out of tolerance.

Correction:

1) Shim the supports to move the pipes in the direction of alignment. If the shift is too high, piping support spacers to be installed.

2) Adjust spring hanger tie-rod turnbuckles.

3) After tuning bolt holes to be aligned as soon as possible, smaller bolt diameters are used with bolt holes of slight offset.

4) Finally, release the base bolts of equipment and assemble the suction and discharge lines with a specified torque wrench. After that, apply soft foot check on equipment foots and correct it before tightening the bolts.